Colloids and Surfaces A: Physicochem. Eng. Aspects 297 (2007) 38–45 Removal of some fungicides from aqueous solution by the biopolymer chitin Tuba S ¸is ¸mano˘ glu Istanbul University, Engineering Faculty, Department of Chemistry, Avcilar Campus, Avcilar, 34850 Istanbul, Turkey Received 5 June 2006; received in revised form 2 October 2006; accepted 7 October 2006 Available online 12 October 2006 Abstract The adsorption of 4,4 ′ -iso-propylidene diphenol (BPA), and diphenylolpropane 4,4 ′ -dioxyaceticacid (BPAc) onto chitin has been investigated at 298.15 K. The uptake of BPA and BPAc from aqueous solutions has been determined by UV–visible spectroscopy. Adsorption isothermal data was interpreted by the Freundlich, Langmuir, BET, D–R and F–H equations. The constants of these equations have been determined. The rate of kinetic processes of BPA and BPAc onto chitin was described by using three kinetics adsorption models. The pseudo-first-order model and intraparticle diffusion were the best choice among the kinetic models to describe the adsorption behaviour of BPA and BPAc onto chitin. © 2006 Elsevier B.V. All rights reserved. Keywords: Fungicides; Chitin; Adsorption kinetics; Adsorption isotherms 1. Introduction Chitin is one of the most abundant organic materials, being second only to cellulose in the amount produced annually by biosynthesis. It occurs in animals particularly incrustocea, mol- luscs and various insects, where it is a major constituent of the exoskeleton, and in certain fungi, where it is the principal fibril- lar polymer in the cell wall. Chitin has a crystalline structure and it constitutes a network of organised fibres, this structure con- fers rigidity and resistance to organisms that contain it. Chitin is [poly(N-acetyl-1,4--d-glucopyranosamine)], and its idealised structure is shown in Scheme 1. Owing to the biodegradable and high adsorption capacities of chitin, it has been utilized as an adsorbent for variety of sub- strates [1,2]. Giles and Hassan have investigated the adsorption of ionic species of sulfonate azo dyes, inorganic and organic acids [3]. Fungicides can be an important component of the disease management program. Unlike insecticides and some herbicides which kill established insects or weeds, fungicides are most commonly applied to protect healthy plants from infection. However, protection from fungicides is temporary because they are subject to weathering from light, irrigation, and rainfall. E-mail address: tusase@istanbul.edu.tr. 4,4 ′ -iso-Propylidene diphenol (BPA), and diphenylolpropane 4,4 ′ -dioxyaceticacid (BPAc) are very important fungicide and their idealised structure are shown in Scheme 2. The adsorption of BPA and BPAc on various adsorbents from aqueous solution has been investigated by many researchers [4,5]. The aim of the present study is to investigate the adsorption of the BPA and BPAc by the biopolymer chitin, utilizing Fre- undlich, Lagmuir, BET, D–R and F–H isotherm to determine the adsorption parameters. Three adsorption kinetic models were also tested in this study for each of the adsorption processes. In order to investigate the mechanism of BPA and BPAc adsorp- tion, characteristic constants of adsorption were determined by using Lagergren pseudo-first-order equation, intraparticle dif- fusion and a pseudo-second-order equation, respectively. The pseudo-first-order kinetic equation and intraparticle diffusion were found to best fit to the adsorption of BPA and BPAc on biopolymer chitin at low concentrations. 2. Experimental 2.1. Materials Chitin [poly(N-acetyl-1,4--d-glucopyranosamine)] (C 8 H 13 NO 5 ) n (molecular weight M r ∼ 400000) purchased from Fluka was used for the removal of BPA and BPAc. BPA, Merck was 0927-7757/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2006.10.017