UV/H_2O_2 CHEMICAL OXIDATION FOR HIGH LOADED EFFLUENTS: A DEGRADATION KINETIC STUDY OF LAS SURFACTANT WASTEWATERS

摘要

This paper describes a laboratory study conducted to elucidate the possibility of treating high loaded solutions of surfactants through an Advanced Oxidation Process. Synthetic solutions of linear alkylbenzene sulfonates are treated in this work as this is a model compound commonly used in the formulation of detergents, with a great presence in urban and industrial waste-waters. The application of UV combined with hydrogen peroxide to oxidise a surfactant effluent is shown to be suitable as a primary oxidation step since conversions of around 50% of the original compound are achieved in the most favourable cases. Initially, the influence of the operating variables on the degradation levels is analysed in this work. A kinetic model that takes into account both the contributions of direct photolysis and radical attack is also worked out. Direct photolysis is performed to determine the quantum yield in the single photodecomposition reaction. Additionally, the rate constant of the reaction between hydroxyl radicals and LAS in the oxidising system H_2O_2/UV is determined for different operational conditions. Finally, the contribution of each oxidation pathway is quantified; a higher contribution of the radical reaction than that of the direct photolysis was found in all cases.