removal of toxic pb(ii) ions from aqueous solution by nano ......a shaker at 300 rpm. effect of...

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Archives in Chemical Research ISSN 2572-4657

DOI: 10.21767/2572-4657.100003

Laila H Abdel-Rahman1,Badriah SF Al-Farhan2, Ahmed M Abu-Dief1,3 and Mallak Megalea Zikry4

1 Chemistry Department, Sohag University, 82534 Sohag, Egypt

2 Chemistry Department, King Khalid University, 61321 Abha, Saudi Arabia

3 Department of organic chemistry and inorganic chemistry, relevant Faculty of Chemistry, University of Oviedo, 33006, Oviedo, Spain

4 MedicinalandAromaticPlantsResearchesDepartment,HorticultureResearchInstitute(HRI),AgricultureResearchCenter(ARC),Giza,Egypt

Corresponding author: Ahmed M Abu-Dief

[email protected]

Chemistry Department, Sohag university, 82534 Sohag, Egypt and Department of organic chemistry and inorganic chemistry, relevant Faculty of Chemistry, University Oviedo, 33006, Oviedo, Spain.

Tel: +0201098856153Fax: +0209346011590020

Citation: Abdel-Rahman LH, Al-Farhan BSF, Abu-DiefAM,etal.RemovalofToxicPb(II)IonsfromAqueousSolutionbyNanoSizedFlamboyantPod(Delonix regia).ArchChemRes.2016,1:1.

IntroductionToxic Heavy metals can be released into water through metalsmelters,effluentsfromplastics,textiles,Thereisevidencethatpresentintheenvironment,eveninlowconcentrationofheavymetalscausedermaldamageandcancer[1,2].Leadisconsideredasthemosttoxicmetalexists inseveral industrialwastes,suchas chemicals, lead acid storage batteries. Lead poisoning inhuman causes damaging to the kidneys, liver, and brain [2,3].The removal of heavy metal from contaminated sites is veryimportant to restoreecosystem functionsand stability [4]. Thesearch for low-cost techniques to remove heavy metals fromwastewater using agricultural materials such as Maize leaves,loquat leaves (Eriobotrya japonica), Psidium guajava leaves, Scolymushis panicus, Azadirachta indica (Neem leaves),Ulmus leaves, Oleaeuropaea(Oliveleaves),andPrunusvium leaves [5], rice straw, ricebran, ricehusk,hyacinthroots, neem leaves [6].Delonix regia isaspeciesoffloweringplantinthefamilyFabaceae, subfamily Caesalpinioideae [7].Delonix regia possesses several

Removal of Toxic Pb(II) Ions from Aqueous Solution by Nano Sized Flamboyant Pod

(Delonix regia)

Received: October 20, 2016; Accepted: November17,2016; Published: November25, 2016

AbstractThe removing of toxic heavy metals from aqueous solution by agriculturalbiosorbentswasinvestigatedbystudyingtheeffectofnanosized(Delonix regia)andchemicallymodifiedbiosorbentcitricacid Delonix regia(CADR)forremovingofPb2+ ions.TEM,XRDandEDS,FT-IR,SEMmethodswereusedforcharacterizingthebiosorbent(Delonix regia).Theeffectofcontacttime,pH,temperature,dosageof biosorbent, andPb2+ ion concentrationon adsorptionprocesswere studied.Themaximumbiosorptioncapacities(qm)ofPb

2+ by Delonix regiabiosorbentwas43.62mg/g.ThehighestR.Ewas(93.5%)atpH5.FT-IRmethodshowedthattheadsorptionofmetal ionsoccursby functional groupson the surfaceof Delonix regia powder. The biosorption process was endothermic from thermodynamicparameters. The pseudo second-order model more fit (R2=0.999) than thepseudo first-ordermodel (R2=0.985) from studying the kinetic parameters. TheexperimentaldatafitwithFreundlichisotherm(R2closeto1).Thisresultsindicatedthat Delonix regia is available agricultural, low cost and environment friendlybiosorbentforremovingthePb2+ions.

