The removal of cupric ions from aqueous solution by natural and dyecoated palm pressed fibres was studied. Sorption was both pH and concentration dependent. The equilibrium data followed the Langmuir isotherm model with maximum copper sorption capacities of 2.41 and 7.71 mg/g for natural and dye-treated fibres respectively. The presence of

other metal ions inhibited copper uptake in the following order Pb> Zn > Ni. The suppressing effects of chelators correspond to their log K values. Column studies showed that bed-depth had a more pronounced

effect on copper sorption than flow rate

Lee, C. K.

Low, K. S.

Tan, C. L.

Universiti Putra Malaysia Institutional Repository

Pertanika J. Sci. & Techno!. 4(1): 41-50 (1996)ISSN:O128-7680© Penerbit Universiti Pertanian MalaysiaEnhancement of Copper Sorption throughAcid Blue 29 Treated Oil Palltl Pressed FibresK.S. Low, C.K. Lee and C.L. TanChemistry Department, Faculty of Science and Environmental Studies,Universiti Pertanian Malaysia43400 Serdang, Selangor, MalaysiaReceived 9 December 1994ABSTRAKPengerapan ion kuprum daripada larutan akueous oleh serabut kelapasawit semulajadi dan tersalut dengan pewarna, Asid Biru 29, telah dikaji.Proses pengerapan bergantung kepada kepekatan dan pH larutan. Dataeksperimen mematuhi model isoterma Langmuir dengan muatanmaksimum 2.41 dan 7.71 mg/g untuk serabut kelapa sawit semulajadidan yang tersalut dengan pewarna berturut-turutan. Kehadiran ionlogam lain merencat pengambilan kuprum mengikut tertib Pb> Zn > Ni.Kesan penghalangan agen kelat bersepadan dengan nilai log K. Kajianturus menunjukkan bahawa faktor 'bed-depth' adalah lebih berkesandaripada kadar aliran dalam pengerapan kuprum.ABSTRACTThe removal of cupric ions from aqueous solution by natural and dye-coated palm pressed fibres was studied. Sorption was both pH andconcentration dependent. The equilibrium data followed the Langmuirisotherm model with maximum copper sorption capacities of 2.41 and7.71 mg/g for natural and dye-treated fibres respectively. The presence ofother metal ions inhibited copper uptake in the following orderPb> Zn > Ni. The suppressing effects of chelators correspond to their logK values. Column studies showed that bed-depth had a more pronouncedeffect on copper sorption than flow rate.Keywords: sorption, copper, dye-treated oil palDl fibre, batch and colUDlnstudiesINTRODUCTIONChemical modifications of the surface of biological materials with theobjective of increasing metal sorption from aqueous solutions have receivedconsiderable attention recently. EDTA modified cellulosic materials showedgreater sorption for Cd, Cu and Pb than untreated materials (Okieimen etat. 1985). Apple waste treated with phosphorus oxychloride was reported tohave greater efficiency in removing heavy metals (Maranon and SastreK.S. Low, C.K. Lee and C.L. Tan1991). Rice hulls coated with monochlorotriazine-type reactive dyes led tomore efficient removal of heavy metals from aqueous solutions (Suemitsu etal. 1986). Similarly, Shukla and Sakhardande (1991) demonstrated that thesorption of several metal ions by jute was enhanced significantly upondyeing the sorbent. The metal sorption capacity of moss was greatlyimproved upon treatment with reactive dyes (Low et al. 1993). This paperreports on the investigation of the potential of dye-treated (Acid Blue 29) oilpalm fibres in removing metal under batch and column conditions. Theresults were compared to those of untreated oil palm fibres.METHODS AND MATERIALSPhysical and Chemical MethodsOil palm fibres were obtained from a nearby palm oil mill. The sample wasdried at 80°C, ground and sieved. Only fraction in the 250-500 mm rangewas used throughout this study. Part of the material was boiled with wateruntil the filtrate was clear before it was treated with 1.5 M NaOH solution.The mixture was boiled until the filtrate was colourless. The basicity of thesample was then neutralized