The ability of the non-living biomass of water hyacinth roots, Eichhomia crassipes, to remove Cr(lll) has been studied at different concentrations, pH levels and in the presence of Na and Ca ions in an attempt to simulate the

real conditions of tannery waste. Ca ions exhibited a greater inhibitory effect on the Cr(lll) sorption than the Na ions. Kinetic studies showed that more than one mode of sorption was operating in the uptake of Cr(lll) by water

hyacinth roots. The equilibrium data obeyed Langmuir isotherm for the Cr(III)-water hyacinth root system, implying mono-layer coverage of the

sorben t material

Lee, C. K.

Low, K. S.

Universiti Putra Malaysia Institutional Repository

Pertanika J. Sci. & Techno!. 5(2): 147-155 (1997)ISSN: 0128-7680© Universiti Putra Malaysia PressNon-living Biomass of Water Hyacinth Roots as a Sorbentfor Chromium (ITI) in Aqueous SolutionK.S. Low and C.K. LeeChemistry DepartmentFaculty of Science and Environmental StudiesUniversiti Putra Malaysia43400 Serdang, Selangor, MalaysiaReceived 24 January 1997ABSTRAKKemampuan biojisim yang tak hidup bagi akar pokok kiambang untuk mangalihCr(III) telah dikaji di bawah beberapa keadaan seperti kepekatan dan pH yangberbeza, kehadiran ion natrium dan kalsium untuk mensimulasikan keadaandalam buangan dari kilang kulit. Ion kalsium lebih berkesan daripada ionnatrium dalam menghalang pengerapan Cr(III) pada akar pokok kiambang.Kajian kinetik menunjukkan terdapat beberapa mekanisme yang terlibat dalamproses pengerapan tersebut. Data keseimbangan sistem Cr(III) - akar pokokkiambang mematuhi isoterma Langmuir dan ini menunjukkan adanya peliputaneka-lapisan pada bahan penerap.ABSTRACTThe ability of the non-living biomass of water hyacinth roots, Eichhomiacrassipes, to remove Cr(lll) has been studied at different concentrations, pHlevels and in the presence of Na and Ca ions in an attempt to simulate thereal conditions of tannery waste. Ca ions exhibited a greater inhibitory effecton the Cr(lll) sorption than the Na ions. Kinetic studies showed that morethan one mode of sorption was operating in the uptake of Cr(lll) by waterhyacinth roots. The equilibrium data obeyed Langmuir isotherm for theCr(III)-water hyacinth root system, implying mono-layer coverage of thesorben t material.Keywords: water hyacinth roots. sorbent. chromium (ill). tannery wasteINTRODUCTIONChromium occurs in aqueous systems in both the trivalent (Cr(lll)) and thehexavalent (Cr(VI)) forms and is widely used in a large number of industries,including metal finishing, inks, dyes, pigments, glass, ceramics and glue. It isalso employed in chromium tannery, textile dyeing, and wood preservation.Chromium compounds are also used to inhibit corrosion in boiling waters.Consequently, untreated effluents from industrial inputs could contain a widerange of concentrations of this element. The toxicity of chromium has beendocumented, and depends on its oxidation state. Cr(VI) is approximately 100times more toxic than Cr(IlI) (Forstner and Wittmann 1979) because Cr(VI) isK.S. Low and C.K. Leecarcinogenic and mutagenic and is also a strong oxidant (Langard 1983).However, both are undesirable in aqueous environments.Various treatment processes for the removal or reduction of Cr are available;the most commonly used include reduction and precipitation, ion exchangeand adsorption. Activated carbon is costly both to use and to regenerate.Recently we investigated the use of chrome sludge for the removal of Cr(lll)(Low et al. 1995) and in this paper we report on the use of the non-livingbiomass of water hyacinth roots, a low cost and easily available material, in theremoval of