Comparative efficiencies of the decolourisation of leather dyes by enzymatic and electrochemical treatments

Leather dyes are important chemical pollutants of industrial origin. The society demand for colour-free waste discharge to receiving waters has made decolourisation of industrial wastes a top priority. Due to their complex chemical structures, the decolourisation of these wastes is a challenging task. In this study, the decolourisation and degradation efficiency of six leather dyes by enzymatic and electrochemical treatments were studied. In the presence of salts, all dyes were totally decolourised by electrochemical treatment in 4 h. Though it has showed appreciable ability of enzymatic degradation, it was observed that the salts present in tannery effluents cause inhibition problems that significantly affected the dye degradation. In addition, enzymatic and electrochemical treatments with a mixture of the six dyes were carried out. Once again, the electrochemical treatment shows better results and after 4 h the obtained decolourisation was total which is squared with a complete total organic carbon (TOC) reduction. Besides, the degradation of this mixture was carried out successfully in a continuous electrochemical bubble reactor. Therefore, the results provide fundamental knowledge for the treatment of a leather wastewater stream. (C) 2011 Elsevier B.V. All rights reserved.