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Habilitation thesis
Contributions to
Nanotechnology Application
in wastewater treatment field
Assoc. Professor PhD. Eng. Cristina-Ileana COVALIU
University POLITEHNICA of Bucharest
2017
Cristina Ileana COVALIU Habilitation thesis
1
SUMMARY
REZUMAT…………………………………………………………………………… 4
ABSTRACT…………………………………………………………………………. 7
Chapter 1. SCIENTIFIC, PROFESSIONAL AND ACADEMIC
ACHIEVEMENTS……………………………………………………………………. 10
1.1. Scientific research activity……………………………………………......... 10
1.2. Academic activity………………………………………………………...... 16
1.3. Results dissemination………………………………………………………. 18
Chapter 2. CONTRIBUTION TO NANOTECHNOLOGY APPLICATION IN
WASTEWATER TREATMENT…………………………………………………… 23
2.1. Contribution to nitrates ions efficient removal from water using
nanoadsorbents………………………………………………………………….. 26
2.1.1. General considerations…………………………………………………….. 26
2.1.2. The investigation nitrates removal from water using Pd-Sn/γ-Al2O3,
NiTiO3 and NiFe2O4 ……………………………………………………………… 29
2.1.3. The investigation of CuTiO3 and CuFe2O4 for nitrates removal from
water………………………………………………………………………………. 36
2.2. Contribution to the removal of Cd (II) ions from wastewater using
maghemite and poly-DL-alanine based core-shell magnetic nanohybrids 44
2.2.1. General considerations…………………………………………………….. 44
2.2.2. The investigation of Cd (II) ions removal from wastewater using
multifunctional maghemite and poly-DL-alanine based core-shell magnetic
nanohybrids……………………………………………………………………… 46
2.3. Contribution to the removal of Cu (II) ions removal from industrial
wastewater using environmental friendly nanomaterials…………………… 62
2.3.1. General considerations…………………………………………………….. 62
2.3.2. The investigation of copper (Cu2+) ions removal from industrial
wastewater using maghemite, γ-Fe2O3 and its corresponding hybrid, γ-Fe2O3-
poly-DL-alanine ………………………………………………………………… 67
Cristina Ileana COVALIU Habilitation thesis
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2.4. Contribution to the removal of Cr (II), Cd (II), Cu (II), Zn (II) and Ni
(II) using magnetite (Fe3O4) and Fe3O4-PAA nanomaterials…………………. 70
2.4.1. General consideration……………………………………………………… 70
2.4.2. The investigation of Cr (II), Cd(II), Cu(II), Zn(II) and Ni(II) removal from
wastewater using magnetite (Fe3O4) and Fe3O4-PAA……………………………. 71
2.5. Contribution to Pb(II) and Cd(II) ions removal from wastewater using
as magnetic adsorbant nanomaterials: Fe3O4, Fe3O4-PEG and Fe3O4-PVP… 82
2.5.1. General consideration………………………………………………………. 82
2.5.2. The investigation of Pb(II) and Cd(II) ions removal from wastewater using
iron-based magnetic hybrid nanoparticles: Fe3O4, Fe3O4-PEG and Fe3O4-PVP ... 83
2.6. Contribution to Cu (II), Zn (II), Cr (II), Cd (II) and Ni (II) removal
from wastewater using Fe3O4 and Fe3O4-PVP magnetic nanomaterials ........ 86
2.6.1. General consideration…………………………………………………….. 86
2.6.2. The investigation of Cu (II), Zn (II), Cr (II), Cd (II) and Ni (II) ions
removal from wastewater using Fe3O4 and Fe3O4-PVP nanomaterials………….. 89
2.7. Study of zeolites nanomaterial as a multifunctional environmental
engineering solution……………………………………………………………... 91
2.8. Contribution to organic (C6H6 and C6H5-CH3) and inorganic (Pb+2 and
Zn+2) pollutants removal from for wastewater using powdered activated
carbon …………………………………………………………………………… 94
2.8.1. General considerations…………………………………………………….. 94
2.8.2. The investigation of removal organic (C6H6 and C6H5-CH3) and inorganic
(Pb+2 and Zn+2) pollutants for wastewater using activated carbon ……………… 97
2.9. Contribution to wastewater treatment by using photocatalysis based
titanium dioxide…………………………………………………………………. 107
2.9.1. General considerations…………………………………………………….. 107
2.9.2. The investigation of removal methylene blue and diclofenac from
wastewater by photocatalysis based titanium dioxide……………………………. 110
Chapter 3. PLAN OF SCIENTIFIC, PROFESSIONAL AND ACADEMIC 113
Cristina Ileana COVALIU Habilitation thesis
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DEVELOPMENT IN THE FUTURE…………………………..............................
Bibliography …………………………………………………………………………… 117
Cristina Ileana COVALIU Habilitation thesis
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REZUMAT
Prezenta teză de abilitare cu titlul “Contribuţii la aplicarea nanotehnologiei în domeniul
epurării apelor” prezintă o parte a rezultatelor activităţii de cercetare a candidatei după susținerea
tezei de doctorat la Universitatea Politehnica din Bucureşti. “Nanotehnologia aplicată în
domeniul epurării apelor”, ce reprezintă domeniul meu de cercetare, este una dintre cele mai
mari descoperiri din timpurile noastre. Nanotechnologia (prin utilizarea nanomaterialelor) oferă
oportunitatea apariţiei şi dezvoltării noii generaţii de tehnologii, foarte eficiente, de epurare a
apelor.
Activitatea de cercetare ştiintifică, ulterioară susţinerii tezei de doctorat, am desfăşurat-o
în mod continuu în cadrul Universitatii Politehnica din Bucureşti, abordând teme cu caracter
multidisciplinar, care au putut fi realizate în colaborare cu cercetători din cadrul universităţii la
care lucrez, dar şi de la Institutul National de Fizica Materialelor (INFIM), Institutul Naţional de
Cercetare – Dezvoltare pentru Chimie şi Petrochimie (ICECHIM), Universitatea din Belgrad,
Institutul Național de Mașini Agricole (INMA),etc.
În Capitolul 1 al tezei de abilitare este descrisă evoluţia carierei profestionale până în
prezent, menționând cele mai importante realizări ştiinţifice şi academice. Sunt prezentate
succinct direcţiile de cercetare abordate, între care mentionez: 1) Îndepartarea eficientă a
nitraţilor din apă utilizând nanoadsorbanţi şi nanocatalizatori; 2) Îndepartarea toluenului din apă
prin oxidare, utilizând diferiţi oxizi micşti. ca de exemplu: MTiO3 (M=Cu,Ni), NiTiO3 şi
NiFe2O4; 3) Îndepărtarea metalelor grele din apa uzată utilizând nanomateriale magnetice
oxidice: maghemita (ɤ-Fe2O3), ferrite (Fe3O4, CuFe2O4), etc; 4) ) Îndepartarea metalelor grele din
apa uzată utilizând nanomateriale magnetice hibride (Fe3O4-PAA, Fe3O4-PEG şi Fe3O4-PVP, ɤ-
Fe2O3-poly-DL-alanine); 5) Îndepartarea poluanţilor organici şi a metalelor grele din apă
utilizând nanomateriale zeolitice- ZSM-5; 6) Îndepărtarea poluanţilor organici din apa uzată
printr-un tratament ce are la bază nanomaterialul fotocatalizator TiO2.
Începând din anul 2015, am adăugat în sfera preocupărilor ştiinţifice, cercetarea privind
îndepărtarea poluanţilor de natură organică din apele uzate (ex: grăsimi) prin procedeul de
flotaţie eficientizat de prezenţa nanomaterialelor. Cercetările aferente acestui subiect constituie
tema unui proiect de cercetare de tip PTE (transfer la operatorul economic) din cadrul
Cristina Ileana COVALIU Habilitation thesis
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programului P2- Creşterea competitivităţii economiei româneşti prin cercetare, dezvoltare şi
inovare, finanţat pe doi ani (2016-2018), la care sunt responsabilă din partea Universităţii
Politehnica din Bucureşti.
Celelalte direcţii de cercetare ştiinţifică sunt dezvoltate în cadrul Bursei de Excelență pe
tema “Aplicaţiile bionanotehnologiei în scopul epurării apelor industriale”, câştigată prin
competiţie şi finanţată din bugetul Universităţii Politehnica din Bucureşti în perioada 2016-2017.
Tot în cadrul acestui capitol este prezentat prestigiul profesional naţional şi internațional
care este susținut de numărul mare de articole publicate în jurnale de prestigiu, de numărul mare
de citări ale articolelor publicate, de numărul mare de conferinţe internaționale la care candidata
a participat, inclusiv având calitatea de membru în comitetul ştiinţific, moderator al unor secțiuni
sau referent pentru lucrări.
Activitatea de cercetare ştiinţifică desfăşurată până în prezent a stat la baza coordonării
a trei proiecte în calitate de director sau responsabil, a publicării a 31 de articole cu factor de
impact având valori cuprinse între 0.3-3.21, citate de 200 de ori în reviste de prestigiu precum:
Nano Research (F.I.-6.963), Advances in Colloid and Interface Science (F.I. - 8,636), Journal of
the American Chemical Society (F.I.-12,113). Până în prezent, candidata are o activitate
ştiinţifică pe plan international cuantificată prin valoarea indicelui Hirsch de 8.
Capitolul 2 intitulat „Contribuţii la aplicarea nanotehnologiei în epurarea apei" este
compus din nouă subcapitole. În primul subcapitol sunt prezentate contribuţiile personale cu
privire la îndepărtarea eficientă a nitraţilor din apă utilizând nanoadsorbanţi de tipul: Pd-Sn/γ-
Al2O3, NiTiO3, NiFe2O4 CuTiO3 ; CuFe2O4. În subcapitolele doi şi trei sunt prezentate
contribuţiile autoarei cu privire la îndepărtarea ionilor de Cd (II) and Cu (II) din apa uzată
utilizând nanomaterialele maghemită (γ-Fe2O3) şi hibridul magnetic "miez-carapace" γ-Fe2O3 -
poli-DL-alanină. În cel de-al patrulea subcapitol sunt prezentate contribuţiile autoarei cu privire
la îndepărtarea ionilor de Cu (II), Zn (II), Cr (II), Cd (II) şi Ni (II) din apa uzată utilizând
nanoametrialele Fe3O4 şi Fe3O4-PAA. Apoi, în subcapitolul al cincilea, sunt prezentate
contribuţiile privind îndepărtarea ionilor de Pb (II) şi Cd (II) din apa uzată utilizând ca adsorbanţi
următoarele nanomateriale magnetice: Fe3O4, Fe3O4-PEG şi Fe3O4-PVP. În subcapitolul al
şaselea sunt evidenţiate contribuţiile autoarei cu privire la îndepărtarea ionilor de Cu (II), Zn (II),
Cristina Ileana COVALIU Habilitation thesis
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Cr (II), Cd (II) and Ni (II) din apa uzată folosind nanomaterialele magnetice: Fe3O4 şi Fe3O4-
PVP. În cel de-al şaptelea subcapitolul se prezintă contribuţiile autoarei legate de
nanomaterialele zeolitice care pot reprezenta o soluţie inginerească, multifuncţională a
problemelor de mediu. În cel de-al optulea subcapitol este descris un studiu complex al
îndepărtării poluanţilor organici (C6H6 and C6H5-CH3) şi anorganici (Pb+2 and Zn+2) din apa
uzată folosind cărbune activ. În cel de-al nouălea subcapitol sunt prezentate contribuţiile autoarei
la epurarea apei prin fotocataliză pe bază de dioxid de titan.
În capitolul 3 este descris planul de dezvoltare ştiinţifică, profesională şi academică
viitoare, din care reiese dorinţa de sporire a prestigiului pe plan naţional şi internaţional, de a
coordona şi studenţi străini în scopul realizării studiilor de doctorat, de a câştiga proiecte
internaţionale şi de a transfera cunoştinţele generaţiilor viitoare de doctori în ingineria mediului.
Teza se încheie cu partea de "Bibliografie" în care se regăsesc enumerate materialele
care au stat la baza realizării studiilor ştiinţifice aferente articolelor publicate şi prezentate în
capitolul 2.
Cristina Ileana COVALIU Habilitation thesis
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ABSTRACT
The present thesis entitled “Contributions to nanotechnology application in wastewater
treatment field” shows a part of the research results of the candidate after sustaining the PhD
thesis at University Politehnica of Bucharest. “Nanotechnology applied in wastewater treatment”
representing my field of research is one of the greatest scientific discoveries of recent times.
Nanotechnology (and thus nanomaterials) provides the opportunity of appearance and
development of the next generation of wastewater treatment technologies having very high
efficiency.
After obtaining the PhD title, I continuously conducted my research activity at the
University Politehnica of Bucharest, addressing multidisciplinary topics that have been
developed in collaboration with researchers from other universities and institutes, such as:
National Institute of Materials Physics (INFIM), National Institute of Research and Development
for Chemistry and Petrochemistry (ICECHIM), University of Belgrade, National Institute of
Agricultural Machines (INMA), etc.
In chapter 1 of the habilitation thesis is described the evolution of the professional
carrier until the present, specifying the most important scientific and academic achievements.
There are highlighted the approached research directions, including: 1) Nitrates ions efficient
removal from water using different nanoadsorbents and nanocatalysts; 2) Toluene removal from
water by oxidation using different mixed oxides as nanocatalysts, such as: MTiO3 (M=Cu, Ni),
NiTiO3 and NiFe2O4; 3) Heavy metals removal from wastewater using magnetic oxides
nanomaterials: maghemite (ɤ-Fe2O3), ferrite (Fe3O4, CuFe2O4), etc; 4) Heavy metals removal
from wastewater using magnetic hybrid nanomaterials having inorganic core and polymeric shell
Fe3O4-PAA, Fe3O4-PEG and Fe3O4-PVP, ɤ-Fe2O3-poly-DL-alanine); 5) Heavy metals removal
from wastewater using zeolites nanomaterials- ZSM-5; 6) Heavy metals and organic pollutants
removal from wastewater using activated carbon nanomaterial; 6) Organic pollutants removal
from wastewater using a treatment based on TiO2 photocatalytic nanomaterial.
Since 2016, I have added to scientific concerns sphere, the research on removing
organic type pollutants from wastewater (eg fats) by flotation process having an increased
efficiency conferred by using the nanomaterials. The research on this topic is the subject of a
Cristina Ileana COVALIU Habilitation thesis
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PTE (transfer to the economic operator) type research project within the program P2- Increase
the competitiveness of Romanian economy through research, development and innovation,
funded over two years (2016-2018), at which I am the responsible from the University
Politehnica of Bucharest.
The other directions of the scientific research are developed within the Excellence
fellowship on "Bionanotechnology applications in industrial wastewater treatment", won
by competition and financed from the budget of the University Politehnica of Bucharest during
2016-2017.
Also, in this section is presented the national and international professional prestige
given by the large number of articles published in journals having high impact factor, the high
number of citations of the published articles, the large number of international conferences
attended by the candidate, including as being member of the Scientific Committee, moderator of
certain sections or referent for scientific articles.
The scientific research carried out so far led to the coordination of the three projects as
director or responsible, the publication of 31 articles having impact factor values between 0.3-
3.21), cited 200 times in prestigious journals such as: Nano Research (F.I.-6963), Advances in
Colloid and Interface Science (F.I. - 8636), Journal of the American Chemical Society (F.I.-
12.113).
So far, the impact of international and national scientific activity of the candidate
measured by the index Hirsch is 8.
Chapter 2 entitled “Contribution to nanotechnology application in wastewater
treatment” consists of nine subchapters. In the first subchapter are presented the contributions to
nitrates ions efficient removal from water using the following nanoadsorbents: Pd-Sn/γ-Al2O3,
NiTiO3, NiFe2O4, CuTiO3 and CuFe2O4. The second and third subchapters present the author
contributions to the removal of Cd (II) and Cu (II) ions from wastewater using γ-Fe2O3
(maghemite) and γ-Fe2O3 -poly-dl-alanine based core-shell magnetic hybrids nanomaterials. In
the fourth subchapter are presented the authors’s contribution to Cu (II), Zn (II), Cr (II), Cd (II)
and Ni (II) removal from wastewater using Fe3O4 and Fe3O4-PAA magnetic nanomaterials.
Then, in the fifth subchapter are presented the contributions to Pb(II) and Cd(II) ions removal
Cristina Ileana COVALIU Habilitation thesis
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from wastewater using as adsorbants the following magnetic nanomaterials: Fe3O4, Fe3O4-PEG
and Fe3O4-PVP. In the sixth subchapter are presented the author contributions to Cu (II), Zn (II),
Cr (II), Cd (II) and Ni (II) removal from wastewater using Fe3O4 and Fe3O4-PVP magnetic
nanomaterials. The seventh subchapter shows the author contributions related to research on
zeolites nanomaterials as a multifunctional environmental engineering solution. In the eighth
subchapter is presented a complex study regarding the removal of organic (C6H6 and C6H5-CH3)
and inorganic (Pb+2 and Zn+2) pollutants from wastewater using powdered activated carbon. The
ninth subchapter describes the author contributions to wastewater treatment by using
photocatalysis based titanium dioxide.
In chapter 3 is presented the plan of future scientific, professional and academic
development, based which results the desire to increase the national and international prestige, to
coordinate foreign students for doctoral thesis, to win national and international projects and to
transfer the scientific knowledge to future generation of PhD students in environment
engineering field.
The thesis ends with "References" where are listed the scientific materials used to
develop the studies related to the published articles presented in Chapter 2.
Cristina Ileana COVALIU Habilitation thesis
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Chapter 1.
SCIENTIFIC, PROFESSIONAL AND ACADEMIC ACHIEVEMENTS
1.1. Scientific research activity
Nanotechnology (and thus nanomaterials) is one of the greatest technology discoveries of
recent times.
The nanotechnology (and thus nanomaterials) market has a huge potential of application in
environmental engineering field.
My own scientific achievements in the field of environmental engineering, regarding the
application of nanotechnology in water treatment field, have focused on the fundamental and applied
research activities regarding the synthesis, characterization and testing of nanomaterials having
special properties suitable for removing various inorganic and organic pollutants from water.
My own scientific activity on fundamental and applied research in the environment
engineering field began in 2003, during the research conducted on "Polyphosphazene materials
applied for treatment of industrial wastewater polluted with 3d type metal ions", aiming to obtain a
new polymer with high efficiency for removing 3d metal ions (Cu2+, Ni2+, Cr3+) from the wastewater
resulted from industrial processes. During this study I investigated the influence of the following
factors such as: pH, contact time, the concentration of metal ions from wastewater upon the degree of
treatment efficiency of the tested material.
The results of the experimental research obtained in the nanotechnology field during
Master, PhD and Postdoctoral studies and the discovery of the special properties of the
nanomaterials conferred by their dimensions in the nanometer range encouraged me to expand the
study of their application in the field of environmental engineering.
Among these special properties of nanomaterials, the adsorption capacity given by the
“nano” dimension is remarkable, because offer them the capacity of retaining various types of
chemical pollutants from water. Thus, I have studied in the last years the adsorption capacity of
various nanomaterials, such as: metallic oxides, composites and hybrids composed by metallic
oxides and biopolymers.
Regarding my personal activities developed in the field of nanotechnology applied in
environmental engineering field, contributions are related to:
Cristina Ileana COVALIU Habilitation thesis
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- New methods for synthesis of nanomaterials applied in environmental engineering field, by
controlling the influencing factors such as: temperature, pH, surfactant concentration;
- Study of the advanced characterization techniques of nanomaterials applied in environmental
engineering field expressing accurately the information obtained by comparing various
characterization and analysis methods such as: transmission electron microscopy (TEM), scanning
electron microscopy (SEM), X-ray diffraction (XRD), atomic absorption analysis (AAS), etc.;
- Investigation of inorganic and organic type pollutants removal from wastewater using
nanomaterials, studying the following issues:
the optimum quantity of nanomaterial suitable to be used for removing a certain value
of pollutant concentration found in water;
the maximum quantity of nanomaterials used for obtaining the highest yield of
wastewater treatment;
the type of nanomaterials used for removing different types of pollutants found in
water, etc.
