Eco-EfficientBiosorbentBasedon Leucaenaleucocephala ...downloads.hindawi.com/journals/bca/2019/2814047.pdf · Leucaena leucocephala as a potential source of poly-phenolsisafast-growing,tropical,leguminoustreespecies

Research ArticleEco-Efficient Biosorbent Based on Leucaena leucocephalaResidues for the Simultaneous Removal of Pb(II) and Cd(II)Ions from Water System Sorption and Mechanism

C A Cima-Mukul1 Youness Abdellaoui2 Mohamed Abatal 3 Joel Vargas 4

Arlette A Santiago5 and Jesus Alberto Barron-Zambrano1

1Facultad de Ingenierıa Quımica Universidad Autonoma de Yucatan Periferico Norte Kilometro 335Chuburna de Hidalgo Inn Merida Yucatan 97203 Mexico2Facultad de Ingenierıa Universidad Autonoma de YucatanAv Industrias no Contaminantes por Periferico Norte Apartado Postal 150 Cordemex 97310 Merida Yucatan Mexico3Facultad de Ingenierıa Universidad Autonoma del Carmen 24155 Ciudad del Carmen Campeche Mexico4Instituto de Investigaciones en Materiales Unidad Morelia Universidad Nacional Autonoma de MexicoAntigua Carretera a Patzcuaro No 8701 Col Ex Hacienda de San Jose de la Huerta 58190 Morelia Michoacan Mexico5Escuela Nacional de Estudios Superiores Unidad Morelia Universidad Nacional Autonoma de MexicoAntigua Carretera a Patzcuaro No 8701 Col Ex Hacienda de San Jose de la Huerta 58190 Morelia Michoacan Mexico

Correspondence should be addressed to Mohamed Abatal mabatalpampanounacarmx

Received 12 July 2018 Revised 14 October 2018 Accepted 12 November 2018 Published 2 January 2019

Academic Editor Imre Sovago

Copyright copy 2019 C A Cima-Mukul et al -is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Leucaena leucocephala is a potential source of polyphenols widely available in southern Mexico -is work highlights the ex-traction of polyphenols from Leucaena leucocephala leaves waste (LLEPs) and the evaluation of their efficiency to remove thesingle and multicomponent Pb(II) and Cd(II) metal ions from aqueous solutions Batch test conditions were carried out toexamine the effects of contact time initial metal ion concentration and adsorbent dosage on the biosorption process -e surfacetextures and the composition of the LLEP biosorbent was characterized using pH of point of zero charge (pHPZC) attenuated totalreflectance Fourier transform infrared (ATR-FTIR) and matrix-assisted laser desorptionionization time of flight (MALDI-TOF)mass spectrometry respectively Further analysis using ATR-FTIR after adsorption contact of biosorbent was also investigated-e highest Langmuir saturationmonolayer adsorption capacity qm for the removal of Pb(II) by LLEPs was obtained as 2551 and2155mgg in mono- and bimetal solutions respectively-e pseudo-second-order model provided the best fit for the kinetic dataobtained for the removal of Pb(II) Cd(II) and their mixture and the k2 values depend on the adsorbent mass -is implied thatthe chemisorption process might be the mechanism of the solute ions-LLEPs interaction in this study Furthermore nearly 100removal of lead and cadmium individually and 95 of their mixture was found using 09 g of LLEPs

1 Introduction

Biosorption has emerged as a potential and promising so-lution to remove toxic heavy metals from water andwastewater and is also considered as an alternative processto the conventional methods such as those based on ionexchange precipitation membranes and electrochemistryprocesses widely applied in industrial effluents treatments

which are very costly and have many limitations [1 2]Recent research studies have directed attention to bio-sorption processes owing to the high metal-binding ca-pacities of various biosorbent materials [3] Algae- fungi-agricultural- and forestry-based materials have proved to beeco-efficient and environmentally friendly sorbent for heavymetals [3 4] Diverse waste materials have been used as low-cost bioadsorbents for heavy metals from water solutions in

HindawiBioinorganic Chemistry and ApplicationsVolume 2019 Article ID 2814047 13 pageshttpsdoiorg10115520192814047

particular for lead Pb(II) and cadmium Cd(II) ions theyhave used fruit shell [5] algae eggshell rice husk sawdust[6] corn cob [7] olive oil by-products [8] livestock waste[9] forest by-products and waste [10ndash14]

-e use of polyphenols as biosorbents has been widelystudied in water and wastewater treatment to remove heavymetals due to the large availability of these compounds inplant material that can be easily extracted from agriculturalwaste using a green solvent Several studies have been carriedout on the extraction of polyphenols from various plantsusing different solvents showing that the structure yieldrecovery and type of phenolic compounds depend on theplant nature and extraction solvents [15]Nepeta melissifoliaPhlomis lanata Ilex paraguariensis and Origanum vulgaredemonstrated a high total phenol content with more than150mg gallic acid equivalent (GAE)g dried samplewhereas Geranium purpureum Matricaria chamomilla andLavandula vera showed a content less than 7mg GAEgdried sample [16 17]

Leucaena leucocephala as a potential source of poly-phenols is a fast-growing tropical leguminous tree speciesthat belongs to Mimosaceae native to southern Mexico(Yucatan Peninsula) and then extends to Nicaragua in-cluding Guatemala Honduras El Salvador and northernCentral America [18 19] Leucaena leucocephala namedthe miracle tree is considered as a multipurpose treespecies for its wider usages as timber and firewood in pulpand paper industry [20] also as a biomass and proteinsource for animal feed with yield production of 50 ton haminus1

yearminus1 under Mediterranean conditions [21] -eir leavesand seeds are composed mainly of lipids crude proteincarbohydrates mimosine saponins coumarins flavonoidscardiac glycosides steroids and phenols and have a highcondensed tannin content [18 22 23] Recently Abu Zarinet al reported the total phenolic content in Leucaenaleucocephala hybrid-Rendang from its crude extract to be321mg GAEg [22]

Polyphenols extracted from plants are characterizedby the abundant phenolic hydroxyls that are capable ofchelating with transition-metal ions especially for thosemetal species with d-orbits [24] Because of the strongchelating ability of phenolic hydroxyls towards transitionmetals the polyphenol-based adsorbent showed to bepotential and efficient sorbent for the removal of Pb(II) andCd(II) from aqueous solutions In this context Copelloet al studied the application of hybrid low-cost SiO2polyphenol matrices as a bioadsorbent for Pb(II) Cr(III)and Cr(VI) [16] Waseem et al have used biomass derivedfrom of Acacia nilotica leaves as an adsorbent material forthe removal of cadmium and lead and they found themaximum adsorption to be 251mgg and 499mgg forPb(II) and Cd(II) respectively [13] Recently Zhang el alhave evaluated the effectiveness of Sagittaria trifolia L stalkplant to remove Pb(II) Cd(II) and Cr(III) [14] Howeverthe maximum adsorption capacities of Pb(II) reported byJayaram and Prasad were 45454mgg using Prosopisjuliflora as a source of polyphenols [25]

However to the best of our knowledge there are noreports of polyphenols extracted from L leucocephala as

potential metal removers from mono- and multicomponentsystems Indeed L leucocephala residues have no applica-tion for human consumption here in Mexico therefore it isexpected that it will remain a waste that could be considereda sustainable low-cost source of polyphenol adsorbents-erefore the aim of this work was to describe the simul-taneous sorption mechanism of Cd and Pb from aqueoussolution using L leucocephala-extracted polyphenols(LLEPs) considering various experimental parameters suchas contact time adsorbent dosage and initial concentration

