research article recovery of ga(iii) by raw and alkali...

Research ArticleRecovery of Ga(III) by Raw and Alkali TreatedCitrus limetta Peels

Sachin C Gondhalekar and Sanjeev R Shukla

Department of Fibres and Textile Processing Technology Institute of Chemical Technology Nathalal Parekh MargMatunga Mumbai 400019 India

Correspondence should be addressed to Sanjeev R Shukla srshukla19gmailcom

Received 5 March 2014 Accepted 4 June 2014 Published 24 July 2014

Academic Editor Shaobin Wang

Copyright copy 2014 S C Gondhalekar and S R Shukla This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Alkali treated Citrus limetta peels were used for recovery of Ga(III) from its aqueous solution The raw and alkali treated peelswere characterized for functional groups The efficiency of adsorption increased from 4762mgg for raw peels to 8333mgg foralkali treated peels Between pH 1 and 3 the adsorption increased and thereafter decreased drastically The adsorption followedpseudosecond order kinetics and Langmuir isotherm gave the best fit for the experimental data Desorption studies showed 9528desorption after 3 cycles for raw peels while it was 8951 for alkali treated peels Simulated Bayer liquor showed 3957 adsorptionfor gallium ions on raw peels which was enhanced to 4113 for alkali treated peels

1 Introduction

Gallium is the 30th in terms of abundance at an averageconcentration of 19mgg It finds significant applications inthe semiconductor industry through use of gallium arsenideand gallium nitride Gallium is classified as a ldquostrategicrdquometal since it is used in high-tech gadgets like microwavetransceivers DVDs laser diodes in CDs and so forth anddefence-related activities [1ndash3] Gallium nitrate and galliumcitrate are used in medical imaging as radio contrast agents[4] Galliumarsenide is used tomake rectifiers and amplifiersDue to good adhesion to glass and high reflectivity galliumis used in high quality mirrors [5] There are no gallium-containing minerals of any economic significance Due to itsuniform distribution in soil its extraction is uneconomical Itis usually associated with aluminium in bauxite nephelinesand other ores and recovered as a by-productwhile producingalumina The United States Geological Survey has estimatedtotal worldrsquos primary gallium production to be about 273tonnes in 2012 [6] the estimated consumption being 280tonnes As per the report of Roskill Information Servicesneomaterial estimated that 50 of gallium consumed world-wide in 2010 came from recycled sources [7] As per workingGroup Report of 12th Five Year Plan India produced around

55 kg of gallium in recent years Two plants namely HindalcoIndustries Ltd at Renukoot and National Aluminium CoLtd at Damanjodi Alumina Refinery Odisha recover gal-lium [8] It is derived fromwastes of industrial processes suchas flue dusts from the zinc industry waste generated duringsmelting of phosphate to produce elemental phosphorus orsludge from the aluminium industry Since aluminium lies inthe same group of periodic table gallium has affinity towardsit Bauxite (the primary aluminium ore) typically contains0003 to 001 gallium Concentrations in zinc ores (egsphalerite) are comparable Since primary sources are scarcethe general strategy is to recover gallium from intermediateindustrial products

Bayer liquor is one of the important resource for recoveryof gallium About 90 of the worldrsquos primary gallium isproduced from Bayer liquor [9] In the Bayer process about70 of the gallium content of bauxite is leached alongwith aluminium and about 30 is retained in the red mudGallium accumulates in the Bayer liquor in successive cyclesattaining concentrations of 100ndash200mgL [10] Gallium isalso obtained from the iron mud or residues that result fromthe purification of zinc sulphate solutions in zinc productionThere are four kinds of recoverymethods for gallium namely

Hindawi Publishing CorporationInternational Scholarly Research NoticesVolume 2014 Article ID 968402 10 pageshttpdxdoiorg1011552014968402

2 International Scholarly Research Notices

fractional precipitation electrochemical deposition solventextraction and ion exchange Fractional precipitation is acomplex process solvent extraction is efficient but veryslow electrochemical method usesmercury cathode which isbanned due to mercury toxicity whereas ion exchange giveseffective recovery of gallium Industrial resins such as DuoliteES-346 and PHG586 may be used however the process isvery expensive Hence further research for cheap efficientand environmentally friendly recovery of gallium is essential[11]

Biosorption studies have mainly focused on the removaland recovery of heavy metal ions from industrial effluentsdetoxification being their primary goal Functional groupspresent in the biosorbents that are responsible for metalbinding are carboxyl phosphoryl sulfhydryl amino sulfateimidazole thioether phenol amide and hydroxyl in variousbiomolecules of peptide protein and polysaccharide moi-eties of the cell walls These functional groups bind the metalionsmainly by adsorption ion exchange and chelating effects[12]

Very few reports have been published on the removalrecovery of gallium using natural adsorbent [13ndash15] Citruslimetta peels are a natural pectinacious agrowaste materialtypically generated in large quantities by the fruit juiceindustry rich in pectin with abundant presence of carboxylgroups It is reported that these peels have a metal bindingmechanism similar to brown algal biosorbents since pectin ischemically similar to the brown algal cell wall polysaccharidealginate [6 7] These peels have been found to be verygood adsorbents for Pb(II) and Cd(II) [16ndash18] Our previousstudies have shown good binding capacity by citrus peels forPb(II) ions [18]

In the present work the adsorption of Ga(III) from theaqueous solution of gallium nitrate and from the simulatedBayer liquor on Citrus limetta peels in its raw as well as alkalitreated form has been reported

2 Materials and Methods

21 Materials Citrus limetta fruit peels procured from localjuice shopwere used as biosorbentsDemineralizedwaterwasused throughout the experiment for dilution and washingpurposes Stock solution of 1000mgL was prepared fromgallium nitrate salt (Sigma-Aldrich India) Gallium standardused for calibration of Atomic Absorption Spectrometer(Model GBC 932plus Austria) was supplied by Merck IncGermany

pH adjustment of metal ion solution was achieved byappropriate addition of 01M NaOH and 01M HCl

22 Methods

221 Preparation of Biosorbent Citrus limetta peels procuredfrom local juice shop were soaked in water for 4 h washedand cleaned using 1 nonionic detergent solution and againwith demineralised water The washed peels were dried at60∘C till constant weight reduced to small particle size usinga grinder sieved to mesh sizes between 425 and 800 120583 and

Table 1 Adsorption capacities of Citrus limetta peels (119862119894

=

100mgL 119905 = 4 h and 119879 = 30∘C) on chemical modification

Modification Metal uptake (mgL)Nil (RCP) 24401M malonic acid treated peels 24311M oxalic acid treated peels 216720 H2O2 treated peels 307801M sodium hydroxide treated peels (ACP) 34591M citric acid treated peels 23901M succinic acid treated peels 2705Acetylated peels 2708Chlorosulphonic acid treated peels 2300Methane sulphonic acid treated peels 233301M potassium dichromate treated peels 2712

stored in zip lock bagsThebiomass thus obtainedwas termedas raw citrus peels (RCP)

222 Modification of Functional Groups on RCP The rawpeels were treated with different chemical agents as reportedto enhance their adsorption capacity This data is furtherpresented in Table 1 [19]