The research directions representing my own contribution to the environmental engineering
field are the following:
1) Nitrates ions efficient removal from water using different nanoadsorbents and
nanocatalysts, such as: Pd-Sn/γ-Al2O3, NiTiO3 and NiFe2O4;
2) Toluene removal from water by oxidation using different mixed oxides as nanocatalysts
such as: MTiO3 (M=Cu2+, Ni2+), NiTiO3 and NiFe2O4;
3) Heavy metals removal from wastewater using magnetic oxides nanomaterials: maghemite
(ɤ-Fe2O3), ferrite (Fe3O4, CuFe2O4), etc;
4) Heavy metals removal from wastewater using magnetic hybrid nanomaterials having
inorganic core and polymeric shell Fe3O4-PAA, Fe3O4-PEG and Fe3O4-PVP, ɤ-Fe2O3-poly-DL-
alanine);
5) Heavy metals removal from wastewater using zeolites nanomaterial- ZSM-5 zeolites;
6) Heavy metals and organic pollutants removal from wastewater using activated carbon
nanomaterial;
7) Organic pollutants removal wastewater from using a treatment based on TiO2
photocatalyst nanomaterial;
All these results were disseminated by publishing of books, articles, manuals.
Cristina Ileana COVALIU Habilitation thesis
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Till the present, the scientific activity was materialized in publishing: 5 books, 1 Laboratory
guide, 27 ISI quoted articles listed on the ISI Web of Science, 28 BDI. I have one national patent
application pending. The published articles were cited 200 times times in prestigious journals such
as: Nano Research (F.I.-6963), Advances in Colloid and Interface Science (F.I. - 8636), Journal of
the American Chemical Society (F.I.-12.113).
According to Scopus Scientific database, my personal Hirsch index is 8, whereas according
to Web of science database Hirsch index is 7. One of publication had the privilege to be published
on the SAO/NASA Astrophysics Data System (ADS) which is a Digital Library portal for
researchers in Astronomy and Physics, operated by the Harvard University and Smithsonian
Astrophysical Observatory (SAO) under a NASA grant:
http://adsabs.harvard.edu/abs/2013ApSS..285...86C.
My ability to coordinate research teams is sustained till the present by: submission of eight
grant applications as project director or responsible, coordination of collective work teams in two
conference organization: "International Symposium ISB-INMA TEH - Agricultural And Mechanical
Engineering" and "International Conference on Thermal Equipment, Renewable Energy and Rural
Development – TE-RE-RD", coordination of students and groups of students in research work for
participation at some scientific national and international competitions:
Annual Session of Scientific Communications for Students organized by University
Politehnica of Bucharest, some example are:
- in 2013, papers presented at Session of Scientific Communications for Students
organized by University Politehnica of Bucharest:
- Priority environmental issues regarding wastewater resulted from hospital,
student: Nicoleta Ghiţeanu;
-Treatment of wastewater containing heavy metals (Cd(II)) using
nanostructured hybrids, student: Iuliana Tudose;
- Study of heavy metals (Pb(II) si Cd (II)) adsorption capacity using oxides
having nanometric size, student: Cristina Popa;
-Unconventional method of wastewater treatment,
student: Raluca Micu;
- in 2014, papers presented at Session of Scientific Communications for Students
organized by University Politehnica of Bucharest and also at International Session
Cristina Ileana COVALIU Habilitation thesis
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of Scientific Communications for Students organized by Maritime University from
Constanţa;
- Orange peels used in wastewater treatment, Turcan Monica Oana, Grama
Silviu Nicolae, premium III at both competitions.
- Innovative method for removing chromium ions from wastewater,
Dumitrache Robert;
- Method for removal lead ions from wasteswater, Burcea Georgeta;
- Versatile system with potential applications in cooper ions removal from
industrial watewater, Stanescu Raluca.
- Strategy of retaining copper from wastewater, Stanescu Raluca, I premium,
at Session of Scientific Communications for Students organized by University
Politehnica of Bucharest;
- Unconventional method for treatment of wastewater polluted with lead,
Burcea Georgeta, I premium, at Session of scientific communications for students
organized by University Politehnica of Bucharest;
- Study of vegetable waste utilization as adsorbants for wastewater treatment,
Turcan Monica Oana, Grama Silviu, III premium, at Session of Scientific
Communications for Students organized by University Politehnica of Bucharest;
- in 2015 papers presented at International Session of Scientific Communications
for Students organized by Maritime University from Constanţa:
- Chromium ions removal from wastewater using carbon nanotubes, Miclescu
Alexandra-Maria;
- Phytoremediation of wastewater polluted with chromium ions, Gheorghian
Alexandra, Cotoara Nicoleta Emanuela;
- Copper ions removal from wastewater using bulrush (Typhaangustifolia),
Oana Stoian, Raluca Damian;
- Versatile system for the removal of copper from industrial wastewater,
Gheorghe Catalin Nicolae.
- in 2015 papers presented at ”XX International Session of Scientific
Communications for Students SECOSAFT 2015” organized by Academia of
terrestrial forces Nicolae Balcescu:
- Wastewater treatment using orange peels, Gritsco Iulian, Munteanu Tatiana;
Cristina Ileana COVALIU Habilitation thesis
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-Ecological depollution of wastewater using plants (Typha latifolia), Stoian
Oana, Damian Raluca;
-Unconventional method for wastewater treatment, Cristescu Andreea
Catalina, Pascu Lucian Eduard;
-Innovative method for treatment of wastewater containing chromium,
Hoaghe Dan, Burlacu Cristina;
- from 2015 papers presented at the Session of Scientific Communications for
Students organized by University Politehnica of Bucharest:
- Innovative method for depollution of wastewater containing chromium ions,
Hoaghe Dan, Burlacu Cristina;
- Versatile system for treatment of industrial wastewater containing copper
ions, Gheorghe Cătălin;
- Unconventional method for Pb (II) removal from industrial wastewater,
Cristescu Andreea Cătălina;
- Wastewater treatment method using ecological nanomaterials, Damian
Raluca;
- Treatment of wastewater from tannery industry, TAMEȘ Ana Maria;
- Ecological nanosystems for treatment of wastewater polluted with chromium
ions, Miclescu Alexandra Maria, Badan Daniela Nicoleta;
- Fitoremediation of wastewater polluted with chromium ions, Stoian Oana;
The Management competences were developed as director or responsible within the
following three research projects:
1) Technology for treatment by flotation of water highly loaded with pollutants, PN III,
PTE nr.25/2016. The project aim is to obtain a wastewater treatment plant which uses the flotation
process for depollution. The flotation process applied for wastewater depollution will use different
types of nanoparticles for increasing its efficiency. Till the present the team of University Politehnica
of Bucharest coordinated by me as responsible had obtained the following results disseminated as
follows:
- Participation with the paper: M. Matache, C.Covaliu, G. Petrescu “Improved
treatment technology through the floatation of heavily loaded waters“, at International Symposium
ISB-INMA TEH’ 2016 Symposium, 27 – 29 October 2016, Bucharest, Romania;
- Participation with the paper: I.C. Moga, C.I.Covaliu, M.G. Matache, “Improved
Cristina Ileana COVALIU Habilitation thesis
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dissolved air flotation technology for highly polluted wastewaters”, at 5th International Conference
on Advanced material Engineering & Technology (ICAMET 2016), 8 – 9 December 2016, Taiwan.
- Participation with the paper: G. Petrescu, M.G. Matache, C.I. Covaliu, I. Voicea,
G. Paraschiv, A.D. Diaconu, B.D. Nasarimba-Grecescu, I. C. Moga, “Improved Flotation treatment
technology for heavily loaded wastewater” presented at International Salon of Inventions –
Kaohsiung International Invention and Design EXPO (KIDE) 2016, 9 – 11 December 2016, Taiwan,
where it was awarded with Diploma of Excellence.
2) Bionanotechnology application in wastewater treatment, No.44/26.09.2016, an
Excellence Fellowship, coordinated by me, within University Politehnica of Bucharest, The project
aim is to obtain various types of nanomaterials as used as photocalaysts or adsorbants for removal of
pollutants from wastewater. Till the present the team of UPB together with me as responsible had
obtained the following results disseminated as follows:
- Participation with the paper: C.I. Covaliu, M. Ionescu, G. Paraschiv, S.St. Biris, C.
Matei, L. Toma, M.G. Matache, New trend in the application of nanotechnology in wastewater
treatment - CeO2 photocatalyst, Internațional Symposium– ISB-INMA TEH’ 2016 International
Symposium, 27 – 29 octombrie 2016, Bucharest, România,
- C. I.Covaliu, G.Paraschiv, S.St.Biris, C.Matei, M.Ionescu, Nanotechnology applied
in wastewater treatment. Photocatalysis based titanium dioxide, 16th International Multidisciplinary
scientific geoconference SGEM 2016, 2 –5 noiembrie 2016, Vienna, Austria. At this conference I
was awarded with the Best oral presentation.
Strictly related with scientific activity is the fact that from 2012 I am the resposible of the
Laboratory “Environment Quality Analysis”, within the Faculty of Biotechnical Systems
Engineering, University Politehnica of Bucharest, which has the infrastructure suitable for doing
analyses of pollutants from wastewater and obtaining nanomaterials used for water depollution.
Also, I am member of the scientific comity of two annual international conferences:
"International Conference on Thermal Equipment, Renewable Energy and Rural Development – TE-
RE-RD" and "International Symposium ISB-INMA TEH - Agricultural And Mechanical
Engineering".
From 2013 till the present I had the honor to win four awards given by UEFISCDI for
scientific research publication in prestigious journals.
Regarding the scientific activity I had the honor to win prizes for the best oral presentation
at international conferences, some of them are:
Cristina Ileana COVALIU Habilitation thesis
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1. I.C. Covaliu, G. Paraschiv, S.St Biris., C. Matei, M. Ionescu, Nanotechnology applied in
wastewater treatment. Photocatalysis based titanium dioxide, 16th International Multidisciplinary
scientific geoconference SGEM 2016, Vienna, 2 –5 noiembrie 2016.
2. C. Covaliu, G. Paraschiv, S. Ş. Biriş, I. Filip, M. Ionescu, Nanotechnology for wastewater
treatment, TE-RE-RD conference, 2-4 June 2016, Golden Sands, Bulgaria.
3. G. Petrescu, M.G. Matache, C.I. Covaliu, I. Voicea, G. Paraschiv, A.D. Diaconu, B.D.
Nasarimba-Grecescu, I. C. Moga, “Improved Flotation treatment technology for heavily loaded
wastewater”, Diploma of Excellence, at International Salon of Inventions – Kaohsiung International
Invention and Design EXPO (KIDE) 2016, 9 – 11 December 2016, Taiwan.
4. C. Covaliu, I.R. Bunghez, S.Şt. Biriş, G. Paraschiv, Research on copper ions removal from
industrial wastewater using environmental friendly nanomaterials, ISB-INMA THE’2014, 30- 31
octombrie 2014.
I am member in various professional international associations, such as: Romanian Society
of Chemistry, Romanian Society of Biomaterials Romanian Society of Magnetic Materials and
Society of Mechanical Engineers from Romania –SIMAR.
1.2. Academic activity
The didactic activity was initiated in 2007 as a collaborator professor at Faculty of Applied
Chemistry and Materials Science within University Politehnica of Bucharest.
Since 2012, I was employed as lector at Faculty of Biotechnical Systems Engineering, from
University Politehnica of Bucharest, being titular at the disciplines: „Ecology and environment
protection”, „Biochemical processes in environmental engineering”, “Ecology fundaments”,
“Analyses techniques of the environment quality”, etc.
In the present time, I am titular at the disciplines: „Ecology and environmen protection”,
„Ecology fundaments”, „Biochemical processes in environmental engineering”, “Analyses
techniques of the environment quality”, “Processes and equipments for separation and purification”.
Currently, I am associate professor at Faculty of Biotechnical Systems Engineering, from
University Politehnica of Bucharest.
In the present time, within the Faculty of Biotechnical Systems Engineering from University
Politehnica of Bucharest I am the president of the commission of diploma thesis evaluation at the
specialization "Biotechnical and Ecological Systems Engineering" and I am member of the
Cristina Ileana COVALIU Habilitation thesis
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dissertation thesis commission of the "Engineering and Management in Environmental Protection”
specialization.
One of my goals as regarding academic activity is continuously transfer of the scientific
researches knowledge to didactic activity in field of environmental engineering.
Currently, within University Politechnica of Bucharest I coordinate both diploma projects
for the field of specialization "Biotechnical and Ecological Systems Engineering" and dissertation
projects for two specializations “Engineering and Management of Biotechnical Systems" and
"Engineering and Management in environmental protection”.
I work closely with the professors from Faculty of Environmental Protection and Land
Improvement from University of Agriculture Science And Veterinary Medicine, where I am
collaborator professor, teaching “Biotechnologies and sustainable industries” discipline within the
“Management of Investments in Ecosystems” master. Moreover, at this master I coordinate
dissertation projects and I am member of dissertation commission.
Some examples of the research topics in the field of environmental engineering which were
studied within the diploma projects and dissertation thesis coordinated by me are the following:
1) System for treatment of leachates from waste disposal landfills;
2) Versatile system for industrial water treatment;
3) Treatment system of wastewater from leather industry;
4) Wastewater treatment using photocatalytic processes;
5) Study of unconventional water treatment technologies;
6) Innovative procedure of removing heavy metals from industrial wastewater;
7) Removal process of chromium ions from industrial wastewater;
8) Treatment of wastewater polluted with cooper ions;
9) Unconventional methods for treatment of wastewater polluted with lead ions;
10) Versatile system for removal of copper from industrial wastewater;
11) Nanomaterials used as adsorbents for heavy metals removal from industrial
wastewater;
12) Application of TiO2 nanomaterial as photocatalyst for methylorange pollutant removal
from wastewater;
13) Application of TiO2 nanomaterial as photocatalyst for methyleneblue pollutant removal
from wastewater, etc.
Cristina Ileana COVALIU Habilitation thesis
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In close connection with the ability to coordinate PhD students, I am member of two
doctoral guidance commissions, as follows:
1) Oxidative photocatalysts with applications in depollution of the environment, PhD
student: Arsenescu Daniela, pHd Coordinator: Prof.Phd.Chem. Ioana Jitaru, from Faculty of
Applied Chemistry and Materials Science, University Politehnica of Bucharest;
2) Contributions to wastewater treatment by decantation and aeration / flotation, PhD
student: Zabava (Dragoiu) Bianca, pHd Coordinator: Prof.Phd.Eng. Gheorghe Voicu, from
Faculty of Biotechnical Systems Engineering, University Politehnica of Bucharest.
1.3. Results dissemination
Till the present I am reviewer at the many journals, some examples are:
1. Journal of Nanaoparticle Research (F.I.-2,184);
2. Scientific Bulettin of University Politehnica of Bucharest;
3. Powder Technology (F.I.-2,349),;
4. Journal of Sol-Gel Science and Technology (F.I.-1,532);
5. Arabian Journal of Chemistry (F.I.-3,725),
6. Journal of American Chemical Society (F.I.- 12.113).
Books and Manuals
I have published 5 books, from which in the field of the habilitation thesis are the following:
1. C. Covaliu, E.Matei, G. Paraschiv, Ecology and Environment Protection, Publisher
Printech, 2014, ISBN 978-606-23-0336-5, 200 pages,
2. C. Covaliu, G. Paraschiv, Biochemichal Processes in environment engineering, Publisher
Printech, 2014, ISBN 606- 23- 0337-2, 150 pages.
3. C. Covaliu, E. Matei, A. Predescu, G. Paraschiv, Analysis Methods of water quality,
Publisher Printech, 2014, ISBN 978-606-23-0329-7, 108 pages.
4. I. Jitaru, C. I.Covaliu, Inorganic Chemistry. Representative elements, Publisher Printech,
2011, ISBN 978-606-521-718-8, 365 pages;
Cristina Ileana COVALIU Habilitation thesis
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The habilitation thesis has been elaborated based on some papers published in journals or
proceedings.
The most relevant articles in the research field of the habilitation thesis:
1. C.I. Covaliu, E. Matei , G. Georgescu, T. Malaeru, SS. Biris, Evaluation of powdered
activated carbon performance for wastewater treatment containing organic (C6H6 and C6H5-CH3)
and inorganic (Pb+2 and Zn+2) pollutants, Environmental Engineering and Management Journal, 15,
Issue: 5, 1003-1008, 2016, F.I=1.008.
2. C.I. Covaliu, M. Ionescu, G. Paraschiv, S.St. Biris, C. Matei, L. Toma, M.G. Matache,
New trend in the application of nanotechnology in wastewater treatment - CeO2 photocatalyst,
Internațional Symposium– ISB-INMA TEH’ 2016 International Symposium, 27 – 29 octombrie
2016, pp. 567-570, Bucharest, România, ISSN 2344 – 4118.
3. C. Covaliu, G. Paraschiv, S. Șt. Biriş, I. Filip, M. Ionescu, Nanotechnology for
wastewater treatment, Proceedings 5th International Conference of Thermal Equipment, Renewable
Energy and Rural Development, TE-RE-RD 2016, pp.205-209, ISSN 2359-7941, ISSN-L 2359-
7941, Golden Sands – Bulgaria.
4. C.I. Covaliu, G. Paraschiv, S.St. Biris, C. Matei, M. Ionescu, Nanotechnology applied in
wastewater treatment. Photocatalysis based titanium dioxide, Proceedings 16th International
Multidisciplinary scientific geoconference SGEM 2016, pp. 99-104, Viena, 2 –5 noiembrie 2016.
5. C. Covaliu, I.R. Bunghez, S.Şt. Biriş, G. Paraschiv, Research on copper ions removal
from industrial wastewater using environmental friendly nanomaterials, International symposium
Isb-Inma teh agricultural and mechanical engineering, 2014, pp.119-124, Bucuresti, Romania, ISSN
2344 – 4118.
6. C.I. Covaliu, G. Paraschiv, S.S. Biris, I. Jitaru, E. Vasile, L. Diamandescu, T.C.
Velickovic, M. Krstic, V. Ionita, H Iovu, E. Matei, Maghemite and poly-DL-alanine based core-shell
multifunctional nanohybrids for environmental protection and biomedicine applications, Applied
Surface Science, 285, 86-95, Part: A, 2013, ISSN: 0169-4332, F.I=2.538.
7. E. Matei, A. M. Predescu, C. Predescu, M.G. Sohaciu, A. Berbecaru, C. I. Covaliu,
Characterization and application results of two magnetic nanomaterials, Journal of Environmental
Quality, 42 (1), pp. 129-136, 2013 ISSN: 0047-2425.
8. G.A. Traistaru, C. I. Covaliu, G. Gallios, D. Cursaru, I. Jitaru, Removal of nitrate from
water by two types of catalysts: Characterization and sorption studies, Revista de Chimie, 63 (3),
pp.268-271, 2012, (corresponding author);
Cristina Ileana COVALIU Habilitation thesis
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9. C.I. Covaliu, S.Şt. Biriş, G. Paraschiv, Fodorean, C. Ghitescu, E. Matei, A. Constantinescu,
Arsenescu D., Jitaru I., TiO2 photocatalyst for wastewater treatment applications – review,
International symposium isb-inma teh agricultural and mechanical engineering, pp.241-244, 2015,
ISSN 2344 – 4118.
