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Batch adsorption of 2,4-dichlorophenol onto activated carbon derived from

agricultural waste

F.W. Shaarani, B.H. Hameed

School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia

a b s t r a c ta r t i c l e i n f o

Article history:

Received 6 September 2009

Received in revised form 20 December 2009Accepted 25 December 2009

Available online 2 February 2010

Keywords:

Oil palm empty fruit bunch

2,4-Dichlorophenol

Adsorption

Isotherm

Kinetics

Activated carbon

The potential feasibility of activated carbon derived from oil palm empty fruit bunch (EFB) for the removal of

2,4-dichlorophenol (2,4-DCP) from aqueous solution was studied. The activated carbon was prepared via

chemical activation with phosphoric acid. The effect of contact time, initial concentration (25 250 mg/L),

temperature (3050 C) and pH (212) were investigated. The experimental data were analyzed by the

Langmuir and Freundlich isotherm models. The equilibrium datawere bestrepresented by Langmuir isotherm

model, with a maximum monolayer adsorption capacity of 232.56 mg/g at 30 C. The adsorption kinetics was

well described by the pseudo-second-order kinetic model. The empty fruit bunch based activated carbon

(EFBAC) was shown to be a promising material for adsorption of 2,4-DCP from aqueous solutions.

2010 Elsevier B.V. All rights reserved.

1. Introduction

Phenols and its derivatives are one of the most common envi-

ronmental contaminants. They are vastly used as intermediates in the

synthesis of plastics, colours, pesticides, insecticides, etc. Most of

these compounds are recognized as carcinogens[1]. According to the

Environmental Protection Agency in USA, phenols and its derivatives

are considered to constitute the 11th of the 126chemicals which have

been designated as priority pollutants, [2] whereas referring to the

Environmental Quality Act of Malaysia, the permissible limits for

phenolic compounds in industrial efuents before discharging into

municipal sewers and surface water is 0.001 mg/L[3].

Phenols in the presence of chlorine will react and form chloro-

phenol, which is quite pronounced with a medicinal taste and objec-

tionable when it gets mixed with drinking water. 2,4-Dichlorophenol

(2,4-DCP) is a chlorinated aromatic that is a primary reagent in the

synthesis of a variety of more highly chlorinated phenols (i.e., pen-

tachlorophenol) and pesticides (i.e., 2, 4-dichlorophenoxyacetic acid).

2,4-DCP is a colourless, crystalline solid which is slightly soluble in

water at neutral pH (0.45% at 25 C) and very soluble in alcohol, ether,

and benzene. 2,4-DCP acts as a weak acid with pKa=7.90[4].

Environmental contamination by 2,4-DCP may occur as a result

of microbial degradation or photodecomposition of the herbicides,

from chlorination of drinking water and industrial wastewater and

municipal wastewater by water disinfection plants, or from agricul-

tural runoff or industrial waste discharges[4].One of the most frequently used methods and unequivocally

effective solution designed to remove phenolic derivatives is adsorp-

tion. Adsorption is a process, which involves the contact of a free

aqueous phase with a rigid particulate phase, which has the propen-

sity to remove or store one or more solutes present in the solution

selectively[5]. Activated carbon is the most widely used adsorbent

for the removal of pollutants from wastewater[6]. This is due to its

extended surface area, microporous structure, high adsorption ca-

pacity and high degree of surface reactivity. However commercially

available activated carbons are very expensive, the higher the quality

the greater the cost thus they may not be economical for wastewater

treatment[7]. This has led to the search of new agricultural based

activated carbon as a substitute to the existing activated carbon.

In Malaysia, the palm oil industry generates huge amount of solid

waste consisting of oil palm empty fruit bunches (EFB), ber and fruit

shell during the palm fruits processing. It was estimated that the

amount of EFB available in Malaysia in a year is about 4.43 million

tonnes (dry wt). At present, 65% of the EFB generated is incinerated

and the bunch ash recycled back to the plantation as fertilizer. How-

ever, incineration for bunch ash is not environmentally acceptable

due to the emission of white smoke with some y ash[8]. To diversify

this abundantly available waste, it has been proposed to convert it

into activated carbons.

Activated carbon can be manufactured by physical or chemical

activation. In physical activation two stages are involved, i.e. car-

bonization in an inert atmosphere at a temperature below 700 C

Desalination 255 (2010) 159164

Corresponding author. Fax: +60 45941013.

