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.