10. G.A. Trăistaru, C.I. Covaliu, G. Paraschiv, G. Gallios, V.Vlăduț, D. Manea, C. Sorică,
Nitrates ions efficient removal from water using three nanoadsorbents, ANNALS of Faculty
Engineering Hunedoara – International Journal of Engineering, Tome XII, Fascicule 4, 235-328,
2014, ISSN: 1584‐ 2673.
11. C.I. Covaliu, G. Paraschiv, S.Șt. Biriș, E. Matei, I. Filip, M. Ionescu, Heavy metals
removal from wastewater using magnetic nanomaterials based adsortion strategies, Conference
Proceedings of “3nd International Conference on Thermal Equipment, Renewable Energy and Rural
Development”, TE-RE-RD 2014, p.205-208, ISSN 2359-7941.
12. C.I. Covaliu, S.Şt. Biriş, G. Paraschiv, G. Voicu, Iron-based magnetic hybrid
nanoparticles for high efficient removal of heavy metals from wastewater, Conference Proceedings
of “2nd International Conference of Thermal Equipment, Renewable Energy and Rural Development
TE-RE-RD 2013, p. 139-140, 2013, ISSN 1843 – 3359.
Awards
Till now I had some ISI articles awarded by UEFISCDI contest, some of them are:
1) F.Ilie, C. I. Covaliu, G. Chisiu, Tribological Study of Ecological Lubricants Containing Titanium
Dioxide Nanoparticles, Applied Mechanics and Materials, 658, 323-328, 2014, PN-II-RU-PRECISI-
2014-8-6840;
2) C.I. Covaliu, G. Paraschiv, S.S. Biris, I. Jitaru, E. Vasile, L. Diamandescu, T.C. Velickovic, M.
Krstic, V. Ionita, H Iovu, E. Matei, Maghemite and poly-DL-alanine based core–shell
multifunctional nanohybrids for environmental protection and biomedicine applications, PN-II-RU-
PRECISI-2013-7-4198;
3) E. Matei, A.M. Predescu, C. Predescu, M.G. Sohaciu, A. Berbecaru, C.I. Covaliu,
Characterization and Application Results of Two Magnetic Nanomaterials, PN-II-RU-PRECISI-
2013-7-3050;
4) C.I. Covaliu, I. Jitaru, G.Paraschiv, E. Vasile, S.Ş. Biriş, L. Diamandescu, V. Ionita, H. Iovu,
Core–shell hybrid nanomaterials based on CoFe2O4 particles coated with PVP or PEG biopolymers
for applications in biomedicine, PN-II-RU-PRECISI-2013-7-4193;
Cristina Ileana COVALIU Habilitation thesis
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Some of the articles in the field of environment engineering presented at conferences are
the following:
1. C.I. Covaliu, G. Paraschiv, S.St. Biris, C. Matei, M. Ionescu, Nanotechnology applied in
wastewater treatment. Photocatalysis based titanium dioxide, 16th International Multidisciplinary
scientific geoconference SGEM 2016, Vienna, 2 –5 noiembrie 2016.
2. C. Covaliu, G. Paraschiv, S. Ş. Biriş., I. Filip, M. Ionescu, Nanotechnology for
wastewater treatment, TE-RE-RD conference, 2-4 June 2016, Golden Sands, Bulgaria.
3. C.I. Covaliu, S.Şt. Biriş, G. Paraschiv, Fodorean, C. Ghitescu, E. Matei, A
Constantinescu., D. Arsenescu, I. Jitaru, TiO2 photocatalyst for wastewater treatment applications –
review, International symposium isb-inma teh agricultural and mechanical engineering, pp.241-244,
2015, ISSN 2344 – 4118.
4. C.I. Covaliu, G. Paraschiv, S.Ş. Biriş, Cr. Cîrtoaje, I. Filip, E. Petrescu Chromium
removal from wastewater using carbon nanotubes, 4th International Conference of Thermal
Equipment, Renewable Energy and Rural Development TE-RE-RD 2015, pp.199-204, 2015, ISSN
2457 – 3302.
5. C.I. Covaliu, G. Paraschiv, S.St. Biris, E. Matei, I. Filip, M. Ionescu, Heavy Metals
Removal from Wastewater Using Magnetic Nanomaterials Based Adsortion Strategies, 3rd Internat.
Conf. on Thermal Equipment, Renewable Energy and Rural Development, 2014, ISSN2359-7941.
6. C.I.Covaliu, E. Matei, G.Paraschiv, M.A. Predescu, Depollution of Wasterwater
Containing Cr (Vi) Ions, Using a Polymer-Magnetite, Analytical and Nanoanalytical Methods for
Biomedical and Environmental Sciences, 2014, ISSN: 2360-3461.
7. C.I.Covaliu, G. Paraschiv, S.St. Biris, D. Stoica, E. Matei, Heavy Metals Removal from
Wastewater usingMagnetic Nanomaterials, Book of Abstracts, 2nd International Conference on
Analytical Chemistry, Romania –Targoviste, September, 2014, ISBN 978-973-712-902-4.
Requested Criteria according to Annex 4 (Annex 18 for 6.560/2012 Order) Annex 18 –
Environmental Engineering
2. Minimum criteria (Ai)
No.
Category
Activity Field Requested Profesor
Conditions Accomplished
Cristina Ileana COVALIU Habilitation thesis
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1 Teaching and training (A1) 210 216,4
2 Research (A2) 500 1539,72
3 Recognition and activity impact (A3) 90 600
TOTAL Minim 800 puncte 2356,12
No. Criteria Minimum requested Accomplished
1 Books and chapters in specialized
books (with ISBN) minim 4 6
2 Articles in ISI Thomson Reuters
journals Punctaj ≥ 400, n ≥ 11 Punctaj≥ 1201,72, n = 29
3 Articles in journals and volumes
of scientificevents indexed in
international databases, ISI
Proceedings
Minim 16 29
4 In competition won grants Minim 2 2
5 Citations in ISI Thomson Reuters
and BDI
Minim 30 200
Research Support Acknowledgements
As author of this thesis I recognize the interdisciplinary team support: CS1. Lucian
Diamandescu from Institute of Physic and Engineering of Materials Magurele, Prof. Horia Iovu,
Prof. Ioana Jitaru, Prof. Ecaterina Matei and CS1 Eugeniu Vasile from University Politehnica of
Bucharest and Prof. Tanja Circovich Velikovichi from University of Belgrade.
Cristina Ileana COVALIU Habilitation thesis
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Chapter 2. CONTRIBUTIONS TO NANOTECHNOLOGY APPLICATION IN
WASTEWATER TREATMENT
Nanotechnology is one of the greatest technology discoveries of recent times. As
presented in Fig.2.1. the global market for nanotechnologies is still developing, being pegged at
approximately $16 billion in 2010, $27 billion in 2015 and expected to reach a value of $76
billion by 2020 [1]. This evolution is generally related, in large part, with the growth of the
interest for research and multiple applications of the “new” materials called nanomaterials and
also with the requirements of environment legislation, the development of industry and
increasing the life quality.
Fig. 2.1. Global nanotechnology market, 2010-2020; p – projections [1].
The nanotechnology (and thus nanomaterials) market has a huge potential of application
in environmental engineering field. The environment applications market was 1.1 billion $ in
2008, 26 billion $ in 2015 and estimated to be 42 billion $ by 2020 as is presented in Fig.2.2.
Nanotechnology provides opportunities to develop next generation of wastewater
treatment technologies.
Nanomaterials are defined as materials with dimension smaller than 100 nm. At this
scale, materials often have novel size-dependent properties different from their large
counterparts, many of which have been explored for applications in water and wastewater
treatment. The scalable size-dependent properties used by these applications are: high specific
surface area, high reactivity, strong capacity of adsorption. Other applications take advantage of
Cristina Ileana COVALIU Habilitation thesis
24
their discontinuous properties, such as superparamagnetism. Most of their applications are still in
the stage of laboratory research.
Fig.2.2. Global market for nanotechnology applied in environmental field applications, 2008-
2012 p – projections [1].
In the environmental field, nanomaterials sustain and enhance the development of
innovative processes pursuing to eliminate the risks associated with pollution from various
industrial activities by providing effective solutions for example in the wastewater treatment
direction. Owing to their physic and chemical characteristics, nanomaterials have a great
capacity to adsorb or decompose pollutants from water.
The scientific importance of this research direction is given by recent discoveries in the
field of nanotechnology which offers the possibility of solving the problem of environmental
pollution with industrial wastewater, containing highly toxic pollutants, having inorganic (e.g.
heavy metals) or organic (e.g. colorants, pesticides) nature, by applying new methods of
treatment more efficient compared with the conventional ones presenting countless
disadvantages of which are worth mentioning: inefficiency for removal low concentrations of
pollutants existing in wastewater, high cost because it involves high reagent consumption,
generation of hazardous wastes from the treatment process that are harmful to the environment
and require additional treatment costs.
For instance, in the case of heavy metals is well known the extremely high toxicity,
even at low concentrations, tending to bioaccumulate in the food chain, the ability to attack the
Cristina Ileana COVALIU Habilitation thesis
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cells of the human body, leading ultimately to default malformations and cancer. The action of
the organic nature pollutants (e.g. pesticides) on the human body leads to abnormal growth, low
fertility, weakening immunity, reduced intellectual capacity and increased morbidity from
cancer. Particularly serious are the consequences of the action of these organic pollutants on the
embryo, fetus and young children.
Therefore, finding the most effective ways of removing inorganic or organic pollutants
from industrial wastewater is a crucial problem that can be solved by making new discoveries in
the field of nanotechnology, involving synthesis of new materials, nontoxic, nano- sized (called
nanomaterials) with special properties, used as adsorbents or catalysts.
The limitations of current approaches by analyzing the current state of knowledge
related to the habilitation thesis theme are the following:
regarding the inorganic pollutants (eg metals heavy) from industrial wastewater-
although can be used various treatments such as chemical precipitation, coagulation
and flocculation, flotation, ion exchange and membrane filtration but they have their
inherent disadvantages such as low efficiency for decreased concentration of
pollutants existing in water and limitation in application.
regarding the elimination of pollutants of organic nature from industrial waters,
the existing techniques such as wastewater treatment with activated sludge, biofilters
or oxidation lakes have the following disadvantages: involve high costs and
generates wastes which are harmful to the environment if are not well treated or
processed.
These limitations led to the research of unconventional methods such as those in area of
nanotechnology that can overcome the disadvantages and inherent limitations of conventional
methods of wastewater treatment.
This research direction, “Nanotechnology applied in wastewater treatment field”, is
distinguished by a lack of scientific data because is relatively new and the transition from
laboratory results to the application in a wastewater treatment plant cannot be done without
significant efforts made to elucidate all aspects still unknown.
Cristina Ileana COVALIU Habilitation thesis
26
2.1. Contribution to nitrates ions efficient removal from water using nanoadsorbents
2.1.1. General considerations
Generally, nitrate ions are present in soil and water, but high levels of nitrates are
considered pollutants for ground and surface waters.
In recent years, it was observed an increase of nitrate concentration in groundwater in
many parts of the world due to increased usage of nitrogenous fertilizers in agriculture practice
and discharge of domestic and industrial wastewater Fig.2.3 and Table 2.1. [2].
Table 2.1. Groundwater nitrate concentration classes (mg NO3/L) and proportion of
groundwater monitoring stations in each class per country (%), 2009, EU-27, EFTA, candidate
and potential candidate countries Source: European Environment Agency [2].
Country Groundwater nitrate concentration classes (mg \NO3/l) and number of groundwater
monitoring stations in each concentration class per country
≤10 10< ... ≤ 25 25< ... ≤ 50 50< Total
Belgium 1024 381 534 835 2774
Bulgaria 52 21 24 15 112
Czech Republic 385 85 70 73 613
Denmark 308 107 119 88 622
France 679 394 431 152 1656
Netherlands 244 16 16 27 303
Romania 476 86 51 46 659
Poland 80 10 14 8 112
United Kingdom 2012 441 99 31 2583
Norway 50 7 1 0 58
Albania 10 1 0 0 11
Generally, the concentration of nitrates in the water from unpolluted areas is less than 1
mg/L. A compromised water is characterized by higher level of nitrates [3-5]. In the human body
nitrate anion is potentially harmful because it can be transformed into nitrite.
Many environmental regulatory agencies including the U.S. Environmental Protection
Agency (U.S. EPA) have set a maximum pollutant level (MCL) of 10 mg/L of NO3- in drinking
Cristina Ileana COVALIU Habilitation thesis
27
water [6].
In case of children, the presence of nitrate levels above the EPA maximum contaminant
level of 10 mg/L N- NO3 or 45 mg/L NO3- is responsible for the appearance of the disease called
methemoglobinemia, also known as blue baby syndrome [7-13].
High concentration of nitrate ions in drinking water is responsible for impairing blood
to carry oxygen throughout the body causing multiple health problems, such as: cancer,
disruption of thyroid function, birth defects and other health risks. As nitrate has no taste, odor or
color, its determination can be done only by laboratory analyses [14-16].
Fig.2.3. Annual average river nitrate concentration averaged by National River Basin Districts
(mg N/L), (2009), EU-27 and EFTA Source: European Environment Agency [2]
Nitrates are water soluble, crossing freely through most soils reaching to groundwater
and surface water (through groundwater connections). Nitrogen based fertilizers (such as
ammonium sulfate, ammonium chloride, ammonium nitrate, urea etc.) within the agriculture
Cristina Ileana COVALIU Habilitation thesis
28
practice are applied on land surface for the growth of plants. Ammonia (NH4+) contained by
fertilizer can leach into the ground below the root zone, reaching into the groundwater and rivers
being transformed to nitrates (NO3-) (see Fig.2.4) according to the following potential reactions:
NH4+ + 1.5 O2 → 2H+ + H2O + NO2 (2.1)
NO2- +0.5 O2 → NO3
- (2.2)
Nitrate ions concentrations from surface water coming from agriculture are especially
from groundwater connections and other subsurface flows. Another important source of nitrate
water pollution from agriculture practice is using as fertilizers the animal manure.
Fig. 2.4. Schematic presentation of leaching ammonia from fertilizer to groundwater as
nitrates [17].
Although there are many sources of nitrogen (natural and anthropogenic) that could
potentially lead to the pollution of the groundwater with nitrates, the anthropogenic sources are
the ones that generally cause the rising of concentration of nitrate to a dangerous level. Many
local sources of potential nitrate pollution of groundwater are: the "sites” used for disposal of
human and animal sewage, industrial wastes related to food processing, munitions, and some
polyresin facilities, septic tanks.
As regarding the industrial pollution with nitrates it worth mentioning industrially-
relevant nitrate esters such as nitroglycerin (1,2,3-trinitroxypropane, NG) or ethylene glycol
dinitrate (EGDN) which have received much scientific attention [18, 19]. These substances are
Cristina Ileana COVALIU Habilitation thesis
29
used for the production of explosives and exist as co-pollutants in nitrate polluted wastewater
originating from manufacturing activities. During the washing steps from the production process
of explosives factories the wastewater is generated in very large volumes (often more than 240
m3/day) [20]. The difficulty of applying a treatment for this type of wastewater is given by its
specific composition, having a high concentration of nitrates (up to 7,500 mg N/L), sulphates and
a low pH value (usually between 1.0 and 1.5). For such industrial wastewater the conventional
physicochemical methods of wastewater treatment are limited in terms of efficiency or
completely inappropriate. For example, the removal of high nitrate concentration could not been
done using ion exchange-based methods. The application of membranes treatment for
nitroglycerin removal has the risk of explosions. Exist few physicochemical methods which can
be applied, such as microwave-assisted degradation [19] and reductive transformation by pyrite
and magnetite [21], but there are inefficient by the economic point of view due to the high
energy consumption, the need to specific chemical reagents, which make the process
economically inefficient.
My own contribution in this research direction was the removal of nitrates from
wastewater by adsorption on various nanomaterials synthesized and characterized before testing.
2.1.2. The investigation of Pd-Sn/γ-Al2O3, NiTiO3 and NiFe2O4 for nitrates removal from
water
This subchapter describes an efficient way of nitrate ions removal from water by using
the following adsorbants: Pd-Sn/γ-Al2O3, NiTiO3 and NiFe2O4. All three adsorbants were
synthesized and characterized prior their testing for depollution of water containing nitrates. The
Pd-Sn/γ-Al2O3 and NiTiO3 were successfully prepared by sol-gel method and NiFe2O4 by co-
precipitation method. The study presented in this subchapter has been published in the scientific
literature [17].
The Pd-Sn/γ-Al2O3 nanomaterial was obtained in two steps:
➢ γ-Al2O3 was prepared by sol-gel method using as template agent lauric acid. The
molar ratio between Al(OC3H7)3: C12H24O2: C4H9OH was 1: 0,15: 30. The molar ratio
between aluminum precursor and water was 1: 1.9. The reaction mixture was kept at
Cristina Ileana COVALIU Habilitation thesis
30
800C for 100 h, until was formed a white precipitate, which was washed with alcohol
several times, filtered, dried in air and finally calcined at 6000C for two hours.
➢ the Pd-Sn bimetallic material was prepared by sol-gel method using as precursor
salts PdCl2 and SnCl2, in a solution of ethylene glycol brought to pH 11 using NH3. The
Pd-Sn/γ-Al2O3 material contained 1 wt% noble metal (Pd) and 1 wt% Sn. The reaction
mixture was homogenized for 12 h, under reflux and then ammonia and ethylene glycol
were removed by washing with alcohol. After drying at 900C, the material was thermal
treated at 2000C for 1h.
➢ the material finally obtained was characterized by scanning electron microscopy
(TEM), X-ray diffraction (XRD) and BET analysis.
The synthesis and characterization of NiFe2O4 and NiTiO3 was published elsewhere [22].
Characterization of prepared adsorbant material
The X-ray diffraction (XRD) analysis shows the distortioned spinel structure of γ-Al2O3
(Fig. 2.5.). The characteristic diffraction peaks for bimetallic particles Pd-Sn are: 2θ =38.50,
43.0. The average crystallite size identified using Scherrer formula was 40 nm.
Fig. 2.5. XRD of Pd-Sn/Al2O3 adsorbant.
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The textural characteristics are presented in Figs. 2.6 and 2.7. The specific surface area of
the nanomaterial Pd-Sn/ γ -Al2O3 is 275m2/g and the value of pores diameter is between 2 and 10
nm.
The morphology characterization done by transmission electron microscopy (TEM)
investigation presented Fig. 2.8 reveal that the Pd-Sn/ γ -Al2O3 mean particle size is of 100 nm.
Fig. 2.6. The adsorption-desorption isotherm of the Pd-Sn/g-Al2O3 adsorbant.
For the other two tested nanomaterials nickel titanated and nickel ferrites the
morphological characterization was done by scanning electron microscopy (SEM). The SEM
image of nickel titanate sample obtained by calcination at 6000C/4h show that the particles are
spherical, having an average particle size of 1µm (Fig.2.9).
The nickel ferrite calcined at 5000C/2h presents spherical shape, with a tendency to
form agglomerates. The average particle size is 90 nm and the average agglomerate is 150 nm
(Fig.2.10).
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Fig. 2.7. Pores size distribution of the material Pd-Sn/ γ -Al2O3.
Fig. 2.8. TEM image of Pd-Sn/ γ -Al2O3
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Fig.2.9. SEM image for NiTiO3 obtained by
precursor calcination at 6000C/4h
Fig.2.10. SEM image for NiFe2O4 obtained
by precursor calcination at 5000C/2h
Nitrate ions adsorption study on the three adsorbants: Pd-Sn/ γ -Al2O3, NiTiO3 and
NiFe2O4
The analysis of nitrates from wastewater was determined using SR ISO 7890/3-1998
standard method applied for drinking water, surface water and wastewater. The method provides
a rapid determination of nitrate from water.