RCP was treated with 005M aqueous NaOH for 3 hat room temperature It was then washed thoroughly withdemineralized water till neutral pH and then dried in anoven at 60∘C for 24 h and stored in zip lock bags to avoidcontamination with moisture It was termed as alkali treatedcitrus peels (ACP) The weight loss of biomass due to alkalitreatment was estimated experimentally

223 Estimation of Gallium Ions Ga(III) concentration inaqueous solution was determined by Atomic AbsorptionSpectrometer (GBC 932 plus Australia) at 2871 nm with anair-acetylene flame Each time AAS was calibrated by usingstandard 1000mgL Ga(III) solution

224 ATR-IR Spectroscopy The functional groups present onthe surface of RCP and ACP were determined by recordingthe infrared spectra of these peels using Shimadzu 8400S FT-IR spectrometer (Figure 2)

225 Scanning Electron Microscopy (SEM) Microscopicimages of RCP and ACP were taken by scanning electronmicroscope (Jeol JSM6380 LA spectrometer Tokyo Japan) toreveal themorphological aspects of the surface of the biomasssamples

226 Estimation of Acidic Groups Number of acidic sitespresent on RCP and ACP were estimated by methylene blueabsorption method [20 21] When a biomass is treated witha cationic dye like methylene blue the coloured cations ofthe dye are quantitatively absorbed by acidic groups presenton the material forming strong ionic linkage A weighedsample of the biomass was added to an Erlenmeyer flask con-taining 25mL of aqueous methylene blue chloride solution

International Scholarly Research Notices 3

(300mgL) and 25mL borate buffer of pH 85 It was kept for3 h at 25∘C and then 5mL of filtered sample was transferredto a volumetric flask containing 10mL 01M HCl followedby dilution to 100mL The decrease in the intensity of colourwas measured on UV-visible spectrometer (Techcomp UV-VIS 8500) at the 120582max = 650 nm Using the calibration plotthe amount of unabsorbed methylene blue was calculatedThe value gives quantitative information about the acidic sitespresent on the surface of peels

227 Batch Wise Adsorption Experiments Unless otherwisestated for all the batch wise adsorption experiments 100mgof dry adsorbent was placed in 40mL Ga(III) solutionhaving varying initial concentrations ranging from 40mgLto 200mgL at pH 30 in a 250mL stoppered Erlenmeyerflask and agitated in an orbital shaker (Rossari BiotechLtd Mumbai) at 150 rpm for 4 h at room temperature Thebiomass was then allowed to settle down and the supernatantsolution was pipetted out The solutions were estimated forthe remaining Ga(III) concentration using flame type AAS

The biosorption capacity of gallium per unit of drybiomass (mg of Gag of dry biomass) was calculated by using

119902eq =(1198620minus 119862eq)119881

119882 (1)

where 119902eq is the equilibrium adsorption capacity (mgg) 1198620

and 119862eq are the initial and equilibrium concentrations ofGa(III) (mgL) respectively119881 is the volume of adsorbate (L)and119882 is the mass of adsorbent (g)

The biosorption efficiency 119864 of the metal ion wascalculated from

119864 =(1198620minus 119862eq)

1198620

times 100 (2)

The optimum pH for the biosorption was evaluated byadjusting the pH between 1 and 3 with an interval of 05 using1M HCl

The kinetics of adsorption of Ga(III) was studied byshaking 25 g of adsorbent samples with 200mL of approxi-mately 100mgL solutions of Ga(III) at pH 30 and at roomtemperature (30∘C) up to 300min in a 250mL Erlenmeyerflask at 150 rpm At each predetermined time 1mL of thesolution was removed and tested for its metal content usingflame type AAS The amount of metal ions adsorbed wasevaluated from the difference between the initial and finalconcentrations of Ga(III) ions in the solution

228 Isotherm Modeling Out of many isotherm models theLangmuir and Freundlich models are the most commonlystudied due to their ease of interpretation [22] Langmuirisothermwas initially derived for adsorption of gases on solidsurfaces (Figure 6) and it considered sorption as a chemicalphenomenon the sorbent surface contains only one type ofbinding site and the sorption is limited to monolayer [23] Itis given by

119902eq =119870119897119902max119862eq

1 + 119870119897119862eq

(3)

Table 2 Effect of concentration of NaOH on weight loss ofbiosorbent

NaOH concentration (N) Weight loss ()0000 0000001 1900010 1920050 1960100 208

where 119902eq is the metal uptake 119902max is the maximum biosorp-tion capacity 119870

119897is the constant related to adsorption energy

and 119862eq is the equilibrium concentration of metal ions TheLangmuir parameters can be determined from the slope andthe intercept of the plot 119862eq119902eq versus 119862eq based on thelinearized form of the above equation can be written as

119862eq

119902eq=

1

119870119897119902max

+119862eq

119902max (4)

Freundlich proposed an empirical isotherm relation asexpressed in

119902eq = 1198701198911198621119899

eq (5)

in which 119870119891and 119899 are Freundlich constants (Figure 7) As

the Freundlich isotherm is exponential it can be reasonablyapplied only in the low to intermediate concentration range[24] The equation can be linearized as

log 119902eq = log119870119891+1

119899log119862eq (6)

Besides these two common adsorption isotherms Sipsisotherm is also widely used to study the biosorption mecha-nism of pectin containing compounds [25] (Figure 8) Thisisotherm is a combination of Langmuir and Freundlichisotherm equations deduced for predicting the heteroge-neous adsorption systems and to overcome the limita-tion of the rising adsorbate concentration associated withFreundlich isotherm model At low adsorbate concentra-tions it reduces to Freundlich isotherm while at highconcentrations it predicts a monolayer adsorption capacitycharacteristic of the Langmuir isotherm (Tables 4 and 5)As a general rule the equation parameters are governedmainly by the operating conditions such as the alteration ofpH temperature and concentration Sips isotherm can beexpressed as

119902eq = 119902max119870119904119862119899119904

eq

1 + 119870119904119862119899119904

eq (7)

in which 119899119904is the Sips constant [26] (Table 6)

229 Kinetic Modeling Biosorption data under nonequilib-rium conditions is usually described by pseudofirst order andpseudosecond order equations [27]


Table 3 Effect of biosorbent on adsorption of Ga(III) from aqueoussolution

Biosorbent usedInitial Ga

concentration(mgL)

119902max(mgg) Reference

Oxidized coir 203 1942 [13]Alkali treated peels 200 7626 This study

000500

1000150020002500300035004000

0000 0001 0010 0050 0100

Ga(

III)

upt

ake (

mg

g)

Concentration of NaOH (N)

Figure 1 Effect of different concentration of NaOH on biosorptioncapacity of Citrus limetta peels (119862

119894

= 100mgL 119905 = 4 h 119879 = 30∘C)

Pseudofirst Order Equation The pseudofirst order kineticequation or Lagergren equation is given as

119889119902119905

119889119905= 1198961(119902eq minus 119902119905) (8)

in which 119902119905is the amount of adsorbate adsorbed at time 119905 119902eq

is the value at equilibrium and 1198961is the constant [28]