with 2 M HCl until the pH of the filtrate wasnear neutral. This sample was labelled as 'natural oil palm fibre' (NF). Theremainder of the original sample was coated with Acid Blue 29 (C.I.20460)according to the method described by Suemitsu et al. (1986) and labelled as'dye-coated oil palm fibre' (DF).Sorption of Copper on Fibres under Various ConditionsAll batch experiments were performed at room temperature on a gyratoryshaker (250 rpm). The fibre-solution mixture was equilibrated for 2 handthe copper content in the solution was measured using an inductively-coupled plasma-atomic emission spectrometer (Labtest 710-2000). Allexperiments were conducted in duplicate and averaged results werepresented. The effect of pH on copper uptake by the fibres was tested byequilibrating the sorption mixture (0.1 g fibre in 25 ml solution) at variousinitial pH values achieved by the addition of 0.1 M HCl or NaOH. Theeffect of other cations and chelators on the sorption of copper on fibre wastested in solutions containing copper and other cationsfchelators in variousmole ratios. The cations studied were Pb, Ni and Zn. Sodium salts ofethylenediamine tetraacetic acid (EDTA), nitrilotriacetic acid (NTA) andsalicylic acid (SA) were chosen as chelators commonly found in the aqueousenvironment.Column StudiesIn the column studies, a glass column of internal diameter 1.4 cm was used.The fibre was packed to a height of 5, 10 and 15 cm corresponding to 1.5,3.0 and 4.5 g of fibre respectively. Columns were preconditioned with42 Pertanika J. Sci. & Techno!. Vol. 4 No.1, 1996Enhancement of Copper Sorption through Acid Blue 29 Treated Oil Palm Pressed Fibresseveral volumes of distilled water. Copper solution (10 mg!l) was passedthrough the column at various flow rates, Eluent was collected in 50-mlfractions and analysed for copper.RESULTS AND DISCUSSIONBatch ExperimentPercentage uptake of copper by fibre is defined as 100 x (Ct - Co)/Cowhere C t is the concentration of the solution at time t and Co the initialconcentration of the solution. The reproducibility of the sorption capacity ofthe fibre was shown by treating 7 samples of 0.1 g DF!NF in 100 ml ofl2.5mg!l Cu solution. At equilibrium, the percentage uptakes and relativestandard deviations were 3.08 and 0.81 mg!g and 1.1 and 3.5%respectively. This shows the high reproducibility of the copper-fibre system.Effect ofpHThe effect of pH on the removal of Cu by the fibres is shown in Fig. 1.Solution pH influences both aqueous Cu chemistry and the surface sorptionsites of the fibres. At low pH values the surface of the fibres is closelyassociated with the hydronium ions (H30+), rendering sorption of Cu2+ onthe fibre's surface unfavourable. This condition is reflected by the non-sorption ofCu at pH 2. At higher pH, more functional groups on the surfaceare made available for binding with Cu. Sorption increased with increasingpH to the point where the Cu ions precipitated; this occurred when the pH10080.-. 60~ell~CIS-c.. 40:::)2002 3 4 5 6pHFig. 1. The ~Iect ojpH on the uptake oj copper by natural palm pressed fibre (.) and dye-coatedfibre (.). Conditions: 0.1 g ojfibre in 25 ml oj 25 mgtl Cu solution; 2 h equilibrating timePertanika J. Sci. & Techno!. Vol. 4 No. I, 1996 43K.S. Low, C.K. Lee and c.L. Tan100080 0~QlX.CllC.::J.to.• •o 20 40 60 80 '100 120 140 160 180Contact time (min)Fig. 2. The uptake of copper at various initial copper concentrations. Conditions: 0.4 g offibre in400 ml of Cu solution at various initial concentrations. NF: • - 5, ... - 15 and. -50 mgll Cu.DF: D - 5, ..... - 15 and. - 50 mgll Cuof fibre-Cu solution reached a value of 6. Optimum pH for the sorption ofmetals by biological materials in the range of 4-6 has been reported usingpeanut shells, paddy husks and acacia bark (Randall et al. 1974; Kumarand Dara 1982). The dye-coated fibre had a greater sorption capacity thanthe natural fibre, reflecting the greater