Adsorption experiments were carried out in Erlenmeyer flasks using a temperature
controlled orbital shaker (stirring speed of 200 rpm) for 36 h. Am amount of 20 mg of the
adsorbent was contacted with 50 mL of nitrate solution solutions (concentration was 5 mg/L)
representing the synthetic polluted wastewater at 20 ±2◦C.
The nitrates ions adsorption capacity of the three prepared materials was calculated with
the formula:
m
CeCiVUptake
)( (2.3.)
where:
Uptake - adsorption capacity at time t, the concentration of nitrates retained per unit mass
of adsorbent materials, (mg/L);
V - volume of solution containing nitrate ions, (mL);
Ci - initial concentration of the nitrate ions, (mg/L);
Ce - equilibrium concentration, (mg/L);
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m - adsorbant weight, (mg).
In order to investigate the effect of pH on nitrate adsorption, the experiments were
conducted in 2-10 pH range.
The pH of the water solution was adjusted using 0.1M HCl or 0.1M KOH.
In figure 2.11 is presented the plot adsorption of nitrate ions on Pd-Sn/ γ-Al2O3, nickel
ferrite and nickel titanate adsorbant nanomaterials. The maximum adsorption capacity of nitrate
was obtained at pH 3.5.
The maximum adsorption capacity values were 3.598 mg/L for Pd-Sn/g-Al2O3, 3.176
mg/L for nickel titanate and 3.051 mg/L for nickel ferrite.
Fig.2.11. Adsorption plot for retaining nitrate anions on Pd-Sn/ γ-Al2O3, NiTiO3 and NiFe2O4
adsorbants.
SIPS isotherm model
The SIPS isotherm model considers that the adsorption efficiency is limited at high
concentration of ions in solution. The model is similar to the Langmuir isotherm, with the
exception of a parameter representing heterogeneous system.
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The SIPS model reduces to Langmuir's model when γ= 1.
)(1
)(max
eS
eS
CK
CKQQe
(2.4)
where:
eQ – the total adsorption capacity at equilibrium, (mg/L);
maxQ – the maximum adsorption capacity of the adsorbent material, (mg/L);
eC – the equilibrium concentration, (mg/L);
SK - the adsorption constant (dissociation parameter);
n – the number of variable parameters (3).
Fig. 2.12. SIPS linear model representation for nitrate ions adsorption of onto
Pd-Sn/ γ -Al2O3, NiTiO3 and NiFe2O4.
The regression factors obtained were 0.9987 for Pd-Sn/γ-Al2O3, 0.9984 for NiTiO3 and
0.9982 for NiFe2O4 (Fig.2.12). The regression factors show that the best results regarding nitrate
ions adsorption were obtained for Pd-Sn/γ-Al2O3 nanomaterial. This fact could be explained and
correlated with the specific surface area values of the three adsorbant nanomaterials: 275m2/g for
Pd-Sn/ γ-Al2O3, 32,6 m2/g for NiTiO3 and 10,1 m2/g for NiFe2O4 [22].
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2.1.3. The investigation of CuTiO3 and CuFe2O4 for nitrates removal from water
In this subchapter is presented the evaluation of the adsorption capacity of CuFe2O4 or
CuTiO3 adsorbents for removing nitrate ions from water.
The metal titanates are known as inorganic functional materials with wide applications in
environment protection [22].
The research results presented in this subchapter were already published in scientific
literature [5].
Prior to describe the tests for removing the nitrates from water, is presented the synthesis
of the two nanomaterials in laboratory:
a) CuTiO3 was synthesized by sol-gel method as follows: as starting precursors
solutions were used 0.5 mmol Cu(CH3COO)2.4H2O in 50 mL ethanol and 0.5 mmol
Ti[OCH(CH3)2]4 in 50 mL of isopropanol (Cu: Ti = 1:1 molar ratio). The solution obtained was
heated under reflux at 800C, 4 hours, until a gel was formed. Then the gel was separated, filtered
and dried at 1500C. The solid precursor was thermal treated at 700oC for 5 hours.
b) CuFe2O4 was synthesized by coprecipitation method as follows: as starting raw
materials were used Fe(NO3)3 . 9H2O and Cu(NO3)2
. 2H2O in a 2:1 molar ratio at pH = 12
obtained by adding NH3 25% as precipitation agent. The reaction mixture was maintained under
reflux at 700C for 3h, until a black precipitate was formed. After the purification process which
implies washing ten times with water and ethanol (10:1), the precursor was calcined at 4000C for
3h in order to obtain a single phase CuFe2O4 powder.
Copper titanate and copper ferrite powders obtained by calcination at 7000C for 5h and
5000C for 2h respectively, were structural, morphological and textural characterized by scanning
electron microscopy (SEM), specific surface area BET and X-ray diffraction (XRD analysis).
The specific surface areas of the two synthesized compounds were measured with ASAP 2020
V3.04 H apparatus by using Brunauer-Emmet-Teller (BET) method using nitrogen at 77K.
Finally copper titanate and copper ferrite were tested for adsorption of nitrate ions from
water. The concentration of nitrate in solutions was determined by UV-VIS spectroscopy.
pH studies
In order to investigate the effect of pH on nitrate adsorption, the pH of the nitrate
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solutions was adjusted from 4 to 6. The initial pH of the solution was adjusted by using 0.1M
HCl or 0.1M NaOH. Each of the two adsorbants was added in the nitrate polluted water
solutions. The objective was to determine which of the pH value conduct to the maximum nitrate
removal from water knowing that the adsorption pH is one of the factors that have been found to
have a important effect upon the adsorption. Maximum nitrate removal occurred at pH of 4,
because the predominant form of nitrate is at this pH.
For conducting the nitrate adsorption study was used a stock nitrate solution. The
required concentration of the nitrate solution was prepared by serial dilution of the stock
solution. Were used different concentrations of nitrate in the range 0 to 300 mg/L, to observe the
capacity of adsorption of the two nanomaterials at different concentration. A fixed amount of the
adsorbent was added to 50 mL nitrate solution into in Erlenmeyer flask, placed on a orbital
control shaker. The solutions were stirred continuously at constant temperature to achieve
equilibrium. After equilibrium, the two nanomaterial powders were separated by centrifugation.
The adsorbent was removed by centrifugation (6000 rpm) and the concentration of the
corresponding anion remaining in the supernatant was determined spectrophotometrically at
λ=220 nm.
X-ray diffraction
The XRD of copper titanate obtained has cubic structure with monoclinic symmetry
(Fig.2.13 and 2.14). The average crystallites size value calculated based on Scherrer formula is
30 nm. The XRD pattern presented in figure 2.14 is characteristic to CuFe2O4 having spinel
structure and cubic symmetry. The average crystallites size was estimated at 40 nm, with
Scherrer formula.
SEM investigation
The morphologies of CuTiO3 and CuFe2O4 powders, calcined at 7000C/5h and 5000C/2h
respectively, were investigated by scanning electron microscopy (SEM) and are shown in Figs.
2.15 and 2.16.
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CuFe2O4 presents a higher tendency of the particles to form agglomerates (Fig.2.16).
Both samples have spherical shape particles. The average particles size is 70 nm for CuTiO3 and
90 nm for CuFe2O4 and the average agglomerates size is 100 nm for CuTiO3 and 150 nm for
CuFe2O4.
Fig.2.13. XRD patern of CuTiO3, calcined at 7000C for 5h.
Fig.2.14. XRD pattern of CuFe2O4, calcined at 5000C for 2h.
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Fig. 2.15. SEM image for CuTiO3.
Fig.2.16. SEM image for CuFe2O4.
Textural characterization
For CuTiO3 nanomaterial the BET surface area is 15.95m2/g (Fig.2.17). The BJH
adsorption cumulative surface area of pores is 20.07m2/g and BJH desorption cumulative surface
area of pores is 21.21m2/g (Fig.2.19) The BJH is the method of Barret, Joyner and Halenda for
the pores distribution. The single point adsorption total volume of pores is less than 271.22 nm
diameter at p/p° = 0.99 is 0.10cm3/g.
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Fig.2.17. Adsorption isotherm for CuTiO3.
Fig.2.18. Adsorption isotherm for CuFe2O4.
Fig.2.19. BJH adsorption dV/Dd pore volume for CuTiO3.
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Fig.2.20. BJH adsorption dV/Dd pore volume for CuFe2O4
For CuFe2O4 the BET surface area for the CuFe2O4 is 9.15 m 2/ (Fig.2.18). The BJH
adsorption cumulative surface area of pores is 10.0 m2/g and BJH desorption cumulative surface
area of pores is 9.91 m2/g (Fig.2.20). Single point adsorption for total pores volume is less than
443.5148 nm and diameter at p/p° of 0.99 is 0.02 cm3/g.
Adsorption isotherms
Experiments were carried out in Erlenmeyer flasks placed in a temperature controlled
orbital shaker (stirring speed of 150 min-1) for 24 h. 15mg of the adsorbant were introduced in 30
mL of nitrate solution at 22 ± 2oC. Before starting the experiments both adsorbents were dried at
1000C for 3 h.
Batch adsorptions studies were performed as a function of contact time, initial nitrate
concentration, pH and influence of other interfering anion.
In figures 2.21a and 2.21.b were presented the plots of adsorption for copper titanate
and copper ferrite used as adsorbant nanomaterials. Good adsorbtion results were obtained both
in the absence of electrolyte and also in the presence of electrolyte.
The maximum adsorption capacity of nitrate was obtained at pH 4, at which is the
predominant form of the anion. In the case of copper titanate the maximum adsorption capacity
was 2.069 mg/L and in the case of copper ferrite was 0.951 mg/L. The adsorption equilibrium
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was obtained at pH = 4.
The influence of sulphate (SO42-) anion on nitrate removal from water in the case of the
studied adsorbents was investigated at for nitrate concentration of 200 mg.L-1. The concentration
of sulphate anion was 0,1M. It was observed that nitrate adsorption was mainly influenced by the
presence of sulphate anion. At ionic strength 0.1M, the concentration of nitrate decreased.
Fig.2.21. a) Plot sorption of NO3-, versus equilibrium concentration for CuTiO3
adsorbant.
Fig.2.21 b) Plot sorption of NO3-, versus equilibrium concentration for
CuFe2O4 adsorbant.
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Langmuir isotherm characteristic equation is:
(2.4)
where: a - adsorption capacity at equilibrium, mg/g;
1 - maximum adsorption capacity for a given set of conditions to balance the entire
monomolecular layer is occupied, mg/g;
Ce - concentration of solute in the system at equilibrium, mg/L;
b - equilibrium constant that depends on the nature of the adsorption system.
Langmuir equation can be written as:
(2.5)
The characteristic equation for experimental data is:
(2.6)
R2 - 0.9960 regression coefficient.
The Langmuir equation fits well the experimental data for nitrate ions adsorption. Since
R2 has values over 0.95 is considered that Langmuir equation is appropriate for nitrate anion
adsorption using the tested adsorbant nanomaterials.
Fig.2.22. Langmuir equation representation for CuTiO3.
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In conclusion, the preliminary result of this study presents the capacities of copper
titanate and copper ferrite for nitrate removal from aqueous solutions. The results show that the
adsorption effectiveness of copper titanate for nitrate was higher in comparison with copper
ferrite when the concentration of nitrate was in the range of 0–300mg/L. It was observed that the
particle dimension, the specific surface area and the pH have influenced the adsorption capacity.
The maximum adsorption capacity was at pH of 4 for copper titanate (2.069 mg/L). The pH
affects the adsorption process, when the pH increased, the adsorption capacity decreased. Better
results for nitrate adsorption were obtained when the experiments were carried out in the absence
of an electrolyte (SO42-). The Langmuir equation characterized very well the adsorption for
nitrate anions.
2.2. Contribution to the removal of Cd (II) ions from wastewater using maghemite and
poly-DL-alanine based core-shell magnetic nanohybrids
2.2.1. General considerations
In this subchapter is presented the application of nanotechnology for the Cd (II) ions
removal from wastewater via core-shell nanohybrids composed by inorganic and organic
components.
Industrial wastewaters are considered the largest source of pollution of the environment
because they contain toxic compounds. Industrial wastewater polluted with heavy metals (Pb2+,
Cd2+, Zn2+, Ni2+, Hg2+, Cr6+, Co2+, Cu2+) has as sources many industrial activities such as:
mining, metallurgy, dyes manufacture, pesticides manufacture, tanning, manufacture of
explosives , electroplating, petrochemical, etc.
This category of pollutants has a multitude of adverse effects on the environment and
humans.
As regarding the sources of cadmium in the environment can be considered the
following: iron and steel industry, waste incineration and disposal, zinc production, mining, ore
dressing, smelting of nonferrous metals, battery manufacturing industry, coal combustion,
phosphate fertilizer manufacture and use, etc. The largest cadmium input to aquatic systems is
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considered the manufacture of cadmium- containing articles, followed by phosphate fertilizer
and zinc manufacture.
Effects of cadmium ions upon human’s health are presented in Fig. 2.23.
Fig.2.23. Effects of cadmium ions upon human’s health.
The core-shell nanohybrids which are the subject of current study are very interesting
because they possess several important properties and are attractive because of their potential to
be used in wastewater treatment. They are formed from a core and a shell between which can
exist chemical interaction Magnetic nanohybrids have special magnetic properties, such as
superparamagnetism, facilitating their removal from the technological system after the
wastewater treatment is ended.
Using biopolymers for coating of the magnetic oxide nanoparticles brings multiple
advantages such as:
a) it prevents the agglomeration by providing a steric barrier;
b) provides a lack of any king of toxicity of the core to the environment.
Poly-DL-alanine is a biodegradable polyaminoacid used as coat for maghemite
nanoparticle and is used in a wide range of applications: as release agents in agriculture, in water
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treatments, as paint additives, in cosmetics composition, as metal adsorbents and as surfactants.
Also, polyaminoacids have clinical applications being used as components for diagnostics,
dialysis membrane, artificial skin, orthopedic implants, drug delivery systems and carriers for
therapeutic protein conjugates.
Until the publication of this research field, poly-DL-alanine polymer has not been used
for inorganic nanoparticles biocompatibilization (Fig.2.24).
N
O
n
H
CH3
Fig. 2.24 Structural formula of poly-DL-alanine
The study presented in this subchapter was already published [23].
2.2.2. Cd (II) ions removal from wastewater using multifunctional maghemite and poly-DL-
alanine based core-shell magnetic nanohybrids
This subchapter describes the synthesis of two core-shell nanohybrid materials based on
maghemite (γ- Fe2O3) and poly-DL-alanine and their testing on Cd (II) ions removal from
wastewater.
The synthesis method is a two-step procedure, which consists in the following:
1. Preparation of maghemite nanoparticles by microemulsion method - starting from the
following raw materials: ferric chloride (FeCl2.6H2O), sodium dodecyl sulfate (SDS), n-butanol,
ammonia solution (NH3) 25 %. Into the transparent mixture obtained by mixing the SDS, water
and n-butanol in a molar ratio of 1:2:5 was added the FeCl2.6H2O 0.5M solution and then NH3
solution to achieve the pH value of 10. After 2 h the precipitate obtained was separated by
centrifugation and washed several times with water and ethanol.
2. Coating of maghemite nanoparticles with poly-DL-alanine. The two nanohybrids
were obtained starting from two molar ratios (1:5 or 1:15) between maghemite nanopowder and
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poly-DL-alanine biopolymer. The maghemite powder was added to 15 mL of poly-DL-alanine
0.5 M solution to obtain 1:5 nanohybrid (H1-5) or to 50 mL of poly-DL-alanine 0.5 M solution
for preparing 1:15 nanohybrid (H1-15) and stirred for 6 h at room temperature. The hybrid
particles were separated by centrifugation and dried at 900C for 2h [23].
In order to evaluate the adsorption properties of the γ- Fe2O3 and its corresponding
polymeric hybrids H1-5 and H1-15 the investigation was done for the removal of Cd (II) ions
from wastewater.
Cd (II) ions removal from wastewater
The synthetic wastewater containing cadmium ions was prepared from Merck reagent-
grade solutions by dissolving into ultrapure water. The stock solution had an initial concentration
of 1000 mg/L and pH value was adjusted by adding NaOH (0.1 mol/L) in order to obtain a
proper value similar to that of industrial wastewater, of pH 5.6. The adsorption studies were
carried out by measuring of the initial and final concentration of the metal by flame atomic
absorption spectrometry (FAAS).
The adsorbed metal amount at equilibrium is calculated by ratio between adsorbed
metal (mg) onto adsorbent mass (g) expressed as qe, according to the Eq. (1):
m
VCCq e
e
0 (2.7)
where:
C0 – initial concentration, mg/L;
Ce – equilibrium concentration, mg/L;
V – volume of solution, L;
m – adsorbent quantity, g.
Adsorption studies were performed by mixing of 0.1 g from each nanomaterial
adsorbents (γ-Fe2O3, H1-5 and H1-15) with 100 mL solution consists of 10, 20, 50, 80 and 100
mg/L of Cd(II) at room temperature (21.5°C).
For adsorption kinetic studies, the wastewater solutions prepared were kept into contact
with each type of adsorbent nanoparticles from 10 to 120 minutes. The adsorbent samples were
recovered by magnetic separation. In order to establish the quantity of adsorbed cadmium onto
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nanomaterials was used FAAS with a GBC 932 AB Plus spectrometer with spectral domain
between 185 and 900 nm.
The adsorption isotherm for Cd (II) onto 0.1 g γ-Fe2O3, H1-5 and H1-15, respectively,
were fitted to the Langmuir model expressed as Eq. (2):
bqC
C
m
e
me
e
11 (2.8)
where:
Ce –aqueous concentration at equilibrium, mg/L;
qe – adsorbed amount at equilibrium, mg/g;
qm and b – constants related to the adsorption capacity and the affinity coefficient.
For adsorption studies only 0.1 g of γ-Fe2O3 was added to 100mL of each mentioned
concentration of Cd (II). The procedure was similarly applied to the other two nanomaterials H1-
5 and H1-15.
Prior to test the water treatment properties, after the synthesis, all three nanomaterials
were characterized by: X-ray diffraction, X-ray photoemission spectroscopy, Mössbauer
spectroscopy, Fourier transform infrared spectroscopy, Transmission electron microscopy, High
resolution transmission electron microscopy with selected area electron diffraction and Atomic
absorption spectroscopy. Some of these analyses are further presented.
X-ray diffraction (XRD)
The XRD data show that uncoated oxide powder is mono-phase and has the crystalline
structure of maghemite (γ-Fe2O3), with cubic symmetry (Fig. 2.25 a). The average crystallite size
calculated by Scherrer formula is 21 nm. The XRD spectra of nanohybrids H1-5 and H1-15,
present beside characteristic peaks of the maghemite crystalline structure, peaks assigned to
poly-DL-alanine (Fig 2.25 b and d).
Atomic Absorption Analysis (AAS)
The content of maghemite from the two prepared nanohybrids determined by Atomic
absorption analysis was 40% for H1-5 and 18% for H1-15 hybrids.
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Mössbauer spectroscopy
Maghemite has the composition of hematite but it exhibits the structure of magnetite
(Fe3O4). In the cubic structure of both maghemite 1/3 of the interstices are tetrahedral
coordinated with oxygen and 2/3 are octahedral coordinated. In maghemite, only 5/6 of the total
available positions are filled by Fe3+, the rest are vacant (□): Fe2.67□0.33O4. Maghemite may have
different structures depending on the degree of ordering of the vacancies. A total ordered
maghemite has a tetragonal symmetry.