Keywords:Lead;Biosorbent;Kineticparameters;Biosorptioncapacities;Delonix regia pod

medicinalcharacters[8].TheeffectDelonix regia biosorbent for theremovingofMethyleneBluedye[9],Hg(II) ionfromwater[10]andPb,CuandCoions[11].ChemicaltreatmentofbiomasswithNaOHand citric acid increases its cationuptakeability asthecarboxylgroupsofthebiomassincreases[12]Ion-exchangehas been suggested as one the mechanisms for heavy metal

https://en.wikipedia.org/wiki/Fabaceae

https://en.wikipedia.org/wiki/Caesalpinioideae

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de-ionizedwatertoobtaina1000mg/Lconcentration.DifferentinitialconcentrationsofPb2+ionswerepreparedbyDilution.

Batch Biosorption ExperimentsEffect of concentration of metal ionAtotalof50mlofPb2+ionssolutionofdifferentconcentrationswasaddedto0.3goftheAdsorbentinaflatbottleandthenthemixturewasstirredfor1hronashakerat300rpm.

Effect of pHExperimentswerecarriedoutatdifferentpH(2:10)andpHwasadjustedbyusing0.1M(NaOH)or0.1M(HCl).Atotalof50mlofPb2+ ionssolutionofconcentration(20mg/L)wasaddedto0.3goftheAdsorbentinaflatbottle,thenthemixturewasstirredfor1hronashakerat300rpm.

Effect of dosageIn each biosorption experiment, 50ml of Pb2+ ions solution ofconcentration (20mg/L)was added to different dosage of theadsorbentinbottleandthenthemixturewasstirredfor1hronashakerat300rpm.

Effect of contact timeInthebiosorptionkineticsexperiment,0.2LofPb2+ ionssolutionofdifferentconcentrationswasaddedto1.2goftheadsorbentinflatbottleandthenthemixturewasstirredfor1hronashakerat300 rpm andacontacttime(20:120)minuteswithtimeinterval20minutes.

Effect of temperature and determination of thermodynamic parametersAtotalof50mlofdifferentconcentrationsofPb2+ ionssolutionwasaddedto0.3goftheadsorbentinbottleatdifferenttemperatureand then themixture was stirred for 1 hr on a shaker at 300rpm.ThenthemixturewascentrifugedandtheconcentrationofPb2+ionswasdetermined.Werecalculatedusingtherelationships(1)and(2)[2,16,17]canbeusedtocalculateΔH,ΔS,andΔG(thethermodynamicparametersfortheadsorptionprocess.

lnb=ΔS°/R-ΔH°/RT (1)

ΔG°=ΔH°-TΔS° (2)

Calculation of metal uptakeThePb2+ionsuptakeatequilibriumwascalculatedby:

( )o ev C Cqe

w−

= (3)

whereqeisPb2+ionsabsorptioncapacity,visthevolumeofthe

Pb2+ ionssolutionandwistheamountoftheadsorbent,Co and Ce areinitialPb

2+ ionconcentrationsandCe arefinal(equilibrium)Pb2+ ionconcentrations.Theefficiency of the Pb2+ ions removal wasalsodeterminedusing;

( )% 100o e

o

C CRE

C−

= × (4)

Where,RE%isthepercentageoftheremovedPb2+ions.

removalfromaqueoussolution[2,13].ThisstudycanintroduceaneconomicvaluebiosorbentforremovingoftoxicheavymetalbyusingnanosizedDelonix regia pod.

Experimental From Sigma-Aldrich, Pb(NO3)2, HCl, citric acid and NaOH werepurchased.

Sample collectionThepodsofDelonix regiawereobtainedfromShandawilResearchStation,AgricultureResearchCenter,Sohag,Egypt.

InstrumentsNanosizeoftheinvestigatedbiosorbentwasobtainedbyusingRetschMuhleBrinkannSpectroMillMSMicro-GrindingMixing.BiosorbentwascharacterizedbyX-raypowderdiffractionusingaPhilipsX'PertPROMPD. (EDAX)unitwasusedtoanalysethechemical compositionof the synthesizednanostructures. Field-emission scanning electron microscopy was used for studyingthemorphologyofsample.Functionalgroupsonthebiosorbentsurfaceweredetectedbyusing (FT-IR,2000,PerkinElmer).mV-ISE-pH-temperature bench Meters was used to adjust pH ofthe solutions. Transmission electron microscopy images wereobtained with a 2000 EX (II0 microscope (J E O L-Japan). Ashakerbath(HeidolphMR-3001)wasusedforshaking.E-B-A,20zentrifugenD78532tuttlingenwasusedtocentrifugethesampleaftertheadsorptionprocess.TheconcentrationofPb2+ionswasdeterminedusing(AAS)(modelPerkinElmer-Analyst,200).

