Study of homogeneous and heterogeneous photocatalysis of benzoic acid

In the present study, homogeneous and heterogeneous photocatalytic degradation of a hazardous and non-biodegradable compound, benzoic acid, in its aqueous solution by strong oxidizing agent, hydrogen peroxide, in the presence of ultraviolet (UV) radiation emitted from UV source is investigated. The different UV+Fe2++H2O2, UV+TiO2and UV+ZnO combinations generate hydroxyl radicals having very high oxidation potential, which helps in complete mineralization of the organic pollutants and are environmentally benign processes. Almost complete degradation of 97·6% and decolorization of the substrate is achieved within 90 min by UV+Fe2++H2O2system, while it takes 240 min with heterogeneous photocatalytic system. The experiments were carried out in a batch photoreactor using 8-W low-pressure mercury vapor lamp. Substrate concentration was determined by UV-visible spectrophotometry. The photocatalytic processes were strongly pH dependent and adhered to first-order kinetics.