International Journal of Biological Macromolecules 42 (2008) 152–157 Spray-dried chitosan microspheres containing 8-hydroxyquinoline -5 sulphonic acid as a new adsorbent for Cd(II) and Zn(II) ions Luciano Vitali a , Mauro C.M. Laranjeira a , Norberto S. Gonc ¸alves b , Valfredo T. F´ avere a,∗ a Departamento de Qu´ ımica, Universidade Federal de Santa Catarina, Cep. 88040-900, Florian´ opolis, SC, Brazil b Departamento de Ciˆ encias Exatas e da Terra, Universidade Federal de S˜ ao Paulo, Cep. 09972-270, Diadema, SP, Brazil Received 7 September 2007; received in revised form 17 October 2007; accepted 22 October 2007 Available online 26 October 2007 Abstract In the present study, a new chelating adsorbent was prepared from chitosan microspheres cross-linked with glutaraldehyde by spray drying using 8- hydroxyquinoline -5 sulphonic acid as chelant agent (CTS-SX-CL). Microspheres of the new adsorbent were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). The effect of pH, contact time and concentration of metallic ions in solution were evaluated on the adsorption behavior of Cd(II) and Zn(II) by CTS-SX-CL. Adsorption was maximum for both Cd(II) and Zn(II) at pH 8.0. Adsorption kinetic curves were obtained and could be fit by the pseudo second-order adsorption model. An analysis of equilibrium adsorption data using the Langmuir isotherm model indicated that the maximum adsorption capacity of CTS-SX-CL was higher than that of CTS-CL for both ions investigated. The adsorption capacity increased 74% for Cd(II). © 2007 Elsevier B.V. All rights reserved. Keywords: Chitosan; Sulphoxine; Adsorption 1. Introduction The remediation of contaminated aquatic environments by toxic metallic ions has been drawing considerable attention [1]. The concentration of such toxic metals in water has increased mainly due to the growth in industrial and agricultural activi- ties. Many metallic ions are toxic even in low concentrations and should be removed from water [2,3]. Solid-phase adsorp- tion or extraction has been widely used to remove metals from contaminated waters. Some of the advantages of adsorption over other commonly employed techniques include the relatively low contents of residues generated, easy recovery of the metals and reuse of the adsorbent [4–6]. The preparation of adsorbents by the microencapsulation of organic complexing agents comes as another interesting applica- tion of Analytical Chemistry [7]. The use of modified adsorbents aiming at separating and pre-concentrating traces of metallic ions depicts a series of positive aspects. For instance, differ- ent complexing agents can be used and, therefore, the same ∗ Corresponding author. Tel.: +55 48 3721 6844; fax: +55 48 3721 6850. E-mail address: favere@qmc.ufsc.br (V.T. F´ avere). adsorbent can be employed in different applications. A selective complexing agent can also be microencapsulated to render selec- tivity for a specific metallic ion. Additionally, the complexing agent can be easily changed or recovered, widening the pos- sibilities of experimental conditions. This is mainly attributed to complexing agents which are not covalently bonded, and, consequently, the ligand is not rigidly attached to the adsor- bent [8,9]. Chitosan is an excellent support, extensively used in the microencapsulation of drugs [10]. It is obtained from the partial deacetylation of chitin in concentrated alkaline solu- tions. Chitosan is a natural copolymer consisting of units of β (1 → 4)-2-amino-2-deoxy-d-glycopyranose and β (11 → 4)-2- acetamide-(1-4)-2-deoxy-d-glycopyranose. The amine groups present in its polymeric chain can be protonated, increasing their positive charge densities and their ionic interaction with a number of anionic chelating agents [11–13]. Hydroxybenzopyridines are organic compounds commonly used as complexing properties. This class of compounds includes versatile materials that can react with a large variety of metallic ions. The presence of different functional groups such as OH, COH, NO and SO 3 result in derivative structures. In particular, the sulfonate group is responsible for the forma- tion of 8-hydroxyquinoline -5-sulphonic acid, also referred to as 0141-8130/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ijbiomac.2007.10.020