Sample pretreatmentDelonix regia pods were cleaned with water, and then dried.Delonix regia podsweregrindedtoobtainafinepowder.Thefinepowderwasusedasbiosorbentintheexperiments.

Treatment of Delonix regia (DR) by Citric AcidChemicalmodificationofnanosizedpowderDelonix regia (DR)usingNaOH followedby citric acid treatment. The synthesisofCADRwascarriedoutasfollowed,200gramsofthepowderwasplacedin4Lof0.1NNaOH,

thenwasstirredat300rpmfor1hat23oCtoremovebase.Thepowderwasrinsedwithwaterandaddedto4Lofdistilledwater.Thisbiomasswasmixedwithcitricacid (CA) ina ratioof1.0gpowder to 7.0mL of CA (0.6M). The acid/powder Slurry wasdried over night at 50oC and then heated to 120oCfor1.5h.Citricacid(CA)treatedDRpowder(CADR)wasfilteredandwashedinaBuchnerfunnelundervacuumwith150–200mLofdistilledwaterper gramof the product to remove excess CA. This volumeofwaterwassufficienttoremoveunreactedCAsincenoturbidityfrom lead citratewasobservedwhen thewashedpowderwassuspendedin10mLofwatertowhich10mLof0.1Mleadnitratewas added. Themodified powderwas dried at 50oC overnight [2,14,15].

Preparation of SolutionAqueoussolutionofPb2+ionswaspreparedbyweighingout1.60gofPb(NO3)2 anddissolved ina1000ml volumetricflaskwith

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Kinetics study ThemechanismoftheadsorptionofPb2+ionswasstudiedusingpseudofirstorderkineticmodels,theintraparticlediffusionandpseudosecondorderkineticmodels[2,18-20]andtheyaregivinginalinearformbyEquations5,6and7,respectively

ln(qe-qt)=lnqe–k1t (5)

(t/qt)=1/(k2q2

e)+(t/qe) (6)

qt = kint t0.5 (7)

kinetic models are tested for suitability using correlationcoefficient(R2)[2,20,21].

Effect of chemical treatment Atotalof50mlofPb2+ionssolutionof(20mg/L)concentrationwasaddedto0.3gofthechemically treatment adsorbent(CADR)inbottle,thenthemixturewasstirredonashakerfor1hrat300rpmandtheconcentrationofPb2+ionswasdetermined.

Results and DiscussionCharacteristics of the biosorbentFTIR spectral analysis: FTIR spectral analysis of Delonix regia pod(DR)(Figure 1a)andPb2+ ions loaded Delonix regia pod (Pb-DR)(Figure 1a)werecarriedout.FTIRdataofDelonix regia (DR)indicatesthefunctionalgroups. Themaincharacteristiccellulosepeak appears in the region of 1000-1200 cm−1 [22].The strongand broad peak at 3298 cm−1, indicatedtheN-Hbondofaminogroupsandhydroxylgroup.Theshiftinthepeakto3330cm−1 in the spectra of the metal loaded Delonix regia pod powdershowsthebindingofLeadionswithhydroxylandaminogroups[23-25]peak at 2916 cm−1in the spectra of the Delonix regia podpowderindicated CH3 and CH 2 groups.Thepeakat1594cm

−1 indicates CO,OHandC-Ogroups,theShiftto1612cm−1indicated the metal binding. Band at 1036 cm−1 indicated the C-O of alcohols, the shiftto1028cm−1indicatedbindingofPb2+ ionswithC-Ogroup[2,24-26]. Peak at 1738 cm−1, which is indicative of carbonylgroup,shiftedtowavenumberof1732cm−1afterPb2+ adsorption

[2,27,28]. Band at 1243 cm−1 indicates carboxylic acids whichshifted to 1233 cm−1after adsorption of Pb2+ [29]. The shifts intheabsorptionpeaks indicate thebindingofmetal ionson thesurface of the Delonix regia powder.

AlsoFT-IRfordetectionthegroupsonthemodifiedbiosorbents[CitricAcid(CA)treatedDRpowder(CADR)beforeandafterthebiosorptionofPb2+ ions(Pb-CADR)wasshowninFigure 1b.

