Sulfide-modified cobalt silicate activated periodate for nitenpyram degradation: Enhanced radical and non-radical pathway

Periodate-based advanced oxidation processes (PI-AOPs) exhibited a promising future for the reduction of emerging refractory organic pollutants. However, the underlying mechanism and the sulfuretted effect of sulfide-modified metal silicate materials for PI activation were still unclear. In this study, sulfide-modified metal silicates (S-CoSi) were first synthesized and applied in the PI-AOPs system. Different from traditional metal silicate materials, sulfurization improved the catalytic performance. The enhanced degradation performance was from the increase in specific surface area and charge transfer efficiency, which derived from the sulfurization in metal silicate. DFT calculations revealed that the enhanced charge densities of Co-S bonds promoted the existence of Co (Ⅱ), which was more conducive to PI activation. Experimental and calculation results further demonstrated that Co was the active site in S-CoSi, and sulfur species strengthened the radical pathway by assisting Co (Ⅱ) regeneration (electron transfer from S to Co) rather than participating in the PI activation. Moreover, sulfurization promoted the generation of 1O2 (non-radical pathway) by increasing oxygen vacancy in the metal silicate. This study provided new insights into the effect of sulfurization on the radical and non-radical pathways in the metal silicates PI system.