Simulated sunlight-driven photocatalytic activation of peroxydisulfate by core–shell Ag@SiO2/TiO2 nanocomposite for efficient methyl orange degradation

Herein, core–shell Ag@SiO 2 /TiO 2 nanocomposites were synthesized and applied to activate peroxydisulfate (PDS) for wastewater purification. The Ag core and Ag-doped TiO 2 shell were obtained by stober method and calcination method. The dispersion degree and size of Ag in TiO 2 would influence the oxygen vacancy. Ag enhanced the visible absorption of TiO 2 and activated PDS. Improved degradation performance was attributed to enhanced PDS activation by photogenerated e − , which separated h + and thus promoted methyl orange(MO) degradation. Reactive oxidative species were verified under dark and light conditions via quenching experiments and electron paramagnetic resonance tests, demonstrating SO 4 •– , h + , O 2 •– , and 1 O 2 were formed in light,whereasSO 4 •– , •OH, O 2 •– , and 1 O 2 were responsible for MO degradation under dark conditions. The Ag@SiO 2 /TiO 2 /PDS/light system showed selectivity for removal of cationic dyes (e.g., methylene blue and malachite green) through adsorption and photocatalysis, whereas anionic dyes (e.g., MO) were degraded by photocatalysis alone. Besides, we found excess adsorption of micropollutant onto catalyst may be adverse to the activation of PDS. Therefore, the adsorption of oxidant (such as PDS) onto the catalyst surface would be beneficial for catalytic activation and micropollutant degradation, especially onto active sites. This work aims to provide a new avenue for core-shell structure catalyst synthesis in wastewater purification.