2 Materials and Methods

21 Chemicals Deionized water (182MΩcmminus1 conduc-tivity) was used for all dilutions and to prepare the syntheticstock solutions of Pb(II) and Cd(II) using PbCl2 (98Aldrich) and CdCl225H2O (799 JT Baker) salts re-spectively Methanol (70) FolinndashCiocalteu reagent andNa2CO3 were used in the procedures for extraction andquantification of total polyphenols

22 Plant Preparation Leaf residues of Leucaena leucoce-phala tree were collected from the campus area of theAutonomous University of Ciudad Del Carmen identified byour botanist Dr Enrique Lopez washed with deionizedwater dried at 70degC and then stored in glass bottles to beused for the polyphenolsrsquo extraction

23 Extraction of Polyphenols -e extraction method ofpolyphenols was described by Scalbert et al 15 g of plant leafsamples was extracted three times with 300mL of 80methanol solution under magnetic agitation at room tem-perature (3 times 2 h) -e supernatant was collected after eachextraction by filtration and then the sample solution wasused for polyphenol quantification -e methanol wasevaporated under reduced pressure and then the poly-phenols were dried and ready to be used in the sorptionprocess [26]

24TotalPolyphenolicContent Total polyphenolic contentswere determined according to the method of Scalbert et al[26] 05mL of a 200-fold diluted aqueous extract wasmixed with 25mL of 10-fold diluted FolinndashCiocalteuphenol reagent and incubated for 1min before 2mL of75 Na2CO3 was added -e mixture was allowed to standfor 15min at 50 degC in a water bath and then transferred intocold water Samples absorbance was measured at 760 nm ina UV-Vis spectrophotometer (Evolution 220) after 30minof incubation A gallic acid aqueous solution (80 microgmL)was used for calibration and the final results wereexpressed as mg gallic acid equivalent (GAE) per g of dryweight (DW)

25 Characterization Methods

251 Point of Zero Charge (pHPZC) -e pH of the point ofzero charge (pHPZC) of LLEPs has been described as

2 Bioinorganic Chemistry and Applications

following 010 g of each adsorbent with 50mL of 001MNaCl adjusted to different initial pH values (pH 2 4 5 68 10 and 12) -e suspensions were allowed to equilibratefor 24 h under agitation decanted and the final pH valuesof each remaining solution were measured using the pHmeter -ermo Scientific (ORION 3-Star pH Benchtop)-e experiments were conducted in duplicate and themeasurement temperature was set at 250 plusmn 01degC -epHPZC of the biosorbent was determined from the point ofintersection of the curves obtained in the plot of pHinitial vspHfinal

252 MALDI-TOF Mass Spectroscopy Matrix-assisted laserdesorptionionization time of flight (MALDI-TOF) massspectrometry was performed on a BrukerMicroflexMALDI-TOF mass spectrometer (Bruker Daltonik Germany)equipped with a nitrogen laser that operates at λ 337 nm-e irradiation target was prepared from a THF solutionusing 2 5-dihydroxy benzoic acid (DHB) as matrix -esample and matrix were combined at a ratio of 2 5 vv -emeasurement was carried out in the linear mode with anacceleration voltage of 20 kV to yield the resulting massspectrum with a pretty good reproducibility regarding boththe ion peaks and their positions

253 ATR-FTIR Spectroscopy Attenuated total reflectanceFourier transform infrared (ATR-FTIR) spectra were col-lected using a -ermo Scientific Nicolet iS10 FTIR spec-trometer fitted with a -ermo Scientific Smart iTRtrade ATRaccessory with a diamond crystal Data were collected by anattached computer running OMNIC software Liquidsamples were added directly onto the crystal for analysis atroom temperature without applying pressure -irty-twospectra were obtained and coadded for each sample coveringa range of 4000ndash650 cmminus1 at a spectral resolution of 4 cmminus1A background spectrum was obtained by collecting 32coadded scans following cleaning of the diamond crystalwith acetone

26 Sorption Process

261 Kinetic For the sorption kinetics of Pb(II) and Cd(II)by LLEPs batch mode experiment was performed 01 g ofLLEPs was added to 10mL of Pb(II) or Cd(II) solutions at100mgL -e mixtures were placed in centrifuge tubes andshaken in a rotary shaker for different time intervals (30minto 24 h) After each specific contact time the tubes werecentrifuged at 3500 rpm for 10min -e concentration oflead and cadmium metals was determined using a flameatomic absorption spectroscopy (AAS -ermo ScientificiCE 3000 Series) In order to ensure the truthfulness ofexperiment results all experiments were duplicated -eamount of metal ions adsorbed per unit mass of the sorbentwas evaluated by using the following equation

qt C0 minusCt( 1113857

mV (1)

where C0 (mg Lminus1) and Ct (mg Lminus1) are the initial and finalmetal concentration in solution respectively V is the vol-ume of aqueous phase (L) and m is the mass of LLEPs (g)

262 Isotherms For isotherms 01 g of LLEPs was mixedwith 10mL of aqueous solution of Pb(II) and Cd(II) withknown initial concentrations (10ndash500 mgLminus1) -e mixtureswere shaken for 24 h in a rotary shaker at room temperatureAt the end of equilibrium time the suspensions werecentrifuged at 3500 rpm for 10min and the concentration oflead metals was analyzed by AAS

263 Influence of LLEPs Dosage In order to study the effectof LLEPs dosage on the Pb(II) and Cd(II) removal efficiency10mL of Pb(II)and Cd(II) solutions with an initial con-centration of 100mgL was mixed in centrifuge tubescontaining 01 g 05 g and 09 g of LLEPs-emixtures wereshaken for 30 60 180 and 360min At the end of eachspecific contact time the mixtures were centrifuged and themetallic ions were determined by AAS

3 Results and Discussions

31 Total Phenol Content In order to determine the totalphenolic content the curves of calibration were obtainedusing known quantities of commercial gallic acid Totalphenolic content of the L leucocephala extracts weremeasured using the FolinndashCiocalteu method in terms ofgallic acid equivalent -e total polyphenols content ofmethanol extracts of Leucaena leucocephalawaste was foundto be 371 plusmn 01mg of gallic acidg of dried extract-is resultwas higher than the one reported from Leucocephala hybrid-Rendang [22]

32 Point of Zero Charge (pHPZC) Figure 1 shows the pointof zero charge results of LLEPs -e pHPZC was found at pH 510 plusmn 001 furthermore a shift of the final pH (pHf) of thesolution toward the slightly acidic region was observedwhich could be attributed to the amphoteric character of thepolyphenols surface that approximates the pH of a solutionto their PZC value [27] -e effect of the amphotericcharacter of the surface can be observed in slight increase inthe pHf on the point of pHi 5 However with respect to thesurface charge of LLEPs above the pHPZC (pH gt 51) theadsorbent surface is negatively charged which could pro-mote the attraction of cations which is the case of our study-erefore it is plausible that a slight acidic range is favorablefor metal retention onto LLEPs

33 Mass Spectroscopy MALDI-TOF To get more detailedinformation on the chemical composition and structureof natural compounds presented in LLEPs MALDI-TOFmass spectroscopy analysis was performed -e fla-vonoidal constituents in the extracts of Leucaena leuco-cephala foliage have been identified earlier by massspectrometry techniques as caffeic acid isorhamnetin

Bioinorganic Chemistry and Applications 3

chrysoeriol isorhamnetin 3-O-galactoside kaempferol-3-O-rutinoside quercetin-3-O-rhamnoside as well asluteolin-7-glucoside among others [28ndash30] -us in or-der to determine the different natural compounds in theextract of Leucaena leucocephala leaves studied in thiswork we have analyzed the MALDI-TOF spectrum of asample without using any cationizing agent (Figure 2)Considering that MALDI-TOF is not a quantitativemethod and the intensities of the signals do not neces-sarily reflect the fractions of the constituents in thesample in this case MALDI-TOF analysis is treated onlyas a confirmation of the presence or absence of naturalproducts such as the aforementioned flavonoids in thetested sample

