Degradation of industrial surfactants by photocatalysis combined with ozonation.

The efficiency of titanium dioxide-mediated photocatalytic degradation of pollutants can be enhanced by combination with another advanced oxidation procedure such as ozonation. Mineralization of hydroxy- and dihydroxybenzenesulfonate based on these methods, both individually and combined, was investigated by monitoring the total organic carbon content, sulfate concentration, pH, high-performance liquid chromatography as well as the absorption spectral changes. The mineralization efficiency of the combined procedure significantly exceeded the sum of those of the individual techniques. The comparison of the disappearance of the starting material and the formation of the sulfate ions indicates that desulfonation is not the primary step of the degradation. Moreover, in the case of the combined method, ring cleavage, and thus, partial mineralization can occur without desulfonation. Efficient degradation of other, widely used industrial surfactants, such as alkylbenzene sulfonates and alkyl ether sulfates, was also achieved by heterogeneous photocatalysis combined with ozonation, offering an applicable method for the removal of these pollutants.