Laboratory batch studies were conducted on adsorption of phenol, 3-chlorophenol and o-cresol from aqueous solution by Norit Granular Activated Carbon (NAC 1240)

Ahmad, Abdul Latif

Hameed, Bassim H.

Maarof, Hawaiah Imam

English

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Aqueous-Phase Adsorption of Phenolic Compounds onActivated CarbonH. 1. Maarof, B. H. Hameed and A. L. AhmadSchool a/Chemical Engineering, Engineering Campus,Universiti Sains Malaysia, Seri Ampangan, Nibong Tebal,14300 Seberang Perai Selatan, Pulau Pinang, Malaysia.E-mail: chbassim\aJ.eng.usm.myABSTRACTlAboratory batch studies were conducted on adsorption of phenol, 3-chlorophenol and o-cresol fromaqueous solution by Norit Granular Activated Carbon (NAC 1240). The effect of various initialconcentrations and time of adsorption on phenols adsorption process were investigated. The timerequired for adsorbates to reach equilibrium condition was about 2S h for range of initial phenolsconcentration between 25-200 mg/I. A maximum percentage of removal of 90% phenol and 99% of3-chlorophenol and o-cresol were obtained under adsorption operating conditions of 30°C, 120 rpm, 25 hadsorption time and initial solute concentrations of 25 and 50 mg/1. It was observed that an increase ininitial solute concentration results in increase of phenols uptake from liquid to solid phase. The suitabilityof Langmuir and Freundlich model were evaluated to estimate the monolayer capacity values of theactivated carbon used for each sorbate-sorbent system. The adsorption behaviour of phenolic compoundson NAC 1240 was best described by Langmuir isothenn model in the whole range of initialconcentrations studied. The order of adsorption capacity among the phenolic compounds was o-cresol >3-chlorophenol > phenol. The values of adsorption capacity of 270.3, 166.7 and 161.3 mg/g wereobtained for o-cresol, 3-chlorophenol and phenol, respectively.Keywords: Adsorption; phenolic compounds; Langmuir and Freundlich models; activated carbon1.0 INTRODUCTIONThe presence of phenol and chlorinated phenol in industrial wastewater stream is stringently regulated atlow limit of concentration before it could be discharged to the environment. Since phenolic substancesare toxic and hannful to human and aquatic life, the removal of these pollutants from waste effluentbecomes environmentally important. Additionally, phenol has been classified as one of the primarypollutants as enacted by Department of Environment (DOE), Malaysia in Environmental Quality Act1979 (Sewage and Industrial Effluent) which should be treated to be less than 1 ppm for inland waterdischarge. Several methods have been proposed in literatures on techniques for removal phenoliccompounds from wastewater such as photocatalytic, microbial degradation, chemical-biological oxidationand catalytic oxidation process (Canton, et al.,.2003; Feng and Li, 2003; Ksibi, et aI., 2003; Seetharamand Saville, 2003; Tukac, et aI., 2003). However, the adsorption process appears to be the mostapplicable method for removing trace amount of contaminant from wastewater effluent (Podkoscielny, etaI., 2003).~dsorption process is broadly used for removal of odor, oil, colours and organic contaminants fromhquid-phase system. The potential of granular and powdered activated carbon have been proven as aneffective adsorbent used in adsorption technology over the century. It provides large surface area, highad~rption capacity and high degree of surface reactivity (Malik, 2003). However, the adsorption system~Ies on some other factors which include the nature of the adsorbate and adsorption condition such asP and temperature. The physical properties of adsorbate depend on its polarity, hydrophobicity and theIllolecular size (Salame and Bandosz, 2003; Weber, 1985): objective of the present study was to investigate the adsorption equilibrium of phenolic compounds, ely, phenol, 3-chlorophenol and o-cresol on granular activated carbon. Laboratory