From Figure 2 it is observed that the signals of at least9 populations of natural constituents are clearly domi-nating For the dimers of isorhamnetin 3-O-galactosidekaempferol-3-O-rutinoside and chrysoeriol the observedmz values are 9599 11873 and 12034 respectively-e mz signals for the trimers of luteolin-7-glucosideand quercetin-3-O-rhamnoside are both observed at13452 Finally for the tetramer of nonanoic acid 9-(o-propylphenyl) methyl ester the observed mz value is11612 -e base chemical structures of some of thesenatural compounds are shown in Figure 3 It is worthnoting that no data were found in the literature that wouldallow adequate identification of the natural compoundspresent in the sample with mz values observed at 979114697 25024 and 26870 respectively Further researchinvolving nuclear magnetic resonance spectroscopy(NMR) and the use of advanced sample purificationtechniques are necessary in order to clarify this issue

34 ATR-FTIR Spectroscopy ATR-FTIR spectroscopy wasused to confirm the heavy metal adsorption carried out by

LLEPs after 6 h of contact with cationic solutions of Pb2+Cd2+ and the mixture of both metals respectively -ecomparative FTIR spectra before and after the differentheavy metal adsorption experiments are shown in Figure 4In order to better appreciate the differences in the absorptionbands of the functional groups present in the chemicalstructure of the samples the infrared spectra have beenshifted by 3 from each other starting from the one cor-responding to (d) (the sample taken after the simultaneousPb2+ and Cd2+ adsorption experiment) followed by (c) (thesample taken after Cd2+ adsorption experiment) then (b)(the sample taken after Pb2+ adsorption experiment) andfinally (a) (the sample taken before metal adsorptionexperiments)

Taking into account the base chemical structures elu-cidated by MALDI-TOF analysis for the LLEPs (Figure 3)one would expect for all of the samples the presence ofcharacteristic absorption bands corresponding to thestretching vibrations of the OndashH group around 3600 cmminus1the stretching vibrations of the CHndash (aromatic) groupabove 3000 cmminus1 the stretching vibrations of the CO(carbonyl) group around 1700 cmminus1 and the stretchingvibrations of the CndashO (ether) group around 1100ndash1200 cmminus1 among others However it is not possible toassign bands in the spectra of these samples unambiguouslyas the absorbance bands are overlapping and poorly re-solved In this sense since we have wet samples the stretchsignal HndashOndashH appears and overlaps the characteristic peakregarding the stretching vibrations of the OndashH bond ob-served around 331435 cmminus1 in Figure 4 Likewise therepresentative flexion vibration band associated to HndashOndashHis also observed at 163573 cmminus1

It is worth noting that there are two well-resolvedcharacteristic bands that appeared only in the blank sam-ple (a) and clearly indicate that the heavy metal adsorptionshave successfully taken place in the molecular architectures

2 4 6 8 10 12

2

4

6

8

10

12

pHinitial = pHfinal

pHfin

al

pHinitial

Figure 1 Point of zero charge (pHPZC) of LLEPs


For instance the band displayed at 111362 cmminus1 is attrib-uted to the stretching vibrations of the CndashO (ether) bondwhereas that shown at 101575 cmminus1 is assigned to thestretching vibrations of the CndashOH bond As the metal ad-sorption has proceeded (b c and d) the absorption banddue to the CndashOH stretching decreases considerably sug-gesting on the one hand that the LLEPs has effectivelyadsorbed the heavy metal ions and on the other hand thatafter 6 h of contact with the cationic solution active sites stillremain to undergo metal adsorption In contrast the ab-sorption band of aromatic CndashO stretching completely dis-appears after deadsorption experiments pointing out thatthe ether moieties in the sorbent also participate effectivelyin the metal uptake It is likely that steric hindrance plays animportant role in the adsorption efficiency of the active sitesdescribed above At this stage FTIR analysis has beenperformed just in a qualitative fashion to corroborate theeffectiveness of the sorbent to capture Pb2+ and Cd2+ frommonocationic as well as polycationic solutions of bothmetals

35 Kinetics -e sorption equilibrium for Pb(II) and Cd(II)in mono- and bimetal system at pH 6 by LLEPs wasexamined Figure 5 shows the plots of the sorption capacitiesof single and simultaneous Pb(II) and Cd(II) q(mgg) as afunction of time It can be well seen that the adsorptionincreases sharply within the first 60min while the equilib-rium time (teq) was reached within 120min for both Pb(II)and Cd(II) -e simultaneous adsorption in bimetal systemshowed a slight decrease in adsorption capacity due to thepresence of a second metal whilst the equilibrium time didnot changed Generally for both the cases the adsorptionprocess consisted of two main reaction stages initial fastadsorption process up to 65 of Pb(II) and 63 Cd(II) inmono- and bimetal system followed by a slow continuoussorption reaction with 8ndash9 of metal -e first stage can beexplained by the abundance of active binding sites that aregradually occupied by Pb(II) and Cd(II) as the contact timeis increasing In the second stage the access to active sitesbecomes limited -is could be attributed to the possiblemetal ions repulsion from the LLEPs surface

OH

OH

OH

OH

OCH3

HO

HO

HO

OOO

O

(a)

OH

OH

OCH3

HO

O

O

(b)

OHOH

OH

OH

HO

HO

HO

O O

O

O

(c)

Figure 3 Base chemical structures of some natural compounds found in LLEPs (a) isorhamnetin 3-O-galactoside (b) chrysoeriol and(c) luteolin-7-glucoside respectively

2000

1500

Inte

nsity

1000

500

0800 1000 1200 1400 1600 1800

mz2000 2200 2400 2600 2800

a b cd

e

g

f

h i

Constituent mzabcdefghi

959969979141

1161248118733712034531345237146978325024622687074

Figure 2 MALDI-TOF spectrum of the LLEPs


In order to describe the mechanism of sorption of Pb(II)and Cd(II) in mono- and bimetal systems onto LLEPsthe pseudo-first-order (Equation (2)) pseudo-second-order(Equation (3)) and Elovich (Equation (4)) models wereused

ln qe minus qt( 1113857 ln qe minus k1t (2)

t

qt

1K2q

2e

+t

qe (3)

989694929088868482807876747270

Tran

smitt

ance

()

686664626058565452504846444240

4000 3800 3600 3400

331435

163573

(a)(b)(c)(d)

111362

101575

3200 3000 2800 2600 2400 2200Wavenumber (cmndash1)

2000 1800 1600 1400 1200 1000 800 600

Figure 4 FT-IR spectra of LLEPs (a) before metal adsorption experiments (blank sample) (b) after Pb2+ adsorption experiment (c) afterCd2+ adsorption experiment and (d) after simultaneous Pb2+ and Cd2+ adsorption experiment respectively

0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Pb(II)Cd(II)

q t (m

gg)

Time (min)

(a)

Pb(II)Cd(II)

q t (m

gg)

0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Time (min)

(b)

Figure 5 Effect of contact time on the adsorption percentage of Pb(II) and Cd(II) by LLEPs in (a) monometal and (b) bimetal systems (Ci

