Embed Size (px)
Citation preview
Research ArticleReceived: 16 October 2017 Revised: 21 December 2017 Accepted article published: 3 January 2018 Published online in Wiley Online Library:
(wileyonlinelibrary.com) DOI 10.1002/jctb.5565
Decontamination of Cr(VI) by grapheneoxide@TiO2 in an aerobic atmosphere: effectsof pH, ferric ions, inorganic anions, and formate
Xinjiang Hu,a,b* Yunlin Zhao,a,b* Hui Wang,c Xiaoxi Cai,e,f Xi Hu,a
Chunfang Tang,a Yunguo Liue,f and Yuanxiu Yangd
Abstract
BACKGROUND: In this study, a graphene oxide@TiO2 composite (GO/TiO2) was prepared and characterized by SEM, EDX, XRD,nitrogen adsorption–desorption isotherm, and XPS. Photocatalytic reduction and removal of Cr(VI) using this composite inan aerobic atmosphere were studied under UV irradiation. The effects of pH, ferric ions, inorganic anions, and formate wereinvestigated systematically.
RESULTS: The Cr(VI) reduction rate decreased with increasing solution pH. The presence of ferric ions in the system improvedthe photocatalytic reduction process. The effects of SO4
2− and PO43− on the process were higher than those of Cl− and NO3
−.Formate slightly inhibited adsorption of Cr(VI), while it improved Cr(VI) reduction. GO/TiO2 has good stability and it maintainedfull photoreduction activity for at least three cycles.
CONCLUSION: The results indicated that GO/TiO2 can thermodynamically reduce Cr(VI) to Cr(III) under UV light. Environmentalconditions and wastewater characteristics (e.g. pH, ferric ions, inorganic anions, and formate) can influence the decontaminationprocess because they affect the interactions between chromium ions and GO/TiO2 and alter the electron-transfer pathways. Theresults suggest that the GO/TiO2 is an attractive material for removing hexavalent chromium from water using a photocatalyticprocess.© 2018 Society of Chemical Industry
Supporting information may be found in the online version of this article.
Keywords: hexavalent chromium; graphene oxide@tio2; ferric ions; inorganic anions; formate
ABBREVIATIONSEnergy dispersive X-ray spectrometer (EDX)Graphene oxide (GO)Graphene oxide@TiO2 composite (GO/TiO2)International Agency for Research on Cancer (IARC)Scanning electron microscopy (SEM)Titanium dioxide (TiO2)X-ray diffraction (XRD)X-ray photoelectron spectroscopy (XPS)
INTRODUCTIONMany industrial processes, such as electroplating, leather tan-ning, printing and dyeing, metal finishing, and textile production,generate large quantities of wastewater containing various con-centrations of chromium.1,2 Cr exists in two stable oxidation statesin natural water and wastewater: Cr(VI) and Cr(III).3 Cr(VI) is highlytoxic to human life and the aqueous environment because of itshighly mobile and nonbiodegradable nature,4 and it has been clas-sified as ‘carcinogenic to humans (Group 1)’ by IARC (InternationalAgency for Research on Cancer).4 In contrast, Cr(III) is a relatively
less-toxic state and easy to precipitate or adsorb as Cr(OH)3.4,5
∗ Correspondence to: X Hu or Y Zhao, College of Environmental Science andEngineering, Central South University of Forestry and Technology, Changsha410004, P.R. China. E-mail: [email protected] (Hu); [email protected](Zhao)
a College of Environmental Science and Engineering, Central South University ofForestry and Technology, Changsha, P.R. China
b Faculty of Life Science and Technology, Central South University of Forestry andTechnology, Changsha, P.R. China
c Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences,Changsha, P. R. China
d College of Natural Resources and Environment, South China AgriculturalUniversity, Guangzhou, P.R. China
e College of Environmental Science and Engineering, Hunan University,Changsha, P.R. China
f Key Laboratory of Environmental Biology and Pollution Control (HunanUniversity), Ministry of Education, Changsha, P.R. China
J Chem Technol Biotechnol (2018) www.soci.org © 2018 Society of Chemical Industry
1Scientific RepoRts | 6:34378 | DOI: 10.1038/srep34378
www.nature.com/scientificreports
Statistical Analysis of Main and Interaction Effects on Cu(II) and Cr(VI) Decontamination by Nitrogen–Doped Magnetic Graphene OxideXinjiang Hu1,2,3,4, Hui Wang3,4,5 & Yunguo Liu3,4
A nitrogen–doped magnetic graphene oxide (NMGO) was synthesized and applied as an adsorbent to remove Cu(II) and Cr(VI) ions from aqueous solutions. The individual and combined effects of various factors (A: pH, B: temperature, C: initial concentration of metal ions, D: CaCl2, and E: humic acid [HA]) on the adsorption were analyzed by a 25−1 fractional factorial design (FFD). The results from this study indicated that the NMGO had higher adsorption capacities for Cu(II) ions than for Cr(VI) ions under most conditions, and the five selected variables affected the two adsorption processes to different extents. A, AC, and C were the very important factors and interactions for Cu(II) adsorption. For Cr(VI) adsorption, A, B, C, AB, and BC were found to be very important influencing variables. The solution pH (A) was the most important influencing factor for removal of both the ions. The main effects of A–E on the removal of Cu(II) were positive. For Cr(VI) adsorption, the main effects of A and D were negative, while B, C, and E were observed to have positive effects. The maximum adsorption capacities for Cu(II) and Cr(VI) ions over NMGO were 146.365 and 72.978 mg/g, respectively, under optimal process conditions.
