Comparison of non-catalytic and catalytic ozonation processes of three different aqueous single dye solutions with respect to powder copper sulfide catalyst

Abstract

Treatment of textile wastewaters containing dyes has not been very successful by conventional methods such as biological treatment. In order to overcome this problem, ozonation based on the oxidation of organic pollutants has been studied by researchers. Catalytic ozonation and advanced oxidation processes (AOPs) are used in order to increase the efficiency of sole ozonation further. In this work, catalytic ozonation in the presence of copper sulfide (CuS) powder as a catalyst was investigated in the treatment of aqueous single dye solutions, namely solutions of Acid Red-151 (AR-151), Remazol Brilliant Blue-R (RBBR) and Reactive Black-5 (RB-5). In the catalytic ozonation experiments, the effects of important ozonation parameters such as solution pH, ozone and catalyst dosages and the initial concentration of each dye on reaction kinetics and mechanism were studied. The catalyst CuS increased the oxidation rates of ozonation side-products measured by the decrease in the total organic carbon (TOC) values of the treated dye solutions. The dye removal rates were enhanced in the treatment of RB-5 dye solutions, while no significant effects were observed on the dye removal rates of RBBR and AR-151 aqueous solutions. The TOC removals above 90% were observed in the catalytic ozonation with CuS for each of the dyes separately at pH 10 and at an initial dye concentration of 100 mg/L. The most important effect of the catalyst addition was observed at pH 3, where TOC removals without catalyst were low. Copper sulfide addition increased the percent TOC removals at the end of a reaction period of 80 min by 123%, 65% and 58% in the treatment of 100 mg/L RBBR, RB-5 and AR-151 aqueous solutions, respectively, at pH 3. Catalytic ozonation kinetics and mechanism were discussed in detail.