number and/or stronger bindinggroups on its surface. The S03 - groups on the dye molecules act as strongbinding sites, in comparison to the weaker functional groups of OH- andC02H on the surface of the natural oil palm fibre. The percentage of Cusorption by the fibres at various initial concentrations is shown in Fig. 2. Forany particular type of fibre the percentage sorption decreases withincreasing concentration of solution. The sorption is characterized by avery rapid initial uptake, followed by a more gradual increase untilequilibrium is established. It is clear from the figure that dye-coating on thesurface of the fibre led to sorption enhancement.Effect of DosageThe effect of sorbent dosage on Cu by the NF is shown in Fig. 3. Asexpected, increasing the fibre/copper ratio leads to increasing sorptionefficiency. Furthermore, the time to reach equilibrium remains relativelyunchanged. This is attributed to the increase in binding sites as the amountof fibre increases. The same phenomenon is also observed for dye-coatedfibre. The only difference is its higher percentage of sorption.44 Pertanika J. Sci. & Techno!' Vol. 4 No. I, 1996Enhancement of Copper Sorption through Acid Blue 29 Treated Oil Palm Pressed Fibres25,---------------------,o 30 60 90 120 150 180Contact time (min)Fig. 3. The iffect of dosage on the uptake of copper by natural palm pressed fibre. Conditions:dijJerent amounts offibre in 400 ml of5 mgtl Cu solution. NF: • - 0.1, .&.- 0.2, D - 0.3 and• - 0.4 g offibreLangmuir IsothermVarious sorption isotherms can be used to describe the sorptionphenomenon of Cu on the fibres. They include Langmuir, Freundlichand BET (Brunauer-Emmet-Teller) types. The Langmuir model wasapplied to the present Cu-fibre system. The isotherm can be represented byCe/qe = l/qob + Ce/qowhere Ce is the equilibrium concentration (mg/l), qe the amount of Cusorbed at equilibrium (mg/g), qo the maximum sorption of the fibre-Cusystem and b the Langmuir constant related to the energy· of sorption (1/mg). Fig. 4 shows that the experimental data for Cu sorption on NF and DFfit the Langmuir isotherm. The agreement of the experimental data withthe model implied that both monolayer sorption and constant sorptionenergy existed for the experimental conditions used. From the graphs, themaximum sorption capacities were estimated to be 2.41 and 7.71 mg/g forNF and DF respectively. Dye-coating led to a threefold sorptionenhancement.Effect of ChelatorsOne problem associated with conventional treatment methods for metal ionremoval is the presence of complexing reagent, which may mask thepresence of metals rendering sorption incomplete or impossible. ThreePertanika J. Sci. & Technol. Vol. 4 No. I, 1996 45K.S. Low, C.K. Lee and c.L. Tan6050402010302520--~,,150---"•U10530Ce (mg/I)Fig. 4. Langmuir isotherms of copper sorption on natural palm pressed fibre r-j and dye-coatedfibre rejchelators commonly found in the aqueous environment were used in thisstudy. The copper sorption by the fibres in the presence of various molarratios is shown in Table 1. The equilibrium is influenced by the nature ofthe chelator and also by free and complexed copper in solution. From thetable it can be seen that the suppressing effect of the chelators corresponds tothe log KI values. EDTA (log K 1 = 16.28) competes most effectively withthe binding sites for copper for both types of fibres. Results show that wherethe concentration of EDTA was lower than the stoichiometric ratio ofEDTA to copper, the uncomplexed part was sorbed. Salicylic acid (logKI = 5.55) exerts the least effect on the sorption of copper. NTA (log KI =9.80) has an intermediate effect. Its log K 1 value is intermediate to those ofEDTA and SA. This shows that the effectiveness of the fibres in removingTABLE 1Sorption of copper in the presence of chelatorsMetal/ligand EDTA EDTA NTA NTA SA SAmole ratio DF NF DF NF DF NF1:0 48.66* 12.84 48.66 12.84 48.66 