Graphene is an attractive two-dimensional (2D) carbon material with a honeycomb structure and a thickness of one atom, where the carbon atoms are sp2-hybridized1–3. Graphene oxide (GO) is a precursor for graphene synthesis by chemical or thermal reduction processes, and is a specific branch of graphene research4. GO has a wide range of functional groups, such as hydroxyl, epoxide, carbonyl, and carboxyl, which makes it strongly hydrophilic, allowing it to readily swell and disperse in water5. In recent years, GO has emerged as a promising material for the removal of metal ions6–8 and organic contaminants3,9,10 from aqueous solutions. However, it is difficult to remove the suspended GO from the water after the adsorption process due to its high hydrophilic-ity, which possibly limits the direct application of GO-based materials in waste water treatment. The functional groups and large specific surface area of GO provide an excellent platform for loading magnetic nanoparticles11. The integration of magnetic properties into GO can combine the advantages of high adsorption capability with the merit of easy separation8,11,12.
The adsorption behavior of GO can be altered by changing the surface properties of the GO sheets by chemi-cal functionalization. Recently, efforts have been made to synthesize chemically modified GO sheets by grafting organic moieties onto GO13. Examples include the grafting of polyaniline14, EDTA8,15, and β -cyclodextrin16 onto GO to improve its adsorption ability and selectivity for metal ions. As an amine derivative, diethylenetriamine (DETA) has two terminal amine groups and one central imine group, all of which are good donor groups for the formation of stable complexes with various metal ions17,18. Therefore, the introduction of DETA in a GO-based
1College of Environmental Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, P. R. China. 2College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, P. R. China. 3College of Environmental Science and Engineering, Hunan University, Changsha 410082, P. R. China. 4Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, P. R. China. 5Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha, 410205, P. R. China. Correspondence and requests for materials should be addressed to X.H. (email: [email protected]) or Y.L. (email: [email protected])
Received: 25 April 2016
Accepted: 08 September 2016
Published: 03 October 2016
OPEN
Journal of Colloid and Interface Science 495 (2017) 68–77
Contents lists available at ScienceDirect
Journal of Colloid and Interface Science
journal homepage: www.elsevier .com/locate / jc is
Regular Article
Decontamination of tetracycline by thiourea-dioxide–reduced magneticgraphene oxide: Effects of pH, ionic strength, and humic acidconcentration
http://dx.doi.org/10.1016/j.jcis.2017.01.0750021-9797/� 2017 Elsevier Inc. All rights reserved.
⇑ Corresponding author at: College of Natural Resources and Environment, SouthChina Agricultural University, Guangzhou 510642, PR China (X. Hu).
E-mail addresses: [email protected] (X. Hu), [email protected] (L. Cui).