100mgL pH 6)


qt 1βln(αβ) +

1β

ln t (4)

where qt (mgmiddotgminus1) and qe (mgmiddotgminus1) are the amounts of metalions adsorbed at time t and equilibrium respectively k1(minminus1) and k2 (gmgminus1middotminminus1) are the equilibrium rateconstants of pseudo-first-order and pseudo-second-ordersorption process respectively α is the sorption rate(mggminus1middotminminus1) and β is a desorption constant related tothe extent of surface coverage and activation energy forchemisorption Table 1 shows the parameters of the kineticmodels and correlation coefficients obtained from the

lineal plots of ln(qe minus qt) vs t (Equation (2)) tqt vs t

(Equation (3)) and qt vs ln t (Equation (4)) of experi-mental data

Figures 6(a) and 6(b) show the plot of tqt vs t for thesingle and simultaneous Pb2+ and Cd2+ respectively Asseen from Figure 6 the experimental data well adjusts tothe pseudo-second-order kinetic model (R2 ge 0999)Moreover it can be observed that qm values calculatedfrom Equation (3) are similar with the experimental qmvalues (Table 1) -is indicates that the sorption kineticsof Pb(II) and Cd(II) show better agreement for thepseudo-second-order model Similar results are reported

Table 1 Kinetics parameter of Pb(II) and Cd(II) removal in both mono- and bicomponent systems by different volumes of LLEPs

mLLEPs (g) Metallic ionsPseudo-second-order Pseudo-first-order Elovich model

qe (cal) qe (exp) k2 r2 qe (cal) k1 r2 α β r2

01

Single removalPb2+ 8203 8199 0007 0999 1497 0004 0814 0008 0288 0584Cd2+ 6887 6844 0007 0999 1105 0002 0957 0003 0267 0954

Simultaneous removalPb2+ 8025 8021 0006 0999 1476 0004 0814 0009 0282 0584Cd2+ 6447 6404 0007 0999 1029 0002 0959 0043 0250 0954

05



09



0

20

40

60

80

100

120

140

160

180

200

220

tqt (

min

middotmgndash1

g)

0 200 400 600 800 1000 1200 1400Time (min)

Pb(II)Cd(II)

(a)

0 200 400 600 800 1000 1200 14000

20406080

100120140160180200220240

tqt (

min

middotmgndash1

g)

Time (min)

Pb(II)Cd(II)

(b)

Figure 6 Pseudo-second-order kinetic plot for (a) single removal and (b) simultaneous removal of Pb(II) and Cd(II) sorption by LLEPs


in the literature where mentioned that in most cases ofbiosorption pseudo-second-order equation fit better forthe whole range of contact times than the pseudo-first-order [16]

36 Effect of Polyphenols Dosage -e study of the effect ofLLEPs dosage is essential as the adsorbent dosage showed tobe an important parameter that influences the metal uptakefrom the solution Figure 7 shows the initial mass introducedof LLEPs as a function of time the results showed that the

percentage removal of metal ions increases with increasingthe amount of LLEPs 01 g to 09 g in mono- and bimetalsystems -is could be attributed to the availability of activebinding sites

As the Figures 7(a) and 7(b) show 09 g of LLEPs wasenough to remove over 98 of Pb(II) and Cd(II) (Ci

100mgL) individually whilst 01 g of LLEPs uptake waslimited in 65 for these metals Similarly in bimetal systemLLEPs showed the same behavior but with a slight decreasein removal uptake where 55 of Pb(II) and Cd(II) wasremoved by 01 g while 09 g of LLEPs was able to remove

0 200 400 600 800 1000 1200 1400

mLLEPs = 01 gmLLEPs = 05 gmLLEPs = 09 g

Time (min)

0

10

20

30

40

50

60

70

80

90

100

rem

oval

(a)


0 200 400 600 800 1000 1200 1400

0

10

20

30

40

50

60

70

80

90

100

re

mov

al

Time (min)

(b)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

10

20

30

40

50

60

70

80

90

100

(c)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

20

40

60

80

100

(d)

Figure 7 Effect of LLEPs dosage on the removal percentage of Pb(II) and Cd(II) in (a b) monometal and (c d) bimetal systems (Ci

100mgL pH 6)


95 of both metals In general the removal of Pb(II) wasfaster than Cd(II) ions as it will be discussed in the nextsection

37 Isotherms Figure 8 presents the isotherms of Pb(II)and Cd(II) in mono- and bimetal system at pH 6 by LLEPs

-e metal removal capacity as a function of metal con-centration at the equilibrium state was analyzed usingLangmuir and Freundlich models -e Langmuir isothermdescribes monolayer adsorption on the surface of an ad-sorbent with a finite number of identical adsorption sites andno interaction between sites -is model is represented asfollows

0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)

Pb(II)Pb(II) + Cd(II) Cd(II)Pb(II) + Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)

Figure 8 Pb(II) and Cd(II) sorption isotherms by LLEPs in (a) monocomponent and (b) bicomponent systems


Ce

qe

1

qmKL+

Ce

qm (5)

where qm (mgmiddotgminus1) is the maximum adsorption capacity ofthe monolayer and KL (Lmiddotmgminus1) is the Langmuir adsorptionequilibrium constant related to the energy of adsorption qmand KL were determined from the slope and intercept of theplots of Ceqe versus Ce

-e Freundlich isotherm is an empirical equation used todescribe heterogeneous systems and it is expressed by thefollowing linear equation

ln qe lnKF +1nlnCe (6)

where KF (mgmiddotgminus1) (Lmiddotmgminus1)1n is the Freundlich isothermconstant and n is the adsorption intensity A plot of log qeversus logCe gives a straight line of slope 1n and interceptslogKF

In the present work the experimental data were fitted tothe Langmuir model for describing the obtained isothermsto propose the sorption mechanism involved with thehighest determination coefficient values R2 (0980 09980996 and 0968) when compared with the Freundlichisotherm However from Table 2 it is clear that the max-imum adsorption capacity of Pb(II) individually by LLEPs(qmPb 25510mgg) is higher than that observed in thepresence of the second metal (qmPbPb+Cd 21552) whereasthemaximumCd(II) adsorption capacity showed the reverseresults when it was higher in bimetal system (qmCdCd+Pb

16807) than monometal system (qmCd 14792) -econstant related to the affinity of the binding site (KL) islower for competent solution metals compared to the onewith individual metal which is in agreement with theabundant binding sites in the latter

It is generally well known that the specific adsorption ofmetals on different adsorption surfaces is dependent on theirhydration energies however higher hydration energy ofcations implies higher hydration radii From the aboveresults the adsorption capacity toward Pb(II) was obviouslyhigher as compared to Cd(II) due to big coordinationsphere offered in its case since it has an energy of hydrationhigher (ΔHhPb(II) minus1485 kJmol) than Cd(II) (ΔHhCd(II)

minus1809 kJmol) thus an ionic radius (119 A) higher thanCd (095 A) [31] Hence Pb(II) ions can bind better withpolyphenols groups Moreover the electronegativity also hasan important role in the preference of biosorbents for metalshowever as the metal is more electronegative it will be

rapidly attracted to the negative surface of a biosorbent inour case to the negative-charged surface of LLEPs at thestudied pH as confirmed by PZC measure -erefore as thelead cation Pb(II) provides the higher electronegativity(233) than the cadmium Cd(II) with value of 169 the Pb2+ions were rapidly diffused to the LLEPs surface negativelycharged

4 Plausible Mechanism

Polyphenols have been widely reported as metal scavengerssuch as flavonoids stilbenes and lignans compounds[32ndash34] In our case three potential metal-binding sites areidentified in flavonoidal compounds of LLEPs (Figure 9) Itis well known that the deprotonated phenolic is a partic-ularly good ligand for metal cations once the oxygen centeris generated possessing a high charge density called Hardligand (Figure 9(a)) On the contrary the presence of a CCdouble bond conjugated with a 3-oxo group is also of greatimportance for partial delocalization that could also bindheavy metal cations (Figure 9(b)) [35] Besides the hy-droxyl groups presented the molecules R-C6O6H9 isprobably involved in the biosorption process of heavymetals as suggested in the Figure 9(c) However the majorcontribution to metal chelation is due to the catecholmoiety (Figure 9(a)) owing to the presence of two hydroxylgroups in ortho-positions provides a strong metal-chelatingcharacter [36]

