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

Herein, perovskite LaCoO3 composites with different Co/La molar ratios (denoted as LCxO) 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 LCxO composites. Notably, as the Co/La ratio decreased from 1.0 to 0.25, the LCxO composites exhibited reduced particle agglomeration, increased specific surface area, and elevated oxygen vacancies (OV) content. Amongst, LC0.25O (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 LC1.0O (0.09545 min-1). Mechanistic investigations through quenching experiments, EPR, XPS, and EIS characterizations demonstrated that both Co and OV jointly facilitated the generation of reactive species, including CH3C(O)OO center dot, center dot OH and singlet oxygen, in LC0.25O/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, LC0.25O 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 LC0.25O/PAA system for practical applications. This study offers new insights into the development of highly efficient and low-cobalt-content catalysts for PAA activation.