Influence of experimental variables on decoloration of azo reactive dyes by hydrogen peroxide and UV radiation.

This paper was intended to study decoloration of azo C.I. Reactive Red 243 under UV radiation in the presence of hydrogen peroxide. The H2O2/UV oxidation process is a feasible and effective alternative in the treatment of effluents that contain such recalcitrant substances as reactive dyes. A statistical factorial design at 2n was used to evaluate how the variables pH (3 and 11), H2O2 concentration (5 and 20 mM), urea concentration (5 and 15 g l(-1)), and NaCl concentration (2.5 and 3.5 g l(-1)) affected the decoloration process efficiency. The results were expressed as percent colour removal from the solution by using absorbance measurements. The H2O2/UV process proved to be effective in degrading reactive dyes, with approximately 99% colour removal being achieved under specific conditions. Hydrogen peroxide concentration had a positive effect and influenced a great deal. Sodium chloride (NaCl) concentration presented a negative effect on the experiments in which it reduced the percent colour removal from the reactive dye solutions. Solution pH and urea concentration did not present any significant effect on the decoloration process.