Fig. 2.25. XRD patterns of γ-Fe2O3 powder (a), H1-15 hybrid (b), poly-DL-alanine (c) and H1-5
hybrid (d)
The maghemite lattice has 8 Fe3+ in tetrahedral sites and 13.33 Fe3+ ions in octahedral
sites. The magnetic field values are 488 KOe for the tetrahedral sites and 499 KOe for the
octahedral ones. The room temperature Mössbauer spectra of the initial maghemite and the
corresponding nanohybrids (H1-5 and H1-15) are displayed together with the computer fit
(continuous lines) in Fig. 2.26 a, b and c. All spectra contain six line magnetic hyperfine pattern
and a very small central doublet.
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(a)
(b)
(c)
Fig. 2.26. Mössbauer spectra of the uncoated maghemite (a) together with the spectra of
maghemite based nanohybrids with poly-DL-alanine in different molar ratio: H1-5 (b) and H1-
15 (c)
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The central doublet with a quadrupole splitting of ~ 0.45 mm/s and isomer shift of ~ 0.15
mm/s is assigned to a very small amount of Fe in the Beryllium detector windows; this is
observed only at very high statistics on the recorded spectra, as it is the case of our spectra. The
magnetic patterns were deconvoluted in two sextets corresponding to Fe3+ in A and respectively
B site of maghemite. The magnetic hyperfine fields are similar with the standard values of
maghemite values of 484 KOe for A sites and 495 KOe for the B sites, respectively. No
significant differences were observed between the Mössbauer spectra of the maghemite sample
and those of the two hybrids.
FTIR spectroscopy
For knowing if exist any kind of interaction between γ-Fe2O3 and poly-DL-alanine was
done FTIR analysis. The γ-Fe2O3 is a deficient magnetite having inverse spinel structure and is
represented as Fe3+[ Fe3+X]O3, where X is the vacancy site from the lattice, Fe3+ inside the square
bracket represents tetrahedral position and Fe3+outside the square bracket represents the
octahedral position.
By comparing the spectra of maghemite and poly-DL-alanine with those of the hybrids
were observed the following:
a) the shift of Fe-O vibration bands placed in octahedral and tetrahedral sites frequencies
located at 467 cm-1 and 615 cm-1 in maghemite spectrum to higher vibration frequencies for H1-
5 (478 cm-1 and 640 cm-1) and H1-15 (487 cm-1 and 637 cm-1) nanohybrids spectra;
b) the shift of vibration bands assigned to amino (N-H) and carbonyl (C=O) groups
located at 3210 cm-1 and 1637 cm-1 in poly-DL-alanine spectrum to higher wavenumbers for H1-
5 (3225 cm-1 and 1661 cm-1) and H1-15 (3227 cm-1 and 1661 cm-1) hybrids spectra (Fig.2.27).
The binding sites of the poly-DL-alanine biopolymer are the amino and carbonyl groups
which interact with Fe3+ ions from the maghemite like in Fig. 2.27 a and b.
XPS analysis
XPS spectroscopy was also used for the investigation of the existence of the
interactions between the poly-DL-alanine biopolymer and maghemite nanomaterials.
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The principal signals in XPS spectra at 712.8 and 727 eV correspond to Fe 2p3/2 and Fe
2p1/2 both being contain in maghemite and nanohybrids spectra.
Fig.2.27. FTIR spectra of H1-5 hybrid (a), poly – DL-alanine (b), H1-15 (c), γ-Fe2O3 (d)
The binding energies assigned to the species presented in the spectra of maghemite,
poly-DL-alanine and nanohybrids are presented in Table 2.2.
Table 2.2. Binding Energy (eV) of γ-Fe2O3, poly-DL-alanine, H1-5 and H1-15 nanohybrids,[23].
Samples Nanopowder
γ-Fe2O3
Nanohybrid
H1-5
Nanohybrid
H1-15
Poly-DL-alanine
Fe 2p3/2 712.81 714.74 714 -
Fe 2p1/2 727 725 726 -
O1s 531.33 533.62 531.14 530.8
C1s - 290.89 286.3 285.47
N1s - 403.32 401.18 400.35
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As regarding the peak of C1s was observed a significant shift of the corresponding
binding energy from 285.4 eV in the poly-DL-alanine to 286.3 eV and 290.8 eV in the
nanohybrids which is a strong argument for the interactions between Fe3+ and oxygen atoms
from the poly-DL-alanine (Fig. 2.28).
Fe3+
Fe3+
N
O
nCH3
N
O
n
H
CH3
(a)
(b)
Fig. 2.28 Expected interactions between Fe3+ ions of maghemite nanoparticles and poly-DL-
alanine molecules in amino group (a) and carbonyl group (b) [23].
Knowing that for the two hybrids the poly-DL-alanine shell thickness is less than 2 nm
(Figs. 2.28a and 2.28b) and the X-ray photoemission depth of surface examination is 3-5 nm, the
purpose of doing XPS analysis was to show the existence of the polymeric layer around the
maghemite nanoparticles and the interactions that exist between the two components of the H1-5
and H1-15 hybrid, not the well-defined poly-DL-alanine shell around the maghemite core.
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Morphological characterization
TEM and high resolution transmission electron microscopy (HRTEM) investigation
show the core-shell nanostructure of the γ-Fe2O3 –poly-DL-alanine hybrids nanoparticles.
SAED investigation of uncoated maghemite and corresponding nanohybrids show the
Miller indices of crystalline structures first identified by XRD (insets of Figs. 2.29 d, 2.30 b, 2.31
c).
Fig. 2.29 a and b present the well defined nanostructure of H1-5 composed of 21 nm
maghemite core and a poly-DL-alanine shell of 1.5 nm.
An H1-5 hybrid nanoparticles have polyhedral shape. More information sustaining the
structure of H1-5 hybrid nanoparticles was revealed through the detailed analysis of HRTEM
which show the interplanar distances of 2.52 Å and 2.10Å assigned to crystallographic planes of
Miller indices (311) and (400) characteristic to cubic γ-Fe2O3 structure (Fig. 2.29 b and c).
For the H1-5 nanohybrid was calculated from the size distribution of 150 particles an
average particle size of 22 nm (Fig.2.30 b).
HRTEM investigation of maghemite nanoparticles present 2.52 Å and 2.95 Å
interplanar distances assigned to crystallographic planes of Miller index (311) and (220),
respectively (Fig. 2.30). In the absence of the polymeric coat, the agglomeration tendency of
maghemite nanoparticles is higher because of the magnetic interaction and the absence of a steric
barrier. The average particle size of uncoated maghemite determined by counting 150 particles is
21 nm (Fig.2.31 a) and their shape is polyhedral (Fig. 2.30 b). HRTEM image of H1-15 hybrid
shows a 2.52 Å interplanar distance assigned to crystallographic plane of Miller index (311) (Fig.
2.32 b).
Three different HRTEM images of H1-15 show that the core is smaller (9 nm and 11nm
Fig. 2.32 a with inset) or equal (21 nm Fig. 2.32 b) in comparison to H1-5, but the poly-DL-
alanine shell thickness is higher (1.7 nm in Fig. 2.29ba and 2 nm in Fig. 2.29 b) indicating that
when it was used an increased amount of polymer for maghemite coating an increased amount of
poly-DL-alanine is was retained on maghemite nanoparticles and, also an increase of the average
particle size of the hybrid was observed (23 nm, Fig. 2.32 c).
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(a) (b)
(c) (d)
Fig.2.29. HRTEM images at different magnitudes (a), (b) and (c); TEM inset SAED (d) of H1-5
nanohybrid, beam direction: B=[ 001] [23]
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(a)
(b)
Fig. 2.30. HRTEM (a) and TEM inset SAED (b) images of γ-Fe2O3 nanopowder, beam direction:
B=[112 ] [23].
By comparing Fig. 2.29 d with Fig. 2.32 c was observed that a higher value of the
polymeric coat thickness of the maghemite nanoparticles conducted to a decrease of the
agglomeration tendency of the hybrid nanoparticles [23] by two mechanisms:
creating a steric barrier;
avoiding the agglomeration of the magnetic particles.
Although exists an agglomeration tendency of maghemite nanoparticles due to their
magnetic properties, the polymeric shell represents a uniform coat and is preserved for each
individual hybrid particle (Figs. 2.29 a and 2.32 a).
The shell of poly-DL-alanine is composed by three-four polymeric layers (observed on
the central particles from Figs. 2.29 a, b and 2.32 b) also observed in XRD pattern at 2θ equal to
20.
TEM investigation revealed that maghemite and hybrid particle samples are nearly
monodispersed (Figs. 2.29 d, 2.30 b and 2.32 c).
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15 20 250
5
10
15
20
25
30
35
40
D= 22 nm
Nan
op
art
icle
s c
ou
nts
Size (nm)
(a)
15 20 250
5
10
15
20
25
30
35
40
D= 22 nm
Nan
op
art
icle
s c
ou
nts
Size (nm)
(b)
15 20 250
5
10
15
20
25
30
35
40
D= 23 nmN
an
op
art
icle
s c
ou
nts
Size (nm)
(c)
Fig. 2.31 Size distribution for γ-Fe2O3 (a), H1-5 nanohybrid (b) and H1-15 nanohybrid (c)
For all the investigated samples the main magnetic parameters are presented in Table
2.3.
Both maghemite and hybrid nanoparticles present superparamagnetic behavior with
very narrow hysteresis cycles, which confirm the reduced size of particles that allows the
presence of a single magnetic domain. Because the density of the nanohybrid materials is
unknown, the comparison is done using the specific (mass) magnetization.
The two nanohybrids exhibit different superparamagnetic behavior, but the saturation
magnetization is diminished for the hybrid containing an increased amount of polymer, due to
the following:
the reduced composition of magnetic component;
the superparamagnetic property.
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(a) (b)
(c)
Fig. 2.32. HRTEM images (a) and (b) at different magnitudes, TEM inset SAED (c) of H1-15,
beam direction: B=[130 ].
The diameter of hybrid particle can be computed as an average size corresponding to an
average susceptibility (e.g. for a half of the maximum susceptibility or it can be detailed for each
measured value). The magnetizations at small magnetic fields correspond to the large
nanoparticles, when the domain wall motion is possible; the smaller particles (monodomain) act
different at high fields. The exact values of the magnetic susceptibility could be known only if
the measured magnitudes can be corrected taking into account the demagnetization phenomenon
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inside the sample, but this correction is possible for bulk materials. The samples as nanoparticles
need special techniques of numerical homogenization. The diameter D can be estimated from
(2.9):
32
0
18
sM
KTD
(2.9)
where χ is the magnetic susceptibility.
Based on (2.9), the calculated particle diameter was in the range of 5-10 nm for all the
investigated samples. These values explain the superparamagnetic behavior of the samples, but
are lower than those obtained from other measurements (e.g. TEM), which give the size range of
21-23 nm. This difference can be explained by the fact that the magnetic field is diminished
inside the sample by the demagnetization field; the real magnetic susceptibility χ is higher than
the measured one and the computed diameter will be higher.
The magnetic properties of the maghemite give the magnetic behavior of the two hybrid
materials. This investigation reveal that the experimental magnetization curves could be used for
the entire characterization of tested magnetic nanoparticles even for coated ones like in
nanohybrid materials. The superparamagnetism of nanoparticles is considering a benefit for
wastewater treatment application and this property requires particle sizes in the range of
nanometers.
Fig. 2.33. Hysteresis loops of - Fe2O3 (a), H1-5 nanohybrid (b), H1-15 nanohybrid.
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Table 2.3. Magnetic properties of the γ-Fe2O3 and corresponding H1-5 and H1-15 hybrids
Material Coercivity
[kA/m]
Remanence
[Am2/kg]
Saturation
[Am2/kg]
- Fe2O3 12.4 17.4 69.8
H1-5 11.8 8.1 38.2
H1-15 7.8 1.32 7.95
Cd (II) ions removal efficiency tests
The removal efficiency of Cd (II) ions after 10 min for all investigated nanomaterials is
presented in Fig. 2.33. After this period of time, the removal efficiency of Cd (II) ions remained
almost unchanged.
During the investigation of the tree nanomaterials as adsorbants for removal Cd (II)
ions form wastewater were observed the following:
the wastewater treatment efficiency obtained for H1-5 was over 50% after 10
min;
the wastewater treatment efficiency of H1-5 was higher than that of - Fe2O3;
a high removal rate for Cd ions was obtained using the nanohybrid H1-15, almost
70% after 10 min;
the rate of removal efficiency of Cd (II) from wastewater decrease in the
following order: H1-15 > H1-5 > - Fe2O3. This can be explained by the
adsorption capacity of the poly-DL- alanine polymer used.
the removal efficiency of Cd (II) from wastewater was 30% for uncoated -
Fe2O3;
the removal efficiency of Cd (II) from wastewater was 70% for H1-15, after 10
min and it remains almost the same after 120 min. The same tendency it was
observed for other concentrations of Cd (II) ions tested: 20, 50, 80 and 100
mg/L;
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regarding the tendency of retaining Cd (II) ions onto the three adsorbents, as
comparison, for concentrations between 10 and 100 mg/L of Cd (II) ions, the
most efficient adsorbent is H1:15 nanohybrid, as it can be seen into Fig. 2.34.
Fig.2.34. Efficiency of removing Cd (II) (%) from wastewater using the three nanomaterials
(H1-15, H1-5, - Fe2O3)
Langmuir model parameters for adsorption of Cd (II) onto 0.1 g adsorbents can be
observed into Fig. 2.35. There were observed the following findings:
the adsorption parameters, regarding the maximum adsorbed quantity (qe, mg/g)
and regression coefficient R2 (almost 0.99) are fitted well with the Langmuir
requirements;
the highest value of R2 was observed for H1-15 hybrid nanomaterial;
the R2 value for - Fe2O3 indicate also a good adsorption but the model can be
improved.
In conclusion the novel nanostructures have the potential to be used as low cost and
efficient adsorbants for removal of cadmium ions for wastewater. The adsorption tests showed a
good correlation between Cd (II) concentrations and adsorbent quantity at pH 5.6. The
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adsorption data fitted well with Langmuir isotherm model. Between the three tested
nanomaterials type adsorbants, the H1-15 nanohybrid presented the highest efficiency for Cd (II)
removal from wastewater.
Fig.2.35. Langmuir parameters for Cd (II) ions adsorption onto H1-15, H1-5, - Fe2O3 .
2.3. Contribution to the removal of Cu (II) ions removal from industrial wastewater using
environmental friendly nanomaterials
2.3.1. General considerations
The larger source of water pollution with heavy metals is considered industrial
wastewater. The fast industry development has lead to generation of huge volumes of wastewater
containing heavy metals which were discharged into rivers and lakes causing serious problems to
the ecosystems and humans health.
The principal sources of pollution with heavy metals are presented in Fig.2.36.
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Fig.2.36. The main sources of pollution with heavy metals [24].
The improper treatment applied to these wastewaters has lead to the pollution of surface
or underground water with various heavy metals such as: cadmium, copper, mercury, zinc,
nickel, lead, etc.
Copper is used for manufacture of alloys and wires in various industries such as:
electrical, electrotechniques, etc. According to statistics, electronics and electrical engineering
industries use approximately 60% of the total quantity of copper processed in industry. The
distribution of copper production at global level is presented in Fig.2.37.
Some examples of various industries from which result effluents polluted with copper
ions are: mining and metallurgy, explosives manufacturing, pesticides manufacturing,
petrochemistry, dyes manufacturing, etc. Other sources of copper pollution are: effluents from
wastewater treatment plants, from tailing and flotation cells, disposal of municipal and industrial
waste, bled electrolyte from electro-refining plant, acid spillage from sulphuric acid plant, and
mine tailing disposal of fly ash, etc. [24,25].
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Fig.2.37 The distribution of copper production in the world [24].
Sources of heavy metals and their cycling in the ecosystem are presented in Fig.2.38.
Fig.2.38. The cyle of heavy metals into the the ecosystem components including soil-water-
air.
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The content of heavy metals generally builds up from up to bottom, indicating the
vulnerability of humans to heavy metal toxicity from all ecosystems. It is imperative finding
efficient, economic and innovative ways of wastewater treatment knowing the major concern
regarding heavy metals toxicity and carcinogenicity and the stringent requirements for removal
of heavy metals from industrial wastewater.
In recent years the adsorption process has become more interesting for the wastewater
treatment owing to its efficiency of removing very stable and non-biodegradable pollutants found
in water and impossible to be decomposed by biological methods. Adsorption process is
considered better in comparison with other technologies for wastewater treatment because of
simplicity of design, convenience and easy operation.
Some general existing procedures for removal of copper ions from wastewater are
presented in Table 2.4.
Table 2.4. General procedures for copper ions removal from wastewater [24]
Procedures Description
1. Precipitation
-Is based on the effectively removal from aqueous solution of copper ions
with lime as hydroxides according to the following reaction:
Cu2+
+ 2(OH)- → M(OH)2
-The reaction is influenced by the concentration of the copper ions and
the pH of the solution.
-The precipitation takes place over a range of pH values with the
formation of hydrate oxides.
-This technique is often use in industry for removal of copper ions from
solution [26,27].
-Moreover for the precipitation of copper ions could be used several
organic compounds [28].
2. Ion exchange -It is used for removal of copper ions from wastewater.
-It is economical only for recovery of copper and recycling of water in
the electroplating processes. Otherwise, it is expensive because involves
the regeneration of the resin and the disposal and depollution of large
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Procedures Description
2. Ion exchange volumes of the solution used for regeneration.
3.
Electrochemical
reduction
(Cementation)
-The recovery of copper ions from solution by transformation to its
elemental metallic state through electrochemical reduction [29].
-An example which describes this procedure is the reaction of copper
ions with iron: Cu2+
+ Fe0 → Cu
0 + Fe
2+
4. Flotation -One of the most important things in flotation is the choosing of suitable
surfactants.
-The suitable surfactants have distinct advantages when dealing with
large volume of highly polluted wastes that are quite dilute in the copper
ions [27].
5. Solvent
extraction
-When a substance is transferred from one liquid into another liquid
phase form a process is called solvent extraction. The liquid-liquid
partition of this process is form in the equilibrium stage.
-A substance with solvent properties used in a solution of a suitable
diluent is named extractant.
-A substance that is used to dissolve the extractant and improve its
physical properties is named diluent. The solvent is formed by the mixing
of extractant and diluent together. In usually systems an aqueous solution is
mixed with an organic solvent capable of dissolving the substance of the
interest.
6. Adsorption -The adsorption process occurs at the interface of an adsorbate (the
substance being adsorbed) and an adsorbant or adsorbent (adsorbing
material) [30].
-The list of adsorbant materials is very wide and contains activated
carbon, clay, flyash etc.
-For copper removal from water some of the adsorbants used are:
polyvinyl benzene trimethyl ammonium chloride [31], kaoline and
montmorillonite [32] etc.
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As a result of the researchers over the world in the wastewater treatment domain, have
been developed many technologies with varying degrees of success, but recently studies have as
principal objective the removal of heavy metals from wastewater using nanomaterials.
2.3.2. The investigation of copper (Cu2+
) ions removal from industrial wastewater using
maghemite, γ-Fe2O3 and its corresponding hybrid, γ-Fe2O3- poly-DL-alanine
In this study were investigated two environmental friendly nanomaterials in order to
demonstrate their efficiency as adsorbants for removal of copper ions from wastewater.
The adsorbants used for testing of copper ions removal from wastewater were
maghemite, γ-Fe2O3 and its corresponding hybrid, γ-Fe2O3- poli-DL-alanine. Their synthesis and
characterization were published elsewhere [23].
