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DESALINATION

www.elsevier.com/locate/desalDesalination 250 (2009) 300–310

Removal of Cu(II) and Pb(II) ions from aqueous solutionsby adsorption on sawdust of Meranti wood

Anees Ahmada*, Mohd. Rafatullahb, Othman Sulaimanb,Mahamad Hakimi Ibrahima, Yap Yee Chiia, Bazlul Mobin Siddiquea

aEnvironmental Technology Division, School of Industrial Technology, Universiti Sains Malaysia,11800 Penang, Malaysia

bBioresource Paper and Coatings Technology Division, School of Industrial Technology,Universiti Sains Malaysia, 11800 Penang, Malaysia

Tel.: +604-653-2214, Fax: +604-657-3678; email: anees@usm.my, aneesahmad_ana@yahoo.com

Received 6 August 2007; accepted 19 January 2009

Abstract

Meranti tree sawdust, an inexpensive material, is currently being investigated as an adsorbent for the removalof Cu(II) and Pb(II) ions from aqueous solutions. In this work, adsorption of Cu(II) and Pb(II) ions on Meranti treesawdust has been studied by using batch techniques. The equilibrium adsorption level was determined to be afunction of the solution of pH, contact time, and adsorbent dosage. Adsorption isotherms of Cu(II) and Pb(II)ions on adsorbents were determined and correlated with common isotherm equations such as Langmuirand Freundlich models. The thermodynamic parameters like free energy, enthalpy, and entropy changes forthe adsorption of Cu(II) and Pb(II) ions have also been computed and discussed. The heat of adsorption[DH = 31.47 kJ/mol for Cu(II) and DH = 20.07 kJ/mol for Pb(II)] implied that the adsorption was endothermicin nature.

Keywords: Heavy metals; Adsorption; Endothermic; Meranti wood; Sawdust

1. Introduction

The presence of heavy metal in the aquaticenvironment has been of great concern to scien-tists and engineers because of their increased dis-charge, toxic nature, and other adverse effects onreceiving waters. Unlike most organic pollutants,

heavy metals are generally refractory and non-degradable or readily detoxified biologically.

Copper is essential to human life and health,but like all heavy metals, it is potentially toxic,especially at high concentrations. Copper andits compounds are ubiquitous in the environmentand are thus found frequently in surface waters.Potential sources of copper bearing wasteinclude plating baths, fertilizer industry, paints*Corresponding author.

0011-9164/09/$– See front matter � 2009 Elsevier B.V. All rights reserved.doi: 10.1016/j.desal.0000.00.000

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and pigments, municipal and storm waterrun-offs. Intake of excessively large doses ofcopper by man leads to severe mucosal irritationand corrosion, widespread capillary damage,hepatic and renal damage, and central nervoussystem irritation followed by depression. Severegastrointestinal irritation and possible necroticchanges in the liver and kidney could occur.The maximum recommended concentration fordrinking water that is regulated in Environmen-tal Quality Act 1974 is 0.2 mg/L [1–3].

Another heavy metal lead has been introducedinto natural waters from a variety of sources suchas storage batteries, lead smelting, tetraethyl leadmanufacturing, mining, plating, ammunition, andthe ceramic glass industries. The permissible limitof lead in drinking water by Environmental Qual-ity Act is 0.10 mg/L. The presence of excess leadin drinking water causes diseases such as anemia,encephalopathy, and hepatitis. Lead ions have anaffinity for ligands containing thiol and phos-phatic groups and they inhibit the biosynthesisof heme, causing damage to both the kidney andliver. However, lead can remain immobilizedfor years, and hence it is difficult to detect themetabolic disorders it causes [4–6].

In developed countries, removal of heavymetals in wastewater is normally achieved byadvanced technologies such as ion exchange,chemical precipitation, ultra filtration, or electro-chemical deposition [7–9]. But these technologiesdo not seem to be economically feasible becauseof their relatively high costs and that developingcountries may not afford such technologies.Therefore, there is a need to look into alternativesto investigate a low-cost method, which is effec-tive and economical. To overcome this difficultythere is a strong need to develop cheap adsorbentswhich can be used in developing countries.