12.841:0.5 20.72 6.12 24.95 8.77 35.16 11.091:1.0 2.08 0.35 8.65 5.43 22.59 6.481:10 0.47 0.02 0.86 0.29 7.02 2.07• Percentage removal at equilibrium. Conditions: 0.1 g fibre in 100 ml of 12.5 mgjl Cu solution.Equilibrating time: 2 h.46 Pertanika J. Sci. & Techno!. Vo!' 4 No. I, 1996Enhancement of Copper Sorption through Acid Blue 29 Treated Oil Palm Pressed Fibrescopper from aqueous solution must be critically assessed if chelators of thisnature are suspected to be present.Effect of Competing Metallic IonsThe maximum sorption capacities of the fibres for copper as derived fromthe Langmuir model are only applicable if no other competing ions arepresent. This situation is normally not realized in real samples. Hence theeffect of competing ions on the Cu sorption by the fibres was investigated.Table 2 shows the results of such a study. The greater metal affinity ofDF isapparent. The number of binding sites on the surface of the fibres is finiteand when more than one metal is present in the same solution, they competefor the binding sites. The amount sorbed depends on the equilibriumbetween sorption competition from the ions present. At low concentration(5 mg/l), a higher percentage of the metals was sorbed as there weresufficient binding sites. However, the competitive effect of other metalsbecame apparent when the concentration of the metals in the solution wasincreased (50 mg/l). The order of sorption affinity is Pb > Cu > Zn > Ni.This is very similar to the sorption of metals on banana pith (Low et al.1994). The order of affinity is determined by a number offactors, includingionic potential qjr (q is the ionic charge; r, the ionic radius), chemicalproperties, ionic radius, and hydrolysis (Tobin et al. 1984).TABLE 2Sorption of copper in the presence of other ionsInitial metal Cu Cu/Pb Cu/Zn Cui Iiconcentration (mg/I)5.00 (single) 92.2*5.00 (mixed) 56.9/71.5 69.3/38.4 78.2/26.050.00 (single) 14.350.00(mixed) 5.6fl1.2 10.8/2.9 18.8/1.3* Percentage uptake at equilibrium.Conditions: 0.1 g fibre in 100 ml of solution at an equilibrating time of 2 h.The ability of the fibres to remove metal ions was demonstrated using asample of electroplating wastewater. The results (Table 3) show that thefibres could be used to reduce the metal content prior to secondarytreatment of the wastewater.Column StudiesThe various parameters obtained under· batch processes are useful inproviding basic information on the effectiveness of the fibre-metal system.However, the data obtained are generally not applicable to a continuousflow system where the contact time is normally too short for equilibrium toPertanika J. Sci. & Techno!. Vo!. 4 No. I, 1996 47K.S. Low, C.K. Lee and C.L. TanTABLE 3Removal of metals from electroplating waste by fibresMetal Concentration (mg/I)Initial FinalCation sorbed(mg/I)Removal(%)CuPbCrNi62.370.594.5894.6246.43* (48.70)**0.33 (0.41)3.62 (4.07)93.16 (94.08)1.59* (1.37) **0.03 (0.02)0.08 (0.05)0.15 (0.05)25.56* (21.92)**44.07 (30.51)20.96 (11.13)1.54 ( 0.57)* related to DF and ** NF. Conditions: 0.1 g of fibre in 100 ml of electroplating solution at pH4.35 at an equilibrating time of 2 h.be established. Hence it is essential to conduct column studies in order toascertain the usefulness of such a system. The copper loading phase wascarried out with a continuous flow of 10 mg/l copper solution. Some typicaleluent concentration profiles for copper at various bed-depths and flow ratesfor the dye-coated fibres are shown in Figs. 5 and 6 respectively. Increasingthe column height leads to higher sorption and a larger breakthroughvolume as seen in Fig. 5. The increase in biomass allows more sorption sitesfor copper ions in the aqueous phase. Natural fibre shows similar trendsthough the sorption capacity was lower. The copper removal efficiency inrelation to the flow rate/residence time of the influent in the column for DFis shown in Fig. 6. There is a significant