batch system was~n:ucted to evaluate the adsorption capacity of the adsorbent using both Langmuir and Freundlich~.eon model. The effects of contacts time and initial adsorbate concentration were studied for theIcular adsorbate-adsorbent system.6302.0 MATERIAL AND METHODThe adsorbent used was Norit Granular Activated Carbon 1240 (NAC 1240). This commercial a f.carbon is produced by steam activation of selected grades of coal. The properties of NAC 12~t~.characterized using Autosorb I (Quantachrome, USA) and presented by Table 1. The activated ;;:~was dried overnight in the oven at temperature of 110°C to remove any moisture COntent. ~ .. ' ",(>99.5%) was purchased from Merck, Germany while 3-chlorophenol (>95%) and o-cresol (99.50/0 hellli .:obtained from Fluka, Swirtzerland. Their physical properties are summarized in Table 2. J~}Table I.Properties of the NAC 1240where Co and Ce are initial and equilibrium adsorbate-concentration (mg/I), respectively, V is volsolution (!) and W is weight of adsorbent (g).The amount of solute adsorbed per unit weight of activated carbon (mg/g) was calculated accordingequation:v(c - C )q. = Ow e (1)2.51.048108.13190.8°CO-cresol2.61.268214°C128.563-Chloro henol1.07194.11Phenol18IA ccTable 2.Physical Properties of the Phenolic CompoundsI Property ValueMulti-point BET, m2/g 7.783 xl02Langmuir surface area, m2/g 1.503 x I03Average pore diameter, nm 2.716A 1000 ppm adsorbate stock solution was prepared by dissolving a desire amount of solutedeionized water in a volumetric flask. Single component experimental test was conductedconventional batch mode system. The stock solution was then dilute to 8 different solute concenrange between 25-200 mg!l in 250 ml volumetric flask. 0.2 g of adsorbent was added to a series of2glass-stoppered flasks filled with 200 ml diluted solutions. The glass-stoppered flasks were then pIa water bath shaker and shaken at 120 rpm and constant temperature of 30°C until equilibrium cowas attained. At desired time interval, the remaining concentrations of all samples were analyzedUvNis spectrophotometer (Shimadzu, UV-1601)3.0 RESULTS AND DISCUSSION3.1 Effect of Initial ConcentrationThe adsorption of phenol, 3-chlorophenol and o-cresol reached the equilibrium condition afteradsorption time. Previous data on the adsorption kinetics of phenolics compounds using activatedhave shown a wide range of adsorption time. Tseng et al. (2003) reported that the adsorption ofusing pinewood-based activated carbons was complete after 4 days. While, lung, et al. (2001) foa batch studied on adsorption of phenol and chlorophenol using four different commercial ~.carbons reached the equilibrium state within 1 h. In the present study, the percentage of phenol"at the equilibrium time was almost 90%, whereas 99% for both 3-chlorophenol and o-cre~o~ ;concentration of 25 and 50 mg/I. The percentage of adsorption decreased as the InltI,concentration increased. Figures 1-3 show the amount of solute adsorbed for all the three631ponents. It could be observed that an increase in initial concentration of solute results in increasing of~te uptake. Higher initial concentration would increases the overall the mass transfer driving force of~rbate between liquid and solid phase (Banat, et ai., 2000). As a result, there is an increase inj1teraction of adsorbate and adsorbent which consequently, enhance the adsorption process.I~-~o-.--------=~----------------------------=------------,--=-----=----_ I! 120 1---25 mgll Ii-0 ; -50mgll ! I! ! I] ,..,,100 1_75 mgll ! i~ ~ 80 I! _IOOmglll I§g 60 1_125 mglll i'p .; 11--150 mglli I~~~ I~ I--+-- 175 mgll-< 20 L- 200~~iI 0 -t0~c----r5---1-,-0---1,-5---2r-0-----!25 Il__~a_) .. ~~_=,t_(~2. . ~Fig.l. Effect of initial concentrations of phenol on the adsorption onto NAC 1240 at 30°C-----. 1~ ~~~ r=;=25 mgin !.c:: 160 1 50 mgll i~ ,.." 140 -.