Degradation of chloroxylenol by CoSx activated peroxomonosulfate: Role of cobalt-sulfur ratio

Abstract

Cobalt sulfide has received widespread attention in the advanced oxidation treatment of wastewater, and its catalytic activity is influenced by crystal structure and exposed active sites. This work successfully constructed three types of cobalt sulfides, namely Co₉S₈, Co₃S₄ and CoS₂, by changing the molar ratio of cobalt to sulfur. The results showed that the degradation efficiency of Co₉S₈, Co₃S₄ and CoS₂ on chloroxylenol by activated peroxomonosulfate (PMS) were 100 %, 88.70 % and 67.73 %, respectively. Combined with density functional theory (DFT), the structural properties and reaction energy barriers of different cobalt-sulfur ratios were calculated. As the ratio of cobalt to sulfur increases, the sulfur vacancies realized a fuller exposure of active sites (Co²⁺_surf.) on the surface of the catalysts, with a highly linear relationship with the reaction rate constant (R² = 0.945). This work explores the structure-activity relationship between cobalt sulfur ratio and degradation efficiency, which can guide new catalyst synthesis.