Yuanxiu Yang a, Xinjiang Hu a,b,c,⇑, Yunlin Zhao b,c, Lihua Cui a,⇑, Zhujian Huang a, Jianliang Long a,Jiawen Xu a, Jianbin Deng a, Cuiyu Wu a, Wenwei Liao a
aCollege of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, PR ChinabCollege of Environmental Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, PR Chinac Faculty of Life Science and Technology, Central South University of Forestry and Technology, Changsha 410004, PR China
g r a p h i c a l a b s t r a c t
a r t i c l e i n f o
Article history:Received 21 October 2016Revised 18 January 2017Accepted 22 January 2017Available online 24 January 2017
Keywords:TetracyclineGraphene oxide nanosheetsThiourea dioxideChemical interaction
a b s t r a c t
Thiourea-dioxide–reduced magnetic graphene oxide (TDMGO) was successfully prepared as an efficientadsorbent for the removal of tetracycline (TC) from aqueous solutions via strong adsorptive interactions.The composite was characterized by SEM, TEM, EDS, TGA, FT-IR, XPS, XRD and VSM. The effects of vari-ables such as the pH, TC concentration, and temperature were successfully analyzed. The kinetics andisothermal parameters were described well by pseudo-second-order and Langmuir isotherm models,respectively, and the maximum adsorption capacity (qm) of TDMGO for TC calculated from theLangmuir isotherm was 1233 mg/g at 313 K. The removal of TC onto TDMGO, as indicated by the thermo-dynamic parameters, was spontaneous and endothermic. The removal performance was slightly affectedby the solution pH. The presence of NaCl in the solution facilitated TC adsorption, and the optimumadsorption capacity was obtained when the NaCl concentration was >0.001 M. The adsorption capacitydecreased slightly with increasing humic acid concentration. In addition, the adsorbent could be regen-erated and reused. Based on these results, TDMGO is a promising adsorbent for the efficient removal of TCantibiotics from aquatic environments for pollution treatment.
� 2017 Elsevier Inc. All rights reserved.
International Journal of
Environmental Research
and Public Health
Article
Efficient Removal of Tetracycline from AqueousMedia with a Fe3O4 Nanoparticles@graphene OxideNanosheets Assembly
Xinjiang Hu 1,2,3,*, Yunlin Zhao 1,2,*, Hui Wang 4, Xiaofei Tan 5,6, Yuanxiu Yang 3
and Yunguo Liu 5,6
1 College of Environmental Science and Engineering, Central South University of Forestry and Technology,Changsha 410004, China
2 Faculty of Life Science and Technology, Central South University of Forestry and Technology,Changsha 410004, China
3 College of Natural Resources and Environment, South China Agricultural University,Guangzhou 510642, China
4 Institute of Bast Fiber Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China;[email protected] (H.W.); [email protected] (Y.Y.)
5 College of Environmental Science and Engineering, Hunan University, Changsha 410082, China;[email protected] (X.T.); [email protected] (Y.L.)
6 Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education,Changsha 410082, China
* Correspondence: [email protected] (X.H.); [email protected] (Y.Z.);Tel.: +86-731-8562-3096 (X.H. & Y.Z.)
Received: 16 October 2017; Accepted: 28 November 2017; Published: 1 December 2017
Abstract: A readily separated composite was prepared via direct assembly of Fe3O4 magneticnanoparticles onto the surface of graphene oxide (GO) (labeled as Fe3O4@GO) and used as anadsorbent for the removal of tetracycline (TC) from wastewater. The effects of external environmentalconditions, such as pH, ionic strength, humic acid (HA), TC concentration, and temperature, on theadsorption process were studied. The adsorption data were analyzed by kinetics and isothermalmodels. The results show that the Fe3O4@GO composite has excellent sorptive properties andcan efficiently remove TC. At low pH, the adsorption capacity of Fe3O4@GO toward TC decreasesslowly with increasing pH value, while the adsorption capacity decreases rapidly at higher pHvalues. The ionic strength has insignificant effect on TC adsorption. The presence of HA affects theaffinity of Fe3O4@GO to TC. The pseudo-second-order kinetics model and Langmuir model fit theadsorption data well. When the initial concentration of TC is 100 mg/L, a slow adsorption processdominates. Film diffusion is the rate limiting step of the adsorption. Importantly, Fe3O4@GO hasgood regeneration performance. The above results are of great significance to promote the applicationof Fe3O4@GO in the treatment of antibiotic wastewater.
