Journal of Hazardous Materials 144 (2007) 634–638 Removal of chromium from electroplating industry effluents by ion exchange resins Sofia A. Cavaco, Sandra Fernandes, Margarida M. Quina, Lic´ ınio M. Ferreira ∗ GERSA Group, Chemical Engineering Department, University of Coimbra, P´ olo II, Street S´ ılvio Lima, 3030-790 Coimbra, Portugal Available online 30 January 2007 Abstract Effluent discharged from the chromium electroplating industry contains a large number of metals, including chromium, copper, nickel, zinc, manganese and lead. The ion exchange process is an alternative technique for application in the treatment of industrial wastewater containing heavy metals and indeed it has proven to be very promising in the removal and recovery of valuable species. The main objective of the present work is to evaluate the performance of commercial ion exchange resins for removing chromium trivalent from industrial effluents, and for this purpose two resins were tested: a chelating exchange resin (Diaion CR11) and a weak cationic resin (Amberlite IRC86). In order to evaluate the sorption capacity of the resins some equilibrium experiments were carried out, being the temperature and pH the main variables considered. The chromium solutions employed in the experiments were synthetic solutions and industrial effluents. In addition, a transient test was also performed as an attempt to understand the kinetic behaviour of the process. © 2007 Elsevier B.V. All rights reserved. Keywords: Chromium recovery; Ion exchange; Equilibrium; Isotherms 1. Introduction Metal surface treatment is one of the major metal work- ing processes that generates a large amount of liquid and solid (sludge) wastes containing heavy metals. According to studies performed by the Waste’s Institute of the Ministry of Environment, this waste represented about 0.9% of the over- all production (25,400 tonnes) of hazard industrial wastes in Portugal during the year 2001. Heavy metals are important sources of environmental pollution, being some of them very toxic even at low concentrations. The traditional techniques used for metal control are based on chemical precipitation cou- pled to pre- or post-oxidation/reduction followed by filtration in order to concentrate the species of interest. The main disad- vantage of these techniques is the production of solid residues (sludges) containing toxic compounds whose final disposal is in general landfilling (which is the last priority in terms of EU poli- cies). Therefore, the use of other alternative techniques (such as adsorption, ion exchange, membrane and biological processes) based on physical, chemical and biological mechanisms is advis- ∗ Corresponding author. Tel.: +351 239 798700; fax: +351 239 798703. E-mail address: lferreira@eq.uc.pt (L.M. Ferreira). able in order to protect the environment and at the same time recovering at least a valuable metal. In the case of the chromium (case studied), the chromate form can be recovered from an effluent and reused in the plating industry or in tanneries after reduction to Cr(III). The selection of this heavy metal is based on health concerns, since hexavalent chromium is potentially car- cinogenic when inhaled [1–3], as well as due to its commercial value. Several studies considering the Cr removal by ion exchange resins have been reported in the literature. Petruzelli et al. [4] reported the IERECHROM process based on the use of a macroporous carboxylic resin that allows the removal of almost pure Cr from other interfering metals. Chmielewski et al. [5] implemented a method for recovering Cr, Cu and water from electroplating wastewater using a combined process involving electrochemical oxidation and ion exchange. Lin and Kiang [6] proposed a procedure to recover chromic acid from a waste acid solution using a multi-step ion exchange process, where a large amount of regenerant chemicals were spent. Yalc ¸in et al. [7] developed a laboratory-scale separation process for the recovery of Cr(VI) and Cr(III) with a strongly basic resin and a weakly acidic resin, respectively. Rengaraj et al. [8] performed equilibrium and kinetics experiments to evaluate the sorption capacity of chromium by three different strongly acid resins. 0304-3894/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2007.01.087