-erefore since lead (Pb2+) and cadmium (Cd2+) wereeffectively sorbed onto the LLEPs they should combine withhydroxyl ions (ndashOH) and pyrone oxygen of flavonoidscompounds as it is exemplified in luteolin-7-glucoside Ingeneral the binding of metal ions on polyphenolic groups aswell as alcoholic groups was considered to take place by theion-exchange mechanism leading to the formation of a 5-membered chelate complex A similar phenomenon forCs(VI)-catechol complex has also been reported [37]

5 Conclusions

From this work it can be concluded that L leucocephala-extracted polyphenols are an effective low-cost biosorbent ofPb(II) and Cd(II) in monosystem and binary system

Successful extraction of polyphenols from Leucaenaleucocephala plant was identified by MALDI-TOF massspectroscopy with high rate compared to reported results ofthis plant

Table 2 Langmuir isotherm constants for single and simultaneous Pb(II) and Cd(II) removal by LLEPs

Metallic ionsLangmuir isotherm

qm (mgg) KL (dm3mg) r2

Single removalPb(II) 25510 6112 0980Cd(II) 14792 55793 0998Simultaneous removalPb(II) 21552 2269 0996CdII 16807 12549 0968


ATR-FTIR spectroscopy clearly indicated that the heavymetal adsorptions have successfully taken place in themolecular architectures

Nearly 100 removal of lead and cadmium was possibleat a neutral pH value by 09 g of LLEPs while 95 removal of

the mixture Pb-Cd was possible at a pH value of 5 under thebatch test conditions

-e pseudo-second-order model best describes thesorption behavior of Pb(II) Cd(II) and their mixture andthe k2 values depend on the adsorbent mass -is implied

(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O

Figure 9 Inferredmechanism forM Pb(II) or Cd(II) adsorption as well as complex formation with (a) catechol (b) hydroxy and carbonyland (c) hydroxyls groups presents in LLEPs


that the chemisorption process might be the mechanism ofthe solute ion-LLEPs interaction in this research work

-e experimental data of both metals Pb(II) and Cd(II)sorption isotherms well fit the Langmuir model -e KLparameter is lower for competent solution metals comparedto the one with individual metal -e maximum adsorptioncapacity (qm) of Pb(II) ions was obtained as 2551 and2155mgg in mono- and bimetal solutions

Data Availability

-e authors declare that they have no inconvenience to sharethe data generated on this study

Conflicts of Interest

-e authors declare that they have no conflicts of interest

Acknowledgments

We thank CONACYT for generous support with the con-tract 239947 Financial support from DGAPA-UNAMPAPIIT through the project IA101817 is gratefullyacknowledged

References

[1] F Fu and W Qi ldquoRemoval of heavy metal ions fromwastewaters a reviewrdquo Journal of Environmental Manage-ment vol 92 no 3 pp 407ndash418 2011

[2] I Michalak K Chojnacka and A Witek-Krowiak ldquoState ofthe art for the biosorption processmdasha reviewrdquo Applied Bio-chemistry and Biotechnology vol 170 no 6 pp 1389ndash14162013

[3] W M Ibrahim A F Hassan and Y A Azab ldquoBiosorption oftoxic heavy metals from aqueous solution by Ulva lactucaactivated carbonrdquo Egyptian Journal of Basic and AppliedSciences vol 3 no 3 pp 241ndash249 2016

[4] R Dhankhar and A Hooda ldquoFungal biosorption-an alter-native to meet the challenges of heavy metal pollution inaqueous solutionsrdquo Environmental Technology vol 32 no 5pp 467ndash491 2011

[5] J Cheng W Yin Z Chang N Lundholm and Z JiangldquoBiosorption capacity and kinetics of cadmium(II) on live anddead chlorella vulgarisrdquo Journal of Applied Phycology vol 29no 1 pp 211ndash221 2017

[6] K Nahar Md A K Chowdhury Md A H ChowdhuryA Rahman and K M Mohiuddin ldquoHeavy metals inhandloom-dyeing effluents and their biosorption by agri-cultural byproductsrdquo Environmental Science and PollutionResearch vol 25 no 8 pp 7954ndash7967 2018

[7] MMahmood-ul-Hassan V Suthor E Rafique andM YasinldquoRemoval of Cd Cr and Pb from aqueous solution by un-modified and modified agricultural wastesrdquo EnvironmentalMonitoring and Assessment vol 187 no 2 2015

[8] I Anastopoulos I Massas and C Ehaliotis ldquoUse of residuesand by-products of the olive-oil production chain for theremoval of pollutants from environmental media a review ofbatch biosorption approachesrdquo Journal of EnvironmentalScience and HealthmdashPart vol 50 no 7 pp 677ndash718 2015

[9] M Zhang Z Hu H Wang and L M McDonald ldquoCom-petitive biosorption of Pb (II) Cu (II) Cd (II) and Zn (II)using composted livestock waste in batch and column

experimentsrdquo Environmental Engineering and ManagementJournal vol 16 no 2 pp 431ndash438 2017

[10] J O Babalola J O Olowoyo A O Durojaiye A M OlatundeE I Unuabonah and M O Omorogie ldquoUnderstanding theremoval and regeneration potentials of biogenic wastes for toxicmetals and organic dyesrdquo Journal of the Taiwan Institute ofChemical Engineers vol 58 pp 490ndash499 2016

[11] C S T Araujo I L S Almeida H C RezendeS M L O Marcionilio J J L Leon and T N de MatosldquoElucidation of mechanism involved in adsorption of Pb(II)onto lobeira fruit (Solanum lycocarpum) using LangmuirFreundlich and Temkin isothermsrdquo Microchemical Journalvol 137 pp 348ndash354 2018

[12] L Cutillas-Barreiro R Paradelo A Igrexas-Soto et alldquoValorization of biosorbent obtained from a forestry wastecompetitive adsorption desorption and transport of Cd CuNi Pb and Znrdquo Ecotoxicology and Environmental Safetyvol 131 pp 118ndash126 2016

[13] S Waseem M Imran Din S Nasir and A Rasool ldquoEvalu-ation of Acacia nilotica as a non conventional low costbiosorbent for the elimination of Pb(II) and Cd(II) ions fromaqueous solutionsrdquo Arabian Journal of Chemistry vol 7no 6 pp 1091ndash1098 2014

[14] D Zhang C Wang Q Bao et al ldquo-e physicochemicalcharacterization equilibrium and kinetics of heavymetal ionsadsorption from aqueous solution by arrowhead plant(Sagittaria trifolia L) stalkrdquo Journal of Food Biochemistryvol 42 no 1 article e12448 2018

[15] O C Adebooye AM Alashi and R E Aluko ldquoA brief reviewon emerging trends in global polyphenol researchrdquo Journal ofFood Biochemistry vol 42 no 4 article e12519 2018

[16] G J Copello M P Pesenti M Raineri et al ldquoPolyphenol-SiO2hybrid biosorbent for heavy metal removal Yerba matewaste (Ilex paraguariensis) as polyphenol source kinetics andisotherm studiesrdquo Colloids and Surfaces B Biointerfacesvol 102 pp 218ndash226 2013

[17] C Proestos K Lytoudi OMavromelanidou P Zoumpoulakisand V Sinanoglou ldquoAntioxidant capacity of selected plantextracts and their essential oilsrdquo Antioxidants vol 2 no 1pp 11ndash22 2013

