Heterogeneous Photocatalytic Degradation of Triton X-100 in Aqueous TiO2 Suspensions

Abstract

The increasing utilization of surfactants generates a great amount of wastes. Surfactants and their more toxic degradation by-products in the environment affect the biota greatly. In particular, the low biodegradation of nonionic surfactants requires efficient oxidation treatments. In addition, the extracted contaminants by high concentrations of non-ionic surfactants in soil remediation may be completely treated using advanced oxidation process and thus the degradation of non-ionic surfactants needs to be checked in this case. The photocatalytic degradation of Triton X-100, a non-ionic surfactant, in aqueous titania suspensions was investigated as a function of catalyst dosage, pH, addition of hydrogen peroxide, potassium persulfate, and Tert-butyl alcohol. For the treatment of 20 mg/L Triton X-100 solutions, the optimum catalyst dosage and pH were determined to be 1 g/L and 6, respectively. The degradation efficiency of Triton X-100 by potassium persulfate was higher than that by hydrogen peroxide when the same mol of oxidants were used. Tert-butyl alcohol can strongly inhibit the photocatalytic oxidation reactions of Triton X-100. The degradation rates as a function of initial surfactant concentrations were interpreted by using a Langmuir-Hinshelwood model. With 0.2 g/L titania or even an additional 0.1 g/L hydrogen peroxide to completely degrade 1 mg/L phenanthrene in a 2 g/L Triton X-100 solution within 30 min, in this case the degradation efficiency of Triton X-100 was less than 5%. This proved that the strategy that surfactants were used as solubilizing agents for the removal of contaminants from soils followed by heterogeneous photocatalytic degradation was feasible.Within 120 min, 2 g/L of Triton X-100 can be degraded up to 67% by the addition of both 1 g/L titania and 1 g/L hydrogen peroxide. Under the right conditions, Triton X-100 can be completely degraded.