ComparisonoftheIRspectraofsamplesofDRandCAmodifiedDR (CADR) revealed that a characteristic stretching vibrationabsorptionbandofcarboxylgroupat1733cm−1 is present in the IR spectrum of CADR samples. This indicates the esterificationbetweenalcoholgroupsofcelluloseinDRandcitricacid

The broad absorptions around 2500-3500 cm−1 centered at 3343 confirm the existence of carboxylic OH groups and freeCOOHgroups afterCAmodification. It appears fromFigure 1b thatthedifferentfunctionalgroupsonCADRareresponsibleforbiosorptionofPb2+.Achange inpeakspositionat3328cm−1 in the spectrum of Pb2+ loaded CADR indicates the binding withhydroxylgroups.Thepeakat1733cm−1shiftedto1728cm−1in the spectrumofPb2+ loadedCAMO indicating thebindingofmetalionstocarboxylicgroupsalso[2,30,31].

Elemental analysis: To determine the chemical compositionof the biosorbent. Elemental analysis ofDelonix regia (pod) isshowninFigure 2.

Scanning electron micrograph (SEM): SEM of biosorbent Delonix regia pod(D-R) (Figure 3) are used to show the morphologyof Delonix regia pod, which exhibits the structure porosity ofbiomass.ThesurfacemorphologyofDelonix regia pod powdershowedthatthepowderwasafineparticle.Theparticleshavealarge number of steps and edges.

XRD analysis: XRD of theDelonix regia pod powder is shownin Figure 4 indicates the amount of amorphous material in the sample. XRD of the adsorbent Delonix regia indicate that the structure of Delonix regia pod powder has a small different

4000 3000 2000 10000.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

3298

3330

1732

1738

1612

1594 1243

1233

1036

1028

Tran

smitt

ance

(%)

wave number cm-1

Pb-DR DR

Figure 1a FT-IRspectralanalysisofbiosorbentDelonix regia pod (D-R)andPb2+ loaded Delonix regia pod(Pb-DR).

4000 3000 2000 10000.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

Pb-CADR

CADR

1027

12351592

1728

3328

1031

1239

15961733

3343

Tran

smitt

ance

(%)

Wave number (cm-1)

CADR Pb-CADR

Figure 1b FT-IR spectral analysis of the modified biosorbentDelonix regia (CADR)andPb2+ loaded themodifiedDelonix regia (Pb-CADR).

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Figure 2 EDSspectrumoftheinvestigatednanosizedplant.

Figure 3 Scanning electron micrograph of biosorbent Delonix

regia pod(DR).

10 20 30 40 50 60 700

50

100

150

200

250

Inte

nsity

(a. u

.)

DR

Pb-DR

2θ/º

Figure 4 XRDpatternsoftheadsorbentDelonix regia pod(DR)powderbeforeandafterequilibrationwithPb2+ ions (Pb-DR).

change due to the appearance of amorphous peak at 2θ=44.7afteradsorptionprocessconfirmingadsorptionofPb2+ ions.

Transmission electron microscopy (TEM): The sample wassubjectedtoTEManalysis(Figure 5a) to indicate the particle sizeandthemajorsizeoftheparticleswasfoundtobe18nm(Figure 5b).

Effect of initial concentration: Figure 6 and Table 1 illustrated the effect ofmetal ions concentrationonPb2+ ions biosorptionis in (qe) increases as the concentration rises, as Pb

2+ ions are more available for interaction with the biosorbent. The Pb2+

ions R. E for initial concentration 10 and 20 mg/L are 94.3%and 93.5%, respectively and decreases as the concentrationincreases.Agreater chancewasavailable formetal removal atlowconcentrations,biosorptionsitestookuptheavailablePb2+ ionswhenincreasingconcentrations.So,initialconcentrationofPb2+ionssolutionsincreasesthebiosorption[2,32-34].

Effect of pH: Figure 7 and Table 2illustratedtheeffectofpHofasolutionintheadsorptionprocess.R.E.andqe increase as the pH increase. The amount of Pb2+ ions removed by the Delonix regia atlowpH2waslow(1.91mg/g)andR.E.57.3%comparedto theamounts removedatpH4 to10were ranged from (2.7mg/gandR.E.81%atpH4)to3.12mg/gandR.E.93.5%atpH5.BecauseatlowpHtheconcentrationofH+ is high [19], as H+

ionswerebeingremovedbythebiosorbent,insteadofthePb2+

ions, [21,35] athigher concentrationofH+ ions, the biosorbent becomesmorepositivechargeonthesurfaceandtheattractionbetween biosorbent and Pb2+ ions is reduced [36]. At higherpH the capacity of the adsorbent reduced, the reduction inadsorptionmaybeduetotheincreasingofOH- ions,orPb2+ ions wereprecipitatedasleadhydroxide[2,37].