-75 mgll 1:g ~ 120 _100 mglllJ., 8 100~ ~ 80 125 mgfl.g ~ 60 --150 mgf~e- 40 --+-- 175 mgllo~ 2~ -=-~?O m~ I(b) 0 5 10 15 20 25 ITime, t (hr)______. . JFig.2. Effect of initial concentrations of3-chlorophenol on the adsorption onto NAC 1240 at 30°C~~m-- --- -- ··------(-~~~~III ~ SIOO 1_IOOmglll.~ g. 75 !-125 mgllilI ~ 50 --150 mgllll~ 25 --+--175mgllllo L~_~ 2~0~m~J I(c) 0 5 10 15 20 25 IT~tM I___________ .JFig.3. Effect of initial concentrations of o-cresol on the adsorption onto NAC 1240 at 30°C.1.2Adsorption Isotherm~~orption isotherm defines the functional equilibri~m distribution with co?centr~tionof.adsorbate in'in n at constant temperature (Weber Jr., 1985). It IS very useful to explam the mteractIon between.~ eand adsorbent and important for prediction in modeling procedures of adsorption system. Figure 4632shows the typical adsorption isotherm which indicates that the systems studied were a n lirelationship characteristic of favourable adsorption. on n~iI • phenol!l II • 3-chlorophenol Ii Il_A o-cr~sol._J \ \I\i--- ------_._-------I !I I.----.--. '-'-'-'- --.----,-.----- --·-r--·--------j I'W ~ ~ W_______ _ C~~~~2.._______ .. .._ J•oo50~:::~--~ 150 ~ i-Sgo 100L._ .. .. _Fig.4. Adsorption isotherm of phenolic compounds by NAC 1240 at 30°C.The adsorption equilibrium data were then analyzed by Langmuir and Freundlich isothenn models. Bothmodels were frequently used in literatures to describe the relationship between the amount of soluteadsorbed and its equilibrium concentration for monolayer adsorption system. The linear fonn ofLangmuir isotherm is represent by,1 1 1 1-=-+-- (2)qe Q bQ Cewhere, qe is the isotherm amount adsorbed at equilibrium (mg/g), Ce is the equilibrium concentration ofthe adsorbate (mg/I), Q (mg/g) and b (l/mg) are the Langmuir constants related to the maximumadsorption capacity and the energy of adsorption, respectively. These constants can be evaluated from theintercept and the slope of the linear plot of experimental data of l/qe versus liCe as shown in Figure 5.The essential characteristics of the Langmuir equation can be expressed in terms of a dimensionlessseparation factor, RL, defined as, (Weber and Chakkravorti, 1974)1RL = "7'(I-+-b-Co-;")(3)where, Co is the highest initial solute concentration and b is the Langmuir's adsorption constant (I/mg).The RL value implies the adsorption to be unfavorable (RL>1), linear (RL = 1), favorable (0 < RL < I), orirreversible (RL = 0).;8.001.j6.004.00lICe2.000.000.00IIL~.i)5-~--==-~-=~=-~~='=-:==-==~~=-~-=~·-~=-~=~==:=~~~=-:=-:'=-',I I ,I • ! :I I Ii I !I 0.04 A! I. g. 0.03 1 I!;::: 0,02 1 r-~pheno'- ~ll0.01 ' ! • 3-chlorophenol [il i!i .. a-cresol ; iL •• .-J I·--·T·---- '--4Fig.5. Langmuir adsorption isotherm ofphenolic compounds adsorption on NAC 1240 at 30°C.633'fbe linear form of the Freundlich isotherm model is according to the following equation:1logq. =10gKF + -loge.n(4)nere KF, (mg/g)(l/mg)l/n and l/n are Freundlich constants related to adsorption capacity and adsorption- tensity of the sorbent respectively. The values of KF and 1/n can be obtained from the intercept and:Iope of the linear plot oflog qe versus log Ce as shown in Figure 6.Fig.6. Freundlich adsorption isothenn of phenolic compounds adsorption on NAC 1240 at 30 °C.The Langmuir and Freundlich constants are summarized in Table 3. By comparing the correlationcoefficient values, R2 of the linear plots, it could be observed that the adsorption equilibrium data of;.enolic compounds was best described by Langmuir isotherm model as compared to Freundlich model.[!be calculated dimensionless separation factors, RL are 0.062, 0.004 and 0.009 for phenol,Xhlorophenol and o-cresol, respectively. The values are less than 1 and greater than 0, indicate that the,esent adsorption systems were favourable for the range of initial concentration studied.Table 3.Langmuir and Freundlich constants for the adsorption of phenolic compounds.\Langmuir Isotherm Model Freundlich Isotherm ModelComponent Q b R2 KF R2(mg/g) (l/mg) (mg/g) (l/mg)"n nPhenol 161.290 0.075 0.93 3.855 2.344 0.883-Chlorophenol 166.667 1.177 0.98 6.420 2.382 0.92O-cresol 270.270 0.536 0.95 6.667 2.096 0.90.......