PtCo with oxidase-like activity and laccase for synergistic catalytic degradation of phthalic acid esters

Abstract

Phthalic acid esters (PAEs) as common plasticizers, providing convenience to humans. However, they also present a potential threat to ecosystems and human health as emerging contaminants. In this study, co-immobilization of nanozyme (PtCo) and laccase (Lac) into dendritic mesoporous silica (DMSN) constitutes nanomaterials (Lac@PtCo@DMSN). PtCo with an atomic ratio of 3:1 has the highest oxidizing activity. DMSN exhibited a maximum Lac loading capacity of 365 mg/g and activity of Lac@PtCo@DMSN exhibits excellent pH, temperature, and storage stability and reusability, and demonstrated greater recoverability. Remarkably, Lac@PtCo@DMSN (50 mg) achieved 81.83% degradation of total PAEs within 72 h and maintained 72.44% degradation of dimethyl phthalate (DMP) in the fifth cycle. Electron transfer between Pt, Co and adsorbed oxygen (O2ads) in PtCo can generate •OH and •O2−, which were the dominant reactants for PAEs degradation. •OH could degrade PAEs to phthalic acid via H-abstration and •OH addition. •OH effectively enhanced Lac activity, and promoted the synergistic catalytic performance of nanozymes and natural enzymes. The degradation of phthalic acid by Lac accelerated the release of PtCo@DMSN reaction sites, resulting in significantly enhanced PAEs degradation. Thus, artificial/natural enzymes can degrade PAEs without exogenous additives to solve the limitation of Lac application, providing a new strategy for degrading contaminants in water.