A Biochar‐Based Composite Hydrogel Microenvironment for Enhanced Biocatalysis

ABSTRACT Addressing water pollution with sustainable and eco‐friendly strategies is a significant global challenge. Traditional methods of decontaminating water via enzyme catalysis have limitations, particularly due to the mass transfer resistance resulting from enzyme immobilization. In this study, we report a novel approach in which biochar (BC), a biomass‐derived porous material rich in surface functional groups, is integrated with polyacrylamide hydrogels to encapsulate the enzyme horseradish peroxidase (HRP). The resulting Gel/BC‐HRP composite hydrogel exhibits superior biocatalytic activity for the oxidation of phenolic contaminants in the presence of hydrogen peroxide (H 2 O 2 ). Our findings demonstrate that the Gel/BC‐HRP composite greatly enhances mass transfer efficiency, achieving a reaction rate 91.4 times faster than the biochar‐free control, together with exceptionally high turnover frequency (TOF) values. The composite maintains approximately 60% efficiency for phenol removal even after eight reaction cycles. Mechanistic investigations suggest that the polyacrylamide gel creates electron‐rich domains, while the biochar segments provide electron‐deficient domains, leading to the formation of an optimal microenvironment that concentrates both H 2 O 2 and phenol in the vicinity of the HRP, thereby significantly accelerating the oxidation process. The innovative integration of biochar with hydrogel‐immobilized biocatalysts offers a promising and environmentally friendly solution for the degradation of organic pollutants in water remediation.