Cr(lll) from synthetic solutions.MATERIALS AND METHODSMaterialsWater hyacinth roots were collected from a pond in the vicinity of UniversitiPutra Malaysia. No attempt was made to sort out the maturity of the plants. Theroots were cleaned with tap water to remove foreign materials, unhealthy partsof the roots were discarded and the roots were finally rinsed with distilled water.The dry roots were then rinsed with I M H °3, The acid treated roots werewashed with distilled water until the pH of the rinse was near neutral. Theywere dried at 80aC before being ground to pass through a sieve of I-mm meshsize. The Fourier transformed infra-red spectrum (KBr) of water hyacinth rootswas recorded using Perkin Elmer FT-IR Model 1650 in an attempt to establishthe functional groups that may be responsible for binding Cr(lll) ions.Batch StudiesAll experiments were carried out in duplicate at room temperature (28 ± 2 0c).Variations of more than 5% were discarded and the experiment repeated.Sorption was measured by equilibrating a known weight of the root withvarious concentrations of aqueous solutions of Cr(III) for a specific time. Atthe end of equilibration, the solution was centrifuged at 3000 rpm for 10min for phase separation. The chromium concentration of the supernatantwas determined using an inductively coupled plasma-atomic emissionspectrometer (Perkin Elmer PI000). Synthetic solutions were prepared fromA.R. grade Cr(N03)3.9Hp. The effect of pH on Cr(III) sorption was studiedby equilibrating sorption-mixtures at different initial pH values, obtained bythe addition of 0.1 M HCI or NaOH before the addition of pre-weighedsorbent.The effect of initial concentration on the sorption of Cr(lll) was studied byvarying the concentration of the Cr(lll) from 4.31 to 136.78 mg/I at pH 3. Inall contact time experiments, the sorption mixture consisted of 1.0 g of rootwith 500 ml of Cr(III) solution of various initial concentrations at pH 3. It wasagitated at 200 rpm at room temperature. Aliquots of solutions were withdrawnand analysed for Cr(lll) content. The effect of Na and Ca ions was carried outusing various weight ratios of Cr(lll) to Na/Ca in contact with a fixed amountof sorbent.148 PertanikaJ. Sci. & Techno!. Vol. 5 0.2, 1997on-living Biomass of Water Hyacinth Roots as a Sorbent for Chromium (III)RESULTS AND DISCUSSIONFr-IR Spectrum of Water Hyacinth RootsThe FT-IR spectrum of the ground water hyacinth roots is shown in Fig. 1. Themost prominent peaks appear to be the hydroxyl groups, 3406 em-I, with a peakat 1638 em-I. As no other functional groups are discernible from the spectrum,it is assumed that the binding of Cr(lll) on the surface of the roots is likely toinvolve the hydroxyl groups.100.00500'000'500o.oo-l--.,...--..---.....----,.....------..,-----..---.....,....J.woo 3500 3000 2500 ~Wave number (em·')Fig. 1. FT-IR spectrum of water hyacinth root obtained in KBrEffect of pH on SorptionThe effect of pH on the sorption of Cr(lll) by the water hyacinth roots isshown in Table 1. The experiment was limited to pH < 4.5 as Cr(lll)TABLE 1Effect of pH on the percentage uptake of Cr(III) by waterhyacinth rootspH Cr(III) uptaken (%)Initial Final1.80 2.01 02.60 3.00 29.93.05 3.80 91.24.80 5.05 precipitationConditions 0.1 g sorbent in 25 ml of 10 mg/l Cr(Ill) solution. Agitationrate and time: 200 rpm and 3 h respectivelyPertanikaJ. Sci. & Techno!. Vo!. 5 No.2, 1997 149KS. Low and e-K Leeprecipitation occurred above this value. Alves et al. (1993) in their study onchromium removal from wastewater 'polishing' by Pinus sylvestris bark reportedthat tests were performed at solution pH < 5 otherwise precipitation ofchromium