[18] L C She C M Liu C T Chen H T Li W J Li andC Y Chen ldquo-e anti-cancer and anti-metastasis effects ofphytochemical constituents from Leucaena leucocephalardquoBiomedical Research (India) vol 28 no 7 pp 2893ndash28972017

[19] S Zarate ldquoLeucaena leucocephala (Leucaena)rdquo BioNET-EAFRINET vol 63 pp 304ndash306 2011

[20] D Vijay S K Gupta and S M Mishra ldquoSeed yield andquality enhancement of pollarded subabul (Leucaena leuco-cephala) by nutrient supplementationrdquo Agroforestry Systemsvol 91 no 4 pp 613ndash621 2017

[21] J M Loaiza F Lopez M T Garcıa J C Garcıa andM J Dıaz ldquoBiomass valorization by using a sequence of acidhydrolysis and pyrolysis processes Application to Leucaenaleucocephalardquo Fuel vol 203 pp 393ndash402 2017

[22] M A Zarin H Y Wan A Isha and N Armania ldquoAnti-oxidant antimicrobial and cytotoxic potential of condensedtannins from Leucaena leucocephala hybrid-rendangrdquo FoodScience and Human Wellness vol 5 no 2 pp 65ndash75 2016

[23] J G Damascena G L D Leite F W S Silva et al ldquoSpatialdistribution of phytophagous insects natural enemies andpollinators on Leucaena leucocephala (fabaceae) trees in thecerradordquo Florida Entomologist vol 100 no 3 pp 558ndash5652017


[24] T Zhang Y Wang Y Kuang et al ldquoAdsorptive removal ofCr3+from aqueous solutions using chitosan microfibersimmobilized with plant polyphenols as biosorbents with highcapacity and selectivityrdquo Applied Surface Science vol 404pp 418ndash425 2017

[25] K Jayaram and M N V Prasad ldquoRemoval of Pb(II) fromaqueous solution by seed powder of Prosopis juliflora DCrdquoJournal of Hazardous Materials vol 169 no 1ndash3 pp 991ndash9972009

[26] A Scalbert B Monties and G Janin ldquoTannins in woodcomparison of different estimation methodsrdquo Journal ofAgricultural and Food Chemistry vol 37 no 5 pp 1324ndash13291989

[27] A Seghier M Hadjel and N Benderdouche ldquoAdsorptionstudy of heavy metal and acid dye on an amphoteric bio-material using barbary fig skinrdquo Arabian Journal for Scienceand Engineering vol 42 no 4 pp 1487ndash1496 2017

[28] R A Hassan W A Tawfik and L M Abou-setta ldquo-eflavonoid constitunts of Leucaena leucocephala growing inEgypt and their biological activityrdquo African Journal of Tra-ditional Complementary and Alternative Medicines vol 11no 1 pp 67ndash72 2014

[29] A F Z Salem M Z Salem M Gonzalez-RonquilloL M Camacho and M Cipriano ldquoMajor chemical constit-uents of Leucaena leucocephala and salix babylonica leafextractsrdquo Journal of Tropical Agriculture vol 49 pp 95ndash982011

[30] M Z Zayed S M A Sallam and N D Shetta ldquoReview articleon Leucaena leucocephala as one of the miracle timber treesrdquoInternational Journal of Pharmacy and Pharmaceutical Sci-ences vol 10 no 1 pp 1ndash7 2018

[31] J Peric M Trgo and N Vukojevic Medvidovic ldquoRemoval ofzinc copper and lead by natural zeolitemdasha comparison ofadsorption isothermsrdquo Water Research vol 38 no 7pp 1893ndash1899 2004

[32] F Fucassi A Heikal L I Mikhalovska et al ldquoMetal chelationby a plant lignan secoisolariciresinol diglucosiderdquo Journal ofInclusion Phenomena and Macrocyclic Chemistry vol 80no 3-4 pp 345ndash351 2014

[33] M Reinisalo A Karlund A Koskela K Kaarniranta andR O Karjalainen ldquoPolyphenol stilbenes molecular mecha-nisms of defence against oxidative stress and aging- relateddiseasesrdquo Oxidative Medicine and Cellular Longevityvol 2015 Article ID 340520 24 pages 2015

[34] K J Korshavn M Jang Y J Kwak et al ldquoReactivity of metal-free and metal-associated amyloid-β with glycosylated poly-phenols and their esterified derivativesrdquo Scientific Reportsvol 5 no 1 pp 1ndash15 2015

[35] R C Hider Z D Liu and H H Khodr ldquoMetal chelation ofpolyphenolsrdquo Methods in Enzymology vol 335 pp 190ndash2032001

[36] I Gulccedilin ldquoAntioxidant activity of food constituents anoverviewrdquo Archives of Toxicology vol 86 no 3 pp 345ndash3912012

[37] M Gurung B B Adhikari S Alam et al ldquoAdsorptive re-moval of Cs(I) from aqueous solution using polyphenolsenriched biomass-based adsorbentsrdquo Chemical EngineeringJournal vol 231 pp 113ndash120 2013


TribologyAdvances in

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Advances inPhysical Chemistry

Hindawiwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2018

Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018

SpectroscopyInternational Journal of


Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Medicinal ChemistryInternational Journal of


NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Applied ChemistryJournal of



Biochemistry Research International


Enzyme Research


Journal of

SpectroscopyAnalytical ChemistryInternational Journal of


MaterialsJournal of



BioMed Research International Electrochemistry

International Journal of


Na

nom

ate

ria

ls


Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

particular for lead Pb(II) and cadmium Cd(II) ions theyhave used fruit shell [5] algae eggshell rice husk sawdust[6] corn cob [7] olive oil by-products [8] livestock waste[9] forest by-products and waste [10ndash14]

-e use of polyphenols as biosorbents has been widelystudied in water and wastewater treatment to remove heavymetals due to the large availability of these compounds inplant material that can be easily extracted from agriculturalwaste using a green solvent Several studies have been carriedout on the extraction of polyphenols from various plantsusing different solvents showing that the structure yieldrecovery and type of phenolic compounds depend on theplant nature and extraction solvents [15]Nepeta melissifoliaPhlomis lanata Ilex paraguariensis and Origanum vulgaredemonstrated a high total phenol content with more than150mg gallic acid equivalent (GAE)g dried samplewhereas Geranium purpureum Matricaria chamomilla andLavandula vera showed a content less than 7mg GAEgdried sample [16 17]

Leucaena leucocephala as a potential source of poly-phenols is a fast-growing tropical leguminous tree speciesthat belongs to Mimosaceae native to southern Mexico(Yucatan Peninsula) and then extends to Nicaragua in-cluding Guatemala Honduras El Salvador and northernCentral America [18 19] Leucaena leucocephala namedthe miracle tree is considered as a multipurpose treespecies for its wider usages as timber and firewood in pulpand paper industry [20] also as a biomass and proteinsource for animal feed with yield production of 50 ton haminus1

yearminus1 under Mediterranean conditions [21] -eir leavesand seeds are composed mainly of lipids crude proteincarbohydrates mimosine saponins coumarins flavonoidscardiac glycosides steroids and phenols and have a highcondensed tannin content [18 22 23] Recently Abu Zarinet al reported the total phenolic content in Leucaenaleucocephala hybrid-Rendang from its crude extract to be321mg GAEg [22]