Adsorption by natural materials is anotheralternative method to solve this kind of problems.The natural materials form complexes with metalions using their ligand or functional groups.Process for metal removal like adsorption

has been suggested as being cheaper and moreeffective than the other technologies [10].Adsorption was first observed by Lowitz in1785 [11] and was soon applied as a processfor removal of color from sugar during refining.In the second half of the nineteenth century,American water treatment plants used inacti-vated charcoal filters for water purification.Currently, adsorption on activated carbon is arecognized method for the removal of heavymetals from wastewater [12, 13], while thehigh cost of activated carbon limits its use inadsorption. A search for a low-cost and easilyavailable adsorbent has led to the investigationof materials of agricultural and biological originas potential metal sorbents [14]. Agriculturalby-products, such as sugar beet pulp andsawdust [15, 16], coconut shell [17], clay [18],red mud [19], tea leaves [20], and so on,have received attention in these types of applica-tion. The sorption of metals by these kinds ofmaterials might be attributed to their proteins,carbohydrates, and phenolic compounds thathave carboxyl, hydroxyl, sulfate, phosphate,and amino groups that can bind metal ions.Most cases have confirmed that the use oflarge quantities of wastes from agriculturalproducts for the treatment of polluted water isan attractive and promising option with a doublebenefit for the environment [21]:

• It reduces the residues whose disposalbecomes a major, costly problem and

• It converts the wastes into useful and inexpen-sive sorbents for water purification

The aim of this article is to assess the poten-tial of Meranti tree sawdust to adsorb Cu(II)and Pb(II) ions from aqueous solutions. Theeffect of the solution pH, temperature, contacttime, and adsorbent doses on the removal ofCu(II) and Pb(II) ions was studied. The adsorp-tion isotherm and probable mechanism areexplained. The thermodynamic parameters for

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the adsorption of Cu(II) and Pb(II) ions havealso been computed and discussed.

2. Experimental

2.1. Apparatus and instrumentation

The concentrations of Cu(II) and Pb(II) inaqueous solutions were determined using atomicabsorption spectrophotometer (Analyst 100 PerkinElmer) operating with an air-acetylene flame. ThepH measurements were done with a pH-meter(HACH Model SensION-3). The pH-meter wasstandardized using buffer solutions with pH valuesof 4.0, 7.0, and 10.0. The BET surface area wasdetermined through N2 gas adsorption by aMicromeritics PulseChemiSorb 2705 instrument.Temperature-controlled shaker (Rillins SainsSdn Bhd Model IKA KS 260) was used for equi-librium studies. All filtrations during this workwere carried out using Whatman No. 1 filter paper.

2.2. Adsorbent

Meranti tree sawdust was collected fromBio-resource, paper and coating (PBC) divisionof School of Industrial Technology of USM.The sawdust was washed with distilled waterand then dried in a dryer at 708C until all themoisture had evaporated. The material wasground to a fine powder in a still mill. The result-ing material was sieved in the size range of100–150 mm particle size. To immobilize thecolor and water-soluble substances, the groundpowder was treated with 2% formaldehyde inthe ratio of 1:4 (sawdust: formaldehyde, w/v)at room temperature for 4 h. After that, the saw-dust was filtered out, washed with distilled waterto remove free formaldehyde, and activated at708C in a dryer for 24 h. The material was placedin an airtight container for further use.

2.3. Adsorbate solution

The aqueous solutions (1000 mg/L) of Cu(II)as well as Pb(II) were prepared in distilled water

using Cu(II) sulfate pentahydrate, CuSO4.5H2Oand Pb(II) nitrate, Pb(NO3) respectively. Thesolutions of different dilutions (25–250 mg/L)required for the adsorption studies were pre-pared by dilution of the stock solutions.

2.4. Batch adsorption studies

Batch adsorption studies were carried out byshaking 0.25 g of the sawdust with 25 ml of theaqueous solutions of Cu(II) and Pb(II) ions indifferent conical flask at 150 rpm, respectively.The mixtures were filtered out and analyzedfor its metal ion concentrations using AtomicAdsorption Spectrometer (AAS) (Analyst 100Perkin Elmer). All metal solutions were usedat neutral pH and performed at room tempera-ture unless otherwise stated. The effect of pHof the initial solution on the equilibrium uptakeof Cu(II) and Pb(II) ions was analyzed over apH range from 2.0 to 7.0 and 2.0 to 7.5, respec-tively. The pH was adjusted using 0.1 M NaOHand 0.1 M HCI solutions. The adsorption experi-ments were also conducted to determine theequilibrium time, the optimum pH, and dosageof the adsorbent for maximum adsorption.