Pseudosecond Order Equation The pseudosecond orderkinetic equation has been frequently employed to analyze thebiosorption data using different adsorbates and biosorbentsas reviewed by Ho and McKay [29] Consider

119889119902119905

119889119905= 1198962(119902eq minus 119902119905)

2

(9)

in which 1198962is a constant

2210 Adsorption-Desorption Cycles Repetitive adsorption-desorption studies were carried out to evaluate the economicfeasibility of the process Desorption of Ga(III) from previ-ously adsorbed peels was carried out by shaking them with40mL of desorbing media at 30∘C for 240min Differentdesorbing media with varied concentrations studied for thedesorption were HCl HNO

3 and H

2SO4 The metal ion

content in the desorbing media was then estimated usingAAS

2211 Regeneration of Biosorbent RCP and ACP were thor-oughly washed with demineralized water after desorptiontreated with 40mL of 0025M NaOH solution for 240minwashed again dried at 60∘C in hot air oven for 24 h andreused for another adsorption-desorption cycle

3600

3000

2400

1950

1650

1350

1050

900

750

T (

)

(1cm)

RCP before experimentACP before experiment

Figure 2 IR plot of RCP and ACP

2212 Preparation of Simulated Bayer Liquor The processfeasibility was checked by adsorbing the Ga(III) ions fromthe simulated spent Bayer liquor on RCP and ACP It wasprepared in laboratory by adding the components which aregenerally present in spent Bayer liquor in their stoichiometricamount [30] Thus 25 g of Na

2CO3were dissolved in hot

water and cooled to room temperature To this 125 g ofNaOHpellets were added slowly with stirring followed by additionof 120 g of Al(OH)

3 The solution was heated near to boiling

point cooled filtered and diluted to 1 L Then 147mL ofgallium stock solution (1362 gL) was transferred into thesolution and the solution was made up to 1 L by adding waterForty mL of this simulated spent Bayer liquor was takenin an Erlenmeyer flask with pH adjusted to 30 by 01MHCl and subjected to adsorption on 01 g of biomass Theconcentration of Ga(III) ions before and after the adsorptionwas estimated onAASWeight loss of the biomaterials duringadsorption process was also estimated gravimetrically

3 Results and Discussion

31 Effect of Pretreatment on Ga(III) Biosorption Citruspeels are mainly made up of pectin (around 30 by mass)which is rich in galacturonic acid [31] In nature around80 of carboxyl groups of galacturonic acid are presentin esterified form as methyl carboxylate The nonesterifiedgalacturonic acid units can be either free acids (carboxylgroups) or salts with sodium potassium or calcium Thesalts of partially esterified pectins are called pectinates Saltsbelow 5 degree of esterification are called pectates and theinsoluble acid form is the pectic acid [32] Alkali treatmentis very effective in hydrolysis of these esterified galacturonicacid units and converts them into free acid sites It alsoruptures the cell wall and exposes more functional groupsthereby promoting the heavymetal adsorption by preferentialion-exchangemechanism [33] Earlier oxidative pretreatment


Table 4 Values obtained from Langmuir and Freundlich isotherms (linear parameters)

Adsorbent Langmuir isotherm Freundlich isotherm119902max (mgg) 119887 119903

2 RMSE 119870119891

119899 1199032 RMSE

RCP 4762 0031 099 302 384 161 099 708ACP 8333 0022 099 369 369 190 098 772

(a) (b)

Figure 3 Scanning electronic micrographs of (a) RCP and (b) ACP with magnification 500x

Table 5 Values obtained from Langmuir and Freundlich isotherms(nonlinear parameters)

Adsorbent Langmuir isotherm Freundlich isotherms119902max (mgg) 119887 119870

119891

119899

RCP 4654 0033 404 050ACP 7626 0024 411 060

of cellulosic biomass such as jute and coir with hydrogenperoxide has shown to enhance the adsorption capacity forPb(II) cations [34 35] Oxidized coir also showed enhancedadsorption of gallium (1942mgg) compared to unmodifiedcoir (1375mgg) [13]

RawCitrus limetta peels (RCP) a pectin containing wastebiomaterial have shown good potential to adsorb Pb(II) ions[18] Initial experiments on RCP also showed the potentialto adsorb Ga(III) ions from its aqueous solution (119862eq =2170mgg for119862

119894=70mgL) RCPwas given various chemical

treatments that are reported to enhance the adsorptioncapacity of biomaterials [19] (Table 1)

Among those it was found that the alkali treatment wasthe most efficient in enhancing the adsorption capacity ofpeels and hence the concentration of NaOH was optimizedat RT (30∘C) and 2 h treatment time (Figure 1) (Table 2)Different acidic groups such as carboxylic and sulphonic acidalso get converted into their sodium forms which have beenshown to promote heavy-metal ion adsorption [36]

32 FT-IR Spectra of Biomass FTIR spectra of peels showedpeak at sim3350 cmminus1 which is characteristic of hydroxyl groupmainly due to water The peak observed at sim1625 cmminus1is attributed to asymmetric stretching of the carboxylic

Table 6 Values obtained from Sips isotherms

Adsorbent Sips isotherm119870119904

120573119904

119886119904

1199032

RCP 1124 1212 0018 099ACP 2412 0787 0038 099

(C=O) double bond The peaks observed at 2924 cmminus1 and2856 cmminus1 in ACP are due to asymmetric and symmetricstretching modes of methylene groups No strong shift in thewave number sim1750 cmminus1 was observed in RCP although theintensity of peak increased in ACP which is characteristicof carbonyl group of carboxylic acid (ndashCOOH) and ester (ndashCOOR) This indicates increase in the number of carboxylicgroups in ACP which has also been quantified by methyleneblue absorption method to 632 times 10minus2mmolg from 540times 10minus2mmolg in RCP Thus the alkali treatment causedmodification of the ester functional groups to carboxylic acidgroups present in raw peels

33 Scanning Electron Microscopy SEM images clearly indi-cate the morphological changes in the peels on alkali treat-ment It can be easily depicted from the SEM that the surfaceof peels is highly heterogeneous As seen in Figure 3 ACPsurface shows more cavities and more number of opened uppores as compared to RCP indicating that it has increasedthe surface area available for adsorption Alkali treatmentproved to be effective in rupturing the cell walls due towhichmore functional groups are exposed on the surface andbecame available for adsorption Apart from that no furthersignificant morphological changes were apparent in the SEMimages


O

O

O

O

O

O

COOH

HOOH COOCH3

COOCH3

HO OH

HO OH

HydrolysisNaOH

COOH

HO

OH

COOH

HO OH

COOH

HO

OH

Figure 4 Structure of pectin before and after alkaline treatment

Table 7 Experimental and pseudosecond order values for RCP and ACP

Adsorbent Experimental 119902 eq(mgg)

1198962

(times10minus3min)119902eq

(mgg) 1199032 Initial rate ℎ

(mggsdotmin)RCP 2411 27 2500 099 169ACP 3226 24 2977 099 250

05

101520253035404550

0 05 1 15 2 25 3 35pH

RCPACP

qeq

(mg

g)

Figure 5 Effect of pH on biosorption of Ga(III)

