Photocatalytic degradation of nonionic surfactant, Brij 35 in aqueous TiO2 suspensions.

The photocatalytic oxidation of nonionic surfactant, Brij 35 in aqueous TiO2 suspensions was investigated as a function of catalysts loading, light intensity (I), initial Brij 35 concentration Brij, dissolved oxygen concentration [p(O2)], and pH. A monolithic swirl-flow photoreactor was used that allowed to perform a systematic analysis of rates at various loadings of TiO22 in order to distinguish "kinetic" and "transport" limited regimes for the photocatalytic degradation of Brij 35 in TiO2 suspensions. The optimal catalyst loading was determined to be 0.1 g L(-1) TiO2 at a neutral pH. The true kinetic dependences of the photocatalytic degradation on I and Brij were determined. A small increase in oxidation rate was observed with an increase in the partial pressure of the oxygen [p(O2)] in the system. The rates as a function of Brij and [p(O2)] were interpreted using a Langmuir-Hinshelwood model. The complete photocatalytic degradation of Brij 35 was obtained in acidic to basic pH range, however, the removal of Brij 35 removal and subsequent decrease in TOC levels were more efficient at a neutral pH than acidic or basic pH.