2.5. Adsorption model

To quantify the adsorption capacity of Mer-anti tree sawdust for the removal of Cu(II) andPb(II) ions from aqueous solution, the Langmuirand Freundlich models were used.Langmuir mode: Langmuir proposed the follow-ing model:

Ce=Am ¼ ð1=KÞð1=bÞ þ ð1=bÞðCeÞ ð1Þ

where Ce is the equilibrium concentration (mg/L)and Am is the amount adsorbed per specifiedamount of adsorbent (mg/g), b is the equilibriumconstant, and K is the amount of adsorbaterequired to form a monolayer. Hence, a plot ofCe/Am versus Ce should be a straight line with aslope (1/b) and an intercept as 1/Kb.

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Freundlich model: According to Freundlichmodel:

Am ¼ ðKÞðCe1=nÞ

logAm ¼ logKþ 1=n logCe ð2Þ

where n is an empirical constant. Thus, a plot oflog Am versus log Ce should be a straight linewith a slope 1/n and an intercept of log K. Thismodel deals with the multilayer adsorption ofthe substance on the adsorbent.

A computer modeling technique has beenapplied to fit the Freundlich and Langmuirequations for the adsorption data. The coeffi-cients of determination of least square fittingto a straight line (r2) were computed for thesetwo models.

2.6. Thermodynamic parameters of sorption

The Gibbs free energy (DG) is the fundamen-tal criterion of spontaneity of a process and canbe determined using equilibrium constant asbelow:

DG ¼ �RT lnK ð3Þ

where R is the universal gas constant(8.314 Jmol�1K�1) and T is the absolute tem-perature (K).

Similarly, the enthalpy was computed fromthe following equation

lnK ¼ DS=R� DH=RT ð4Þ

DH8 can be obtained from the slope of plot of lnK versus 1/T.

The entropy was calculated from the equation,

DG ¼ DH� TDS ð5Þ

3. Results and discussion

3.1. Characterization of Meranti tree sawdust

A SEM micrograph of Meranti tree sawdustis shown in Fig. 1. Meranti tree sawdust is a het-erogeneous material consisting largely of smallspheres, irregular, porous, coke like particles ofcell wall of plant cells. The surface seems tobe rough, and protrusions can be seen through-out the micrograph. Pores can be seen however,not extending into the matrix. The surfaceroughness is indicative of high surface area.

3.2. Physical–chemical characteristics

Characteristics of the adsorbent such as sur-face area, bulk density, moisture content, ashcontent, solubility in water (inorganic andorganic matter) were determined. The resultsare summarized in Table 1.

3.3. The pH of adsorbent surface

A 25 ml of metal solution of 100 mg/L con-centration was agitated with 0.25 g of adsorbentat room temperature for 60 min at 150 rpm to

Fig. 1. SEM image (Mag:�500) of sawdust of merantitree.

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reach equilibrium. Then, the pH of the slurrywas measured. The results are shown in Table 1.

3.4. Effect of contact time

The dependence of adsorption of Cu(II) andPb(II) ions with time is presented in (Fig. 2). Thedata obtained from the adsorption of Cu(II) andPb(II) ions on the Meranti tree sawdust showedthat the adsorption increases with an increasingcontact time. The plot reveals that the rate of

percentage removal of Cu(II) and Pb(II) ions isinitially high which is probably due to the avail-ability of larger surface area of the sawdust forthe adsorption of these ions. As the surface adsorp-tion sites become exhausted, the rate of uptake iscontrolled by the rate of transport from the exteriorto the interior sites of the adsorbent particles. Fur-ther, the maximum percentage removal of Cu(II)and Pb(II) ions was attained after 60 min of stirringtime at different concentrations. Therefore, thecontact time of 60 min was sufficient to achieveequilibrium for both these ions. The adsorptiondid not change much with further increase in con-tact time. Therefore, in each experiment, the shak-ing time was set to be 60 min. Figure 2 shows thatthe percentage adsorption of Pb(II) ions is higherthan Cu(II) ions. The adsorption of Pb(II) ionsonly slightly increases with the increase in contacttime compared to the Cu(II) ions. A similar resulthas been found by Unlu and Ersoz [22] in adsorp-tion characteristic of heavy metal ions onto a low-cost biopolymeric sorbent from aqueous solutions.

It is necessary to point out that these tests weredone under a condition without any pH adjust-ment. However, it is supposed that the pH of themetal ions solution may affect metal affinity foradsorption on the Meranti tree sawdust and thatthe process of metal adsorption may change thepH of an unbuffered solution. Anyway, pH mayplay an important role in the metals adsorption,which is an important aspect of our further studies.