The standard used for the testing of the copper ions removal from synthetic wastewater
was SR EN ISO 11885-2009 - "Water Quality. Determination of selected elements by optical
emission spectrometry with inductively coupled plasma (ICP-AES).
The adsorption capacity evaluation of the two samples was done by measuring the
evolution of copper ions concentrations during 140 min.
For both investigated adsorbants, the values of Cu2+
concentration measured during the
experiments show a linear evolution, having R2
values of 0.975 and 0.989, respectively
(Fig.2.39).
The Cu2+
ions removal efficiency from wastewater using the two studied nanomaterials
was calculated using the formula:
Ei =[ (Ci – Cf,t)/ Ci] x100 (2.10)
where:
Ei – Cu2+
ions removal efficiency from wastewater, (%);
Ci – initial concentration of Cu2+
in wastewater, (mg/L);
Cf,t – final concentration of Cu2+
measure at time t, (mg/L)
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Fig.2.39 and Fig.2.40 show that the higher efficiency of removal of copper ions from
wastewater was obtained for γ -Fe2O3- -poly-DL-alanine hybrid nanomaterial. This fact is
explained by the presence of poly-DL-alanine polymer component in hybrid nanomaterial
composition which has a suplimentar contribution to the retention of the of copper (Cu2+
) from
wastewater by its functional groups.
(a)
(b)
Fig. 2.39 Variation of Cu2+
concentration values vs. time for γ-Fe2O3 (a) and γ-Fe2O3- poly-DL-
alanine (b), [24]
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The efficiency of copper removal from wastewater was 85% for experiments when
maghemite (γ-Fe2O3) was used as adsorbant and 89% for those when was used as adsorbant γ-Fe2O3-
poly-DL-alanine.
In conclusion whithin this study was investigated a new route for removing toxic copper
ions from wastewater that is effective, and involve reusable and ecofriendly adsorbants.
(a)
(b)
Fig.2.40. Variations of copper (II) removal efficiency (%) vs. time for γ-Fe2O3 (a) and γ-
Fe2O3- poli-DL-alanine (b), [24].
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The experimental results obtained for these two adsorbant nanomaterials offers
promising perspectives regarding the wastewater treatment implying the application of
nanotechnology.
In the future the studies for testing of the potential of applying these nanoadsorbants
for the depollution of wastewater containing other heavy metals will be done.
2.4. Removal of some toxic metals Cr, Cd, Cu, Zn and Ni using two magnetic
nanomaterials- magnetite (Fe3O4) and Fe3O4-PAA composite
2.4.1. General consideration
Because of the existence of toxic heavy metals in surface waters and underground water
is a huge environmental and public health problem, the effluents discharged from different
industrial activities having high concentrations of these metals have to be very well treated for
reducing their concentrations according to the legislative standards [33].
Adsorption represents one of the most efficient technologies for reducing the
concentration of heavy metals from industrial wastewater by using different types of adsorbents,
activated C being one of the most commonly used adsorbents [34].
The discovery of nanotechnologies led to the development of nanomaterials for
wastewater treatment [33]. Recently, in scientific literature has been presented Fe oxides type
nanomaterials used for the remove of toxic heavy metal and organic pollutants from water [35].
This is type of nanomaterial possess not only strong adsorption capacities but also the capacity of
being easily separated and collected by an external magnetic field [36, 37, 38]. Capacity of being
adsorbant for many heavy metal ions of magnetite nanoparticles has been reported in the
scientific literature [39, 40, 41]. The capacity of adsorption of Cr(VI) from wastewater onto
magnetite nanoparticles has also been reported [40, 42, 43]. As regarding the magnetite
nanoparticles recent studies have reported favorable results regarding adsorption capacity of
several toxic metal ions (e.g., Cu2+
, Ni2+
, Zn2+
, Cd2+
and Cr6+
) and its catalytic degradation
capacity of some organic pollutants [44]. Ions such as Ni2+
, Cu2+
and Cr6+
from multicomponent
wastewater were adsorbed with good results onto magnetite nanoparticles under acidic or basic
conditions [45].
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Moreover, another study presented zero -valent Fe nanoparticles synthesized in a water–
oil microemulsion followed by homogenization with a cellulose acetate–acetone solution and
finally being formed into a porous membrane by phase inversion supported on cellulose acetate.
The magnetic nanomaterial finally obtained was tested for the dechlorination of trichloroethylene
in water highlighted [46].
In this subchapter is presented a research containing the investigation of two
nanomaterials: magnetite (Fe3O4) and its corresponding composite (magnetite covered with
sodium alginate, noted as Fe3O4–PAA). These two nanomaterials were used as adsorbents for
Cu, Cr, Zn, Cd and Ni from aqueous solutions. The dissolution capacity of Fe from uncoated
Fe3O4 nanoparticles (average size of 7 nm) under acidic conditions has been reported, showing
that 40% of the Fe was dissolved [43,47].
Sodium alginate is a polysaccharide type polymer known as a flocculation additive with
a high potential for removal of pollutants such as: Zn (II), Cd (II), Cu (II) and Pb (II) from
wastewater [48].
The combination between magnetite and sodium alginate to obtain a nanocomposite,
may lead to removal of heavy metals under acidic conditions without or with a lower tendency of
Fe to dissolve from Fe3O4–PAA nanocomposite in comparison with uncoated Fe3O4.
For obtaining the similar conditions of acidic wastewater released from the iron and
steel industries and from acid mine drainage the adsorption experiments were conducted at pH of
2.5. The experimental results obtained from the evaluation of the adsorption capacity of the two
magnetic adsorbents tested were correlated to the Langmuir adsorption model.
The research presented in this subchapter was published in scientific literature [49].
2.4.2. Cr (II), Cd(II), Cu(II), Zn(II) and Ni(II) using two magnetic nanomaterials
magnetite (Fe3O4) and Fe3O4-PAA
Prior to investigate the Cr (II), Cd(II), Cu(II), Zn(II) and Ni(II) removal from wastewater,
the two magnetite nanomaterials Fe3O4 and Fe3O4-PAA were synthesized and characterised.
Magnetite was prepared by coprecipitation method starting from the following compounds:
Fe(NO3)3.9H2O 0.4 M and FeCl2
.9H2O 0.4 M, NaOH 0.5 M, at room temperature. The reaction
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mixture pH was kept at 10 for 3 hours. The molar ratio between the ferrous and ferric ions was
1:2. The precipitate obtained was separated by centrifugation and washed with distillated water
several times. The Fe3O4-PAA composite nanomaterial was obtained from of magnetite powder
and 5% sodium alginate solution (50%wt).
After the synthesis the nanomaterials used as adsorbents, Fe3O4 and Fe3O4 - PAA were
characterized by the following analyses:
X-ray diffraction (XRD) - using the Panalytical X`Pert PRO MPD X-ray
diffractometer with high-intensity Cu Kα radiation (λ = 1.54065 Å) with the 2θ
range from 10o to 90
o;
Transmission electron microscopy (TEM) and selected area electron diffraction
(SAED) - using TECNAI F30 G2STWIN high resolution transmission electron
microscope with 1Å line resolution;
Scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry
(EDS) – using the Quanta INSPECT F scanning electron microscope (SEM)
equipped with field emission gun (FEG) with a resolution of 1.2 nm and an
energy dispersive X -ray spectrometer (EDXS) with the resolution for MnKα of
133 eV.
After structural and morphological characterization the two magnetic nanomaterials
were tested as adsorbant following the following procedure:
All stock standard solutions (wastewater) of nickel, zinc, and cadmium, copper
were obtained from Merck reagent by dissolving into ultrapure water;
The solution containing chromium was prepared by dissolving of potassium
chromate (K2CrO4) p.a. into ultrapure water.
Each stock solution had an initial concentration of 1000 mg/L and pH value was
adjusted by adding HCl (0.1 mol/L) in order to obtain a value similar to that of
the industrial effluents.
The adsorption tests were conducted by measuring the initial and final
concentration of the metal using flame atomic absorption spectrometry (FAAS)
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method- using the GBC 932 AB Plus spectrometer with spectral domain
between 185 and 900 nm in order to establish the quantity of adsorbed metal.
An amount of Fe3O4 and Fe3O4-PAA respectively were homogenized with 100
mL solution of 20 mg/L from each metal studied: Cd (II), Zn (II), Cr (VI), Cu(II)
and Ni(II), in a glass vial at room temperature (21.5°C). The Fe3O4 and Fe3O4-
PAA quantities used for tests were 0.05 g, 0.1 g and 0.2 g from each compound.
For adsorption kinetic studies, synthetic wastewater samples prepared were kept
into contact with each type of adsorbent nanoparticles from 10 to 100 minutes.
The pH value of each synthetic wastewater was 2.5 obtained by using HCl (0.1
mol/L) for pH adjustment.
At the end of each experiment the adsorbents were recovered by magnetic
separation.
For each magnetic nanomaterial was calculated the adsorbed metal amount at
equilibrium using the following by ratio between adsorbed metal (mg) onto adsorbent mass (g)
expressed as qe, according to Eq. (2.11):
m
VCCq e
e
0 (2.11)
where:
C0 – initial concentration, mg/L;
Ce – equilibrium concentration, mg/L;
V – volume of solution, L;
m – adsorbent quantity, g.
The XRD spectrum of Fe3O4 is presented in Fig.2.41 showing the crystalline structure
of the powder, having a face centered cubic structure, according to 75-1610 ICDD, with the
diffraction peak with maximum intensity at 35.44° for 2θ.
The same crystalline peaks were observed for Fe3O4-PAA nanocomposite as it can be
seen in the Fig. 2.41 (b). This indicated the preservation of stability of Fe3O4 crystalline phase
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during polymer coating. The influence of the sodium alginate polymer on diffraction line can be
identified as a characteristic increasing of background between 10 and 50°, as being an
amorphous phase. The TEMBF (transmission electron microscopy bright field) image of Fe3O4
nanoparticles from Fig.2.42 (a) showed nanoparticles with sizes between 40 and 100 nm, with an
average size of 80 nm. A few nanoparticles had dimensions up to 250 nm.
(a) (b)
Fig.2.41. XRD images (CuKα radiation) for Fe3O4 (a) and Fe3O4 – PAA (b).
Fig. 2.42. TEM (bright field) with inset SAED images of Fe3O4 nanoparticles.
.
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The SAED image confirmed the crystalline structure of Fe3O4. The SEM analysis of
Fe3O4-PAA showed the spherical shape of the magnetite particles wrapped into polymer, the
mean particle dimension being about 200 nm. Another SEM image is presented in Fig. 2.43.
Fig. 2.43. Scanning electron microscopy (SEM) - secondary electron image for Fe3O4 – PAA,
[49].
Fig. 2.44 presents the energy dispersive X-ray spectrum which reveals the existence of
sodium, oxygen and iron elements from the Fe3O4 – PAA nanocomposite. Also, it is obviously
that the sodium and oxygen are uniform distributed, these two elements covering the areas where
the iron is concentrated which correspond with agglomerated nanoparticles of magnetite as it can
be seen from the left up-corner image (Fig.2.44(a)) [49].
The adsorption isotherms for Zn (II), Cu(II), Cr (II), Cd (II), and Ni (II) onto 0.05, 0.1
and 0.2 g of Fe3O4 and Fe3O4-PAA, respectively, were fitted to the Langmuir model expressed as
Eq. (2.12.):
bqC
C
m
e
me
e
11 (2.12)
where:
Ce –aqueous concentration at equilibrium, mg/L;
qe – adsorbed amount at equilibrium, mg/g;
qm and b – constants related to the adsorption capacity and the affinity coefficient.
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(a) (b)
Fig. 2.44 Mapping of the elements (a) and energy dispersive X-ray spectra (b) for Fe3O4 – PAA,
[49].
All samples were analyzed at specific time intervals from 10 to 100 minutes (21.5°C).
For evaluation of the quantity of the adsorbed metal the supernatant layer from all tested
samples was analyzed by AAS.
Also, was evaluated the effect of contact time for the adsorption of metals onto Fe3O4
and Fe3O4-PAA. The removal efficiency is shown in Fig. 2.45 for Fe3O4 and Fig. 2.46. for
Fe3O4-PAA.
The efficiency of removal for Zn (II), Cd(II), Cu(II), Cr(VI) and Ni(II) was initially
very high using Fe3O4 nanomaterial being between 70 and 80% after 10 minutes but remaining
almost the same after 100 minutes.
The highest removal efficiency was obtained in the case of chromium removal and the
smallest for nickel ions removal.
For all the metal ions tested, the adsorption equilibrium was achieved within 10
minutes. In case of using Fe3O4-PAA as adsorbent, the removal efficiency was between 70 and
80% after 10 minutes. Moreover, the efficiency was higher than that obtained for Fe3O4 in case
of the other metals: Zn (II), Cu (II), Cd (II). This can be explained by the adsorption capacity of
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the sodium alginate polymer. The quantities used were the same as in the case of Fe3O4, but
percentage of Fe contained by Fe3O4-PAA was about 45% in the mass of the nanocomposite.
In case of Fe3O4-PAA as adsorbent it can be assumed that the adsorbtion process takes
place on the polymer surface. Also, the removal efficiency was higher and remained the same
after 100 minutes.
Increasing the quantity of the adsorbent from 0.05 g to 0.2 g did not lead to a significant
increase of the adsorption efficiency as can be seen in the Fig. 2.45. Also was observed that the
high adsorption efficiency was obtained for chromium and the lowest efficiency was obtained for
nickel, under acidic conditions [49].
The adsorption affinity was ordered as follows: Cr > Cd > Cu > Zn > Ni. This affinity
can be explained by zero point of charge pHpzc of Fe3O4 which is 6.5, according to [50]. Below
this value, the adsorbent surface is positively charged and the anions are adsorbed by
electrostatic attraction. Above this value of pHpzc, the adsorbent surface is negative charged and
the metal ions are adsorbed on the magnetite.
The retained of Cr (VI) ions will decrease with the increase of pH, because in the
aqueous phase the surface of the metal oxides is covered with hydroxyl groups that varies at
different pH values [49, 51, 52]. The species of hexavalent chromium from solution are
chromates (CrO42-
), dichromates (Cr2O72-
) and bichromates (HCrO4-). In case of the negative
charge of the adsorption surface, the electrostatic repulsions will increase between negatively
charged Cr (VI) species and negatively charged nanoparticles, leading to the removal of some
adsorbed species such as bichromates (HCrO4-) or chromates (CrO4
2-) [49]. The used quantities
do not have a major influence on adsorbed quantity of metal.
It can be seen for both adsorbents that the optimum quantity used in the experiments is
0.05 g, because in this case the amount adsorbed is higher in comparison with others common
adsorbent such as activated carbon or diatomite, according to the results from literature, namely:
11.5 mg/g for diatomite and 15.47 mg/g for activated carbon, respectively [51,53]. Langmuir
model parameters for adsorption of all metals onto 0.05, 0.1 and 0.2 g Fe3O4 and Fe3O4-PAA,
respectively, are given in the table 2.5.
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(a)
Fig.2.45 Effect of contact time for metal removal onto 0.05, 0.1 and 0.2 g Fe3O4 (a) and Fe3O4-
PAA (b) nanoparticles at pH 2.5, [49].
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(b)
Fig.2.46 Effect of contact time for metal removal onto 0.05, 0.1 and 0.2 g Fe3O4 (a) and Fe3O4-
PAA (b) nanoparticles at pH 2.5, [49].
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Fig. 2.47. Metal amount quantity adsorbed onto 0.05, 0.1 and 0.2 g Fe3O4 (a) and Fe3O4-
PAA (b) adsorbents, [49].
Fig. 2.48. Metal amount quantity adsorbed onto 0.05, 0.1 and 0.2 g Fe3O4 (a) and Fe3O4-PAA
(b) adsorbents, [49].
(a)
(b)
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Both type of magnetic nanoparticles exhibited a strong affinity for the metal ions found
in water. From the data listed in the table 2.5, the qe values indicate a weaker affinity of Fe3O4 in
comparison with Fe3O4-PAA [49].
Also, the optimum quantity for adsorption process was 0.05 g nanoparticles. It can be
observed that data are fitted well Langmuir monolayer adsorption isotherm [49].
Table 1.5 Langmuir parameters for adsorbed metals onto Fe3O4 and Fe3O4-PAA [49]
Metal
Quantity
of
adsorbe
nt
Langmuir parameters
Fe3O4 Fe3O4-PAA
qe (mg/g)* R2
qe
(mg/g)* R
2
Zn 0.05 29.80 0.9973 30.12 0.9998
0.1 14.84 0.9976 15.33 0.9989
0.2 7.99 0.9995 7.95 0.9980
Cd 0.05 31.00 0.9994 30.80 0.9975
0.1 15.57 0.9967 17.00 0.9975
0.2 7.94 0.9983 7.87 0.9977
Cu 0.05 30.97 0.9991 30.06 0.9987
0.1 15.50 0.9984 15.32 0.9986
0.2 7.50 0.9986 7.71 0.9982
Cr 0.05 31.99 0.9971 29.50 0.9972
0.1 16.36 0.9983 15.24 0.9981
0.2 7.82 0.9976 7.56 0.9985
Ni 0.05 29.97 0.9988 29.03 0.9981
0.1 15.13 0.9978 14.73 0.9976
0.2 7.57 0.9986 7.33 0.9987
* time- 10 minutes
The conclusions of this study were the following [49]:
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the adsorption studies indicated a good correlation between metal ions concentration and
adsorbent quantity at pH 2.5. At pH 8.5 the most quantity of metals was precipitated (almost
100% for Cd and Cu) by adding NaOH;
under basic conditions two phenomena can appear: precipitation and adsorption.
between the two used adsorbent, the composite (Fe3O4-PAA) formed by magnetite
wrapped into sodium-alginate had a good protection from acid leaching, the leached Fe
content being smaller than magnetite (Fe3O4), after 24 hours.
2.5. Contribution to Pb(II) and Cd(II) ions removal from wastewater using as magnetic
adsorbant nanomaterials: Fe3O4, Fe3O4-PEG and Fe3O4-PVP
2.5.1. General considerations
Pb(II) and Cd(II) ions were chosen as the metal adsorbates because they commonly
exist in the effluents from plating factories, electrolytic refining plants and acid mining
industries.
Source of Cd (II) pollution are the following activities:
Zn production which constitutes the larger source of Cadmium pollution: Zn refining
in which Zn ores could contain 5% Cd;
metal electroplating;
production of stabilizer or pigments in plastics (PVC) ;
fabrication of nickel-cadmium batteries;
production of alloys.
fabrication of anticorrosive agent;
a neutron-absorber in nuclear power plants;
fabrication of phosphate fertilizers also show a big cadmium load.
dumping and incinerating cadmium-polluted waste.
Source of Pb (II) pollution are the following industrial activities:
petroleum;
mining;
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smelting;
lead-acid battery manufacturing,;
waste incineration.
The effects of cadmium pollution on human health are the following:
Kidney damage;
Gastrointestinal problems;
Bone damage and the Itai-Itai-disease (a disease under witch patients show a wide
range of symptoms such as: low grade of bone mineralization, high rate of fractures,
increased rate of osteoporosis, and intense bone associated pain);
Cancer.
Some of the effects of lead pollution on human health are the following:
damages of internal organs;
damages of the brain and nervous system;
reproductive disorders and/or osteoporosis.
The using of iron based magnetic hybrid nanoparticles as novel adsorbants is expected
to be an attractive and inexpensive option for the removal of heavy metals taking into
considerations the following: simple obtaining method, high surface area value, special magnetic
properties.