occurred for solutions of concentration of 5-20 mg/I. The effect ofpH is important in establishing the optimum sorption of Cr (III) at theliquid/solid interface. At pH 2, there was practically no sorption due to theunfavourable electrostatic repulsion between the positively charged surfaceand the chromium ions. With the increase of pH from 2 to 3.05, the sorptionincreased rapidly from 0 to almost 91 %. There was a corresponding increasein the final pH of all the solutions, indicating possible exchange of H+ ionsof the solution with metals that were natural constituents of the waterhyacinth roots. A similar phenomenon was observed in the study of theuptake of Cr(IlI) by Pinus sylvestris bark. All subsequent experiments wereconducted at pH 3.Uptake of Gr(ll!) as a Function. of TimeVariation of uptake levels of Cr(III) with contact time by water hyacinth rootsat room temperature is shown in Fig. 2. Pseudo-equilibrium was reached inabout 120 minutes in all the solutions regardless of their initial concentrations.The sorption isotherms are characterized by two waves. The first one occurredin the first 20 min and was relatively well-defined; the second one was a slowlyrising isotherm. Hence the sorption process is complex and may involve more100.---------------------,20•o 20 40 60 80 100 120 140 160 180Time (minute)150Fig. 2. Sorption of Cr(ll!) as a function of agitation time; • - 5 mg/.A - 10 mg/l and. - 20 mg/l. Conditions: 1.0 g of sorbentin 500 ml of Cr(ll!) solution of various initial oncentration.Agitation rale: 200 rpm at pH value Clf 3PertanikaJ. Sci. & Techno!. Vo!. 5 No.2, 1997Non-living Biomass of Water Hyacinth Roots as a Sorbent for Chromium (III)5 3,000--r -Uptake42,500Cl'Em Ql.§. 2,000 'uQl 3;:~ Ql~ 0<)c. c:::l 1.500.2E :i::l'f 2: ~0 1.000 U;..~ i:3(.)5004020oDistribution_ coefficientoi~~_-l-_-=::r=====:r::~::::::r===::J:::=:1Io60 80 100 120Equilibrium concentration (mg/I)Fig. 3. UptaM (.) and distribution coefficient (e) of Cr(ll!) on waterhyacinth root. Conditions: 0.1 g of sorbentin 25 ml of Cr(ll!)solution of various initial concentrations. Agitation rate andquilibration time: 200 rpm and 3 h at pH 3than one mechanism. Percentage uptake, which is defined as ~C x 100 whereC;C = C; - Ctwhere C; is the initial concentration and Ctthe concentration of Crat time t, follows the usual trend of a greater percentage uptake with decreasingconcentration.Sorption as a Function of Initial ConcentrationThe roots were .treated with solution of initial Cr(III) concentrations of 4.31 to136.78 mg/l with the final bulk solution concentration varying from 0.35 to117.39 mg/1. The sorption isotherm, as shown in Fig. 3 resembles those of otherbiological materials. The percentage uptake increases with decreasingconcentration. The distribution coefficient as defined by [mg Cr(IlI) per gsorbent]/ [mg Cr(Ill) per g solution at equilibrium] varies from 2853 to 41from the least to the most concentrated starting solutions. The large distributioncoefficient of the root-Cr(III) system means that the non-living mass of thewater hyacinth roots possesses useful separation properties, especially for dilutesolution. A plot of chromium uptake (mg Cr/ g sorbent) versus equilibriumconcentration shows that sorption increased until all sorption sites were saturatedwith Cr(III) ions. Extrapolation of the curve provides a maximum sorption of4.83 mg Cr(Ill) / g sorbent.The results from the sorption data obtained after equilibrium were fittedinto a modified Langmuir isotherm model of the following form:PertanikaJ. Sci. & Techno\. Vo\. 