Effect of biosorbent dosage: Itisaneffectivefactortostudythecapacityofabiosorbent.R.E.increaseswithleastvalueof64.65%obtainedwith25mgandhighestvalueof95.04%with500mgofthe biosorbent, this because at high dosage, there is an increase in surfaceareaandavailabilityofbiosorptionsites,butqe decreases asadecreaseintheamountofPb2+ionsadsorbedperunitweightofbiosorbent[2,38-40].Theseresultsare illustrated in Figure 8 and Table 3.

Effect of contact time: Table 4 and Figure 9 illustratedtheeffectofcontacttimefortheadsorptionofPb2+ ions by Delonix regia. The amount of Pb2+ ions absorbed increasedwith an increasein the contact time and reach equilibrium in 60minutes. Thisbecauselongcontacttimeandavailabilityofactivesites, itwasfollowedbyareductioninthemetaluptake.Therewasaslightlyincreasing or remain constant in the Pb2+ ions removal, as the sitesarelessavailable[2,41,42].

Effect of temperature: Table 5 and Figure 10 illustrated the effectofthetemperatureonadsorption,thePb2+ R.E.andqe by Delonix regia increaseswhilethetemperatureisincreasing,astheactivesiteshaveincreasedandencouragestheprocessofbiosorption,duetoincreaseinthemovementofthePb2+ ions and poresize indicatinganendothermicprocess[2,43-45].

Adsorption isotherm: Pb2+ionsdistributionbetweenthesolidandliquid phases can be described by the Freundlich and Langmuir


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pH Ce (mg/L) ± Sd

Pb2+ ions R. E.%± Sd

qe (mg/g) ± Sd

2 8.54±0.09 57.30±0.12 1.91±0.04

4 3.80±0.05 81.00±0.08 2.70±0.07

5 1.30±0.02 93.50±0.32 3.12±0.03

6 1.32±0.04 93.40±0.07 3.11±0.06

7 1.430.02 92.85±0.61 3.10±0.01

8 1.62±0.013 91.92±0.18 3.06±0.02

10 1.60±0.01 92.00±0.43 3.07±0.03

Table 2 Pb2+ ionsremovalefficiencyqeatinitialconcentrationof20mg/LatdifferentpHvalues.

2 4 6 8 10556065707580859095

q e(mg/

g)

Pb

R.E

%

pH

R.E %

1.82.02.22.42.62.83.03.2

qe

Figure 7 EffectofpHonPb2+ ionsremovalefficiencyandqe at initialconcentration20mg/L.

Figure 5a TEMimageof nanosizedbiosorbentDelonix regia pod(D-R).

0 5 10 15 20 25 300

10

20

30

40

50

60

70

80

Freq

uenc

y

Diameter (nm)

Figure 5b CalculatedHistogramforparticleSizedistributionofDelonix regia pod.

0 100 200 300 40050

60

70

80

90

100

q e(mg/

g)

Pb

R.E

%

initial Pb2+ ions conc.(mg/L)

Pb R.E%

0

10

20

30

40

50

qe

Figure 6 Effectof initialPb2+ ionsconcentrationonPb2+ ions removalefficiencyAndqe(b)byDelonix regiapod.

Co (mg/L) Ce (mg/L) ± Sd Pb2+ ions R. E.% ± Sd qe(mg/g) ± Sd

10 0.57±0.03 94.30±0.06 1.57±0.0220 1.30±0.10 93.50±0.09 3.16±0.0450 4.84±0.12 90.33±0.30 7.53±0.10

100 15.30±0.13 84.70±0.40 14.12±0.13200 35.88±0.23 82.06±0.06 27.35±0.11300 69.08±0.20 76.97±0.08 38.49±0.07400 138.28±0.34 65.43±0.23 43.62±0.21

Table 1 Pb2+ions Removal Efficiency and qe at different initialconcentrations.

isotherms [46] qe increasedwiththeinitialconcentrationofPb2+,

asexpected[47,48].qmis15.26mg/gofDelonix regia.Langmuirmodelsuggeststhattheadsorptiontakeplacesonhomogeneoussites.Langmuirisothermequationisrepresentedbyequation8in a linear form [2,49].