0

05

1

15

2

25

0 20 40 60 80

RCPACP

Cfq

e

Cf

Figure 6 Linearized Langmuir isotherm

100

110

120

130

140

150

160

170

100 120 140 160 180 200log Cf

RCPACP

log q

e

Figure 7 Linearized Freundlich isotherm

05

1015202530354045

0 10 20 30 40 50 60 70Ceq

qeq

RCPACP

Figure 8 Nonlinear Sips isotherm


Table8Re

peated

adsorptio

n-desorptio

ncycle

sfor

Ga(III)adsorptio

n

Adsorbent

Cycle

1Cy

cle2

Cycle

3adsorptio

ndesorptio

nweightloss

adsorptio

ndesorptio

nwe

ight

loss

Overallweightloss

adsorptio

ndesorptio

nweightloss

Overallweightloss

RCP

5898

9871

1919

3437

9577

1621

3940

3708

9526

476

4016

ACP

6851

9537

1753

5600

8978

1290

3043

5546

8951

288

3331


000

200

400

600

800

1000

1200

0 50 100 150 200 250 300t (min)

RCPACP

tqt

Figure 9 Pseudosecond order plot for1198620

= 100mgL (RCP) and1198620

= 100mgL (ACP)

Table 9 Synthetic Bayer liquor adsorption-desorption cycle

Adsorbent Adsorption () Desorption () Weight loss ()RCP 3957 9835 2998ACP 4113 9223 1803

34 Estimation of Acidic Groups on the Surface of PeelsThe carboxyl groups present in the biosorbents have beenproved to be directly responsible for the sorption of heavymetals [17 18]These are the most abundant acidic functionalgroups and the adsorption capacity of peels is directly relatedto the presence of these sites in pectin in the form ofgalacturonic acid Estimation of acidic groups on the surfaceof peels available for sorption reveals that ACP containscontains more carboxylic acid groups (632 times 10minus2mmolg)as compared to RCP (540 times 10minus2mmolg) This has beenattributed to the alkaline hydrolysis of some of the estergroups present on the surface of the peels under the treatmentconditions Structure of pectin before and after hydrolysis isas shown in Figure 4

35 Effect of Initial Solution pH pH is one of themost crucialfactors which drives the efficiency of adsorption as it governsthe speciation of the metal ions in aqueous solution andalso determines the degree of protonation on the biomassAt lower pH protons compete with the metal ions therebydecreasing the adsorption while at higher pH metal ionsform corresponding hydroxides get precipitated out

The biosorption of Ga(III) was strongly affected by initialsolution pHThe sorption capacity of RCPhas increased from1629mgg at pH 10 to 3559mggGa(III) at pH 30 (Figure 5)indicating an increase in adsorption capacity Beyond pH30 precipitation occurs as gallium forms a hydroxide geland loses its solution characteristics [36] In case of ACPthe increase in adsorption capacity registered was from1823mgg to 4444mgg at similar pH values

In aqueous solution gallium is always present in itshydrated form with six molecules of water held strongly tomake an octahedral complex The strength of metal-oxygenbond weakens OndashH bond hence hydrolysis occurs andprotons are released thus giving acidic solution The moremetal ion concentration in the solution is the more thehydrolysis is and hence themore acidic the solution becomes[37 38] Ga(III) ions are Lewis acids and in aqueoussolution they form aqua ions of the formula Ga(H

2O)6

3+The aqua ions undergo hydrolysis the hydrated gallium ionshave six molecules of water which are held firmly givingan octahedral complex The first hydrolysis step is givengenerically as

Ga(H2O)6

3+

+H2O 999445999468 [Ga(H

2O)5

(OH)]+2 +H3O+ (10)

Thus the aqua cations behave as acids in termsof Broslashnsted-Lowry acid-base theory This effect is easilyexplained by considering the inductive effect of the positivelycharged metal ion which weakens the OndashH bond of anattached water molecule causing the liberation of a protonrelatively easy to make the solution acidic

Like other metal ions the adsorption of Ga(III) is alsohighly influenced by pH [39ndash41] At lower pH the affinitytowards the proton of the binding site of peels is much greaterthan that of themetal ion (H+ ≫M3+) compared with that athigher pH where M3+ ≫ H+ [36] Therefore the adsorptionis less at a lower pH of 10 which remains almost unaffectedtill pH 15 as Ga(III) has strong competition with protons andthen it increases with the pH as the concentration of protonsdecreases till pH 25 is attained

From the data given in Table 3 it is clear that theadsorption of Ga(III) on Citrus limetta peels is much higherthan any other biosorbent used in earlier studies [13] Thismay be attributed to enhanced carboxylic acid sites in ACPpectin

36 Adsorption Isotherm The adsorption data were fitted toLangmuir and Freundlich adsorption isotherms The metalloading capacities (119902max) of RCP and ACP as calculatedfrom the slope of the plot 119862eq119902eq versus 119862eq were foundto be 4762 and 8333mgg respectively Though the dataseems to be fitting equally well with the Langmuir (1199032 =

099) and Freundlich (1199032

= 099) isotherms RMSE errorvalue for Langmuir plot is much lower than Freundlich plotThis suggests that the Langmuir model gives better fit forboth the adsorbents ldquo119870

119891rdquo and ldquonrdquo were calculated from

the intercept and slope of the plot log 119902eq versus log119862eqFreundlich isotherm values of ldquo119899rdquo were 161 and 190 for RCPand ACP respectively suggesting favourable adsorption byACP

37 Kinetic Modelling Pseudosecond order (1198772 = 099) plotshows better fit than pseudofirst order (1198772 = 094) for RCPand ACP Figure 9 represent the linearized plots for secondorder model for RCP and ACP Higher value of initial rateh in ACP (250mggsdotmin) suggests favorable adsorptionThe values for pseudosecond order model has been listed in


Table 7 The kinetic study reveals closeness of the predictedand experimental 119902max values which are 2500 and 2411 forRCP and 3226 and 2977 for ACP respectively Pseudosecondorder plot gives best fit for RCP as well as ACP hence it wasconsidered that adsorption of Ga(III) on RCP and ACP takesplace via pseudosecond order kinetics

38 Desorption Studies Desorption efficiency of the adsor-bent is crucial to the recovery of gallium The metalion loaded adsorbent was most effectively desorbed byusing 05M HCl when different acids (HCl H

2SO4 and

HNO3) with different concentrations (01Mndash10M) were

tried Ga(III) adsorbed on the surface of the adsorbentexchanges with the H+ ion of the acid due to its highaffinity towards the functional groups behaving as a cationexchanger Desorption in the first cycle was observed tobe more than 95 which decreased marginally in thesubsequent cycles The weight loss study of the adsorbentsduring the adsorption-desorption cycles indicated that afterthe first complete cycle the weight loss for RCP was 1919while that for ACP was 1753 It increased to 3705 for RCPand to 5545 for ACP after the second cycle Even after thethird cycle the same adsorbent can be used by seeing its goodadsorption capacity

39 Regeneration Studies Although theCitrus limetta peels isa waste material obtained from the orange fruit any chemicaltreatment to convert it into a better adsorbent adds to the costIn order to make the process economically viable the peelsafter desorption of Ga(III) were regenerated using 0025NNaOH and reused for another adsorption-regeneration cycleLow concentration of alkali is used as regeneration media foreconomic viability Regeneration of the peels was studied for 3cycles and showed comparative adsorption in the next cycles