2.5.2. The investigation of Pb(II) and Cd(II) ions removal from wastewater using iron-
based magnetic hybrid nanoparticles: Fe3O4, Fe3O4-PEG and Fe3O4-PVP
Thus, the purpose of this study was to assess the performances of magnetite
nanoparticles and its polymeric nanohybrids for the removal of Cd (II) and Pb (II) ions from
synthetic wastewater. The research presented in this subchapter was already published in
scientific literature [54].
In this subchapter the tested magnetite nanomaterial was synthesized using sol–gel
method starting from cheap and environmentally friendly iron salts in the presence of a soft
template. The obtained magnetite nanoparticles were coated with polyethylene glycol (PEG) and
polyvinylpyrrolidinone (PVP) polymer, for obtaining the two magnetic nanohybrids: Fe3O4-PEG
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and Fe3O4-PVP (Fig.2.49). After the synthesis, the magnetite nanomaterial was tested for the
selective removal and recovery from industrial wastewater of toxic heavy metals such as: Pb(II)
and Cd(II) ions (Fig.2.49).
Fig.2.49. The scheme of nanostructured hybrids proposed for Pb(II) and Cd(II) heavy metals
removal from wastewater, [54].
For performing the adsorption studies an amount of Fe3O4, Fe3O4-PEG and Fe3O4-PVP
respectively were mixed with 100 mL mixed solution of Pb(II) and Cd(II), at room temperature
(21.5°C), stirred speed of 400 rpm.
The adsorbent samples were recovered by magnetic separation and were analyzed by
atomic absortion analysis (AAS) using GBC 932 AB Plus spectrometer with spectral domain
between 185 and 900 nm.
The influence of contact time on the efficiency of metal ions adsorption onto Fe3O4,
Fe3O4-PEG and Fe3O4-PVP is presented in Fig. 2.50.
Between the two magnetic hybrid nanomaterials, Fe3O4-PVP had a higher efficiency for
adsorption of Pb (II) ions from wastewater. Regarding the Cd (II) ions the removal efficiency
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was higher for Fe3O4 (almost 90%) and less than 50% for the two magnetic hybrid
nanomaterials.
0.00
20.00
40.00
60.00
80.00
100.00E
ffic
ien
cy, %
Fe3O4-PEG, Pb 90.30 90.16 89.92 83.00
Fe3O4-PVP, Pb 90.34 90.32 89.86 82.60
Fe3O4-PEG, Cd 49.13 46.33 47.95 49.75
Fe3O4-PVP, Cd 48.51 47.45 47.97 47.70
Fe3O4, Pb 89.68 89.97 91.94 89.82
Fe3O4, Cd 91.15 93.62 91.33 91.47
15 min. 30 min. 60 min. 24 hours
Fig.2.50. The removal efficiency vs. time for Pb (II) and Cd (II) using the magnetic
nanomaterials: Fe3O4, Fe3O4-PEG and Fe3O4-PVP, [54].
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2.6. Contribution to Cu (II), Zn (II), Cr (II), Cd (II) and Ni (II) removal from wastewater
using Fe3O4 and Fe3O4-PVP magnetic nanomaterials
2.6.1. General considerations
The study present in this subchapter was already published [55]. The following metal
ions: Cu2+
, Zn2+
, Cr2+
, Cd2+
and Ni2+
are part of “heavy metals” class which refers to metallic
elements with atomic density value higher than 4 g/cm3 or five times or more higher than water
and are toxic even at low concentration.
In Tabel 2.6. are presented some natural and atrophic sources of drinking water
pollution with heavy metals and their corresponding concentration related by U.S.
Environmental Protection Agency. There are multiple neurotoxic, carcinogenic, mutagenic or
teratogenic effects associated with the presence of cadmium, lead, arsenic, mercury, zinc, and
copper poisoning in human body.
Tabel 2.6. List of heavy metals pollutants found in drinking water, [55, 56].
Pollutant
substance
Concentration
(mg/L) 2
Sources of Pollutant in Drinking Water
Cadmium
Zinc
0.005
7
Erosion of natural deposits, anticorrosion coating,
electroplating, alloying activity in solders, stabilizer in
plastics (organic cadmium), pigments, drying of zinc
concentrates and roasting, smelting, refining of ores
corrosion of galvanized pipes, discharge from metal
refineries, runoff from waste batteries
Protecting steel against corrosion, brass and other alloys,
automotive equipment, household appliances, fittings, tools,
toys, building and construction, pharmaceuticals, medical
equipment, cosmetics, tyres and rubber goods, fertilizers,
animal feed.
Chromium 0.1 Erosion of natural deposits, discharge from steel and pulp
mills.
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Pollutant
substance
Concentration
(mg/L) 2
Sources of Pollutant in Drinking Water
Copper 1.3 Erosion of natural deposits, industrial operations such as
smelters, foundries, power stations, incinerators, various
combustion sources, corrosion of household plumbing
systems.
Lead 0.015 Erosion of natural deposits, corrosion of household
plumbing systems, industries such as the petroleum, mining,
smelting, lead-acid battery manufacturing, waste
incinerating, mining industries.
Mercury 0.002 Erosion of natural deposits, discharge from refineries and
factories, runoff from landfills and croplands, medicinal
industry, cosmetics industry, waste incineration, coal
combustion, base metal smelting, chlor-alkali industry.
Some of the effect of heavy metals associated with their presence in human body are:
-tremor;
- ataxia;
- paralysis;
- vomiting;
-convulsion when volatile vapors are inhaled;
- the gastrointestinal disorders;
- stomatitis;
- hemoglobinuria causing a rust–red color to stool;
- depression.
The directly discharging into natural waters of wastewaters containing heavy metals
without any treatment, will lead to risks for the aquatic ecosystem and public health.
The direct discharge of wastewaters containing heavy metals into the sewerage system
may result in malfunctioning of the conventional wastewater treatment [57].
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The conventional physico-chemical processes for heavy metals removal such as: ion-
exchange, precipitation, and so one are considered inefficient in treating wastewater having low
heavy metals concentration and expensive.
In the present, one of the most efficient technologies for reducing or removal the heavy
metal from wastewater is through adsorption using various adsorbents.
Due to development of nanotechnologies, nanomaterials have been developed for
wastewater treatment. In Fig. 2.51 is presented the scheme of drinking water production plant
which uses as adsorbants nanostructured zeolites [58].
Recently, many researchers found that using of the magnetic iron oxides nanoparticles
for removal of heavy metal ions from wastewater [59] presents multiple advantages because their
huge adsorption potential and the benefits of being easily separated and recovered by using an
external magnetic field [60].
Fig.2.51 Scheme of drinking water production plant (A) and pilot plant “filter guards” (B) using
nanostructured adsorbants (NZ-, MNZ-CRO natural and modified zeolite from Croatia; NZ-,
MNZ-SRB natural and modified zeolite from Serbia), [56, 58].
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2.6.2. The investigation of Cu (II), Zn (II), Cr (II), Cd (II) and Ni (II) ions removal
from wastewater using Fe3O4 and Fe3O4-PVP nanomaterials
The present subchapter presents the utilization of two magnetic nanomaterials Fe3O4
and Fe3O4-PVP adsorbents for the removal of heavy metal ions such as Cu2+
, Zn2+
, Cr2+
, Cd2+
and Ni2+
from synthetic acidic wastewater.
The wastewater treatment performance of the two magnetic nanomaterials (Fe3O4,
Fe3O4-PVP) was investigated by atomic absorption spectroscopy.
The experimental results of the adsorption studies are presented in Tabel 2.7, [55].
The available and active sites for nanoparticles are mostly present on the surface and
based on this assumption a higher surface area will provide more sites for adsorption.
The conclusions that can be drawn from fulfilling the investigation are the following:
the maximum efficiency was up to 80% for Cr(VI) and between 74 – 76% for the other
heavy metals ions tested. It is expected to decrease the Cr (VI) uptake with increasing of
pH, because in the aqueous phase the metal oxides surface is covered with hydroxyl
groups that vary at different pH values.
for uncoated Fe3O4 nanoparticles, the percentage of removal efficiency decreased in the
order: Cr(VI) > Cu(II) > Zn(II) > Ni(II) > Cd(II).
adsorption can be explained by the zero point of net charge pHpnzc of Fe3O4 which is 6.5.
Below pH of 6.5, the magnetite surface is more positively charged and anions are
adsorbed by electrostatic attraction. Above this value of pHpnzc, the magnetite surface is
more negatively charged and the metal ions are adsorbed on its surface.
with respect to the Fe3O4-PVP hybrid nanomaterial the adsorption phenomena varies as
follows: Cr(VI) > Cd(II) > Cu(II) ~ Zn(II) > Ni(II). Its adsorption capacity could be
explained taking into considerations the contribution of nitrogen or oxygen from PVP
polymer composition to bind the heavy metal ions found in wastewater.
The experimental results indicate that Fe3O4-PVP had the removal efficiency for metal
ions at approximately the same values as for the uncoated Fe3O4.
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the hybrid nanomaterial Fe3O4-PVP could be used as adsorbent with the same
performance as uncoated Fe3O4 having the supplementary advantage of its stability in real
conditions when the industrial wastewaters have a low pH value.
Table 2.7. Wastewater treatment efficiency (η %) of two nanomaterials studied on metal
ions (Cr, Cu, Zn, Ni, Cd), [55].
Metal ion Co,
mg/L
Fe3O4, η % Fe3O4-PVP, η %
0.05 g 0.1 g 0.2 g 0.05 g 0.1 g 0.2 g
Cr (VI) 20 80 79 78 82 80 80
50 78 77 76 78 71 72
100 79 75 70 75 69 68
Cu (II) 20 76 76 72 75 72 70
50 75 74 70 72 70 67
100 75 73 68 70 66 65
Zn (II) 20 76 74 71 75 72 69
50 75 72 70 72 70 68
100 74 71 67 70 66 64
Ni (II) 20 74 70 69 70 68 65
50 72 68 67 68 66 64
100 69 65 64 67 65 64
Cd (II) 20 70 68 65 76 75 73
50 67 65 61 74 73 72
100 65 63 60 74 72 70
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2.7. Study of zeolites nanomaterials as a multifunctional environmental engineering
solution
Natural zeolites are environmentally friendly aluminosilicates minerals which have an
open crystal structure containing cations, such as: Na+, K
+, Ca
2+, Mg
2+ and H2O molecules
having various morphologies such as those presented Fig.2.52 [61].
By ionic exchange and reversible rehydration the ions and water molecules from zeolite
structure can readily be exchanged within the large cavities.
Zeolites have some particularities:
display unique physical and chemical features;
the large system of three-dimensional cavities and channels of molecular size
crystal structure confers a huge storage space.
have a variety of industrial and agricultural applications Fig.2.53.
their features are useful for solving many environmental problems including
offensive odors and heavy metal pollution.
(a) (b) (c)
Fig.2.52. The image of (a) Scolecite on stilbite CaAl2Si3O10.3H2O-NaCa4[Al9Si27O72]
.30
H2O; (b) Scolecite - CaAl2Si3O10.3H2O; (c) analcime Na16[Al16Si32O96]
. 16 H2O, [62,63].
.
have the ability of turning waste into valuable fertilizer explained by their strong
affinity for ammonia ions (NH4+) and store it up instead of allowing it to
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volatilize. The ammonium ion NH4+ is attracted to the negative charge of the
zeolite crystal.
due to their high cation exchange capacity have the ability, to absorb nutrients
needed by plants and improve fertilizer efficiency.
plant nutrient cations e.g. potassium (K+) and zinc (Zn
2+) can be also stored in
the zeolite crystal structure.
could be used to eliminate or to reduce, many longstanding environmental,
agricultural and industrial pollution problems.
In scientific literature is found that zeolites, have strong affinity for heavy metal ions
[64]. The mechanism of retaining heavy metals was found to be ion-exchange. In their three
dimensional structure exist large channels containing negatively charged sites resulting from
Al3+
replacement of Si4+
in the O tetrahedral–linked by sharing oxygen atoms in rings and cages-
cavities occupied by cations which are weakly kept in the crystal structure for compensation of
the charge imbalance [63]. The negative charges of the anions are balanced by cations that are
placed in the channels and can be replaced with heavy metal ions [63].
Zeolites are considered low-cost adsorbants.
It was reported that zeolites are materials that can be used for mercury removal from
flue gases and solutions [63].
Magnetic zeolite composites nanomaterial suited for environmental applications
obtained by condensation of silica film on magnetite (Fe3O4) particles having nanometer size,
had an adsorption capacity for Hg retaining at room temperature of 95%, whereas at 120 0C was
obtained a complete adsorption.
The zeolite can adsorb mercury by physical adsorption/condensation.
Another study, [65] the zeolite containing 70% clinoptilolite, 9% silica and clays, 5%
mica, 15% of zeolite water was tested on the effluent resulted from copper smelter and refinery
for obtaining electrolytic copper- cathodes. The low values of sorption capacity were explained
by the low concentration of mercury ions and competition of other cations that also undergo
sorption (Table 2.8).
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Fig.2.53. The industrial and agricultural applications of zeolites, [63]
Table 2.8. Mercury removal from industrial effluents with zeolite, [63,65]
Sorbent
concentration
(g/l)
Hg concentration in
effluent Sewage
(mg/kg)
Sorption
capacity
(mg/g)
Hg concentration in
effluent
industrial and
domestic (mg/kg)
Sorption
capacity
(mg/g)
0 0.0109 0.0246
0.35 0.0080 0.0083 0.0174 0.021
0.70 0.0062 0.0067 0.0143 0.015
2.10 0.0028 0.0039 0.0117 0.006
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2.8. Contribution to organic (C6H6 and C6H5-CH3) and inorganic (Pb+2
and Zn+2
) pollutants
removal from for wastewater using powdered activated carbon
2.8.1. General considerations
Wastewaters treatment resulted from various industries such as: chemical factories,
coke plant, pharmaceutical, textile, food, storage installations, munitions factories, herbicides
manufacturing, pesticides manufacturing, petroleum refineries installations, organic pigments
and dyes, mineral processing plants, insecticides, pesticides, resins, detergents, explosives and
dyes [66,67]
One of the most efficient adsorbant for removing various organic pollutants from water
is represented by activated carbon. In Table 2.9 are some examples of chemical pollutants with
high, very high, moderate and low probability of being adsorbed by activated carbon [68].
The structure of pores of activated carbon sustains its application in wastewater
treatment being suitable for retaining small, medium or large pollutant molecules (Fig. 2.54).
Fig. 2.54. Scheme of retaining small, medium or large molecules of pollutants by one of the
pores of activated carbon, [68].
Large or medium molecules are considered organic compounds, whereas heavy metals
are considered small molecules.
Some characteristics regarding toluene (methyl benzene) and benzene representig two
of the pollutants studied in this subchapter are the following:
are colorless, flammable liquids;
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are contained by petroleum crude oil and can reach in the environment during
manufacture or use of these substances or products containined by them;
in United States, large quantities of the toluene recovered from crude oil is
utilise for benzene production or in the composition of adhesives, printing ink,
paint strippers, antifreeze, aerosol spray paints, perfumes, cosmetics, lacquers,
wall paints, spot removers, etc.
the benzene pollution sources are: combustion processes, industries producing or
using it such as production of dyes, plastics, fibers, detergents, coatings
pesticides, lubricants, adhesives and dry cleaning agents
(http://www.epa.gov/chemfact/f_toluen.txt).
Table 2.9. Chemical pollutants with high, very high, moderate and low probability of being
adsorbed by activated carbon, [68].
Chemical compounds
with high probability
of being adsorbed by
activated carbon
Chemical compounds
with very high
probability of being
adsorbed by activated
carbon
Chemicals with
moderate
probability of
being adsorbed
by activated
carbon
Chemical compounds
for which adsorption
with activated carbon
is low and it is viable
method for
low wastewater flow
or concentration
Aniline
Aldrin
Acetic acid
Methyl chloride
Benzene
Anthracene
Acrylamide
Acetone
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Table 2.9. Chemical pollutants with high, very high, moderate and low probability of being
adsorbed by activated carbon, [68].
Chemical compounds
with high probability
of being adsorbed by
activated carbon
Chemical compounds
with very high
probability of being
adsorbed by activated
carbon
Chemicals with
moderate
probability of
being adsorbed
by activated
carbon
Chemical compounds
for which adsorption
with activated carbon
is low and it is viable
method for
low wastewater flow
or concentration
Benzyl alcohol
Atrazine
Chloroethane
Acetonitrile
Benzoic acid
Azinphos-ethyl
Chloroform
Acrylonitrile
Bis(2-chloroethyl)
ether
Bentazone
1,1-
Dichloroethane
Dimethylformaldehyde
To the aquatic organisms both benzene and toluene are considered harmful
(http://www.epa.gov/chemfact/f_toluen.txt).
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The human health and environment effects of toluene are influenced by some factors
such as: the length of time and frequency of exposure, concentration, health of the person
exposed, the environment conditions when exposure occurs [69]. Unfortunately, it was already
proved that benzene is carcinogen.
This subchapter presents the study of activated carbon for the removal of two types of
toxic pollutants that can exist in wastewater: organic and inorganic nature. The research from the
scientific literature is focused on testing activated carbon for the removing from wastewater of
the organic nature pollutants.
Consequently, in this study was approached a new research direction, by testing the
adsorption capacity of powdered activated carbon for treatment of synthetic wastewater
containing, inorganic pollutants such as Pb(II) and Zn(II) ions and as organic pollutants toluene
(C6H5-CH3) and benzene (C6H6).
2.8.2. The investigation of removal organic (C6H6 and C6H5-CH3) and inorganic (Pb+2
and
Zn+2
) pollutants for wastewater using activated carbon
The experimental procedures consisted in the following, [68]:
were used different heavy metals (Pb and Zn) concentrations (20, 40, 60, 80 mg/L
for each pollutant) together with organic compounds consisting of 0.5% C6H6 and
0.5% C6H5CH3;
organic compounds initial concentration was 100 mg/L expressed as chemical
oxygen demand (COD);
wastewater solutions were put together with 1 g of activated carbon;
activated carbon powder was purchased from Sigma-Aldrich, with the following
characteristics: vapor pressure < 0.1 mm Hg (20°C), resistivity 1375 μΩ-cm at
20°C, size dimension 37 – 149 μm;
the measurements of Pb(II) and Zn(II) concentrations were done by atomic
absorption spectrometry using the use of Deuterium lamp as background correction
and air/oxidized acetylene flame. The specific wavelength for Pb was 217 nm and
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for Zn was 213.9 nm. The equipment used was 932 GBC Avanta Plus atomic
absorption spectrometer with flame;
For the measurements of concentration of organic compounds as COD, before and
after adsorption tests, was applied the following procedure: 100 mL of sample was
poured into an Erlenmeyer flask together with 5 mL H2SO4 1:3 and 10 mL
potassium permanganate accurately measured were added to the samples. All
mixtures were boiled on a hotplate for 10 minutes. Into the hot mixture were added
10 mL oxalic acid precisely measured. Titration operation was made with
potassium permanganate until a persistent pink color appeared.
Chemical oxygen consumption was calculated using the Eq. (2.12):
3
21
4V
10000.316VfVV/LmgKMnO
(2.12)
where:
V - volume of potassium permanganate initially added in the sample, mL;
V1 - volume of 0.01 N potassium permanganate used for sample titration, mL;
V2 - volume of oxalic acid added to the sample before titration, mL;
f - the factor of the potassium permanganate solution;
0.316 - equivalent expressed in mg of KMnO4 of 1 mL of 0.01 KMnO4 0.01 N;
V3 - volume of wastewater analyzed, in mL.
For adsorption capacity tests the experimental procedure consisted in the following:
two synthetic wastewater: 100 mL of sample with different concentrations of Zn(II) and
Pb(II) and 100 mg/L benzene and toluene solution were added into contact with 1 g of
activated carbon.
the samples were analyzed during the experiments after 10 minutes, 1 hour, 2 hours and
24 hours.
the time interval of measurements was chosen according to the previous researches
regarding the adsorption tests [70] in which was observed that the adsorption appears
after 10-15 minutes and the same results are observed after 2 hours.