Ce/qe=1/qmb + Ce/qm (8)

Plot of Ce /qe against Ce give a line with intercept 1/qm b and slope1/qm is obtained (Figure 11),whichshowsLeadbiosorptionisothermsofLangmuir.FromtheinterceptandslopetheLangmuirparameters(bandqm)arecalculated.ThesevaluesmaybeusedforcomparedandcorrelatethebiosorptivepropertiesofDelonix regia of the Freundlich has the linear form [2,50].

Log qe = log Kf+1/nlogCe (9)

From a plot, a line with slope and intercept 1/n and log Kf respectivelyisobtained(Figure 12).Theslope,1/n,indicatetheintensityofadsorptionandlogKfindicatetheadsorptioncapacity

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[51] parameters of Pb2+ ions adsorptionwas given in Table 6a dimensionless constant separator factor (RL) can classify theIsotherms [52] statedas:

R L=1/(1+bC°) (10)

RL Mathematical calculation indicates the shape of isotherm, irreversible if (RL=0), linear if (RL=1), unfavorable if (RL>1)favorable if (0<RL<1). RL values have arrange from 0.059 to0.333(Table 7)nvaluesweregreaterthan1[53], these values indicatingaformationofabondbetweenPb2+ ions and adsorbent andindicatingfavorablebiosorption.ThisindicatethatPb(II)ionsadsorption on Delonix regia is favorable. Linearity coefficient(R2)canbeusedtoexaminethefittingofthemodels.Accordingto linearity coefficients (R2=1) Freundlich models has a goodfitmodels and adsorption of Lead ion onDelonix regia followFreundlichisothermmodels.

Thermodynamic studies From a plot lnb against1/T, thermodynamics equilibrium constant wasused toobtain theother thermodynamicparameters. Thebiosorptioncapacityof theDelonix regia for Lead increased as temperature increased, indicating the adsorption process was

qe (mg/g) Pb2+ ions R. E.% ± Sd Ce(mg/L) ± Sd

Biosorbent

± Sd Dosage(mg)

25.98±0.20 64.95±0.33 7.01±0.09 25

13.18±0.13 65.90±0.41 6.82±0.05 50

8.12±0.09 81.24±0.09 3.75±0.02 100

4.37±0.07 87.30±0.012 2.54±0.04 200

3.12±0.04 93.50±0.07 1.30±00.01 300

2.36±0.02 94.25±0.16 1.15±0.02 400

1.91±0.01 95.04±0.07 0.99±0.01 500

Table 3 Pb2+ ions removal efficiency and qe at different biosorbentdosage.

0 100 200 300 400 50065707580859095

100

Pb

R.E

%

biosorbent dosage (mg)

Pb R.E %

481216202428

q e(mg/

g)

qe

Figure 8 Effect of biosorbent dosage on Pb2+ ions removal efficiencyandqe.

20 40 60 80 100 120808284868890929496

Pb

R.E

%

Time(min)

R.E(10 mg/L) R.E(30 mg/L) R.E(50 mg/L)

20 40 60 80 100 1201.52.02.53.03.54.04.55.05.56.06.57.07.5

q e (mg/

g)

Time(min)

(R.E 10 mg/L) (R.E 10 mg/L) (R.E 10 mg/L)

Figure 9 EffectofcontacttimeonPb2+ ionsremovalefficiencyand qeatdifferentinitialconcentrations(10,30and50)mg/LbyDelonix regia pod.

25 30 35 40 45 5090

91

92

93

94

95

96

Pb

R.E

%

Temperature

R.E(10 mg/L) R.E(20 mg/L) R.E(50 mg/L)

Figure 10 EffectoftemperatureonPb2+ionsremovalefficiencyatdifferentInitialconcentrations(10,20,50)mg/Lby Delonix regia pod.

0 1 2 3 4 5 60.0

0.2

0.4

0.6

0.8

1.0C e /

q e

Ce(mg/L)

25 οC 30 οC+ 0.1 40 οC+0.2 50 οC+0.3

Figure 11 LinearizedbiosorptionisothermsofLangmuir.


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-0.4 -0.2 0.0 0.2 0.4 0.6 0.80.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Log

q e

Log Ce

25 οC 30 οC+ 0.1 40 οC+0.2 50 οC+0.3

Figure 12 LinearizedbiosorptionisothermsofFreundlich.