E-mail address:chbassim@eng.usm.my(B.H. Hameed).

0011-9164/$ see front matter 2010 Elsevier B.V. All rights reserved.

doi:10.1016/j.desal.2009.12.029

Contents lists available at ScienceDirect

Desalination

j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / d e s a l

mailto:chbassim@eng.usm.myhttp://dx.doi.org/10.1016/j.desal.2009.12.029http://www.sciencedirect.com/science/journal/00119164http://www.sciencedirect.com/science/journal/00119164http://dx.doi.org/10.1016/j.desal.2009.12.029mailto:chbassim@eng.usm.my

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and then activation in the presence of steam, carbon dioxide and/or

air at higher temperatures (8001000 C). In contrast to physical

activation, chemical activation is carried out in only one stage at

much lower temperature (400800 C) in the presence of dehydrat-

ing agents such as ZnCl2, H3PO4, and KOH [9]. The advantages of

chemical activation are low energy cost due to lower temperature of

process and higher product yield[10].

Currently EFB prepared activated carbon has been utilized for the

removal of phenol [11], 2,4-dichlorophenol [12] and 2,4,6-trichlor-ophenol [13]. For adsorption of phenol, EFBAC were prepared via

physical activation and thermal activation. In adsorption of 2,4-DCP

from aqueous solution, the activated carbon was produced by thermal

activation at 800 C for 30 min while for the removal 2,4,6-trichlor-

ophenol, it was prepared using physiochemical activation method

consisting of potassium hydroxide (KOH) treatment followed by car-

bon dioxide (CO2). None of the methods above involved preparation

of activated carbon by EFB via chemical activation.

The objective of this work was to evaluate the adsorption poten-

tial of oil palm empty fruit bunch based activated carbon (EFBAC)

prepared via chemical activation using phosphoric acid for the re-

moval of 2,4-DCP from aqueous solution. Theequilibrium and kinetics

data of the adsorption process were then analyzed to study the ad-

sorption characteristics and mechanism of adsorption.

2. Materials and methods

2.1. Preparation and characterization of activated carbon

The EFB used for preparation of activated carbon in this study

was obtained from local Palm Oil Mill, Nibong Tebal, Malaysia. As

received, the precursor was washed, sun dried, and crushed to a

particle size of 12 mm. The pre-treated precursor was then soaked

with 20 wt.% of phosphoric acid solution with an impregnation ratio

of 16:1 (acid: precursor). The mixture of precursor and acid solution

was then left overnight at room temperature. Subsequently the pre-

cursor was ltered from phosphoric acid solution and then was de-

hydrated in the oven at 105 C for 24 h. The impregnated precursor

was then placed inside the tubular tube in the stainless steel reactorfor activation. Activation takes place at 450 C with constant heating

rate 10 C/min, under puried nitrogen (99.995%) ow of 150 cm3/

min for 2 h before it was cooled down to room temperature. The

nal product was then washed with 0.1 M hydrochloric acid and hot

distilled water until the pH of the washing solution reached 67,

then dried in the oven at 105 C for 24 h and nally kept in an airtight

container for further use.

Textural characterization of the activated carbon was carried out

by N2adsorption at 77 K using Micromeritics (Model ASAP 2020, US).

The BrunauerEmmettTeller (BET) is the most common standard

procedure used when characterizing an activated carbon [14]. Scan-

ning electron microscopic (SEM) (Leica Cambridge S-360) analysis

was carried out for the prepared activated carbon to study the surface

morphology and to verify the porosity.

2.2. 2,4-Dichlorophenol

2,4-Dichlorophenol (2,4-DCP) of analytical reagent grade (Merck)

was used as an adsorbate in this study. 2,4-DCP has a chemical for-

mula of C6H3Cl2OH, with a molecular weight of 163.0 g/mol.

