Reactivation and reuse of TiO2-SnS2 composite catalyst for solar-driven water treatment.

One of the most important features of photocatalytic materials intended to be used for water treatment is their long-term stability. The study is focused on the application of thermal and chemical treatments for the reactivation of TiO2-SnS2 composite photocatalyst, prepared by hydrothermal synthesis and immobilized on the glass support using titania/silica binder. Such a catalytic system was applied in solar-driven treatment, solar/TiO2-SnS2/H2O2, for the purification of water contaminated with diclofenac (DCF). The effectiveness of studied reactivation methods for retaining TiO2-SnS2 activity in consecutive cycles was evaluated on basis of DCF removal and conversion, and TOC removal and mineralization of organic content. Besides these water quality parameters, biodegradability changes in DCF aqueous solution treated by solar/TiO2-SnS2/H2O2 process using simply reused (air-dried) and thermally and chemically reactivated composite photocatalyst through six consecutive cycles were monitored. It was established that both thermal and chemical reactivation retain TiO2-SnS2 activity in the second cycle of its reuse. However, both treatments caused the alteration in the TiO2-SnS2 morphology due to the partial transformation of visible-active SnS2 into non-active SnO2. Such alteration, repeated through consecutive reactivation and reuse, was reflected through gradual activity loss of TiO2-SnS2 composite in applied solar-driven water treatment.