Time (min) Pb2+ R. E. % at Co(10)

Pb2+ R. E. % at Co(30)

Pb2+ R. E. % at Co(50 )

qt at qt at qt at Ct at Ct at Ct atCo(10) Co(30) Co(50) Co(10) Co(30) Co(50)

20 83.9 81.95 80.32 1.4 4.1 6.69 1.61 5.41 9.8440 91 86.43 86.51 1.52 4.3 7.2 0.9 4.1 6.7460 94.2 90.6 900 1.57 4.53 7.52 0.57 2.81 4.980 94.8 91.73 90.49 1.58 4.59 7.54 0.52 2.5 4.75

120 94.97 91.97 90.71 1.58 4.6 7.59 0.5 2.4 4.65

Table 4 EffectofcontacttimeonPb2+ ionsremovalefficiencyandqe atdifferentinitialconcentrations(10,30and50)mg/LbyDelonix regia pod.

Temp.( oC) Pb2+ R. E. %at Co(10 )

Pb2+ R. E. %at Co(20)

Pb2+ R. E. %atCo(50 ) qe at Co(10) qe at Co(20) qe at Co(50) Ce at Co(10) Ce at Co(20) Ceat Co( 50)

25 94.30 93.50 90.33 1.57 3.17 7.53 0.57 1.30 4.8430 94.46 93.92 90.70 1.57 3.13 7.56 0.55 1.22 4.6540 95.99 94.44 91.21 1.60 3.15 7.60 0.41 1.11 4.4050 95.70 94.34 90.62 1.59 3.14 7.55 0.43 1.13 4.69

Table 5EffectoftemperatureonPb2+ionsremovalefficiencyandqeatdifferent initialconcentrations(10,20,50)mg/LbyDelonix regia pod.

T (K)Langmuir Friendlich

qm (mg/g) ± Sd b(L/mg) ± Sd R2 n ± Sd 1/n Kf(mg/g)

± Sd R2

298 15.26±0.18 0.200±0.01 0.995 1.377±0.09 0.726 2.46±0.01 1303 15.41±0.09 0.207±0.02 0.994 1.372±0.01 0.73 2.53±0.09 0.999313 12.99±0.23 0.315±0.06 0.983 1.520±0.06 0.657 2.91±0.03 0.999323 12.56±0.35 0.317±0.05 0.991 1.540±0.07 0.65 2.81±0.05 0.998

Table 6IsothermconstantsofPb2+ ionsbiosorptiononDelonix regia pod at various temperatures.

endothermic.Thermodynamicparameters(ΔG,°ΔS°andΔH°)weredeterminedusingtheequations(1),(2)[54],theslopeΔH°/R, and interceptΔS°/R areobtainedandthevaluesofΔH°andΔS°werecalculated (Table 8).TheadsorptionprocessofLeadionsontheDelonix regia was endothermic as ΔH° values were Positive. apositiveΔG°valuesuggestedanion-exchangemechanismoccurin the biosorption of Pb2+ and a complex formed by Pb2+ withthe Delonix regia [2,55] An increase in randomness during the biosorptionasthePositiveΔS◦ value [2,56-58].

Kinetic studies on the biosorption of Pb2+ ionsPseudo first order, pseudo second order kinetic and the intraparticlediffusionmodelscanbeusedtotestthemechanismoftheadsorptionofmetalions[2,19-21].TheadsorptionkineticoftheadsorbedPb2+ionswasstudied(Figures 13 and 14).Correlationcoefficient,R2 can be used to test the suitability of these models [2,21] The variable and constant of each kinetic model werecalculated and were presented in Table 9, the calculated qe determinedfromtheplotofthepseudofirstordermodeldiffersfromtheexperimentalqe.This indicatesthatpseudofirstordermodelisnotgoodinstudyingthekineticsofthebiosorptionofPb2+ ions compared to pseudo second order models (R2=0.999)for Pb2+ ions, Table 9.Sothesecondorderkineticsisgoodinstudying

0 10 20 30 40 50 60 70-8

-6

-4

-2

0

2

4

Y=-0.14244X+2.59329R2=0.9296(50mg/L)

Y=-0.07852X+0.50156R2=0.6061(30mg/L)

Y=-0.12093X-0.01518R2=0.9755(10mg/L)

ln(q

e-qt)

Time (min)

10 mg/L 30 mg/L 50 mg/L

Figure 13 Pseudo-first order for sorption of Pb2+ ions by Delonix regia pod.