3.5. Effect of pH

The pH is one of the most important environ-mental factors influencing not only the site dissoci-ation, but also the solution chemistry of the heavymetals: hydrolysis, complexation by organic and/or inorganic ligands, redox reactions, and precipi-tation are strongly influenced by pH and, on theother hand, strongly influence the speciation andadsorption availability of heavy metals.

The effect of pH on the adsorption of Cu(II)and Pb(II) ions on Meranti tree sawdust has

0 30 60

Time (min)

90 120 150

copperlead

180

10

% A

dsor

ptio

n

0

20

30

40

50

60

70

80

Fig. 2. Effect of time in the removal of Cu(II) and Pb(II)by sawdust.

Table 1

Various physical parameters for the adsorbent (Meranti

tree sawdust)

Parameters Values

pH (aqueous solution) 7.10Particle size (mm) 100–150Surface area (m2/g) 630.00Bulk density (g/cm3) 0.27Moisture contents (%) 6.25Water soluble components

(inorganic matter) (%)21.73

Insoluble components (organic matter) (%) 76.22

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been studied by varying it in the ranges of2.0–7.0 for Cu(II) ions and 2.0–7.5 for Pb(II)ions as shown in (Fig. 3). As shown in Fig. 3,the uptake of Cu(II) and Pb(II) ions dependson pH, it increases with the increase in pHfrom 2.0 to 6.6 and 2.0 to 7.0, respectively.Above this pH range, a decrease in the uptakeof both the metal ions was observed. The peakpercentage adsorptions of Cu(II) as well asPb(II) ions were attained at pH 6.6 and 7.0,respectively.

Based on the behavior of heavy metal adsorp-tion on sawdust, it is speculated that the ionexchange and hydrogen bonding may be theprincipal mechanism for the removal of heavymetals [15]. There are a number of parametersto support this speculation, including the compo-nents and complexing properties of the sawdust,the properties of heavy metals and the adsorp-tion behavior, such as the effect of pH of theaqueous media leading to change in speciation.

Based on the electron-donating nature of theO-, S-, N-, and P-containing groups in sawdustand the electron-accepting nature of heavymetal ions, the ion exchange mechanism could

be preferentially considered. For instance, adivalent heavy metal ion may attach itself totwo adjacent hydroxyl groups and oxyl groupswhich can donate two pairs of electrons to themetal ion, forming four coordination numbercompounds and releasing two hydrogen ionsinto solution. It is then readily understood thatthe equilibrium is quite dependent on pH ofthe aqueous solution. At lower pH, the H+ ionscompete with metal cations for the exchangesites on the sawdust, thereby partially releasingthe latter. The heavy metal cations are com-pletely released under circumstances of extremeacidic conditions [23, 24].

At pH value lower than 3, the adsorptioncapacities were found to be low due to the com-petitive adsorption of HO3

+ ions and metal ionsfor the same active adsorption site. As the pHincreases, the adsorption surface becomes lesspositive and therefore electrostatic attractionbetween the metal ions and sawdust surface islikely to be increased. The maximum sorptionefficiency in the range of 2.0–6.6 for Cu(II)and 2.0–7.0 for Pb(II) ions may be due to theinteraction of M+, M(OH)+, and M(OH)2 withsurface functional groups present in the sawdust.A decrease in adsorption at high pH is due to theformation of soluble hydroxyl complexes.

3.6. Effect of adsorbent dosage

Adsorbent dosage is an important parameterbecause it determines the capacity of an adsorb-ent for a given concentration of the adsorbate.The adsorption studies of Cu(II) and Pb(II) ionson Meranti tree sawdust were done at room tem-perature by varying the quantity of adsorbentfrom 0.25 to 2.00 g while keeping the volumeof the metal solutions constant at different pH.The influence of adsorbent dosage in the removalof Cu(II) and Pb(II) ions is shown in Fig. 4. Theincrease in the adsorbent dosage from 0.25 to2.0 g at pH 6.6 for Cu(II) resulted in an increaseof adsorption from 90% to 97.5%. On the other

10 2 3 4

pH

5 6 7

copperlead

8

10

% A

dsor

ptio

n

0

20

30

40

50

60

70

80

90

100

Fig. 3. Effect of pH in the removal of Cu(II) and Pb(II)by sawdust.

