Photocatalytic degradation of carbaryl in aqueous TiO2 suspensions containing surfactants

The effect of ionic and non-ionic aliphatic surfactants on the photocatalytic degradation of Carbaryl (1-naphtyl-N-methylcarbamate) in aqueous solutions containing suspended TiO2 (anatase) particles, under irradiation with simulated AM1 solar light, was investigated. A neat inhibitory effect on the degradation rate was observed, depending on the nature of the surfactant and on the initial pH of the solution. The decay profiles of the primary process corresponded to the usual pseudo-first order kinetics for surfactant concentrations below the critical micellar concentration range, whereas a more complicate behaviour was observed in the presence of micellar aggregates. Mineralization of the pesticide to CO2, NO3− and NH4+ was evidenced also in the presence of added amphiphiles, suggesting the feasibility of photocatalytic treatment of surfactant-containing aqueous wastes.