increase in uptake with decreasing70,------------------------,5010 20 30 40Eluent volume (x 50 ml)Fig. 5. The iffect of bed-depth on the sorption ofcopper at a constantjlow rate of 10 ml/min. DF:o - 5, f::" - 10 and 0 - 15 cm of dye-coated palm pressedfibre. Conditions: concentration of injluentCu solution - 10 mg/l1060oU~30UIcJ 20~. ~50oox4048 Pertanika J. Sci. & Techno!. Vo!. 4 No.1, 1996Enhancement of Copper Sorption through Acid Blue 29 Treated Oil Palm Pressed Fibres60,--------------------;;-'----....,50xoU 30------r.SI 20oU10OL--.JlC'-'--C)-=--O----'--""""""'---'-------l L-_----'o 5 10 15 20 25 30Eluent volume (x 25 ml)Fig. 6. The effect offlow rate on the sorption of copper at afixed bed-depth of 5 cm. Conditions:concentration of influent Cu solution - 10 mgJl Cu. DF: 0 - 10, 0- 25 and 6. - 50 mlJminflow rate or increasing residence time. The sorption process is essentially aphase equilibrium involving sorption and desorption. There is a time lag forthe copper ions to reach and interact with the binding sites on the fibresurface, a process controlled by the overall mass transfer coefficient. Hence,decreasing the flow rate will enable the copper ions to be in better contactwith the surface of the fibre. However, too slow a flow rate will also allowdesorption to occur. In our study, the flow rate was not low enough to allowdesorption to take place.CONCLUSIONBatch and column experiments of natural and dye-treated oil palm fibreshave been shown to be effective in removing copper from aqueous solutions.The enhancement effect of dye coating on the fibres is demonstrated in bothprocesses. Uptake is influenced by pH, initial concentr:ation and thepresence of other metal ions and chelators in the batch process whereas flowrate and column height control the percentage removal in the continuousflow study. As no apparent leaching of dye occurred throughout theexperiments, the dye-treated oil palm fibre is a potentially useful materialfor removing or reducing metal in aqueous solution.ACKNOWLEDGEMENTThe authors are grateful to Majlis Penyelidikan Kemajuan Sains NegaraMalaysia for financial support (grant no. 04-07-05-017).Pertanika J. Sci. & Techno!. Vo!. 4 No. I, 1996 49K.S. Low, C.K. Lee and c.L. TanREFERENCESKUMAR, P. and S.S. DARA. 1982. Utilization of agricultural wastes for decontaminat-ing industrial/domestic wastewaters from toxic metals. Agri. Wastes 4: 213-233.LOW, K.S., C.K. LEE, F.Y. CHEONG and G.S. LIM. 1993. Enhancement effect of dye-coating on the .sorption of copper by moss. ]. Environ. Sci. Health 4A(28): 1689-1704.LOw, K.S., C.K. LEE and A.C. LEO. 1995. Removal of metals from electroplatingwastes using banana pith. Bioresource Technol. 51: 227-231.MARANON, E. and H. SASTRE. 1991. Heavy metal removal in packed beds using applewastes. Bioresource Technol. 38: 39-44.OKIEMIMEN, F.E., D.E. OGBEIFUN, G.N. NWALA and C.A. KUMSAH. 1985. Bindingof cadmium, copper and lead ions by modified cellulosic materials. Bull. Environ.Contam. Toxicol. 34: 866-870.RANDALL, J.M., E. HANTELLA and A.C. WAISS. 1978. Binding of heavy metals ionsby formaldehyde polymerized peanut skins. ]. Anal. Polym. Sci. 22: 379-389.SHUKLA, S.R. and V.D. SAKHARDANDE. 1991. Novel method of using reactive dye foreffiuent treatment. Am. Dyestuff Reporter July: 38-42.SUEMITSU, R., R. UENISHI, I. AKASHI and M. AKA O. 1986. The use of dyestuff-treated rice hulls for removal of heavy metals from waste water. ]. Appl. Polym. Sci.31: 75-83.TOBIN,J.M., D.G. COPPER and R.]. NEUFELD. 1984. Uptake of metal ion by Rhizopusarrhizus biomass. Appl. Environ. Microbiol. 47: 821-824.50 Pertanika J. Sci. & Techno!. Vo!. 4 No.1, 1996

Enhancement of Copper Sorption through

Acid Blue 29 Treated Oil Palm Pressed Fibres

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Enhancement of Copper Sorption through Acid Blue 29 Treated Oil Palm Pressed Fibres

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