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hand, the percentage for Pb(II) ions adsorption atpH 7.0 is 90.4% to 93.9% with the adsorbent dos-age ranging from 0.25 to 2.00 g. The results showthat the adsorption increases with the increase inthe dose of sawdust. This is because of the avail-ability of more binding sites on the surface athigher concentration of the adsorbent for com-plexation of metal ions. From this point ofview, it is easily understandable that the initialconcentration of Cu(II) and Pb(II) ions gavesome effect on its percentage removal (Fig. 4).

3.7. Adsorption behavior of sawdust(isotherm studies)

The related parameters for the fitting ofFreundlich and Langmuir equations at differenttemperatures are summarized in Table 2 and iso-therm plots are shown in Figs 5–8 for Cu(II) andPb(II) ions, respectively. The adsorption ofCu(II) and Pb(II) ions on sawdust at pH 6.6 and7.0, respectively, follow both Freundlich- andLangmuir-type adsorption isotherms. However,the Freundlich equation is better obeyed by thesystem than the Langmuir one as is evidentfrom the values of regression coefficient shownin Table 2. The Freundlich-type adsorption iso-therm is an indication of surface heterogeneityof the adsorbent while Langmuir-type isothermhints toward surface homogeneity of the adsorb-ent. This leads to the conclusion that the surfaceof sawdust is made up of small heterogeneousadsorption patches which are very much similarto each other with respect to adsorption phenom-enon. With the increase in concentration at ele-vated temperature, the activation of adsorptionsites takes place leading to increased adsorptionprobably via a surface exchange reaction.Actually at high temperatures, the aggregationof Cu(II) ions at the surface of sawdust increaseswhich results in an exchange reaction with thealready-adsorbed species along with the normalphysio-sorption.

0.50 1Amount of adsorbent (g)

1.5 2 2.5

copperlead

89

% A

dsor

ptio

n

90

91

93

92

94

95

96

97

98

Fig. 4. Effect of adsorbent dosage in the removal ofCu(II) and Pb(II) by sawdust.

Table 2

The related parameters for the Cu(II) and Pb(II) adsorption on sawdust at different temperatures

Temp (8C) Freundlich constants Langmuir constants

Cu(II) Pb(II) Cu(II) Pb(II)

r2 K(mg/g)

1/n r2 K(mg/g)

1/n r2 b(mg/g)

K(L/mg)

r2 b(mg/g)

K(L/mg)

30 0.99 2.74 0.70 0.99 1.01 0.76 0.95 37.17 0.07 0.97 37.04 0.0240 0.99 3.20 0.68 0.99 1.17 0.74 0.96 34.84 0.09 0.99 34.84 0.0250 0.99 3.83 0.67 0.99 1.28 0.73 0.97 34.13 0.12 0.99 33.90 0.03

60 0.99 5.43 0.59 0.99 1.76 0.68 0.95 30.67 0.22 0.97 31.95 0.04

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It was reported in our previous study [15] thatthe efficiency for the removal of copper fromriver water using Mango sawdust was 63%,and it was thus concluded that the sawdust is

an excellent adsorbent for copper removalfrom aqueous solution. In 2001, Yu et al. [25]on the adsorption behavior of maple sawdustfor the removal of heavy metals, such as Cu(II)

0.5�0.5�1 0 1 1.5

30°C40°C50°C60°C

log

Am

log Ce

0.2

0.4

0.8

0.6

1

1.2

1.4

0

1.6

Fig. 5. Freundlich plots for the adsorption of Cu(II) bysawdust.

0 5

Ce (mg/L)

Ce/A

m (m

g/L)

10 15 20

30°C40°C50°C60°C

25

0.2

0

0.4

0.6

1

0.8

1.2

Fig. 6. Langmuir plots for the adsorption of Cu(II) bysawdust.

0

log Ce

log

Am

0.5 1 1.5

30°C40°C50°C60°C

2

0.2

0

0.4

0.6

1

0.8

1.2

1.4

1.6

Fig. 7. Freundlich plots for the adsorption of Pb(II) bysawdust.

0

Ce (mg/L)

Ce/A

m (m

g/L)

10 20 30

30°C40°C50°C60°C

40 50 60

0.5

0

1

1.5

2.5

2

3

Fig. 8. Langmuir plots for the adsorption of Pb(II) bysawdust.

