Interfacial photo-enzyme coupled on sodium alginate microbeads co-immobilizing lipase and CeO2@Bi2WO6 heterojunction for stepwise degradation of dimethyl phthalate.

Abstract

To address the challenge of simultaneously achieving efficient removal, enhanced mineralization, and risk mitigation of dimethyl phthalate (DMP), a multifunctional sodium alginate (SA) microbead platform integrating photocatalysis, enzymatic catalysis, and magnetic recovery was developed. A CeO2@Bi2WO6 heterojunction was first constructed, and the optimized C20BW80 sample exhibited enhanced charge separation through intimate interfacial coupling, S-scheme charge-transfer mechanism, and a built-in electric field. Candida rugosa lipase was subsequently immobilized in magnetic SA microbeads using an EDTA-Ca/GDL internal gelation strategy, enabling spatial integration of enzymatic activation and photocatalytic oxidation. The optimal coupled process consisted of 20 min dark pretreatment followed by 80 min irradiation. Under the optimized conditions, DMP removal reached 99.12% within 100 min, with an apparent pseudo-first-order rate constant of 0.0521 min-1. TOC removal reached 27.41% at 100 min and further increased to approximately 50% at 180 min, demonstrating progressive but incomplete mineralization of residual intermediates. Three-dimensional fluorescence spectroscopy, Fukui function analysis, and LC-MS identification revealed a sequential mechanism involving adsorption enrichment, enzymatic ester-bond hydrolysis, and photocatalytic oxidation of aromatic intermediates. Toxicity prediction and mung bean germination tests further confirmed reduced ecological risk after treatment. This work provides an integrated and recoverable photo-enzyme platform for improving the degradation and mineralization of phthalate contaminants.