Keywords: tetracycline; antibiotic wastewater; Fe3O4@GO; humic acid; ionic strength
1. Introduction
In recent years, pharmaceuticals and personal care products (PPCPs) have been frequentlydetected in the environment, and they have attracted scrutiny as a new type of pollutant that threatensthe biosphere and human health [1,2]. Antibiotics are one of the main PPCPs. Since penicillinwas discovered in 1929, antibiotics have been used extensively to improve the health of animalsand humans, and antibiotics have also been used as growth promoters for livestock, bees, aquaticproducts and other aquaculture industries [3,4]. Globally, the average total annual use of antibiotics is
Int. J. Environ. Res. Public Health 2017, 14, 1495; doi:10.3390/ijerph14121495 www.mdpi.com/journal/ijerph
RESEARCH ARTICLE
Ethylenediamine grafted to graphene
oxide@Fe3O4 for chromium(VI)
decontamination: Performance, modelling,
and fractional factorial design
Xinjiang Hu1,2,3*, Jiawen Xu3, Cuiyu Wu3, Jianbin Deng3, Wenwei Liao3, Yuxiang Ling3,
Yuanxiu Yang3, Yina Zhao3, Yunlin Zhao1,2*, Xi Hu1*, Hui Wang4, Yunguo Liu5,6
1 College of Environmental Science and Engineering, Central South University of Forestry and Technology,
Changsha, P.R. China, 2 Faculty of Life Science and Technology, Central South University of Forestry and
Technology, Changsha, P.R. China, 3 College of Natural Resources and Environment, South China
Agricultural University, Guangzhou, P.R. China, 4 Institute of Bast Fiber Crops, Chinese Academy of
Agricultural Sciences, Changsha, P.R. China, 5 College of Environmental Science and Engineering, Hunan
University, Changsha, P.R. China, 6 Key Laboratory of Environmental Biology and Pollution Control (Hunan
University), Ministry of Education, Changsha, P.R. China
* [email protected], [email protected] (XJH); [email protected] (YZ); [email protected] (XH)
Abstract
A method for grafting ethylenediamine to a magnetic graphene oxide composite (EDA-
GO@Fe3O4) was developed for Cr(VI) decontamination. The physicochemical properties of
EDA-GO@Fe3O4 were characterized using HRTEM, EDS, FT-IR, TG-DSC, and XPS. The
effects of pH, sorbent dose, foreign anions, time, Cr(VI) concentration, and temperature on
decontamination process were studied. The solution pH can largely affect the decontamination
process. The pseudo-second-order model is suitable for being applied to fit the adsorption pro-
cesses of Cr(VI) with GO@Fe3O4 and EDA-GO@Fe3O4. The intra-particle diffusion is not
the rate-controlling step. Isotherm experimental data can be described using the Freundlich
model. The effects of multiple factors on the Cr(VI) decontamination was investigated by a 25−1
fractional factorial design (FFD). The adsorption process can significantly be affected by the
main effects of A (pH), B (Cr(VI) concentration), and E (Adsorbent dose). The combined factors
of AB (pH ×Cr(VI) concentration), AE (pH × Adsorbent dose), and BC (Cr(VI) concentration ×Temperature) had larger effects than other factors on Cr(VI) removal. These results indicated
that EDA-GO@Fe3O4 is a potential and suitable candidate for treatment of heavy metal
wastewater.
Introduction
Heavy metal pollution is a current worldwide environmental concern because it can harm eco-
systems and endanger human health. Since the industrial revolution, chromium has been
widely used in electroplating, tanning, dying, smelting, and corrosion protection [1–3]. Cr
(VI), one form of chromium, is very harmful to most organisms due to its mammalian toxicity
PLOS ONE | https://doi.org/10.1371/journal.pone.0187166 October 30, 2017 1 / 14
a1111111111
a1111111111
a1111111111
a1111111111
a1111111111
OPENACCESS
Citation: Hu X, Xu J, Wu C, Deng J, Liao W, Ling Y,
et al. (2017) Ethylenediamine grafted to graphene
oxide@Fe3O4 for chromium(VI) decontamination:
Performance, modelling, and fractional factorial
design. PLoS ONE 12(10): e0187166. https://doi.
org/10.1371/journal.pone.0187166
Editor: Yogendra Kumar Mishra, Institute of
Materials Science, GERMANY
Received: August 10, 2017
Accepted: October 14, 2017
Published: October 30, 2017
Copyright: © 2017 Hu et al. This is an open access
article distributed under the terms of the Creative
Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in
any medium, provided the original author and
source are credited.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
files.
Funding: This study was financially supported by
the National Natural Science Foundation of China
(Grant No. 5160820 to Xinjiang Hu), the Project
funded by China Postdoctoral Science Foundation
(Grant No. 2017M610513 Xinjiang Hu), the
Research Foundation of Education Department of
Hunan Province, China (Grant No. 17K105 to
Xinjiang Hu), the Natural Science Foundation of
