Adsorption of Phenolic Compounds from Aqueous Solutions onto Chitosan-Coated Perlite Beads as Biosorbent N. S. Kumar, †,‡ M. Suguna, † M. V. Subbaiah, † A. S. Reddy, † N. P. Kumar, † and A. Krishnaiah* ,† Biopolymers and Thermophysical Laboratories, Department of Chemistry, Sri Venkateswara UniVersity, Tirupati - 517 502, A.P., India, and Department of Safety EnVironmental System Engineering, Dongguk UniVersity, Gyeongju 780-714, Republic of Korea Chitosan-coated perlite (CCP) beads were prepared by dropwise addition of a liquid slurry containing chitosan and perlite to an alkaline bath. The resulting beads were characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and surface area analysis. The chitosan content of the beads is 23% as determined by a pyrolysis method. Adsorption of phenolic compounds (phenol, 2-chlorophenol, and 4- chlorophenol) from aqueous solutions on chitosan-coated perlite beads was studied under batch equilibrium and column flow conditions. The binding capacity of the biosorbent was investigated as a function of initial pH, contact time, initial concentration of adsorbate, and dosage of adsorbent. Adsorption kinetic and isotherm studies, respectively, showed that the adsorption process followed a pseudo-first-order kinetic model and the Langmuir isotherm. The maximum monolayer adsorption capacity of phenol, 2-CP, and 4-CP on to the chitosan-coated perlite beads was found to be 192, 263, and 322 mg g -1 , respectively. 1. Introduction Phenols are generally considered to be one of the important organic pollutants discharged into the environment causing unpleasant taste and odor. The major sources of phenol pollution in the aquatic environment are waste waters from the paint, pesticide, coal conversion, polymeric resin, petroleum, and petrochemicals industries. Degradation of these substances produces phenol and its derivatives in the environment. The chlorination of natural waters for disinfection produces chlori- nated phenols. Phenols are considered as priority pollutants since they are harmful to organisms at low concentrations. Phenol contents in the drinking water should not exceed 0.002 mg L -1 as per the Indian standard. 1 In recent years, interest has been focused on the removal of phenols from aqueous solution. A variety of techniques have been implemented to purify water contaminated by phenols. Ozonolysis, photolysis, and photocatalytic decomposi- tion have been used with limited success. 2 Traditionally, biological treatment, activated carbon adsorption, reverse osmosis, ion exchange, and solvent extraction are the most widely used techniques for removing phenols and related organic substances. 3-6 Adsorption of phenols onto solid supports such as activated carbons allows for their removal from water without the addition of chemicals. Activated carbon exhibits good adsorption ability for many organic pollutants but is expensive due to its difficult regeneration and high disposal cost. 7 In recent years, polymeric adsorbents have been used increas- ingly as an alternative to activated carbon due to their economic feasibility, adsorption-regeneration properties and mechanical strength. Chitosan is a polysaccharide prepared by the de-N- acetylation of chitin, which makes up shells and shrimps. 8 Due to the primary, secondary hydroxyl groups and highly reactive amino groups of chitosan as well as the property of nontoxicity and biodegradability, it has been regarded as a useful material to remove inorganic and organic substances from wastewater. 9 However, several investigators have attempted to modify chitosan to facilitate mass transfer and to expose the active binding sites to enhance the adsorption capacity. Grafting specific functional groups onto a native chitosan backbone allows its sorption properties to be enhanced. 10 Many applica- tions are due to the secondary amino groups of chitosan which show polycationic, chelating, and film-forming properties along with high solubility in dilute acids. Chitosan has already been described as a suitable natural polymer for the collection of phenolic compounds, through chelation, due to the presence of an amino and hydroxyl groups on the glucosamine unit. 11 In most of the studies chitosan has been used in the form of flakes, powder, or hydrogel beads. Enzymatic removal of various phenol compounds from a synthetic water sample was studied by the use of mushroom tyrosinase and chitosan beads as a function of pH, temperature, tyrosinase dose, and the hydrogen peroxide-to-substrate ratio. 12 The adsorption of 4-nonylphenol ethoxylates (NPEs) onto chitosan beads having cyclodextrin was investigated by Aoki et al. 13 Adsorption of phenol onto chitosan- coated bentonite was studied by Cheng et al. 14 Biosorption of phenol and o-chlorophenol from aqueous solutions onto chitosan-calcium alginate blended beads was reported by Siva Kumar et al. 15 Removal of chlorophenols from groundwater by chitosan sorption was studied by Zheng et al. 16 Adsorption of phenol, p-chlorophenol, and p-nitrophenol onto functional chitosan was studied by Jian-Mei et al. 17 Biosorption of phenolic compounds from aqueous solutions onto chitosan-abrus preca- torius blended beads was studied by Siva Kumar et al. 18 The maximum adsorption capacities of different adsorbents obtained from different sources are included in Table 1 along with the values obtained in the present study. In this study a new composite chitosan biosorbent is prepared by coating chitosan, a glucosamine biopolymer, over perlite, an inorganic porous aluminosilicate and formed into beads. Perlite is a siliceous volcanic glassy rock with an amorphous structure. It is expected that the more active sites of chitosan will be available due to the coating thus enhancing the adsorption capacity. The percent of chitosan coated on perlite was determined by pyrolysis technique. Surface area, pore volume, and pore diameter were obtained on the basis of Brunauer, Emmet, and Teller (BET) measurements. The chito- * To whom correspondence should be addressed. Tel.: +91- 9393621986. E-mail address: abburikrishnaiah@gmail.com. † Sri Venkateswara University. ‡ Dongguk University. Ind. Eng. Chem. Res. 2010, 49, 9238–9247 9238 10.1021/ie901171b  2010 American Chemical Society Published on Web 08/26/2010