Diclofenac degradation properties of a La-doped visible light-responsive TiO2 photocatalyst

Abstract

Diclofenac (DCF), which is detected in the aquatic environment, can act as a harmful factor to the ecosystem and human health, but it is difficult to remove it with existing water treatment methods. DCF can be removed using the TiO2 photocatalysis process, and in this study, a method for removing it using visible light was sought. A visible-light reactive TiO2 photocatalyst doped with lanthanum (La) was synthesized using an LPP (Liquid Phase Plasma) process, and the photocatalytic activity was investigated by decomposing diclofenac. La was doped uniformly into the TiO2 powder, and the content of doped La increased with increasing concentration of the initial precursor. The La dopant was in the form of La2O3, and the bandgap and photoluminescence intensity decreased with increasing amount of doped La. In the photolysis experiment using a UV light source, the La-doped TiO2 photocatalysts (LDTPs) showed slightly higher activity than the bare TiO2, but the photocatalyst activity of the LDTPs under the visible light irradiation was superior. In the degradation experiment of DCF by LDTP, four major by-product intermediates were detected. Moreover, it was estimated that degradation proceeded through two pathways: hydroxylation and ring closure.