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  Journal of Hazardous Materials B92 (2002) 263–274 Use of cellulose-based wastes for adsorptionof dyes from aqueous solutions Gurusamy Annadurai a , Ruey-Shin Juang b , ∗ , Duu-Jong Lee a a  Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan, ROC  b  Department of Chemical Engineering, Yuan Ze University, Chung-Li 320, Taiwan, ROC  Received 26 October 2001; received in revised form 16 January 2002; accepted 17 January 2002 Abstract Low-cost banana and orange peels were prepared as adsorbents for the adsorption of dyes fromaqueous solutions. Dye concentration and pH were varied. The adsorption capacities for both peelsdecreased in the order methyl orange (MO) > methylene blue (MB) > Rhodamine B (RB) > Congored(CR)>methylviolet(MV)>amidoblack10B(AB).Theisothermdatacouldbewelldescribedby the Freundlich and Langmuir equations in the concentration range of 10–120mg/l. An alkalinepH was favorable for the adsorption of dyes. Based on the adsorption capacity, it was shown thatbanana peel was more effective than orange peel. Kinetic parameters of adsorption such as theLangergren rate constant and the intraparticle diffusion rate constant were determined. For thepresent adsorption process intraparticle diffusion of dyes within the particle was identified to berate limiting. Both peel wastes were shown to be promising materials for adsorption removal of dyes from aqueous solutions. © 2002 Elsevier Science B.V. All rights reserved. Keywords:  Adsorption; Dyes; Banana and orange peels; Isotherms; Kinetics 1. Introduction Many industries often use dyes and pigments to color their products. Most dyes areinert and non-toxic at the concentration discharged into the receiving water, however, theyimpart color undesirable to the water user. Color removal from textile effluents is a majorenvironmental problem because of the difficulty to treating such streams by conventionalphysicochemical and biological treatment methods [1]. Liquid-phase adsorption has beenshown to be an effective way for removing suspended solids, odors, organic matter, andoil from aqueous solutions. Nassar and El-Geundi [2] evaluated the cost of dye removal ∗ Corresponding author. Tel.: + 886-3-4636800x555; fax: + 886-3-4559373.  E-mail address: (R.-S. Juang).0304-3894/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved.PII: S0304-3894(02)00017-1  264  G. Annadurai et al./Journal of Hazardous Materials B92 (2002) 263–274 usingnaturalclay,bagassepith,andmaizecob.Whilemanyphysicalandchemicalmethodsincluding adsorption, coagulation, precipitation, filtration and oxidation have been used forthe treatment of dye-containing effluent, adsorption appears to offer the best prospects overall the other treatments [3].Activated carbon is the most widely used adsorbent for this purpose because it has ahigh capacity for adsorption of organic matter, but its use is limited because of its high cost[4–7]. This has led to search for cheaper substitutes. Coal, fly ash, wood, silica gel, claymaterials (bentonite, montmorillonite, etc.), agricultural wastes (bagasse pith, maize cob,coconut shell, rice husk, etc.), and cotton wastes have been tried with varying success forcolor removal [5–9].The purpose of this work was to test the possibility of using cellulose-based wastes,banana and orange peels, for adsorption removal of various dyes: methyl orange (MO),methyleneblue(MB),RhodamineB(RB),Congored(CR),methylviolet(MV),andamidoblack 10B (AB) from water. The amounts of equilibrium adsorption were measured. Thebatchcontacttimemethodwasusedtomeasuretheadsorptionrate.Kineticparameterswerethen evaluated and were finally correlated with process variables such as dye concentrationand solution pH. 2. Materials and methods 2.1. Adsorbents and dyes Banana and orange peels were obtained from a local fruit stall at Chung-Li, Taiwan. Thepeelsweredried,crushed,andwashedthoroughlywithdeionizedwater(Milli-Q,Millipore)to remove the adhering dirt. They were air dried in an oven at 100–120 ◦ C for 24h. Afterdrying, the adsorbent was sieved through a 5mm mesh size. The densities of banana andorange peels were 1.72 and 1.47g/ml, respectively. The BET surface areas of both peelswere in the range 20.6–23.5m 2  /g obtained from N 2  adsorption isotherms by sorptiometer(Quantachrome Co., NOVA 2000). All dyes were obtained from Merck Co. The solutionpH was adjusted by adding a small amount of 0.1M HCl or NaOH. 2.2. Adsorption studies Adsorption equilibrium experiments were carried out by adding the dried adsorbent(0.1g) in 100ml of dye solution with desired concentration and pH at 30 ◦ C in a shaker at180rpm.After24hthesuspensionwasfilteredandthefinalconcentrationofdyeinsolutionwas measured using an UV–VIS spectrophotometer (Hitachi U-2000). The amount of dyeadsorbed onto the peels,  q e  (mg/g), was calculated by a mass balance relationship (Eq. (1)). q e  = (C 0 − C e )V W  (1)where  C  0  and  C  e  are the initial and equilibrium liquid-phase concentrations of dyes,respectively (mg/l),  V   the volume of the solution (L), and  W   the weight of the dry peelused (g).  G. Annadurai et al./Journal of Hazardous Materials B92 (2002) 263–274  265 The procedures of kinetic experiments were basically identical to those of equilibriumtests. The aqueous samples were taken at preset time intervals, and the concentrations of dyes were similarly measured. 3. Results and discussion 3.1. Adsorption isotherms Figs.1and2showtheadsorptionisothermsofdifferentdyes( q e  versus C  e )usingbananaand orange peels, respectively. Two isotherm equations are tested in this work. One isthe Langmuir equation (Eq. (2)), which has been successful applied to many adsorptionprocesses [10–15].1 q e =   1 q mon  +   1 K L q mon   1 C e   (2)where K  L  istheLangmuirconstantand q mon  theamountofdyeadsorbedwhenthesaturationisattained.Aplotof1/  q e  versus1/  C  e  gives K  L  and q mon  iftheisothermfollowstheLangmuirequation. Table 1 lists the parameters calculated. The present adsorption capacities ( q mon )are smaller than those obtained using activated carbons, mainly because their BET surfaceareas are significantly different (21–24m 2  /g versus 600–1000m 2  /g) [1,2]. Fig. 1. Adsorption isotherms of dyes using banana peel.  266  G. Annadurai et al./Journal of Hazardous Materials B92 (2002) 263–274 Fig. 2. Adsorption isotherms of dyes using orange peel. The Freundlich equation [14,15], which is also often used for heterogeneous surfaceenergy systems.ln q e  = ln K F +  1 n  ln C e  (3)The intercept  K  F  obtained from the plot of log  q e  versus log  C  e  is roughly a measure of thesorption capacity and the slope (1/  n ) of the sorption intensity (Table 2). It was indicated bythat magnitude of the term (1/  n ) gives an indication of the favorability and capacity of theadsorbent/adsorbate systems [15]. Table 1Parameters obtained for the Langmuir equationDye Banana peel Orange peel q mon  (mg/g)  K  L  (l/mg)  R q mon  (mg/g)  K  L  (l/mg)  R MO 21.0 11.4 0.9340 20.5 16.5 0.9541MB 20.8 16.5 0.9524 18.6 19.9 0.9659RB 20.6 32.6 0.9572 14.3 32.0 0.9377CR 18.2 37.7 0.9480 14.0 46.8 0.9739MV 12.2 29.1 0.9616 11.5 56.7 0.9794AB 6.5 17.4 0.9632 7.9 59.2 0.9747
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