Polyphenols extracted from plants are characterizedby the abundant phenolic hydroxyls that are capable ofchelating with transition-metal ions especially for thosemetal species with d-orbits [24] Because of the strongchelating ability of phenolic hydroxyls towards transitionmetals the polyphenol-based adsorbent showed to bepotential and efficient sorbent for the removal of Pb(II) andCd(II) from aqueous solutions In this context Copelloet al studied the application of hybrid low-cost SiO2polyphenol matrices as a bioadsorbent for Pb(II) Cr(III)and Cr(VI) [16] Waseem et al have used biomass derivedfrom of Acacia nilotica leaves as an adsorbent material forthe removal of cadmium and lead and they found themaximum adsorption to be 251mgg and 499mgg forPb(II) and Cd(II) respectively [13] Recently Zhang el alhave evaluated the effectiveness of Sagittaria trifolia L stalkplant to remove Pb(II) Cd(II) and Cr(III) [14] Howeverthe maximum adsorption capacities of Pb(II) reported byJayaram and Prasad were 45454mgg using Prosopisjuliflora as a source of polyphenols [25]

However to the best of our knowledge there are noreports of polyphenols extracted from L leucocephala as

potential metal removers from mono- and multicomponentsystems Indeed L leucocephala residues have no applica-tion for human consumption here in Mexico therefore it isexpected that it will remain a waste that could be considereda sustainable low-cost source of polyphenol adsorbents-erefore the aim of this work was to describe the simul-taneous sorption mechanism of Cd and Pb from aqueoussolution using L leucocephala-extracted polyphenols(LLEPs) considering various experimental parameters suchas contact time adsorbent dosage and initial concentration

2 Materials and Methods

21 Chemicals Deionized water (182MΩcmminus1 conduc-tivity) was used for all dilutions and to prepare the syntheticstock solutions of Pb(II) and Cd(II) using PbCl2 (98Aldrich) and CdCl225H2O (799 JT Baker) salts re-spectively Methanol (70) FolinndashCiocalteu reagent andNa2CO3 were used in the procedures for extraction andquantification of total polyphenols

22 Plant Preparation Leaf residues of Leucaena leucoce-phala tree were collected from the campus area of theAutonomous University of Ciudad Del Carmen identified byour botanist Dr Enrique Lopez washed with deionizedwater dried at 70degC and then stored in glass bottles to beused for the polyphenolsrsquo extraction

23 Extraction of Polyphenols -e extraction method ofpolyphenols was described by Scalbert et al 15 g of plant leafsamples was extracted three times with 300mL of 80methanol solution under magnetic agitation at room tem-perature (3 times 2 h) -e supernatant was collected after eachextraction by filtration and then the sample solution wasused for polyphenol quantification -e methanol wasevaporated under reduced pressure and then the poly-phenols were dried and ready to be used in the sorptionprocess [26]

24TotalPolyphenolicContent Total polyphenolic contentswere determined according to the method of Scalbert et al[26] 05mL of a 200-fold diluted aqueous extract wasmixed with 25mL of 10-fold diluted FolinndashCiocalteuphenol reagent and incubated for 1min before 2mL of75 Na2CO3 was added -e mixture was allowed to standfor 15min at 50 degC in a water bath and then transferred intocold water Samples absorbance was measured at 760 nm ina UV-Vis spectrophotometer (Evolution 220) after 30minof incubation A gallic acid aqueous solution (80 microgmL)was used for calibration and the final results wereexpressed as mg gallic acid equivalent (GAE) per g of dryweight (DW)

25 Characterization Methods

251 Point of Zero Charge (pHPZC) -e pH of the point ofzero charge (pHPZC) of LLEPs has been described as





26 Sorption Process



mV (1)















2 4 6 8 10 12

2

4

6

8

10

12

pHinitial = pHfinal

pHfin

al

pHinitial





OH

OH

OH

OH

OCH3

HO

HO

HO

OOO

O

(a)

OH

OH

OCH3

HO

O

O

(b)

OHOH

OH

OH

HO

HO

HO

O O

O

O

(c)


2000

1500

Inte

nsity

1000

500

0800 1000 1200 1400 1600 1800

mz2000 2200 2400 2600 2800

a b cd

e

g

f

h i


959969979141

1161248118733712034531345237146978325024622687074





t

qt

1K2q

2e

+t

qe (3)

989694929088868482807876747270

Tran

smitt

ance

()

686664626058565452504846444240

4000 3800 3600 3400

331435

163573

(a)(b)(c)(d)

111362

101575


2000 1800 1600 1400 1200 1000 800 600


0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Pb(II)Cd(II)

q t (m

gg)

Time (min)

(a)

Pb(II)Cd(II)

q t (m

gg)

0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Time (min)

(b)


100mgL pH 6)


qt 1βln(αβ) +

1β

ln t (4)








01



05



09



0

20

40

60

80

100

120

140

160

180

200

220

tqt (

min

middotmgndash1

g)

0 200 400 600 800 1000 1200 1400Time (min)

Pb(II)Cd(II)

(a)

0 200 400 600 800 1000 1200 14000

20406080

100120140160180200220240

tqt (

min

middotmgndash1

g)

Time (min)

Pb(II)Cd(II)

(b)








0 200 400 600 800 1000 1200 1400


Time (min)

0

10

20

30

40

50

60

70

80

90

100

rem

oval

(a)


0 200 400 600 800 1000 1200 1400

0

10

20

30

40

50

60

70

80

90

100

re

mov

al

Time (min)

(b)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

10

20

30

40

50

60

70

80

90

100

(c)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

20

40

60

80

100

(d)


100mgL pH 6)





0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)


q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)



Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls







26 Sorption Process



mV (1)















2 4 6 8 10 12

2

4

6

8

10

12

pHinitial = pHfinal

pHfin

al

pHinitial





OH

OH

OH

OH

OCH3

HO

HO

HO

OOO

O

(a)

OH

OH

OCH3

HO

O

O

(b)

OHOH

OH

OH

HO

HO

HO

O O

O

O

(c)


2000

1500

Inte

nsity

1000

500

0800 1000 1200 1400 1600 1800

mz2000 2200 2400 2600 2800

a b cd

e

g

f

h i


959969979141

1161248118733712034531345237146978325024622687074





t

qt

1K2q

2e

+t

qe (3)

989694929088868482807876747270

Tran

smitt

ance

()

686664626058565452504846444240

4000 3800 3600 3400

331435

163573

(a)(b)(c)(d)

111362

101575


2000 1800 1600 1400 1200 1000 800 600


0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Pb(II)Cd(II)

q t (m

gg)

Time (min)

(a)

Pb(II)Cd(II)

q t (m

gg)

0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Time (min)

(b)


100mgL pH 6)


qt 1βln(αβ) +

1β

ln t (4)








01



05



09



0

20

40

60

80

100

120

140

160

180

200

220

tqt (

min

middotmgndash1

g)

0 200 400 600 800 1000 1200 1400Time (min)

Pb(II)Cd(II)

(a)

0 200 400 600 800 1000 1200 14000

20406080

100120140160180200220240

tqt (

min

middotmgndash1

g)

Time (min)

Pb(II)Cd(II)

(b)








0 200 400 600 800 1000 1200 1400


Time (min)

0

10

20

30

40

50

60

70

80

90

100

rem

oval

(a)


0 200 400 600 800 1000 1200 1400

0

10

20

30

40

50

60

70

80

90

100

re

mov

al

Time (min)

(b)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

10

20

30

40

50

60

70

80

90

100

(c)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

20

40

60

80

100

(d)


100mgL pH 6)





0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)


q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)



Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls










2 4 6 8 10 12

2

4

6

8

10

12

pHinitial = pHfinal

pHfin

al

pHinitial





OH

OH

OH

OH

OCH3

HO

HO

HO

OOO

O

(a)

OH

OH

OCH3

HO

O

O

(b)

OHOH

OH

OH

HO

HO

HO

O O

O

O

(c)


2000

1500

Inte

nsity

1000

500

0800 1000 1200 1400 1600 1800

mz2000 2200 2400 2600 2800

a b cd

e

g

f

h i


959969979141

1161248118733712034531345237146978325024622687074





t

qt

1K2q

2e

+t

qe (3)

