A Biochar-Based Composite Hydrogel Microenvironment for Enhanced Biocatalysis

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 (H₂O₂). 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 H₂O₂ 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.