Peracetic acid activation by oxygen vacancy-enriched LaCoO3 perovskite for expediting naproxen degradation: Structural properties and activation mechanism

Herein, perovskite LaCoO 3 composites with different Co/La molar ratios (denoted as LC x O) were synthesized and exploited to activate peracetic acid (PAA) for naproxen (NPX) degradation. Comprehensive characterizations were employed to elucidate the physicochemical properties, morphology, and surface functionalization of LC x O composites. Notably, as the Co/La ratio decreased from 1.0 to 0.25, the LC x O composites exhibited reduced particle agglomeration, increased specific surface area, and elevated oxygen vacancies (O V ) content. Amongst, LC 0.25 O (Co/La = 0.25) exhibited the highest catalytic efficiency for PAA activation, achieving complete NPX degradation within 3 min, with a rate constant of 0.3764 min −1 , approximately four times greater than that of LC 1.0 O (0.09545 min −1 ). Mechanistic investigations through quenching experiments, EPR, XPS, and EIS characterizations demonstrated that both Co and O V jointly facilitated the generation of reactive species, including CH 3 C(O)OO • , • OH and singlet oxygen, in LC 0.25 O/PAA system. Additionally, DFT calculations and transformation product (TP) identification were used to propose the NPX degradation pathway, revealing the oxidation preferentially occurred in the electron-rich sites. Ecotoxicity assessment using ECOSAR suggested an overall increase in the toxicity of TPs due to the intactness of naphthalene ring. Moreover, LC 0.25 O exhibited excellent reusability and stability, maintaining 100 % NPX degradation efficiency over four consecutive cycles. The fixed-bed column experiments demonstrated consistent NPX removal efficiency above 90 % during continuous operation for 30 h, highlighting the robust potential of LC 0.25 O/PAA system for practical applications. This study offers new insights into the development of highly efficient and low-cobalt-content catalysts for PAA activation.