310 Simulated Bayer Liquor Sample Analysis SyntheticBayer liquor sample was analyzed for the efficiency ofbiosorbent for adsorption-desorption cycles (Table 9) It wasobserved that RCP showed 3957 adsorption of galliumfrom the simulated spent Bayer liquor while ACP showed4113 adsorption Both the adsorbents showed nearly com-plete desorption in 05M HCl as desorbing media Theweight loss of biomass after first cycle was observed to be2998 for RCP and 1803 for ACP The decrease in theadsorption capacity as compared to pure aqueous solutionof gallium may be attributed to the presence of other metalions such as Na(I) and Al(III) present in the solutionThese results are presented in Table 8 It may be seen thatRCP and ACP are competitive to synthetic ion exchangeresin showing adsorption capacities of 732 and 761mggrespectively which are higher than that of reported value(60mgg) on resin with hydroxamic acid ligand [3]

4 Conclusion

Waste biomass Citrus limetta peels were effectively used toadsorb gallium ions from aqueous solution When treatedwith sodiumhydroxide the alkali treated peels (ACP) showed

enhanced metal removal capacity Optimum pH for adsorp-tion was found to be 30 Kinetic data showed that theequilibrium reachedwithin 180minutes Pseudosecond ordermodel proved to be the best fit whereas isotherm studiesreveal that the metal ion adsorption capacity of 4762mggfor RCPwas enhanced to 8333mgg for ACPThe adsorbentsshowed good stability up to three adsorption-desorptioncycles and hence proved practical to use at scale up level AlsoRCP and ACP showed significant adsorption in syntheticBayer liquor sample which highlights the use ofCitrus limettapeels at commercial level

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author Sachin C Gondhalekar gratefully acknowledgesthe funding by the University Grants Commissionrsquos fellow-ship under Special Assistance Programme

References

[1] R R Moskalyk ldquoGallium the backbone of the electronicsindustryrdquo Minerals Engineering vol 16 no 10 pp 921ndash9292003

[2] I R Grant ldquoGallium arsenide from mine to microcircuitrdquoTransactions of the Institution of Mining and Metallurgy CMineral Processing and Extractive Metallurgy vol 97 pp 48ndash521987

[3] P Selvi M Ramasami M H P Samuel P Adaikkalam andG N Srinivasan ldquoRecovery of gallium from Bayer liquorusing chelating resins in fixed-bed columnsrdquo Industrial andEngineering Chemistry Research vol 43 no 9 pp 2216ndash22212004

[4] G Iosilevsky D Front L Bettman R Hardoff and Y Ben-Arieh ldquoUptake of gallium-67 citrate and [2-3H]deoxyglucosein the tumormodel following chemotherapy and radiotherapyrdquoJournal of Nuclear Medicine vol 26 no 3 pp 278ndash282 1985

[5] E F Borra R Content L Girard S Szapiel LM Tremblay andE Boily ldquoLiquidmirrors optical shop tests and contributions tothe technologyrdquoAstrophysical Journal Letters vol 393 no 2 pp829ndash847 1992

[6] US Geological SurveyMineral Commodity Summaries 2013[7] A 2011 Roskill Report ldquoGallium global industry markets amp

outlookrdquo Roskill Report 2011[8] Govt of India Ministry of Mines Indian Beauro of Mines

Indian Mineral Year Book vol 2 2011[9] X Lu LWang XWang andXNiuesearch ldquoResearch progress

in gallium recovery technologyrdquo Nonferrous Metals vol 60 pp105ndash108 2008

[10] A M G Figueiredo W Avristcher E A Masini S C Dinizand A Abrao ldquoDetermination of lanthanides (La Ce Nd Sm)and other elements inmetallic gallium by instrumental neutronactivation analysisrdquo Journal of Alloys and Compounds vol 344no 1-2 pp 36ndash39 2002


[11] Z Zhao Y Yang Y Xiao and Y Fan ldquoRecovery of gallium fromBayer liquor a reviewrdquo Hydrometallurgy vol 125-126 pp 115ndash124 2012

[12] J Wang and C Chen ldquoBiosorbents for heavy metals removaland their futurerdquo Biotechnology Advances vol 27 no 2 pp 195ndash226 2009

[13] U S Suryavanshi and S R Shukla ldquoAdsorption of Ga(III) onoxidized coirrdquo Industrial and Engineering Chemistry Researchvol 48 no 2 pp 870ndash876 2009

[14] H Eroglu S Yapici C Nuhoglu and E Varoglu ldquoBiosorptionof Ga-67 radionuclides from aqueous solutions onto wastepomace of an olive oil factoryrdquo Journal of Hazardous Materialsvol 172 no 2-3 pp 729ndash738 2009

[15] H Eroglu S Yapici and E Varoglu ldquoAn investigation of thebiosorption of radioactive gallium-67 in an aqueous solutionusing rose residuerdquo Journal of Chemical and Engineering Datavol 55 no 8 pp 2848ndash2856 2010

[16] S Schiewer and A Balaria ldquoBiosorption of Pb2+ by original andprotonated citrus peels equilibrium kinetics and mechanismrdquoChemical Engineering Journal vol 146 no 2 pp 211ndash219 2009

[17] E Njikam and S Schiewer ldquoOptimization and kinetic modelingof cadmium desorption from citrus peels a process for biosor-bent regenerationrdquo Journal of HazardousMaterials vol 213-214pp 242ndash248 2012

[18] U Suryavanshi and S R Shukla ldquoAdsorption of Pb2+ byAlkali-treated citrus limetta peelsrdquo Industrial and EngineeringChemistry Research vol 49 no 22 pp 11682ndash11688 2010

[19] S Srivastava and P GoyalNovel Biomaterials Decontaminationof Toxic Metals fromWastewater Springer 2010

[20] G Sebe P Pardon F Pichavant S Grelier and B De Jeso ldquoAninvestigation into the use of eelgrass (Zostera noltii) for removalof cupric ions from dilute aqueous solutionsrdquo Separation andPurification Technology vol 38 no 2 pp 121ndash127 2004

[21] D Klemm B Philipp T Heinze U Heinze and WWagenknecht ldquoFundamentals and analytical methodsrdquo inComprehensive Cellulose Chemistry vol 1 p 236 JohnWiley ampSons Weinheim Germany 1998

[22] K Y Foo and B H Hameed ldquoInsights into the modeling ofadsorption isotherm systemsrdquo Chemical Engineering Journalvol 156 no 1 pp 2ndash10 2010

[23] I Langmuir ldquoThe adsorption of gases on plane surfaces ofglassmica and platinumrdquoThe Journal of the AmericanChemicalSociety vol 40 no 9 pp 1361ndash1403 1918

[24] A Z Freundlich ldquoUber die adsorption in losungenrdquo Zeitschriftfur Physikalische Chemie vol 57 pp 385ndash470 1906

[25] K V Kumar and K Porkodi ldquoRelation between some two- andthree-parameter isothermmodels for the sorption ofmethyleneblue onto lemon peelrdquo Journal of Hazardous Materials vol 138no 3 pp 633ndash635 2006

