CHEMICAL ENGINEERING TRANSACTIONS VOL. 52, 2016 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Petar Sabev Varbanov, Peng-Yen Liew, Jun-Yow Yong, Jiří Jaromír Klemeš, Hon Loong Lam Copyright © 2016, AIDIC Servizi S.r.l., ISBN 978-88-95608-42-6; ISSN 2283-9216 Equilibrium and Thermodynamic Studies on Adsorption of Trivalent Chromium by Sericin-Alginate Particles Prepared from Bombyx Mori Cocoons Júlia R. de Andrade a , Meuris G. C. da Silva b , Marcelino L. Gimenes a , Melissa G. A. Vieira* b a State University of Maringa, School of Chemical Engineering, Colombo Av., 5790, 87020-900 Maringá, Brazil b University of Campinas, School of Chemical Engineering, Albert Einstein Av., 500, 13083-852 Campinas, Brazil melissagav@feq.unicamp.br Particles prepared from the blend between sericin and alginate were used as biosorbent of Cr(III) ions form aqueous solution. In order to show how is the Cr(III) distribution between the liquid phase and the solid phase at the equilibrium, biosorption isotherms were obtained at four different temperatures (20, 30, 40, 60 °C). The isotherm models of Langmuir, Freundlich and Dubinin–Radushkevich were used to test the equilibrium biosorption data. Better fittings were obtained for both Langmuir and Dubinin–Radushkevich models. Additionally, the thermodynamic parameters enthalpy change, entropy change, and Gibbs free energy change were calculated and the biosorption process was found to be exothermic and spontaneous. The results shown that sericin-alginate particles are a promising biosorbent material for the efficient removal of Cr(III). 1. Introduction Sericin constitutes from 20 to 30 % of the total mass of the silkworm Bombyx mori (B. mori) cocoons. It is a macromolecular and hydrophilic protein with molecular weight ranging from about 10 to 300 kDa. Sericin has to be removed during silk processing and is mostly discarded in wastewater. It is estimated that the processing of 400,000 t of dry cocoons produces about 50,000 t of sericin (Zhang, 2002). Recently, the use of sericin as alternative biosorbent of metal contaminants has been evaluated. For instance, Chen et al. (2011) investigated the selective removal of gold employing sericin powder as biosorbent and obtained biosorption capacity of 1 mmol/g. Nevertheless, the weak structural properties and high solubility in water of sericin, added to its gelatinous nature and wide range of molecular weight, causes this protein to form fragile 2D and 3D structures that limit its application as biosorbent. The blending with other polymers can enhance these inferior biophysical properties and it is possible thanks to the polar side chain of sericin, made of hydroxyl, carboxyl and amino groups (Dash et al., 2009). The trapping of biosorbents in calcium alginate beads is one of the most favourable alternatives (Sillerová et al., 2015). Alginate is a natural polymer composed of 1,4´ -linked β-ᴅ-mannuronic acid (M) and α-L-guluronic acid (G) residues. The sodium salt of alginate is most frequently extracted from brown algae. Calcium alginate beads are instantly produced by dripping sodium alginate to a cross-linking solution of CaCl2. The “egg-box” model explains that the 3D network is formed due to the interaction of the divalent cation (Ca 2+ ) with the blocks of M and G residues (Sillerová et al., 2015). Recently, da Silva et al. (2014) investigated the production of particles from the blend between sericin and alginate, ionic cross-linked in both aqueous and alcoholic solutions of CaCl 2 and thermal cross-linked. Da Silva et al. (2015) evaluated the application of those particles as biosorbent of Cu(II) and Zn(II) ions and the obtained percentages of reduction of those metals concentrations were up to 75 % and 65 %. The present work aims to study the biosorption of trivalent chromium ions [Cr(III)] from aqueous solution on sericin-alginate particles. The interest in the removal of Cr(III) lies in the fact that, although it is an essential element to human metabolism, long-term exposures can cause cancer and skin allergic reactions (Yun et al., 2001). The drinking water guideline from the World Health Organization (WHO) for total chromium is of DOI: 10.3303/CET1652029 Please cite this article as: de Andrade J. R., da Silva M. G. C., Gimenes M. L., Vieira M. G. A., 2016, Equilibrium and thermodynamic studies on adsorption of trivalent chromium by sericin-alginate particles prepared from bombyx mori cocoons, Chemical Engineering Transactions, 52, 169-174 DOI:10.3303/CET1652029 169