2.3. Batch equilibrium studies

Batch adsorption was performed in a set of 250 mL Erlenmeyer

asks where 200 mL of 2,4-DCP solutions with various initial con-

centrations (25250 mg/L) were placed in these asks. Equal mass of

EFBAC (0.20 g) was added to each ask and kept in an isothermal

shaker (30 C) at 130 rpm for 24 h to reach equilibrium. The pH of

the solution was kept original without any pH adjustment. Aque-

ous samples were taken from the solution and the concentrations

were analyzed. All samples were ltered prior to analysis in order to

minimize interference of the carbon nes with the analysis. Each

experiment was duplicated under identical conditions. The concen-

trations of 2,4-DCP before and after adsorption were determined

using a double beam UVVis spectrophotometer (Shimadzu, Japan)

at 280 nm. The amount adsorbed at equilibrium, qe(mg/g), was cal-

culated by:

qe = C0CeV= W 1

whereCo and Ce (mg/L) are the liquid-phase concentrations of 2,4-

DCP at initial and equilibrium, respectively. V(L) is the volume of the

solution andW(g) is the mass of dry adsorbent used.

2.4. Effect of temperature

The effect of temperature on the adsorption capacity and kinetics

of the EFBAC on 2,4-DCP was studied by varying the adsorption tem-

perature at 30, 40 and 50 C, while other operating parameters (ini-

tial 2,4-DCP concentration, activated carbon dosage, pH and agitation

speed) remained the same.

2.5. Effect of solution pH

Theeffect of solution pH on the 2,4-DCP removal was examined by

varying the initial pH of the solutions from pH 2 to 12. The pH was

adjusted using 0.1 M HCl and/or 0.1 M NaOH and was measured using

pH meter (Model Ecoscan, EUTECH Instruments, Singapore). The 2,4-

DCP initial concentration wasxed at 100 mg/L,with activatedcarbon

dosage of 0.2 g/100 mL and solution temperature of 30 C.

3. Results and discussion

3.1. Textural characterization of prepared activated carbon

Table 1 summarizes thesurface area andpore volumeproperties of

EFBAC. The BET surface area was found to be 1031.515 m/g whereas

the total pore volume of EFBAC was 0.583 cm/g. Fig. 1 shows the SEM

image of the derived activated carbon. Many large pores were clearly

found on the surface of the activated carbon. The well-developed

pores have led to the large surface area and porous structure of the

activated carbon.

3.2. Effect of initial 2,4-DCP concentration and contact time on 2,4-DCP

adsorption

Fig. 2 shows the adsorption capacity versus the adsorption time

at various initial 2,4-DCP concentrations. It is clear that adsorption of

2,4-DCP on activated carbon depends on its initial concentration.

An increase in the concentration led to an increase in the amount of2,4-DCP adsorbed on activated carbon. This may be attributed to an

increase in the driving force of the concentration gradient with the

increase in the initial 2,4-DCP concentration. The amount of 2,4-DCP

adsorbed increased from 22.936 to 185.185 mg/g as the concentra-

tion was increased from 25 to 250 mg/L. Sathishkumar et al. reported

Table 1

Surface area and pore volume properties of EFBAC.

Properties

BET surface area (m2/g) 1031.515

Total pore volume (cm3/g) 0.583

Average pore diameter (nm) 2.261

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similar result for the adsorption of 2,4-DCP on maize cob activated

carbon[15].

It is also apparent fromFig. 2that the contact time needed for 2,4-

DCP solutions with initial concentrations of 25100 mg/L to reach

equilibrium was less than 2 h. However, for 2,4-DCP solutions with

higher initial concentrations, longer equilibrium times were required.

This observation could be explained by the fact that in the process of

adsorption, initially the adsorbate molecules had to rst encounter

the boundary layer effect and then diffuse from the boundary layer

lm onto adsorbent surface and then nally, they had to diffuse into

the porous structure of the adsorbent[16]. This phenomenon took a

relatively long contact time. Therefore, 2,4-DCP solutions with higher

initial concentrations would take a longer contact time to attain

equilibrium due to the higher amount of 2,4-DCP molecules to be

adsorbed. A similar phenomenon was observed on the adsorption of

phenol by carbonaceous adsorbents derived from coconut shell and

the equilibrium time attained was 5 h[17].

3.3. Effect of temperature on adsorption capacity of activated carbon

Fig. 3shows the effect of solution temperature on the uptake of

2,4-DCP by EFBAC at various initial concentrations (25250 mg/L). It

exemplies that the increase of temperature slightly increased the

removal of 2,4-DCP, indicating the endothermic nature of the

adsorption reaction. In addition, changing the temperature will

change the equilibrium capacity of the adsorbent for a particular

adsorbate[18]. This observation is in agreement with Tan et al. who

reported that the uptake of 2,4,6-trichlorophenol on activated carbon

increases as the solution temperature increases[13].