[26] R Sips ldquoCombined form of langmuir and freundlich equa-tionsrdquo Journal of Chemical Physics vol 16 pp 490ndash495 1948

[27] Y Liu and Y-J Liu ldquoBiosorption isotherms kinetics andthermodynamicsrdquo Separation and Purification Technology vol61 no 3 pp 229ndash242 2008

[28] S Lagergren ldquoZur theorie der sogenannten adsorption gelosterstoffe Kungliga Svenska Vetenskapsakademiensrdquo Handlingarvol 24 no 4 pp 1ndash39 1898

[29] Y S Ho and G McKay ldquoPseudo-second order model forsorption processesrdquo Process Biochemistry vol 34 no 5 pp 451ndash465 1999

[30] F-F Zha A G Fane and C J D Fell ldquoLiquid membrane pro-cesses for gallium recovery from alkaline solutionsrdquo Industrialand Engineering Chemistry Research vol 34 no 5 pp 1799ndash1809 1995

[31] C DMay ldquoIndustrial pectins sources production and applica-tionsrdquo Carbohydrate Polymers vol 12 no 1 pp 79ndash99 1990

[32] P Sriamornsak ldquoChemistry of pectin and its pharmaceuticaluses a reviewrdquo Journal of Pharmacy and Pharmaceutical Sci-ences vol 44 pp 207ndash228 1998

[33] S R Shukla R S Pai and A D Shendarkar ldquoAdsorption ofNi(II) Zn(II) and Fe(II) onmodified coir fibresrdquo Separation andPurification Technology vol 47 no 3 pp 141ndash147 2006

[34] S R Shukla and R S Pai ldquoComparison of Pb(II) uptake by coirand dye loaded coir fibres in a fixed bed columnrdquo Journal ofHazardous Materials vol 125 no 1ndash3 pp 147ndash153 2005

[35] S R Shukla and R S Pai ldquoAdsorption of Cu(II) Ni(II) andZn(II) on modified jute fibresrdquo Bioresource Technology vol 96no 13 pp 1430ndash1438 2005

[36] P PerssonK Zivkovic and S Sjoberg ldquoQuantitative adsorptionand local structures of gallium(III) at the water-120572-FeOOHinterfacerdquo Langmuir vol 22 no 5 pp 2096ndash2104 2006

[37] J BurgessMetal Ions in Solution Ellis Horwood NewYork NYUSA 1978

[38] D T RichensThe Chemistry of Aqua Ions Synthesis Structureand Reactivity A Tour Through the Periodic Table of theElements John Wiley amp Sons 1997

[39] N Fiola I Villaescusaa M Martınezb N Mirallesb J Pochcand J Serarols ldquoSorption of Pb(II) Ni(II) Cu(II) and Cd(II)from aqueous solution by olive stone wasterdquo Separation andPurification Technology vol 50 no 1 pp 132ndash140 2006

[40] R H S F Vieira and B Volesky ldquoBiosorption a solution topollutionrdquo International Microbiology vol 3 no 1 pp 17ndash242000

[41] B Volesky Biosorption of Heavy Metals vol 3 CRC Press BocaRaton Fla USA 1990

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


fractional precipitation electrochemical deposition solventextraction and ion exchange Fractional precipitation is acomplex process solvent extraction is efficient but veryslow electrochemical method usesmercury cathode which isbanned due to mercury toxicity whereas ion exchange giveseffective recovery of gallium Industrial resins such as DuoliteES-346 and PHG586 may be used however the process isvery expensive Hence further research for cheap efficientand environmentally friendly recovery of gallium is essential[11]

Biosorption studies have mainly focused on the removaland recovery of heavy metal ions from industrial effluentsdetoxification being their primary goal Functional groupspresent in the biosorbents that are responsible for metalbinding are carboxyl phosphoryl sulfhydryl amino sulfateimidazole thioether phenol amide and hydroxyl in variousbiomolecules of peptide protein and polysaccharide moi-eties of the cell walls These functional groups bind the metalionsmainly by adsorption ion exchange and chelating effects[12]

Very few reports have been published on the removalrecovery of gallium using natural adsorbent [13ndash15] Citruslimetta peels are a natural pectinacious agrowaste materialtypically generated in large quantities by the fruit juiceindustry rich in pectin with abundant presence of carboxylgroups It is reported that these peels have a metal bindingmechanism similar to brown algal biosorbents since pectin ischemically similar to the brown algal cell wall polysaccharidealginate [6 7] These peels have been found to be verygood adsorbents for Pb(II) and Cd(II) [16ndash18] Our previousstudies have shown good binding capacity by citrus peels forPb(II) ions [18]

In the present work the adsorption of Ga(III) from theaqueous solution of gallium nitrate and from the simulatedBayer liquor on Citrus limetta peels in its raw as well as alkalitreated form has been reported

2 Materials and Methods

21 Materials Citrus limetta fruit peels procured from localjuice shopwere used as biosorbentsDemineralizedwaterwasused throughout the experiment for dilution and washingpurposes Stock solution of 1000mgL was prepared fromgallium nitrate salt (Sigma-Aldrich India) Gallium standardused for calibration of Atomic Absorption Spectrometer(Model GBC 932plus Austria) was supplied by Merck IncGermany

pH adjustment of metal ion solution was achieved byappropriate addition of 01M NaOH and 01M HCl

22 Methods

221 Preparation of Biosorbent Citrus limetta peels procuredfrom local juice shop were soaked in water for 4 h washedand cleaned using 1 nonionic detergent solution and againwith demineralised water The washed peels were dried at60∘C till constant weight reduced to small particle size usinga grinder sieved to mesh sizes between 425 and 800 120583 and

Table 1 Adsorption capacities of Citrus limetta peels (119862119894

=

100mgL 119905 = 4 h and 119879 = 30∘C) on chemical modification

Modification Metal uptake (mgL)Nil (RCP) 24401M malonic acid treated peels 24311M oxalic acid treated peels 216720 H2O2 treated peels 307801M sodium hydroxide treated peels (ACP) 34591M citric acid treated peels 23901M succinic acid treated peels 2705Acetylated peels 2708Chlorosulphonic acid treated peels 2300Methane sulphonic acid treated peels 233301M potassium dichromate treated peels 2712

stored in zip lock bagsThebiomass thus obtainedwas termedas raw citrus peels (RCP)

222 Modification of Functional Groups on RCP The rawpeels were treated with different chemical agents as reportedto enhance their adsorption capacity This data is furtherpresented in Table 1 [19]

RCP was treated with 005M aqueous NaOH for 3 hat room temperature It was then washed thoroughly withdemineralized water till neutral pH and then dried in anoven at 60∘C for 24 h and stored in zip lock bags to avoidcontamination with moisture It was termed as alkali treatedcitrus peels (ACP) The weight loss of biomass due to alkalitreatment was estimated experimentally

223 Estimation of Gallium Ions Ga(III) concentration inaqueous solution was determined by Atomic AbsorptionSpectrometer (GBC 932 plus Australia) at 2871 nm with anair-acetylene flame Each time AAS was calibrated by usingstandard 1000mgL Ga(III) solution

