Photocatalytic degradation of a low concentration pharmaceutical pollutant by nanoporous TiO2 film with exposed {001} facets

Abstract

Photocatalytic degradation of low concentration ethenzamide, a pharmaceutical pollutant, by nanoporous TiO₂ film with exposed {001} facets under UV and 185 nm vacuum UV (VUV) irradiation was studied. Nanoporous TiO₂ film was found to have considerably higher UV photocatalytic activity than non-porous TiO₂ film and P25 coated on the Ti sheet, close to Pt deposited TiO₂ film with exposed {001} facets (Pt-TiO₂) when initial ethenzamide concentration was higher than 0.45 ppm. It exhibited higher activity than Pt-TiO₂ film when initial ethenzamide concentration decreased to 0.1 ppm. The performance of nanoporous TiO₂ film was also confirmed in the flow-through system, which exhibited superior UV photocatalytic activity at different residence time and long-term stability within 47 days' continuous experiments. The nanoporous TiO₂ film also showed significant activity under VUV irradiation. VUV photocatalytic degradation of ethenzamide was greatly improved in comparison with the results under UV irradiation. The nanoporous TiO₂ film still showed significant photocatalytic activity when the concentration of ethenzamide was as low as 15 ppb under VUV irradiation even when the residence time was only 1.8 min. The mass transfer limits the degradation of low concentration ethenzamide under VUV irradiation, improved flow state, i.e. high Reynolds number can help to increase the photocatalytic efficiency of ethenzamide by nanoporous TiO₂ film under VUV irradiation. Nanoporous TiO₂ film with exposed {001} facets shows considerable potential for application in removing low concentration pollutants.