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in order to evaluate tendency of pollutants desorption a sample was analyzed after 24
hours.
the analysis of Zn(II) and Pb(II) were done according to the SR ISO 8288/2001 standard
for heavy metals.
pH value of wastewater samples tested was 3.17.
The removal efficiency of Zn(II) and Pb(II) pollutants was calculated according to the
Eq. (2.13):
%C
CC
i
ei 100
(2.13)
where:
- removal efficiency, %;
Ci – initial concentration, mg/L;
Ce - concentration at equilibrium, mg/L.
The adsorption process can be described based on the Langmuir equation, as monolayer
process where adsorbent surface has a specific number of sites available for reaction and linking
of retained molecules. Adsorption process is ended when all sites are occupied [71].
Langmuir model for adsorption [70] is given by the Eq. (2.14):
qe = Qmax.KL.Ce (1+KLCe) (2.14)
where:
qe - adsorbed quantity at equilibrium, mg/g;
Ce - concentration at equilibrium, mg/L;
Qmax - maximum quantity adsorbed, mg/g;
KL - Langmuir constant, L/mg.
Also, the adsorbed quantity at equilibrium, qe, was calculated with Eq. (2.15):
m
VCCq e
e
0
(2.15)
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where:
qe - adsorbed quantity at equilibrium, mg/g;
C0 – initial concentration, mg/L;
Ce – equilibrium concentration, mg/L;
V – volume, L;
m – adsorbent quantity, g.
In order to evaluate the profile of the Langmuir isotherm the separation factor (RL),
defined by the Eq. (2.16), can be used as dimensionless constant [71, 72]:
(2.16)
The profile of the isotherm could be according to RL values as follows: favorable
(0<RL<1), unfavorable (RL>1), linear (RL=1) or irreversible (RL=0).
The Freundlich model was applied for a better description of adsorption process [70],
given in the Eq. (2.17):
log qe = log KF + 1/n log Ce (2.17)
where:
Ce - the equilibrium liquid phase ion concentration, mg/L;
qe - the equilibrium solid phase ion concentration, mg/L;
n - empirical constant Freundlich;
KF - Freundlich constant.
Freundlich model sustains the possibility of adsorption on a heterogeneous surface,
[73]. The values of n indicate degree of nonlinearity between solution concentration and
adsorption as follows: n=1 for linear adsorption; n < 1 for chemical process; n > 1 for physical
process.
The tested activated carbon was morphological characterized by scanning electron
microscoy by using a Quanta Inspect F scanning microscope, with a field emission gun (FEG)
equipped with an EDAX spectrometer with a resolution at MnK of 133Ev.
The morphology of tested active carbon was investigated by SEM analysis Fig. 2.55.
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The results obtained after the experiments of investigation of adsorption capacity of
activated carbon were expressed as the average of five measurements.
The efficiency removal values of activated carbon regarding Pb(II), Zn(II) and COD as
indicator for organic compounds, during the experimental procedure measured in time (10
minutes and 24 hours) are presented in Fig. 2.56 (a). Initial concentration of lead and zinc was 80
mg/L and 100 mg/L for organic compounds.
Fig.2.55. SEM image of the activated carbon used as adsorbant.
The equilibrium quantity (qe) for Pb (II), Zn (II) and COD adsorbed at different time
intervals is showed in Fig. 2.56(b).
The efficiency for organic compounds (COD) removal is higher than 90% in
comparison with lead (almost 70%) and zinc (higher than 15%), [68] Fig. 2.56 (a).
Moreover, results seem to be keeping the same tendency of removal from 10 minutes to
24 hours, [68]. This is the reason for which, the experiments were continued until 2 hours. After
24 was made only an analysis for checking of the results.
Results regarding the equilibrium quantity adsorbed (qe) onto activated carbon are
presented in Fig. 2.57 (b) where is observed of retaining by a possible adsorption for organic
compounds (as COD), [68].
The time interval and the quantity were kept at the same values as in the case of
efficiency removal evaluation.
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Moreover, it can be observed the same tendency of Pb adsorption higher than Zn.
(a)
(b)
Fig. 2.56. (a) Efficiency removal (%) for Pb, Zn and COD at different period of time and (b)
Equilibrium quantity (qe) for Pb, Zn and COD adsorbed at different time intervals, [68].
Taking into account these observations was applied Langmuir model for single layer
adsorption. Results are presented in Fig. 2.57.
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Considering Langmuir isotherm, correlation factors for COD were 0.91 and for Pb (II)
was 0.92 in comparison with Zn (II) (0.81), [68]. These values show a good correlation between
experimental data and Langmuir model for COD and Pb.
It is possible that the adsorption takes place at upper layer of solid material. In
accordance with RL values this process could be favorable one. RL are between 0 and 1, thus:
COD: 0.004, Pb: 0.09, Zn: 0.43, [68].
Fig.2. 57 Langmuir model for Pb, Zn and COD adsorbed onto activated carbon
Freundlich isotherm indicates possibility of a chemical process for Pb (II) and COD and
physical process for Zn (II), according to the n values, [68]. The obtained experimental results
are presented in Fig. 2.58.
According to the correlation factors for COD (0.9857), Pb (II) (0.8236) and Zn (II)
(0.7649), obtained experimental data are fitted with Freundlich model in case of COD.
Values of n that indicate the degree of nonlinearity between wastewater concentration
and adsorption are 0.676 for COD, 0.815 for Pb (II) and 1.245 for Zn (II), [68].
In these conditions, Freundlich isotherm indicates a chemical process for Pb and COD
(n < 1) and a physical process for Zn (n > 1).
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Fig.2.58 Freundlich model for Pb, Zn and COD adsorbed onto activated carbon.
Moreover, KF values of 0.97 for Pb (II), 1.44 for COD and 0.88 for Zn (II) indicate a
higher adsorption capacity for COD and Pb (II) in comparison with Zn (II).
For a global view in Fig. 2.59 are presented the results for Pb(II) removal from
wastewater samples for a contact time between 10 minutes and 24 hours in presence of organic
compounds (Pb1) and organic compounds and zinc (Pb2), [68].
The process became important in the first 10 minutes and the results for different
concentration of Pb, Zn and COD were in accordance with two adsorption models, Langmuir and
Freundlich, [68].
The maximum adsorbed quantity of lead ions by the tested activated carbon is presented
in Fig. 2.60.
The results for Zn(II) removal from wastewater samples for a contact time between 10
minutes and 24 hours in presence of organic compounds (Zn1) and organic compounds and lead
(Zn2) are showed in Fig. 2.61.
Zn (II) removal efficiency after 10 min was 15.96% and increases to 23.42% during 24h
of investigation. After 24h, the removal efficiency of zinc was slightly lower in case of Pb (II)
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presence. The maximum quantity of zinc adsorbed in presence of organic compunds (Zn1) and
organic compunds and lead (Zn2) is showed in Fig. 2.62.
Fig.2.59. The activated carbon wastewater treatment efficiency for Pb(II) removal during the
experiments.
Fig.2.60. Maximum quantity of lead adsorbed by the activated carbon.
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Fig.2.61. The activated carbon wastewater treatment efficiency for Pb(II) removal during the
experiments.
Fig. 2.62. Maximum quantity of zinc adsorbed by the activated carbon.
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Chemical oxygen demand (COD) represents an important parameter regarding organic
compounds content for wastewater.
As a conclusion the tendency of organic compounds removal was higher than for Zn(II)
about 6 times and almost 1.28 times in comparison with Pb(II), [68].
The highest efficiency removals decrease in the following order: COD (as benzene,
toluene) > Pb >Zn, [68].
Based on the experimental results we sustain the utilization of the powdered carbon as
adsorbants for removal of lead, zinc, benzene and toluene from wastewater.
2.9. Contribution to wastewater treatment by using photocatalysis based titanium dioxide
2.9.1. General considerations
Nanotechnology provides through utilization of semiconductor nanomaterials used in
photocatalysis process an alternative way for eliminating of organic pollutants from wastewater
being able to replace the traditional wastewater technologies having the advantage of pollutants
decomposition instead of their transformation in other potential pollutants.
In the present time, the semiconductor nanomaterials are in various stages of research
and development, each having unique properties and functionalities which could be useful for
example in the depollution of industrial wastewater, surface water or groundwater.
Photocatalysis as one of AOPs (advanced oxidation process) represents a relatively new,
and “green” application of nanotechnology, which have a vast potential in the near future [74].
During the photocatalysis the organic compounds are mineralized up to CO2 and H2O, under the
action of photon energy equal to or greater than the band gap of the semiconductor nanomaterial.
The degradation of the organic pollutants take place through oxidation/reduction
reactions initiated by the dissolved oxygen from aqueous solution, which generates superoxide
ion (O2.-) or hydroperoxyl radicals (HO2
.).
Moreover photocatalysis has shown a great potential of being a sustainable wastewater
treatment technology because of it's low-cost, non-toxicity to the environment use and because
of these aspects is being a sustainable wastewater treatment technology [75].
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TiO2 represents the most used photocatalytic nanomaterial used for the removal of
organic pollutants under the action of UV light.
Some of the advantages which sustain the titanium dioxide as the most popular
photocatalyst are the following: low cost, non-toxicity and high photocatalytic activity. Its main
disadvantage is the limited photocatalytic activity in the visible region. Overcoming this
limitation may be carried out by doping TiO2 with metals and non metallic elements [76].
Various types of organic pollutants can be removed by using photocatalysis from
wastewaters, such as: herbicides, pesticides, and others. In Fig.2.63 is showed the decomposition
of phenol during photocatalysis process [74, 78].
The principle of photocatalysis with TiO2 is represented in the Fig. 2.64 [77].
Fig.2.63 The decomposition of phenol during photocatalysis.
When TiO2 absorb the light with energy equal or greater than the band gap energy, the
electrons (having negative charge) existing in the valence band move to the conduction band,
leaving in the conduction band positively holes (h+) Fig. 2.65 and thus resulting the formation of
electron-hole pairs. These charge carriers reduce and oxidize the pollutants adsorbed on the
surface of photocatalyst [75].
The titanium dioxide is the most studied material for photocatalytic applications [77].
In the present times exist some passing attempts from the laboratory scale to the next
level. One example is a cylindrical reactor for photodegradation of some VOCs (i.e. acetone,
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acetaldehyde, ethanol and toluene) tested for 0.05 g of photocatalyst Fig.2.65. The diameter
reactor is of 200 mm and the effective volume of 5 L [78]. Another example is a photocatalytic
membrane reactor which has two configurations: a) with separated membrane filtration unit and
b) with submerged membrane in the reactor Fig.2.65 [79]
Fig. 2.64 Schematic representation of TiO2 photocatalyst [74,75].
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Fig. 2.65. VOC photodegradation—set-up [74,78].
Fig.2.66. Photocatalytic membrane reactor: (a) slurry reactor followed by a membrane filtration
unit; (b) submerged membrane in a slurry reactor [74,79].
An ideal photocatalyst should present the following properties:
stable in photocatalytic reactions;
chemically and biologically inert;
easy to produce and use;
not expensive;
efficient under sun irradiation;
not dangerous for humans and environment
2.9.2. The investigation of removal methylene blue and diclofenac from wastewater by
photocatalysis based titanium dioxide
In this study presented in this subchapter the experimental part is about testing the TiO2
nanomaterial in photocatalysis for depollution of wasterwater containing diclofenac and
methylene blue (Fig.2.67).
Methylene blue is a widely used dye in textile industry (Fig.2.67.b).
Diclofenac is a common anti-inflammatory drug used as analgesic, antiarthritic and
antirheumatic which shows the highest concentrations detected in effluents (Fig.2.67.1a) [80].
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The measurements of the titanium dioxide efficiency for wastewater treatment were
carried out using UV-Vis spectrophotometer. The experiments were carried out in a
photocatalytic reactor.
The preliminary experimental results obtained are presented in Fig.2.67 a and b. The
highest removal efficiency was obtained for the removal of diclofenac from wasterwater.
In the case of the diclofenac removal from water by photocatalysis the efficiency was
(98%) whereas the metyleneblue removal from water (83%). Moreover the removal of
diclofenac from water was done in a shorter time (less than 160 min) than in the case of
methylene blue (aprox. 400 min), [74].
In the case of diclofenac removal investigation from water using TiO2 after 400 min still
was observed a slight increase of depollution efficiency (η) up to 700 min of measurement after
which it remained constant. After only 20 minutes of investigation, 97 % of diclofenac was
removed from the water.
As a conclusion, the utilization of TiO2 nanomaterial in photocatalysis had a high
efficiency of removing both tested pollutants, but the highest (97%) one was obtained in case of
diclofenac investigation. Moreover, there was a significant difference regarding the time required
for each pollutant removal from water meaning that while diclofenac was immediately removed
by photocatalysis using titanium dioxide nanomaterial, in the case of methyleneblue, it took
more time to achieve a high effective removal.
a)
b)
Fig. 2.67. The structural formula of a) diclofenac and methylene blue b).
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0
10
20
30
40
50
60
70
80
90
0 200 400 600 800 1000 1200
T[min]
η[%
]
a)
b)
Fig. 2.68 The variation of removal efficiency in time for a) diclofenac and b) methylen
blue during the photocatalysis process, [74].
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Chapter 3. PLAN OF SCIENTIFIC, PROFESSIONAL AND ACADEMIC
DEVELOPMENT IN THE FUTURE
After a scientific activity, uninterrupted, for 11 years, I shall continue the research on
the application of nanotechnology in environmental engineering field, both in order to find the
best adsorbents from nanomaterials class, as well as the best catalysts to degrade and remove the
pollutants found in wastewater. Also, I will start the research on other scientific themes that are
currently at the beginning, such as: levigates treatment, wastewater treatment using plants, etc.
In the future, I will establish the research topics depending on their social importance,
considering the evolution of scientific research over time.
The basis of the future research activities is represented by the experience developed for
publishing ISI articles or within various projects, as responsible or member of the research team
represents.
The scientific results that will be obtained in the future will be published in ISI quoted
journals, books and will sustain the winning of international and national research projects.
Till the present the scientific studies were possible with the help of multidisciplinary
research team, from many research institutes and universities. In the future I intend to continue
the existing collaborations and also to build many others, because only by collaborations can
result research innovations at a high scientific level.
The existence of the Laboratory of Environment Quality Analysis from Faculty of
Biotechnical Systems Engineering of University Politehnica of Bucharest coordinated by me
having an infrastructure suitable for doing doctoral studies, together with my professional
competences and abilities acquired so far, allowed me to create a suitable frame for sharing the
scientific experience and coordinating the students for sustaining their PhD thesis. This
represents the principal motivation for which I appreciate that I have capacity and competence
for coordination doctoral activities.
Regarding the scientific development plan I intend to work within international
programs such as Erasmus with foreign students from universities having the similar research
field for developing a good international collaboration that can sustain the gaining of
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international research projects. Also, I will use my international prestige to attract foreign
doctoral students for doctoral theses in co- tutelage.
I will continue to participate to national and international competitions for research
grants and I will enhance the connections with partners from the country and abroad with whom
I worked before. I will conduct a constant activity of attracting extra budgetary funds through
research funded by economic agents and also from European funds projects by implication in
high-level scientific research.
I will try to contribute to the development of a pole of excellence in environmental
engineering in which will be involved reference persons in the field, from the country and
abroad, young students, master and PhD students.
Regarding the scientific objective in the future, I will continue to work in
nanotechnology field, obtaining and studying new nanomaterials having special properties
suitable for applying in environmental engineering field for replacing old and inefficient
environment technologies with new and efficient ones. Also, my future scientific research will
have a positive effect on improving life quality by preventing reaching in the environment and in
human body of hazardous substances (such as heavy metals). Another future scientific objective
will be industrial transfer of the new developed nanomaterials and technologies.
Some of my future research directions, according to the scientific domain that require a
sustained development with respect to international trends and may represent subjects of PhD
theses are the following:
Wastewater treatment using nanotechology: through nanotechnology by
synthesis and application of new nanomaterials with high potential for pollutants removal.
Nanotechnology exhibits potential to improve and develop new wastewater treatment
technologies, both through direct applications of nanomaterials for preventing reaching into
environment and/or removing pollutants.
The nanotechnology application benefits derived from the nanomaterials characteristics:
enhanced reactivity, huge surface area, non-toxicity, reusability, regenerability etc.
In this context, nanomaterials with magnetic properties will continue to be one of the
attracted nanomaterials, together with zeolites, titanium dioxide, etc.
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This research goal mach very well with stringent wastewater discharge standards which
require the necessity to improved wastewater treatment performance.
Also, I will continue the research regarding the new and promising technology of water
treatment technology named photocatalysys based on “Advanced Oxidation Processes (AOPs)”
which consist of in situ generation of highly reactive species (i.e. H2O2,OH*, O2*-, O3) for
mineralization of pollutant organic compounds, water pathogens by using semiconductor
nanomaterials as catalysts (TiO2, ZnO2, CeO2).
Wastewater treatment using phytoremediation: by utilization of some plants
which have the ability to degrade, transform or absorb and store toxic substances found in water.
By approaching such a research subject, some mechanisms of heavy metals intake into plants
could be develop by using new experimental methods and so one.
Waste reuse by identification, characterization and processing of some valuable
by-products in order to synthesize nanomaterials with valuable properties (adsorption, ionic
exchange or oxidative properties). Some of the advantages of this research direction are:
decreasing pressure on natural resources, a good waste management. For example, scrap metals
can be recovered from ash, thereby avoiding mining and the consumption of primary metals,
while the mineral fraction can be utilized within the construction industry, substituting natural
aggregates and other natural materials.
Leachate treatment: is a major environmental concern associated of landfills and
the generation and eventual discharge of leachate into the environment. The objectives are:
finding relevant measures to reduce the production of leachate and methods to treat leachate
which include new nanomaterials for pre-treatment and/or methods to enhance the rate of
stabilisation/mineralisation.
All above mentioned research topics are in accordance with international level in the
field of environmental engineering. Thus, specialized publications will consist in scientific
articles, targeted educational journals and especially high impact factor journals.
The academic work will be based on the desire to transfer the knowledge gained till
now to future generations, targeting in the same time, the correlation with the labor market.
Cristina Ileana COVALIU Habilitation thesis
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The results of research activities and permanent professional training will have to be
found as elements of added value in courses, seminars and laboratory activities with the students.
Consistently, I will pursue the improvement and perfecting courses from didactical
norm, paying attention to scientific content and the modern educational methods and tools used
in teaching activities.
During the development of didactical career I will considered: the students development
in order to increase their independent thinking, their intellectual and practical spirit of initiative,
creativity and originality.
Academic career development on medium and long-term will be supported by:
ensuring international visibility of the didactic career;
achieving national and international collaborations;
involvement in projects and programs dedicated to academics;
conducting academic exchanges with foreign universities involving students,
graduates, PhD students and professors.
guiding the students through coordination of diploma and dissertation thesis;
utilization of a student’s evaluation system more objective;
contributions to curriculum development by proposing new courses and practical
applications;
diversification of knowledge cumulated till now by attending new training
courses.
All future proposed objectives will be fulfilled if we take into account my professional
activity carried out until now.
In parallel with the academic work I intend to carry out further scientific work through
which I can contribute to the improvement of the infrastructure of laboratory (Analysis of
environment quality) coordinated by me within the Department of Biotechnical Systems, Faculty
of Biotechnical Engineering.
I will focus even more on publishing articles in ISI journals in ISI Thomosn Reuters, in
order to increase the visibility of own research results in the international scientific community.
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