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and Pb(II), presented some guidelines for theapplication of sawdust adsorption. In thesestudies, it was investigated that the adsorptionbehavior, capacity, and other factors, such aspH and sawdust dose, using untreated maplesawdust. Under optimized conditions, the per-centage of metal removal by maple sawdustadsorption was over 90%; indicating sawdust isan appealing adsorbent for the removal ofheavy metals.

Raji and Anirudhan reported studies on theremoval of Pb(II) using polyacrylamide graftedsawdust [26] and polymerized sawdust [27]. Inthose studies, adsorption and desorption experi-ments were conducted, and various affectingfactors tested. Research data showed that thetreated sawdusts might be effectively used assorbents for the removal of Pb(II) from aqueousmedia. The maximum removal of over 98%was reported.

By comparison of the results obtained fromthis study to the previously reported work onpercentage removal of various low-cost adsorb-ents in aqueous solution for Cu(II) and Pb(II)ions, it can be stated that our findings are well.

3.8. Thermodynamic parameter of sorption

The various thermodynamic parameters, that isfree energy (DG), enthalpy (DH), and entropy(DS), and its values associated with the sorption

of Cu(II) and Pb(II) ions onto the Meranti treesawdust are listed in Table 3 which show thatthe overall processes for both ions are endother-mic. The DH for Cu(II) is 31.47 kJ/mol and theDH for Pb(II) is 20.07 kJ/mol. Besides that, theK value from Table 2 indicates the affinitytoward the binding of metal ions [28]. Thehighest value of K was found at 608C for eachmetal ion.

The free energy of adsorption (DG) can berelated with the equilibrium constant K, corre-sponding to the reciprocal of the Langmuir con-stant from Eqn (3). The free energy of theprocess at all temperature is negative for bothions and it decreases with an increase in temper-ature which indicates that the process is sponta-neous in nature and the spontaneity increaseswith the rise in temperature.

Also enthalpy (DH) and entropy (DS)changes can be estimated by Eqns (4) and (5).The values of DS were found to be positivedue to the exchange of the metal ions withmore mobile ions present on the exchanger,which would cause increase in the entropy,during the adsorption process. Besides that, theentropy also can be increased in the case ofphysisorption which may also contribute to thetotal adsorption process. This is due to thewater molecules released from the hydratedions or water molecules present on the surfaceduring the adsorption process [29].

Table 3

Thermodynamic parameters for the Cu(II) and Pb(II) adsorption on sawdust at different temperatures

Temp (8C) For Langmuir isotherms

Cu(II) Pb(II)

ln K DG DS DH (30–608C) ln K DG DS DH (30–608C)

30 8.37 �21.09 0.17 31.47 8.33 �20.99 0.13 120.0740 8.64 �22.51 0.17 8.55 �22.26 0.1350 8.92 �23.98 0.17 8.69 �23.34 0.1360 9.53 �26.40 0.17 9.08 �25.16 0.14

DG = kJmole�1, DS = kJmole�1K�1, and DH = kJmole�1

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4. Conclusions

Based on the present study, it is clearly shownthat sawdust obtained from Meranti wood is aneffective adsorbent for the removal of Cu(II)and Pb(II) ions from aqueous solution. Theadsorption process is strongly affected byparameters such as time, pH, adsorbent dosage,and temperature. The equilibrium time forCu(II) and Pb(II) ions is determined as 60 min.The percentage adsorption for Pb(II) seems tobe greater than adsorption of Cu(II) in this equi-librium time. The plot of pH versus percentageadsorption shows significant adsorption at pH6.60 for the Cu(II) ions and at pH 7.00 for thePb(II) ions. The removal is almost 100% forCu(II) at this pH value being 99.39%. On theother hand, percentage removal for Pb(II) atthis pH is 94.61%. The percentage adsorptionof Cu(II) and Pb(II) ions was increased withincreasing the adsorbent dosage. The adsorptionof Cu(II) and Pb(II) ions on sawdust at pH 6.60and 7.00, respectively, follow both Freundlich-and Langmuir-type adsorption isotherms. Ther-modynamic constants were also evaluatedusing equilibrium constants changing with tem-perature. The negative value of DG for Cu(II)and Pb(II) ions indicated the spontaneity of theprocess. The positive value of DH showed theendothermic nature of Cu(II) and Pb(II) sorp-tion, respectively.

Acknowledgment

The study was funded through USM short-term grant number 304/ PTEKIND/ 637044.The authors acknowledge the USM for provid-ing research facilities.

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