Journal of Colloid and Interface Science 285 (2005) 288–295 www.elsevier.com/locate/jcis Determination of kinetic parameters of Cu(II) interaction with chemically modified thin chitosan membranes Antonio R. Cestari ∗ , Eunice F.S. Vieira, Joana D.S. Matos, Débora S.C. dos Anjos Laboratory of Materials and Calorimetry, Departamento de Química/CCET, Universidade Federal de Sergipe, 49100-000 São Cristóvão, Sergipe, Brazil Received 20 September 2004; accepted 10 November 2004 Available online 8 January 2005 Abstract In this work, vanillin-modified thin chitosan membranes were utilized as adsorbents for the removal of Cu(II) from aqueous solutions. A rise of temperature accelerates mass transfer of Cu(II) to the membranes surfaces. The kinetic data did present a rough fit to the traditional Lagergren adsorption kinetic equations. An alternative Avrami kinetic equation was successfully fitted to the kinetic adsorption quantities. From this new equation, from one to three regions presenting distinct kinetic parameters were found, and the use of the parameter n was also related to the determination of the kinetic orders. Variations of the adsorption rate in relation to the contact time and the temperature were also calculated and are discussed.  2004 Elsevier Inc. All rights reserved. Keywords: Chitosan membranes; Vanillin; Cu(II) adsorption; Adsorption kinetic modeling; Avrami adsorption model 1. Introduction Chitin is a biodegradable and nontoxic polysaccharide wide spread among marine and terrestrial invertebrates and fungi [1]. It is usually obtained from waste materials of the seafood processing industry, mainly shells of crabs, shrimp, prawns and krill. Native chitin occurs in such nat- ural composite materials, usually combined with inorgan- ics, proteins, lipids, and pigments. Its isolation calls for chemical treatments to eliminate these contaminants [2,3]. By treating crude chitin with aqueous 40–50% sodium hy- droxide in the range 110–115 ◦ C chitosan is obtained [4]. Fig. 1 presents a schematic representation of the struc- tures of chitin and chitosan. Both biopolymers are chem- ically similar to cellulose, differing only in the R group attached to carbon 2 of the general carbohydrate struc- ture. Chitin and chitosan are closely related, since both are linear polysaccharides containing 2-acetamido-2-deoxy-D- glucopyranose and 2-amino-2-deoxy-D-glucopyranose units * Corresponding author. Fax: +55-79-212-6684. E-mail address: cestari@ufs.br (A.R. Cestari). Fig. 1. Structures of chitin and chitosan. joined by β(1 → 4) glycosidic bonds. Due to the features mentioned, the chemical and physical properties of these polymers are different in nature [5]. The fully deacetylated product is rarely obtained due to the risks of side reactions and chain depolymerization [6]. Applications for chitosan currently are found in indus- trial wastewater treatment and in recovery of feed grade material from food processing plants [7]. Numerous studies have demonstrated the effectiveness of chitosan and derived products in the uptake of metal cations such as lead, cad- mium copper, and nickel and the uptake of oxyanions as well complexed metal ions. In other areas, chitosan has been em- ployed as an excellent adsorbent for sorption of phenols and 0021-9797/$ – see front matter  2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2004.11.035