989694929088868482807876747270

Tran

smitt

ance

()

686664626058565452504846444240

4000 3800 3600 3400

331435

163573

(a)(b)(c)(d)

111362

101575


2000 1800 1600 1400 1200 1000 800 600


0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Pb(II)Cd(II)

q t (m

gg)

Time (min)

(a)

Pb(II)Cd(II)

q t (m

gg)

0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Time (min)

(b)


100mgL pH 6)


qt 1βln(αβ) +

1β

ln t (4)








01



05



09



0

20

40

60

80

100

120

140

160

180

200

220

tqt (

min

middotmgndash1

g)

0 200 400 600 800 1000 1200 1400Time (min)

Pb(II)Cd(II)

(a)

0 200 400 600 800 1000 1200 14000

20406080

100120140160180200220240

tqt (

min

middotmgndash1

g)

Time (min)

Pb(II)Cd(II)

(b)








0 200 400 600 800 1000 1200 1400


Time (min)

0

10

20

30

40

50

60

70

80

90

100

rem

oval

(a)


0 200 400 600 800 1000 1200 1400

0

10

20

30

40

50

60

70

80

90

100

re

mov

al

Time (min)

(b)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

10

20

30

40

50

60

70

80

90

100

(c)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

20

40

60

80

100

(d)


100mgL pH 6)





0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)


q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)



Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls






OH

OH

OH

OH

OCH3

HO

HO

HO

OOO

O

(a)

OH

OH

OCH3

HO

O

O

(b)

OHOH

OH

OH

HO

HO

HO

O O

O

O

(c)


2000

1500

Inte

nsity

1000

500

0800 1000 1200 1400 1600 1800

mz2000 2200 2400 2600 2800

a b cd

e

g

f

h i


959969979141

1161248118733712034531345237146978325024622687074





t

qt

1K2q

2e

+t

qe (3)

989694929088868482807876747270

Tran

smitt

ance

()

686664626058565452504846444240

4000 3800 3600 3400

331435

163573

(a)(b)(c)(d)

111362

101575


2000 1800 1600 1400 1200 1000 800 600


0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Pb(II)Cd(II)

q t (m

gg)

Time (min)

(a)

Pb(II)Cd(II)

q t (m

gg)

0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Time (min)

(b)


100mgL pH 6)


qt 1βln(αβ) +

1β

ln t (4)








01



05



09



0

20

40

60

80

100

120

140

160

180

200

220

tqt (

min

middotmgndash1

g)

0 200 400 600 800 1000 1200 1400Time (min)

Pb(II)Cd(II)

(a)

0 200 400 600 800 1000 1200 14000

20406080

100120140160180200220240

tqt (

min

middotmgndash1

g)

Time (min)

Pb(II)Cd(II)

(b)








0 200 400 600 800 1000 1200 1400


Time (min)

0

10

20

30

40

50

60

70

80

90

100

rem

oval

(a)


0 200 400 600 800 1000 1200 1400

0

10

20

30

40

50

60

70

80

90

100

re

mov

al

Time (min)

(b)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

10

20

30

40

50

60

70

80

90

100

(c)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

20

40

60

80

100

(d)


100mgL pH 6)





0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)


q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)



Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls






t

qt

1K2q

2e

+t

qe (3)

989694929088868482807876747270

Tran

smitt

ance

()

686664626058565452504846444240

4000 3800 3600 3400

331435

163573

(a)(b)(c)(d)

111362

101575


2000 1800 1600 1400 1200 1000 800 600


0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Pb(II)Cd(II)

q t (m

gg)

Time (min)

(a)

Pb(II)Cd(II)

q t (m

gg)

0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

7

8

9

Time (min)

(b)


100mgL pH 6)


qt 1βln(αβ) +

1β

ln t (4)








01



05



09



0

20

40

60

80

100

120

140

160

180

200

220

tqt (

min

middotmgndash1

g)

0 200 400 600 800 1000 1200 1400Time (min)

Pb(II)Cd(II)

(a)

0 200 400 600 800 1000 1200 14000

20406080

100120140160180200220240

tqt (

min

middotmgndash1

g)

Time (min)

Pb(II)Cd(II)

(b)








0 200 400 600 800 1000 1200 1400


Time (min)

0

10

20

30

40

50

60

70

80

90

100

rem

oval

(a)


0 200 400 600 800 1000 1200 1400

0

10

20

30

40

50

60

70

80

90

100

re

mov

al

Time (min)

(b)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

10

20

30

40

50

60

70

80

90

100

(c)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

20

40

60

80

100

(d)


100mgL pH 6)





0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)


q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)



Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls




qt 1βln(αβ) +

1β

ln t (4)








01



05



09



0

20

40

60

80

100

120

140

160

180

200

220

tqt (

min

middotmgndash1

g)

0 200 400 600 800 1000 1200 1400Time (min)

Pb(II)Cd(II)

(a)

0 200 400 600 800 1000 1200 14000

20406080

100120140160180200220240

tqt (

min

middotmgndash1

g)

Time (min)

Pb(II)Cd(II)

(b)








0 200 400 600 800 1000 1200 1400


Time (min)

0

10

20

30

40

50

60

70

80

90

100

rem

oval

(a)


0 200 400 600 800 1000 1200 1400

0

10

20

30

40

50

60

70

80

90

100

re

mov

al

Time (min)

(b)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

10

20

30

40

50

60

70

80

90

100

(c)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

20

40

60

80

100

(d)


100mgL pH 6)





0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)


q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)



Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls









0 200 400 600 800 1000 1200 1400


Time (min)

0

10

20

30

40

50

60

70

80

90

100

rem

oval

(a)


0 200 400 600 800 1000 1200 1400

0

10

20

30

40

50

60

70

80

90

100

re

mov

al

Time (min)

(b)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

10

20

30

40

50

60

70

80

90

100

(c)


re

mov

al

0 200 400 600 800 1000 1200 1400Time (min)

0

20

40

60

80

100

(d)


100mgL pH 6)





0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)


q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)



Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls







0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

20

Pb(II) Cd(II)

q (m

gg)

q (m

gg)

Ce (mgL)0 50 100 150 200 250

0

2

4

6

8

10

12

14

Ce (mgL)

(a)


q (m

gg)

q (m

gg)

Ce (mgL) Ce (mgL)0 50 100 150 2000 50 100 150 200 250

0

2

4

6

8

10

12

14

16

0

2

4

6

8

10

12

(b)



Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls




Ce

qe

1

qmKL+

Ce

qm (5)













5 Conclusions












(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls








(a)

(b)

(c)

R1

HOHO

HO

HOOH

O

O

O

O

R3R2

OH

OHHO

HOHO

HO

O O

+ PbCd2+PbCd+

R3

R2 R3

R2

+ H+

OH

OO

O

O

O

R4

OHHO

HO

O

O

OH

+ PbCd2+ PbCd

R1 R1

+ 2H+

OH

O

O

+ PbCd2+ PbCd + 2H+

R4

R4

HO

HO

OH

OH

O

O

OO

O

OHOH

O





Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls






Data Availability




Acknowledgments


References














































Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls
























Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls









Journal of

Chemistry





Journal of

Volume 2018






Volume 2018




Journal of






Enzyme Research


Journal of



MaterialsJournal of






Na

nom

ate

ria

ls




Documents

Eco-EfficientBiosorbentBasedon Leucaenaleucocephala ...downloads.hindawi.com/journals/bca/2019/2814047.pdf · Leucaena leucocephala as a potential source of poly-phenolsisafast-growing,tropical,leguminoustreespecies