Biochar-supported Prussian blue-derived CuFe bimetallic composite for efficient laccase immobilization and benzo[a]anthracene degradation.

The efficient removal of polycyclic aromatic hydrocarbons (PAHs) from contaminated environments remains a major environmental challenge. Although laccase has attracted considerable attention for PAH remediation owing to its high catalytic efficiency and environmental friendliness, its poor stability and reusability limit practical applications. In this study, a biochar-supported Prussian blue-derived CuFe bimetallic composite (CuFe@BC) was designed as a multifunctional carrier for laccase immobilization through coordination interactions and adsorption. Benefiting from its porous structure and abundant Cu/Fe coordination sites, CuFe@BC achieved a laccase loading of 648 mg/g and enabled magnetic recovery of the immobilized biocatalyst. Compared with free laccase, immobilized laccase (CuFe@BC-Lac) exhibited enhanced stability and reusability. Kinetic analysis indicated that immobilization improved the substrate affinity of laccase while maintaining high catalytic efficiency. CuFe@BC-Lac achieved a benzo[a]anthracene (BaA) removal efficiency of 98.9 % and retained 71.8 % removal efficiency after six reuse cycles. Mechanistic investigations revealed that dynamic Cu/Fe redox cycles promoted interfacial electron transfer, facilitating O2 activation and 1O2 generation. Furthermore, CuFe@BC-Lac maintained satisfactory degradation performance in real water samples, demonstrating its potential for practical BaA remediation. Product analysis and toxicity prediction revealed that BaA was transformed into less toxic intermediates through sequential oxidation and aromatic ring cleavage, thereby reducing its environmental risk. This work provides an effective strategy for developing redox-active immobilized biocatalysts for PAH remediation and offers new insights into the rational design of multifunctional immobilization carriers for environmental biocatalysis.