224 ATR-IR Spectroscopy The functional groups present onthe surface of RCP and ACP were determined by recordingthe infrared spectra of these peels using Shimadzu 8400S FT-IR spectrometer (Figure 2)

225 Scanning Electron Microscopy (SEM) Microscopicimages of RCP and ACP were taken by scanning electronmicroscope (Jeol JSM6380 LA spectrometer Tokyo Japan) toreveal themorphological aspects of the surface of the biomasssamples

226 Estimation of Acidic Groups Number of acidic sitespresent on RCP and ACP were estimated by methylene blueabsorption method [20 21] When a biomass is treated witha cationic dye like methylene blue the coloured cations ofthe dye are quantitatively absorbed by acidic groups presenton the material forming strong ionic linkage A weighedsample of the biomass was added to an Erlenmeyer flask con-taining 25mL of aqueous methylene blue chloride solution





119902eq =(1198620minus 119862eq)119881

119882 (1)




119864 =(1198620minus 119862eq)

1198620

times 100 (2)




119902eq =119870119897119902max119862eq

1 + 119870119897119862eq

(3)






119862eq

119902eq=

1

119870119897119902max

+119862eq

119902max (4)


119902eq = 1198701198911198621119899

eq (5)



log 119902eq = log119870119891+1

119899log119862eq (6)


119902eq = 119902max119870119904119862119899119904

eq

1 + 119870119904119862119899119904

eq (7)






concentration(mgL)



000500

1000150020002500300035004000

0000 0001 0010 0050 0100

Ga(

III)

upt

ake (

mg

g)



119894

= 100mgL 119905 = 4 h 119879 = 30∘C)


119889119902119905

119889119905= 1198961(119902eq minus 119902119905) (8)




119889119902119905

119889119905= 1198962(119902eq minus 119902119905)

2

(9)



3 and H

2SO4 The metal ion



3600

3000

2400

1950

1650

1350

1050

900

750

T (

)

(1cm)













2 RMSE 119870119891

119899 1199032 RMSE

RCP 4762 0031 099 302 384 161 099 708ACP 8333 0022 099 369 369 190 098 772

(a) (b)




119891

119899

RCP 4654 0033 404 050ACP 7626 0024 411 060









120573119904

119886119904

1199032

RCP 1124 1212 0018 099ACP 2412 0787 0038 099




O

O

O

O

O

O

COOH

HOOH COOCH3

COOCH3

HO OH

HO OH

HydrolysisNaOH

COOH

HO

OH

COOH

HO OH

COOH

HO

OH




1198962




05

101520253035404550

0 05 1 15 2 25 3 35pH

RCPACP

qeq

(mg

g)


0

05

1

15

2

25

0 20 40 60 80

RCPACP

Cfq

e

Cf


100

110

120

130

140

150

160

170

100 120 140 160 180 200log Cf

RCPACP

log q

e


05

1015202530354045

0 10 20 30 40 50 60 70Ceq

qeq

RCPACP



Table8Re

peated

adsorptio

n-desorptio

ncycle

sfor

Ga(III)adsorptio

n

Adsorbent

Cycle

1Cy

cle2

Cycle

3adsorptio

ndesorptio

nweightloss

adsorptio

ndesorptio

nwe

ight

loss

Overallweightloss

adsorptio

ndesorptio

nweightloss

Overallweightloss

RCP

5898

9871

1919

3437

9577

1621

3940

3708

9526

476

4016

ACP

6851

9537

1753

5600

8978

1290

3043

5546

8951

288

3331


000

200

400

600

800

1000

1200

0 50 100 150 200 250 300t (min)

RCPACP

tqt


= 100mgL (RCP) and1198620

= 100mgL (ACP)







2O)6


Ga(H2O)6

3+

+H2O 999445999468 [Ga(H

2O)5

(OH)]+2 +H3O+ (10)













2SO4 and





4 Conclusion





Acknowledgment


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







119902eq =(1198620minus 119862eq)119881

119882 (1)




119864 =(1198620minus 119862eq)

1198620

times 100 (2)




119902eq =119870119897119902max119862eq

1 + 119870119897119862eq

(3)






119862eq

119902eq=

1

119870119897119902max

+119862eq

119902max (4)


119902eq = 1198701198911198621119899

eq (5)



log 119902eq = log119870119891+1

119899log119862eq (6)


119902eq = 119902max119870119904119862119899119904

eq

1 + 119870119904119862119899119904

eq (7)






concentration(mgL)



000500

1000150020002500300035004000

0000 0001 0010 0050 0100

Ga(

III)

upt

ake (

mg

g)



119894

= 100mgL 119905 = 4 h 119879 = 30∘C)


119889119902119905

119889119905= 1198961(119902eq minus 119902119905) (8)




119889119902119905

119889119905= 1198962(119902eq minus 119902119905)

2

(9)



3 and H

2SO4 The metal ion



3600

3000

2400

1950

1650

1350

1050

900

750

T (

)

(1cm)













2 RMSE 119870119891

119899 1199032 RMSE

RCP 4762 0031 099 302 384 161 099 708ACP 8333 0022 099 369 369 190 098 772

(a) (b)




119891

119899

RCP 4654 0033 404 050ACP 7626 0024 411 060









120573119904

119886119904

1199032

RCP 1124 1212 0018 099ACP 2412 0787 0038 099




O

O

O

O

O

O

COOH

HOOH COOCH3

COOCH3

HO OH

HO OH

HydrolysisNaOH

COOH

HO

OH

COOH

HO OH

COOH

HO

OH




1198962




05

101520253035404550

0 05 1 15 2 25 3 35pH

RCPACP

qeq

(mg

g)


0

05

1

15

2

25

0 20 40 60 80

RCPACP

Cfq

e

Cf


100

110

120

130

140

150

160

170

100 120 140 160 180 200log Cf

RCPACP

log q

e


05

1015202530354045

0 10 20 30 40 50 60 70Ceq

qeq

RCPACP



Table8Re

peated

adsorptio

n-desorptio

ncycle

sfor

Ga(III)adsorptio

n

Adsorbent

Cycle

1Cy

cle2

Cycle

3adsorptio

ndesorptio

nweightloss

adsorptio

ndesorptio

nwe

ight

loss

Overallweightloss

adsorptio

ndesorptio

nweightloss

Overallweightloss

RCP

5898

9871

1919

3437

9577

1621

3940

3708

9526

476

4016

ACP

6851

9537

1753

5600

8978

1290

3043

5546

8951

288

3331


000

200

400

600

800

1000

1200

0 50 100 150 200 250 300t (min)

RCPACP

tqt


= 100mgL (RCP) and1198620

= 100mgL (ACP)







2O)6


Ga(H2O)6

3+

+H2O 999445999468 [Ga(H

2O)5

(OH)]+2 +H3O+ (10)













2SO4 and





4 Conclusion





Acknowledgment


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






concentration(mgL)



000500

1000150020002500300035004000

0000 0001 0010 0050 0100

Ga(

III)

upt

ake (

mg

g)



119894

= 100mgL 119905 = 4 h 119879 = 30∘C)