3.4. Effect of solution pH

The effect of pH on adsorption of 2,4-DCP was studied over a pH

range of 212 with the initial concentration of 2,4-DCP xed at

100 mg/L. As shown in Fig. 4, the adsorption capacity of 2,4-DCP

decreases with increase in pH of the solution. The highest uptake wasachieved at pH 2, with 2,4-DCP uptake as high as 91.57 mg/g where-

as the lowest uptake was recorded at pH 12 with only 55.88 mg/g.

This observation is similar with the trend reported by Hameed et al.,

[19] and Gao and Wang [20]. The behaviour clearly suggests that

the adsorption was dominated by the interaction between undisso-

ciated organic compounds and the organophilic nature of the ad-

sorbent surface.

3.5. Adsorption isotherms

Adsorption isotherms are usually determined under equilibrium

conditions. It indicates how the adsorption molecules distribute be-

tween the liquid phase and the solid phase when the adsorptionprocess reaches an equilibriumstate. Theanalysisof theisothermdata

by tting them to different isotherm models is an important step

to nd the suitable model that can be used for design purpose [21].

Several models have been published in the literature to describe

the experimental data of adsorption isotherms. The most frequently

employed models are Langmuir and Freundlich were used to describe

the relationship between the amount of adsorbate adsorbed and its

equilibrium concentration. The applicability of the isotherm equation

to describe the adsorption process was judged by the correlation

coefcientR2 values.

Fig. 1.SEM image of EFBAC (magnication=500).

Fig. 2. Adsorption capacity versus adsorption time at various initial 2,4-DCP concentra-

tions (25

250 mg/L) at 30 C.

Fig. 3. Effect of solutiontemperatureon 2,4-DCP uptake at various initial concentrations.

Fig. 4.Effect of solution pH on 2,4-DCP removal at 30 C (2,4-DCP initial concentration=

100 mg/L).

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The linear form of Langmuir's isotherm [22] model is given by

Eq. (2):

Ce= qe = 1

Q0

. Ce +

1Q0b

. 2

whereCe (mg/L) is the equilibrium concentration of the adsorbate,

qe (mg/g) is the amount of adsorbate adsorbed per unit mass of

adsorbent, Qo and b are Langmuir constants related to adsorption

capacity and the adsorption equilibrium constant, respectively.For the Langmuir isotherm, when Ce/qe is plotted against Ce, a

straight line with slope of 1/Qo is obtained as shown in Fig. 5. The

correlation coefcient, R2 of 0.999 indicated that the adsorption data

of 2,4-DCP on the EFBAC was well tted to the Langmuir isotherm.

The Langmuir constants b and Qo were calculated from Eq. (2) and are

listed inTable 2.

Conformation of the experimental data with the Langmuir iso-

therm model indicates the homogeneous nature of oil palm empty

fruit bunch carbon surface, i.e., each 2,4-DCP molecule/EFBAC adsorp-

tion has equal adsorption activation energy; the results also demon-

strate the formation of monolayer coverage of 2,4-DCP molecule at

the outer surface of prepared EFBAC.

The essential characteristics of the Langmuir isotherm can be ex-

pressed in terms of a dimensionless equilibrium parameter (RL)[23].The parameter is dened by:

RL= 1 =1 + bC0 3

whereb is the Langmuir constant and Co (mg/L) is the highest ini-

tial 2,4-DCP concentration. The parameter RL indicates the shape of

isotherm as follows;

Value ofRL Type of isotherm

RL> 1 Unfavorable

RL=1 Linear

0 < RL< 1 Favorable

RL=0 Irreversible

Value of RL was found to be 0.063 at T=30 C. This again

conrmed that the Langmuir isotherm was favorable for adsorption

of 2,4-DCP on the EFBAC used in this study. The well-known linear

form of Freundlich isotherm[24]is given by the following equation:

log qe = 1 = n log Ce + log KF 4

where Ce (mg/L) is the equilibrium concentration of the adsorbate,

qe (mg/g) is the amount of adsorbate adsorbed per unit mass of

adsorbent, KF(mg/g (L/mg)1/n) and nare Freundlich constants with n

giving an indication of how favorable the adsorption process.KFis the

adsorption capacity of the adsorbent which can be dened as the

adsorption or distribution coefcient and represents the quantity

of 2,4-DCP adsorbed onto activated carbon for a unit equilibrium

concentration. The slope of 1/nranging between 0 and 1 is a measure

of adsorption intensity or surface heterogeneity, becoming more het-

erogeneous as its value gets closer to zero. A value for 1/nbelow one

indicates a normal Langmuir isotherm while 1/nabove one is indic-

ative of cooperative adsorption. The plot of log qe versus log Ce(Fig. 6)

gave a straight line with slope of 1/nwhereasKFwas calculated from

the intercept value. The constants (KF, nandR2) are listed inTable 2.

As illustrated in Table 2, the value of n is 1.689 which indicates

favorable adsorption [25,26]. The correlation coefcient, R2 for

Freundlich isotherm is 0.962. Comparing the R2 values for both iso-

therms, it showed that the adsorption data obtained are better tted

to the Langmuir isotherm model.

Table 3lists the comparison of the maximum monolayer adsorp-

tion capacity of various types of chlorophenols on various adsorbents.

The activated carbon prepared in this work showed relatively large

2,4-DCP adsorption capacity of 232.56 mg/g, as compared to some

previous works reported in the literature.

3.6. Kinetic studies

3.6.1. Pseudo-rst-order model

A linearformof pseudo-rst-order model was described by Lagergren

and Svenska[27]in the form:

logqeqt= log qek1= 2:303t 5

whereqe and qt refer to the amount of 2,4-DCP adsorbed (mg/g) at

equilibrium and at any time, t(h), respectively, and k1 is the equi-

librium rate constant of pseudo-rst-order sorption (1/h).

As such, the values of log (qeqt) for 2,4-DCP were calculated and

plotted against time. If the plots were found to be linear with good

correlation coefcient, indicating that Lagergren's equation is appro-

priate to 2,4-DCP adsorption on EFBAC. So, the adsorption process is

a pseudo-rst-order process. The pseudo-rst-order rate constants

Fig. 5.Langmuir adsorption isotherm of 2,4-DCP onto EFBAC at 30 C.

Table 2

Langmuir and Freundlich isotherm model constants and correlation coefcients.

Langmuir isotherm

Qo(mg/g) 232.560

b(L/mg) 0.060

R2 0.999

RL 0.063

Freundlich isotherm

n 1.689

KF[(mg/g)(L/mg)1/n] 18.806

R2 0.962

Fig. 6.Pseudo-rst-order kinetics for adsorption of 2,4-DCP on EFBAC at 30 C.

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were calculated from the slope of the plots ( Fig. 6). From the results

obtained, although the correlation coefcient values at high concen-

tration are higher than 0.90, the experimental qevalues do not agree

with the calculated ones, obtained from the linear plots (Table 4). This

indicates that the adsorption of 2,4-DCP onto EFBAC is not obeying

pseudo-rst-order kinetics model.

3.6.2. Pseudo-second-order

The pseudo-second-order equation[28]is expressed as:

t= qt = 1 = k2q2e +1 = qet 6

whereqe and qt are the adsorption capacities at equilibrium and at

time t, respectively (mg/g) and k2 (g/mg h) is the rate constant of

pseudo-second-order sorption. By plotting t/qt versus t (Fig. 7), qeandk2can be determined from slope and intercept. The linear plot of

t/qt versus tat 30 C, as shown inFig. 7, yieldedR2 values that were

greater than 0.990 for all 2,4-DCP concentrations. It also showed a

good agreement between the experimental and the calculated qevalues (Table 4), indicating the applicability of this model to describe

theadsorption process of 2,4-DCP onto the prepared activated carbon.

Similar kinetics were also observed for the removal of 2-chlorophenol

by coir pith carbon[29], 2,4-DCP by activated carbon ber[30]and

4-chlorophenol on rattan sawdust activated carbon[31].

3.6.3. Intraparticle diffusion model

Intraparticle diffusion model based on the theory proposed by

Weber and Morris [32], was tested to identify the diffusion mechanism.

