CHEMICAL ENGINEERING TRANSACTIONS VOL. 32, 2013 A publication of The Italian Association of Chemical Engineering Online at: www.aidic.it/cet Chief Editors: Sauro Pierucci, Jiří J. Klemeš Copyright © 2013, AIDIC Servizi S.r.l., I SBN 978-88-95608-23-5; I SSN 1974-9791 Adsorption of Synthetic Orange Dye Wastewater in Organoclay Onélia A. Andreo dos Santos* a , Camila Z. Castelli b , Maria Fernanda Oliveira b , Ambrósio F. de Almeida Neto b , Meuris G. C. da Silva b a Chemical Engineering Department, University of Maringá. Av. Colombo, 5790, Jardim Universitário, 87020-900, Maringá-Paraná, Brazil b School of Chemical Engineering, University of Campinas, Cidade Universitária Zeferino Vaz, P.O. Box, 6066, 13083- 970, Campinas-São Paulo, Brazil onelia@deq.uem.br The aim of this study is to evaluate adsorption kinetics and isotherms of synthetic orange dye onto organoclay prepared from commercial sodium bentonite (Fluidgel called) from aqueous solutions. The effects of pH, contact time, initial dye concentrations, dosage clay and temperature were investigated experimentally. Commercial sodium bentonite was modified by using quaternary ammonium cations (hexadecyltrimethylammonium bromide) as a modifying agent. The characterization of commercial Fluidgel and modified clay (organophifilic Fluidgel) was accomplished by using XRD, TGA, BET and SEM/EDX techniques. The optimum pH value for the adsorption experiments was found to be next of 6 (pH not adjusted) and all the experiments were carried out at this pH value. The pseudo-first-order kinetic model agrees very well with the experimental results. Equilibrium data were also fitted to the Freundlich isotherm model in the studied temperature range for low initial concentrations of synthetic orange. The results indicate that organoclay is a suitable adsorbent for the adsorption of dyes. 1. Introduction The pollution of water resources with industrial effluents containing organic compounds and toxic substances is a matter of great concern. Environmental contamination has been pointed as one of the greatest problems of modern society, mainly due to the population explosion and the increased industrial activity (Zhang et al., 1998; Colpini et al., 2008). Generally, effluents from textile industries, paper printing and photography contain residues of dyes and chemicals. However, the textile industry stands out because it produces large amounts of effluents which can cause serious environmental problems since they contain colored compounds resulting from dyes unfixed to fibers during the dyeing process (Colpini et al., 2008). Synthetic dyes have increasingly been used in the textile and dyeing industries due to low-cost in synthesis, high stability to light and temperature, compared with natural dyes (Gök et al., 2010). Dye molecules have two major components: the chromophore groups, responsible for making the colour such as -C=C- and -N=N-, and the auxochrome groups, as for example: -NH2 , -OH, -COOH and –SO 3 H, which render the solubility of the molecules and give affinity for the fibers (Colpini et al., 2008; Gök et al., 2010). Synthetic dyes in the water bodies, even at very low concentrations, can be highly toxic to living organisms, reducing the growth of bacteria and preventing the photosynthesis in aqueous flora (Hameed, 2008; Vimonses et al., 2009; Fiorentin et al, 2010). Due to the dyes having complex aromatic structures, they are usually biologically non-degradable and present high stability and toxicity and it is therefore necessary to eliminate organic pollutants by proper treatment techniques. Removal methods of dye molecules from water can be classified in many categories such as physical, chemical, biological, radiation and electrochemical processes. Among these methods, adsorption can be thought to be efficient process for the treatment of wastewater due to its low-cost and ease of operation as well as greater efficiency. Although activated carbon seems to be an efficient adsorbent, it has high operation costs. For this reason, many studies revealed that other alternative adsorbents such as clays, including bentonite (Özcan et al, 307