119889119902119905

119889119905= 1198961(119902eq minus 119902119905) (8)




119889119902119905

119889119905= 1198962(119902eq minus 119902119905)

2

(9)



3 and H

2SO4 The metal ion



3600

3000

2400

1950

1650

1350

1050

900

750

T (

)

(1cm)













2 RMSE 119870119891

119899 1199032 RMSE

RCP 4762 0031 099 302 384 161 099 708ACP 8333 0022 099 369 369 190 098 772

(a) (b)




119891

119899

RCP 4654 0033 404 050ACP 7626 0024 411 060









120573119904

119886119904

1199032

RCP 1124 1212 0018 099ACP 2412 0787 0038 099




O

O

O

O

O

O

COOH

HOOH COOCH3

COOCH3

HO OH

HO OH

HydrolysisNaOH

COOH

HO

OH

COOH

HO OH

COOH

HO

OH




1198962




05

101520253035404550

0 05 1 15 2 25 3 35pH

RCPACP

qeq

(mg

g)


0

05

1

15

2

25

0 20 40 60 80

RCPACP

Cfq

e

Cf


100

110

120

130

140

150

160

170

100 120 140 160 180 200log Cf

RCPACP

log q

e


05

1015202530354045

0 10 20 30 40 50 60 70Ceq

qeq

RCPACP



Table8Re

peated

adsorptio

n-desorptio

ncycle

sfor

Ga(III)adsorptio

n

Adsorbent

Cycle

1Cy

cle2

Cycle

3adsorptio

ndesorptio

nweightloss

adsorptio

ndesorptio

nwe

ight

loss

Overallweightloss

adsorptio

ndesorptio

nweightloss

Overallweightloss

RCP

5898

9871

1919

3437

9577

1621

3940

3708

9526

476

4016

ACP

6851

9537

1753

5600

8978

1290

3043

5546

8951

288

3331


000

200

400

600

800

1000

1200

0 50 100 150 200 250 300t (min)

RCPACP

tqt


= 100mgL (RCP) and1198620

= 100mgL (ACP)







2O)6


Ga(H2O)6

3+

+H2O 999445999468 [Ga(H

2O)5

(OH)]+2 +H3O+ (10)













2SO4 and





4 Conclusion





Acknowledgment


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






2 RMSE 119870119891

119899 1199032 RMSE

RCP 4762 0031 099 302 384 161 099 708ACP 8333 0022 099 369 369 190 098 772

(a) (b)




119891

119899

RCP 4654 0033 404 050ACP 7626 0024 411 060









120573119904

119886119904

1199032

RCP 1124 1212 0018 099ACP 2412 0787 0038 099




O

O

O

O

O

O

COOH

HOOH COOCH3

COOCH3

HO OH

HO OH

HydrolysisNaOH

COOH

HO

OH

COOH

HO OH

COOH

HO

OH




1198962




05

101520253035404550

0 05 1 15 2 25 3 35pH

RCPACP

qeq

(mg

g)


0

05

1

15

2

25

0 20 40 60 80

RCPACP

Cfq

e

Cf


100

110

120

130

140

150

160

170

100 120 140 160 180 200log Cf

RCPACP

log q

e


05

1015202530354045

0 10 20 30 40 50 60 70Ceq

qeq

RCPACP



Table8Re

peated

adsorptio

n-desorptio

ncycle

sfor

Ga(III)adsorptio

n

Adsorbent

Cycle

1Cy

cle2

Cycle

3adsorptio

ndesorptio

nweightloss

adsorptio

ndesorptio

nwe

ight

loss

Overallweightloss

adsorptio

ndesorptio

nweightloss

Overallweightloss

RCP

5898

9871

1919

3437

9577

1621

3940

3708

9526

476

4016

ACP

6851

9537

1753

5600

8978

1290

3043

5546

8951

288

3331


000

200

400

600

800

1000

1200

0 50 100 150 200 250 300t (min)

RCPACP

tqt


= 100mgL (RCP) and1198620

= 100mgL (ACP)







2O)6


Ga(H2O)6

3+

+H2O 999445999468 [Ga(H

2O)5

(OH)]+2 +H3O+ (10)













2SO4 and





4 Conclusion





Acknowledgment


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




O

O

O

O

O

O

COOH

HOOH COOCH3

COOCH3

HO OH

HO OH

HydrolysisNaOH

COOH

HO

OH

COOH

HO OH

COOH

HO

OH




1198962




05

101520253035404550

0 05 1 15 2 25 3 35pH

RCPACP

qeq

(mg

g)


0

05

1

15

2

25

0 20 40 60 80

RCPACP

Cfq

e

Cf


100

110

120

130

140

150

160

170

100 120 140 160 180 200log Cf

RCPACP

log q

e


05

1015202530354045

0 10 20 30 40 50 60 70Ceq

qeq

RCPACP



Table8Re

peated

adsorptio

n-desorptio

ncycle

sfor

Ga(III)adsorptio

n

Adsorbent

Cycle

1Cy

cle2

Cycle

3adsorptio

ndesorptio

nweightloss

adsorptio

ndesorptio

nwe

ight

loss

Overallweightloss

adsorptio

ndesorptio

nweightloss

Overallweightloss

RCP

5898

9871

1919

3437

9577

1621

3940

3708

9526

476

4016

ACP

6851

9537

1753

5600

8978

1290

3043

5546

8951

288

3331


000

200

400

600

800

1000

1200

0 50 100 150 200 250 300t (min)

RCPACP

tqt


= 100mgL (RCP) and1198620

= 100mgL (ACP)







2O)6


Ga(H2O)6

3+

+H2O 999445999468 [Ga(H

2O)5

(OH)]+2 +H3O+ (10)













2SO4 and





4 Conclusion





Acknowledgment


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Table8Re

peated

adsorptio

n-desorptio

ncycle

sfor

Ga(III)adsorptio

n

Adsorbent

Cycle

1Cy

cle2

Cycle

3adsorptio

ndesorptio

nweightloss

adsorptio

ndesorptio

nwe

ight

loss

Overallweightloss

adsorptio

ndesorptio

nweightloss

Overallweightloss

RCP

5898

9871

1919

3437

9577

1621

3940

3708

9526

476

4016

ACP

6851

9537

1753

5600

8978

1290

3043

5546

8951

288

3331


000

200

400

600

800

1000

1200

0 50 100 150 200 250 300t (min)

RCPACP

tqt


= 100mgL (RCP) and1198620

= 100mgL (ACP)







2O)6


Ga(H2O)6

3+

+H2O 999445999468 [Ga(H

2O)5

(OH)]+2 +H3O+ (10)













2SO4 and





4 Conclusion





Acknowledgment


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




000

200

400

600

800

1000

1200

0 50 100 150 200 250 300t (min)

RCPACP

tqt


= 100mgL (RCP) and1198620

= 100mgL (ACP)







2O)6


Ga(H2O)6

3+

+H2O 999445999468 [Ga(H

2O)5

(OH)]+2 +H3O+ (10)













2SO4 and





4 Conclusion





Acknowledgment


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






2SO4 and





4 Conclusion





Acknowledgment


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article recovery of ga(iii) by raw and alkali...

Documents