~also apparent that the adsorption capacity, Q, (mg/g) increased with the order of o-cresol > 3-ophenol > phenol. The solubility of solute in the solvent/water has a significant effect to the~tion process. The solubility of phenolic compound in this present studied follow this order, phenoll.chlorophenol > o-cresol. The higher of solute polarity as well as its solubility to the respect of solvent: will decrease the tendency of adsorbate to be adsorbed from that aqueous phase. The bonding~_een adsorbate and water must be broken before the adsorption process can occurred (Weber Jr.,~). B~sicany, greater solubility provides stronger bonding between adsorbate and adsorbent. Thus,0.1 WIth the higher solubility as compared to 3-chlorophenol and o-cresol has the lowest adsorption~IlY. The effect of solute solubility in water explained the adsorption capacity of phenolic compounded which followed the trend, phenol < 3-chlorophenol < o-cresol.6344.0 CONCLUSIONSPhenol, 3-chlorophenol and o-cresol were found to adsorb strongly onto NAC 1240. The experiJne.",batch study indicates that equilibri~m time r~quired for the adsorption of phenolic compound On ~~~1240 was almost 25 hours. AdsorptIOn behaVIOr of the three adsorbate~adsorbant systems was descn~", 1very well by Langmuir isotherm model. The adsorption capacity of the particular system was found~'4..affected by the solubility of the adsorbate. ~5.0 ACKNOWLEGMENTThe authors acknowledge the research grant provided by Universiti Sains Malaysia, Penang that ~ .~resulted in this article.6.0 REFERENCESI. Banat, F.A., AI-Bashir, B., Al-Asheh, S. and Hayajneh, 0., Adsorption of Phenol by Bentonlt JEnviron. Pollut., 107,391-398, (2000).2. Canton, c., Esplugas, S. and Casado, J., Mineralization of Phenol in Aqueous Solution by Ozonatkausing Iron or Copper Salts and Light. Appl. Catal., B 43(2), 139-149, (2003).3. Feng, Y.J., and Li, X.Y., Electro-Catalytic Oxidation of Phenol on several Metal-oxide Electrodes IAqueous Solution. Water Res., 37(10), 2399-2407, (2003).4. Jung, M.W., Ahn, K.H., Lee, Y, Kim, K.P., Rhee, lS., Park, J.T. and Paeng, KJ., AdsorptnCharacteristics of Phenol and Chlorophenols on Granular Activated Carbon (GAC). Microchem. L70, 123-131, (2001).5. Ksibi, M., Zemzemi, A. and Boukchina, R. Photocatalytic Degradability of Substituted Phenolso\'C!UV Irradiated Ti02• J. Photochem. and Photobiol., A 159(1),.61-70, (2003).6. Malik, P.K., Use of Activated Carbons Prepared from Sawdust and Rice-husk for Adsorption ofAcid Dyes: a case study of Acid Yellow 36. Dye. Pig., 56, 239-249, (2003).7. Podkoscielny, P., D~drowski, A. and Marijuk, O.V., Heterogeneity of Active Carbons in Adsorptiooof Phenol Aqueous Solutions, Appl. Surface Sci., 205, 297-303, (2003).8. Salame, I.I. and Bandosz, TJ., Role of Surface Chemistry in Adsorption of Phenol on ActivalrrlCarbons. J. Colloid and Interface Sci., 264, 307-312, (2003).9. Seetharam, G.B. and Saville, B.A. Degradation of Phenol using Tyrosinase Immobilized (1lSiliceous Supports. Water Res., 37(2),436-440, (2003).10. Tseng, R.L., Wu, F.C. and Juang, R.S., Liquid-phase Adsorption of Dyes and Phenols usingPinewood-based Activated Carbons. Carbon, 41, 487-495, (2003).II. Tukac, V., Hanika, J. and Chyba, V. Periodic State of Wet Oxidation in Trickle-Bed Reaetl.'lCatalysis Today, Volume 79-80, 427-431, (2003).12. Weber Jr., W.J. In Adsorption Technology: A Step-by-step Approach to Process Evaluation ~Application; Slekjo, F. L., New York: Marcel Dekker, Inc., 1-35, (1985).13. Weber, T.W. and Chakkravorti, P. Pore and Diffussion Models for Fixed-bed Adsorbers. Nehf J·20,228, (1974).635

Aqueous-Phase Adsorption Of Phenolic Compounds On Activated Carbon.

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Aqueous-Phase Adsorption Of Phenolic Compounds On Activated Carbon.

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