Titanium-doped stainless steel nanotubes for the photocatalytic degradation of an organic compound

Abstract

Titanium-doped stainless steel nanotubes (SSNT@Ti) were synthesized by electrochemical anodization and chemical reduction. Benzoic acid was subjected to degradation by photolysis, photocatalysis, photolytic oxidation, and photocatalytic oxidation using SSNT@Ti under simulated solar irradiation in a laboratory-scale system. Photocatalytic oxidation employing SSNT@Ti along with hydrogen peroxide (H2O2) as an oxidant exhibited the highest degradation rate (8.08 x 10(-3) s(-1)). Pseudo-first-order rate constants were expressed as functions of initial benzoic acid concentration, irradiation intensity, and initial H2O2 concentration. An empirical kinetic model was developed based on the kinetic equations in respect of each factor, which resulted in good prediction of the photocatalytic oxidative degradation rates (R-2=0.98). Compared to the other photocatalysts reported in the literature, this economical SSNT@Ti showed competitive photocatalytic ability. The O-center dot(2)- and center dot OH played dominant roles for the degradation of benzoic acid in the photocatalysis and photocatalytic oxidation, respectively. SSNT@Ti was stable during five repeated experiments, and it maintained its catalytic activity.