Photochemical and heterogeneous photocatalytic degradation of waste vinylsulphone dyes: a case study with hydrolysed Reactive Black 5

Aqueous solutions of hydrolyzed Reactive Black 5 (RB5) dye, a well-known surrogate for non-biodegradable azo dyes, were photochemically and photocatalytically treated by employing the H2O2/W-C and TiO2/UV-A advanced oxidation systems, respectively. The observed effects of reaction pH, oxidant dose and initial dyestuff concentration were used to explain the OH. induced color disappearance kinetics empirically. Accordingly, the waste dyestuff solutions could be completely decolorised (k(d.max) = 0.155 min(-1); H2O2/UV-C system) and effectively mineralised (k(TOC.max) = 0.01 min(-1); H2O2/UV-C system), with an average overall TOC removal of 78% after 120 min advanced oxidation at the specified optimised reaction conditions. The treatment via H2O2/UV-C was mainly governed by OH. type oxidation rather than direct UV-C or UV-A photolysis, and the bleaching effect of the TiO2/UV-A process could be successfully fitted to the empirical Langmuir-Hinshelwood (L-H) kinetic model (k(L-H) = 4.47 mg l(-1) min(-1); KL-H = 2.01 l mg(-1)). (C) Elsevier Science 2001 B.V. All rights reserved.