Co(mg/L) RL at 25oC RL at 30oC RLat 40oC RL at 50oC

10 0.333 0.326 0.241 0.23920 0.200 0.195 0.137 0.13650 0.091 0.088 0.060 0.059

Table 7Adimensionlessconstantseparatorfactor(RL)forLangmuirtypebiosorptionprocess.

2016Vol. 1 No. 1: 3



0 20 40 60 80

0

10

20

30

40

50

Y=0.1833+0.131XR2=99.87 (50 mg/L)

Y=0.315+0.216XR2=99.86 (30 mg/L)

Y=0.873+0.6255XR2=99.88 (10 mg/L)

t /q t

Time (min)

(10 mg/L) (30 mg/L) (50 mg/L)

Figure 14 Pseudo-secondorderforsorptionofPb2+ ions by Delonix regia pod.

Temperature (K) ΔG° (KJ/mol) ΔH°(KJ/mol) ΔS° (J/mol. K)298 4.73

17.69 43.84303 4.51313 4.08323 3.64

Table 8Thermodynamicparametersforthebiosorptionprocess.

Co (mg/L)

Pseudo-first order Pseudo-second order

Intraparticle diffusion Observed qe

(mg/g)k1 qe

R2

k2

qe(mg/g)± Sd R2 Kint C R2

± Sd(1/min) (mg/g) (g/mg.min)± Sd

± Sd ± Sd

10 0.083±0.005 1.36±0.06 0.985 0.448±0.01 1.6±0.03 0.9988 0.027 0.57 0.755 1.58±0.02

30 0.069±0.003 3.41±0.07 0.956 0.148±0.03 4.6±0.05 0.9986 0.818 2.81 0.861 4.59±0.06

50 0.091±0.009 7.23±0.12 0.972 0.094±0.01 7.6±0.09 0.9987 0.137 4.9 0.807 7.54±0.10

Table 9KineticparametersofPb2+ionsbiosorptionatdifferentinitialconcentration.

Biosorbent Delonix regiaCo(20mg/L)

of metal ions

DR CADR

Ce(mg/L)±Sd R.E.%±Sd Ce(mg/L)±Sd R.E.%±Sd

Cd2+ 1.52±0.02 92.42±0.19 0.259±0.03 98.71±0.15Pb2+ 1.30±0.06 93.50±0.11 0.390±0.01 98.05±0.17

Table 10 Effect of chemical treatment of Biosorbent on biosorptionefficiency.

thekineticsofthebiosorptionofPb2+ ions, as the calculated qe (7.54 mg/g are very close to the experimental qe (7.6 mg/g),suggestingthatthebiosorptionofthePb2+ ionssolutionsinvolvesthe Pb2+ ion and the Delonix regiabiosorbentparticles[2,58,59].

Effect of chemical treatment of the biosorbents on biosorption efficiencyTheeffectof chemical treatment of the biosorbents by esterifying withNaOHfollowedbycitricacidtreatment(CADR)ontheR.Ecomparedwith(DR)wasstudiedandshowninTable 10. ItwasobservedthattheR.E.%ofmetalionsby(CADR)washigherthantheR.E.%ofmetalionsby(DR)andthiswasduetotheChemicaltreatment of biomass with NaOH and citric acid increases itscation uptake ability as the carboxyl groups of the biomassincreases[2,31,32].

Conclusion1.NanosizeofFlamboyantPod(Delonixregia)wasusedforbiosorptionoftoxicPb2+ionsfromsolutionandisconsideraveryeffectivebiosorbentintheremovalofheavymetals.Thisstudyindicatedthat:TheAdsorptionprocessdependsontemperature,pH,Contacttime,dosageandmetalionconcentration.

2. Adsorption of Pb2+ ions from solutions obeyed Freundlich isothermmodels.qmofPb

2+ ionsonDelonixregiais43.62mgg−1.

3. The biosorption process was endothermic an ion-exchangemechanismapplies inthebiosorptionof (Pb2+ ions).Thisconfirmedbythermodynamicstudies.

4.SecondorderkineticsmodelsisabetterthanthepseudofirstorderinstudyingthekineticsofthebiosorptionofPb2+ ions.


Vol. 1 No. 1: 3


ISSN 2572-4657

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