5 o. 2, 1997 151K.S. Low and C.K. LeeC / = I/N" b + C / *e e ewhere Ceis the concentration of the Cr(III) solution at equilibrium (mg/l), Nethe amount of Cr(lll) sorbed by the water hyacinth roots at equilibrium (mg/g), * the maximum sorption capacity of the system as predicted by the modeland b is a constant associated with the energy of the sorption system. Thelinearity of such a plot shown in Fig. 4 indicates sorption of Cr(lll) on waterhyacinth roots follows the Langmuir isotherm. Value ofN* was found to be 4.77mg/g which agrees very well with the experimental value of 4.83 mg/g.25.....------------------,20~ 15i<110520 40 60 80 100 120Equilibrium concentration, C., (mgll)Fig. 4.. Langmuir isotherm of Cr(ll!) sorption on water hyacinth root.Conditions.: 0.1 g of water hyacinth TOots in 25 ml of variousCr(ll!) initial concentrations. Agitation rate and time: 200rpm and 3 h at pH 3Effect of Sodium and Calcium Ions on SorptionAs the tannery waste contains a large amount of Na and Ca ions, their effect onthe Cr(III) -water hy~cinth root system was investigated. It has been reportedthat levels of Na and Ca ions in treated tannery wastewater can attain values ofup to 2000 and 300 mg/l respectively (Sengul and Curel 1993). Other metalions such as AI, Zn, Cu and Mg appeared to be low. Hence investigation of theeffect of Ca and Na ions on Cr(lll) sorption using the above modified valueswas carried out. The results of such a study are shown in Table 2. In thepresence of 1000 mg/l of sodium ions the sorption of Cr(III) was inhibited by15.1 % . This is probably due to the steric hindrance of sodium ions preventingCr(lll) ions access to the binding sites of the water hyacinth roots. Calcium ionsexhibit a greater inhibitory effect on the Cr(III) sorption as seen by thereduction of Cr(lll) sorption by 17.3% in the presence of 100 mg/l of Ca ions.Hence experimental data obtained from the study of pure Cr(lll) solution has152 PertanikaJ. Sci. & Technol. Vol. 5 0.2, 1997Non-living Biomass of Water Hyacinth Roots as a Sorbent for Chromium (III)TABLE 2Effect of sodium and calcium ions on the sorption ofCr(lll) by water hyacinth rootsCa(mb/L) Na(mg/l CrUptaken0 0 70.10 100 67.60 1000 55.010 0 67.950 0 57.9100 0 52.8100 1000 34.4Condition: O.lg of sorbent in 25ml of 25 mg/l Cr(lll)solution. Equilibration time: 3 h, agitation rate: 200 rpmat room temperature at solution pH 3.to be interpreted with caution when it is applied to a real sample, especiallywhen the presence of other ions is suspected.Effect of Agitation RateThe effect of agitation rate on the uptake of Cr(lll) by water hyacinth roots isshown in Fig. 5. Increasing agitation rate increases the external film masstransfer coefficient and hence the rate of uptake. This is due to the reductionof the film boundary layer surrounding the sorbent particles. However in ourpresent study there is very little difference in the sorption curves at agitationrates of 10, 100 and 200 rpm, the higher rate giving slightly higher sorption.According to McKay (1982), the sorption process could involve four distinctsteps: (i) migration of sorbate molecules to the sorbent surface from solution(ii) diffusion through the boundary to the surface of sorbent (iii) sorption atbinding sites and (iv) intraparticle diffusion into the interior of the sorbent. Atan agitation rate of 10 rpm there was sufficient energy to overcome theboundary layer effect. This is borne out by the time course curves in Fig. 5 . Ina system where the agitation of solid-solution is vigorous, intraparticle diffusionis likely to be the limiting step. This possibility was examined in terms of agraphical relationship between amount of Cr(III) sorbed, qt (mg/g) and thesquare root of agitation time t (min) in the relation of to.5 Kd = q, Gayson et at.1993). Such plots are shown in Fig. 6. All the graphs show similar features; aninitial curve followed by a straight line, this indicates that more than one modeof sorption was operating in the sorption of Cr(III) by water hyacinth roots.The initial curve is due to boundary layer diffusion while the linear portion canbe attributed to intraparticle diffusion. The rate constants for the intraparticlediffusion, Kd , determined from the slopes of the linear portions are5.24 x 10-2, 7.58 X 10-2 and 12.99 x 10-2 mg/g;l min- l/2 for Cr(III) solutions of 5,10 and 20 mg/l respectively. As the lines do not pass through the origin, itPertanikaJ. Sci. & Techno!. Vo!. 5 0.2, 1997 153K.S. Low and c.K. Lee10080~ 60Ql.)/.~::J 402000 20 40 60 80 100 120 140 160Time (minute)Fig. 5. Effect of agitation rate on the smption of Cr(ll!) lJy water hyacinthroot; • - 10 rpm, .A - 100 rpm and • - 200 rpm. Conditions:1.0 g of sorbent in 500 ml of 10 mg/l Cr(ll!) solution at pH 35,----------------==....-,_.......-.. -•4-----_ ..-. • •2 -------..-. • ...1'--_--I.__--'-__-'-__.........__.l--_----J'--_--'123 5678t1/2 (min1/2)Fig. 6. Plots of amount sorbed as a function of tl / 2 for the intraparticletransport of Cr(ll!) on water hyacinth root at room temperatureat pH 3; • - 5 mg/~ • - 10 mg/l and .. - 20 mg/l154 PertanikaJ. Sci. & Technol. Vol. 5 No.2, 1997Non-living Biomass of Water Hyacinth Roots as a Sorbent for Chromium (III)appears that particle diffusion is not the only rate-controlling step in thesorption of Cr(lll) by water hyacinth roots (Singh et at. 1988).CONCLUSIONThe non-living biomass of water hyacinth roots, an easily available bio-material,has been shown to have the ability to remove/reduce Cr(lll) from syntheticsolution and tannery waste. The roots offer several advantages over livingplants. It can be stored easily and there is no associated problems of maintainingliving plants. The material can be used as a source of fuel if regeneration is notdesired.ACKNOWLEDGEMENTThe financial support of the Malaysian government under Research Grant No.IRPA 04-07-05-017 is gratefully acknowledged.REFERENCESALVES, M.M., C.G.G. BECA, R.G. de CARVALHO,J.M. CAsTANHElRA, M.C.S. PEREIRA and LAT.VASCONCELOS, 1993. Chromium removal in tannery wastewater "polishing" by Pinussylvestris bark. Wat. Res. 27: 1333-1338.jA\'SON, G.G., J.A. SA.NGSTER, G.THOMPSON and M.C. WILKINSON. 1993. Adsorption ofchromium from aqueous solution onto activated charcoal cloth. Carbon 31(3): 487-492.LANGARD, S. 1982. The carcinogenicity of chromium compounds in man and animals. InChromium: Metabolism and Toxicity, ed D. Burrows, p. 13. Boca Raton, Florida: CRCPress.Low, KS., C.K LEE and S.T. OW-WEE. 1995. Removal of chromium (III) from aqueoussolution using chrome sludge. Bull. Contam. Environ. ToxicoL 55: 270-275.McKAY, G. 1982. Adsorption of dyestuffs from aqueous solutions with activated carbonI: Equilibrium and batch contact-time studies. Wat. Res. 32: 759-772.SENGUL, F and O. GURE!. 1993. Pollution profile of leather industries; waste characterizationand pretreatment of pollutants. Wat. Sci. Tech. 28(2): 87-89.SINGH, A.K, D.P. SINGH, KK PANDY and V.N. SINGH, 1988. Wollastonite as adsorbent forremoval of Fe(II) from water. J Chern. Tech. Biotechnol. 42: 39-49.PertanikaJ. Sci. & Techno!. Vo!. 5 No.2, 1997 155

Non-living Biomass of Water Hyacinth Roots as a Sorbent

for Chromium (ITI) in Aqueous Solution

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Non-living Biomass of Water Hyacinth Roots as a Sorbent for Chromium (ITI) in Aqueous Solution

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