Decolorization of Azo Dye C.I. Direct Black 38 by Photocatalytic Method Using TiO2 and Optimizing of Process

Dye wastewaters are considered as major pollutants to surface waters. The dye C.I. Direct Black 38 is one of the most important azo dyes used in dying industry and contaminated waters containing this harmful material are produced in large volumes. The purpose of this study is investigation removing of C.I. Direct Black 38 by photocatalytic method as one of advanced oxidation processes (AOPs) using TiO2 as photocatalyst and determination of optimum values of effective parameters against color removing efficiency. Spectrophotometric results showed that photocatalytic process has decolorization ability of wastewaters containing C.I. Direct Black 38 in different dye concentrations. The operating conditions for 90% decolorization of C.I. Direct Black 38 were obtained for initial dye concentration of 50 ppm, hydrogen peroxide dosage of 26.56 mM, TiO2 dosage of 0.75 g/l and pH of 5. TiO2 can’t be used in basic solution. The proper addition of hydrogen peroxide improved the decolorization, while the excess amount of hydrogen peroxide could quench the formation of hydroxyl radicals.