According to this theory:

qt = kidt12 +C 7

where Cis the intercept and kid (mg/g h1/2) is the intraparticle diffusion

rate constant, which canbe evaluatedfrom theslope of the linear plot of

qt versus t1/2. The intercept of the plot reects the boundary layer effect.

The larger the intercept, the greater the contribution of the surface

sorption in the rate-controlling step. If the regression ofqtversus t1/2 is

linear, and passes through the origin, then intraparticle diffusion is thesole rate-limiting step. Fig. 8 illustrates the plots ofqt versus t

1/2 for

differentrangeof 2,4-DCPinitial concentrations at 30 C.It wasobserved

that the linear plots at each concentration did not pass through the

origin. This indicates that the intraparticle diffusion was not only rate-

controlling step. Such trend wasreportedby several researchers on their

previous investigation on adsorption[3335].

3.7. Validity of kinetic model

Kinetic model used to describe the adsorption process was veried

by the normalized standard deviation, q(%), which is dened as:

q%=

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiqexpqcal

=qexp

h i2= N1

r 8

whereN is the number of data points, qexp and qcal(mg/g) are the

experimental and calculated adsorption capacity, respectively. The

lower thevalueofq thebetter themodelts. Listed in Table 4 arethe

calculated values ofq determined for the two kinetic models. It is

clearly shown that the pseudo-second-order kinetic model yielded

the lower qvalues. This is in agreement with the R2 values obtainedearlier and proves that the adsorption of 2,4-DCP onto the EFBAC

Table 3

Comparison of maximum monolayer adsorption capacity of various chlorophenols on

various adsorbents.

Adsorbent Adsorbate Maximum monolayer

adsorption capacity

(mg/g)

Reference

EFBAC 2,4-Dichlorophenol 232.56 This work

Rattan sawdust

activated carbon

4-Chlorophenol 188.68 [31]

Maize cob carbon 2,4-Dichlorophenol 17.94 [15]Palm pith carbon 2,4-Dichlorophenol 19.16 [36]

Oil palm empty

fruit bunch

2,4-Dichlorophenol 27.25 [12]

Activated carbon ber 2,4-Dichlorophenol 372.00 [30]

Table 4

Comparison of the pseudo-rst-order model and pseudo-second-order model for adsorption of 2,4-DCP on EFBAC at 30 C.

Initial 2,4-DCP

concentration

(mg/L)

qe, exp(mg/g)

Pseudo-rst-order kinetic model Pseudo-second-order kinetic model

qe, cal(mg/g)

k1(1/h)

R2 q

(%)

qe, cal(mg/g)

k2(g/mg h)

R2 q

(%)

25 23.3022 2.5948 0.6851 0.9801 33.5877 22.9358 1.2673 0.9998 0.5943

50 46.9268 20.7683 2.4430 0.9634 21.0689 49.5050 0.1943 0.9994 2.0766

100 89.6500 20.0124 0.7830 0.9835 29.3592 87.7193 0.1444 0.9994 0.8140

150 127.9730 50.7107 0.8189 0.9827 22.8192 126.5823 0.0480 0.9962 0.4107

200 159.0220 76.7538 0.8945 0.984 19.5536 161.2903 0.0275 0.9990 0.5391

250 181.3430 102.9438 0.8701 0.9916 16.3404 185.1852 0.0182 0.9972 0.8008

Fig. 7.Pseudo-second-order kinetics for adsorption of 2,4-DCP on EFBAC at 30 C.

Fig. 8. Plot of intraparticle diffusion model for adsorption of 2,4-DCP onto EFBAC at

30 C.

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could be best described by the pseudo-second-order kinetic model

which is based on the equilibrium chemical adsorption.

4. Conclusion

Activated carbon prepared from EFB via chemical activation using

phosphoric acid was found to be effective to remove 2,4-DCP from

aqueous solution. The adsorption equilibrium was best described by

the Langmuir isotherm model with maximum monolayer adsorptioncapacity of 232.56 mg/g at 30 C. Over the range of concentration

studied, the adsorption kinetic obeys the pseudo-second-order model

which proves that the chemical adsorption is a rate-controlling

parameterin this adsorption study.Theseindicatethat oil palm empty

fruit bunch is a promising activated carbon precursor.

Acknowledgement

The authors acknowledge the research grant provided by Univer-

sity of Science Malaysia under The Fundamental Research Grant

Scheme (FRGS) (Project No: 6070015).

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