Enhanced Active Site Accessibility of Co-Si Catalysts for Alachlor Degradation by Peroxymonosulfate Activation

Cobalt-based catalysts prepared via conventional approaches frequently suffer from severe particle aggregation, which restricts active site accessibility and impedes mass transfer efficiency, thereby limiting their practical applicability in advanced oxidation processes. This study employed a simple citrate-assisted combustion method to synthesize a mesoporous catalyst with highly dispersed active sites, which was then evaluated for the degradation of alachlor (ACL) via peroxymonosulfate (PMS) activation. By precisely controlling the incorporation of cobalt species into monodisperse microspheres, the catalyst’s structure and chemical properties were finely tuned, enhancing accessibility to active sites and exposing abundant oxygen vacancies. ACL was efficiently degraded over a wide initial pH range of 5–9 (removal > 88%), and complete degradation was achieved within 8 min at pH 9, using low dosages of catalyst (50 mg/L) and PMS (0.08 mM). Furthermore, radical quenching experiments combined with EPR analysis revealed that the oxidation process was primarily driven by radicals (SO4•−, •OH and O2•−) and non-radicals (singlet oxygen, 1O2). This catalytic process was continuously driven by the redox cycle on the silica support. The catalyst showed promising activity for PMS activation towards organic pesticide contaminant degradation in water.