CoFe2O4 catalyst with abundant oxygen vacancies as peroxymonosulfate activator for enhanced diclofenac degradation

Advanced oxidation processes (AOPs) using peroxymonosulfate (PMS) have gained attention for the removal of organic pollutants such as diclofenac (DCF) from wastewater. This paper presents an innovative approach for the preparation of CoFe₂O₄ (CFO) with abundant oxygen vacancies (OVs) (CFO (2.5)). Compared to conventional CFO, CFO (2.5) exhibits superior catalytic performance owing to the abundance of OVs on its surface, which enhances the oxygen conversion rates and facilitates the efficient redox cycling of Co²⁺/Co³⁺ and Fe²⁺/Fe³⁺. The CFO (2.5)/PMS system achieved 99.9 % DCF removal within 10 min, with a rate constant that was 15 times higher than that of the CFO system. In addition, the CFO (2.5)/PMS system demonstrated wide pH applicability and consistently achieved a DCF removal efficiency >99.9 %. This system generates both radical and non-radical species for effective DCF degradation. CFO (2.5) also showed high stability, maintaining a 99.9 % removal efficiency after four cycles. This study provides a method for designing catalysts with abundant oxygen vacancies for efficient PMS activation and the treatment of wastewater contaminated with organic pollutants.