A novel immobilized horseradish peroxidase platform driven by visible light for the complete mineralization of sulfadiazine in water

A novel immobilized enzyme driven by visible light was prepared and used for complete mineralization of antibiotics in water bodies. The immobilized enzyme was composed of carbon nitride modified by biochar (C/CN) and horseradish peroxidase (HRP), establishing the photo-enzyme coupling system with synergistic effect. Among them, the introduction of biochar not only improves the stability and loading capacity of the enzyme, but also improves the light absorption capacity and carrier separation efficiency of the photocatalyst. After the optimization of immobilization process, the solid load of HRP could reach 251.03 mg/g, and 85.03 % enzyme activity was retained after 18 days of storage at 4 °C. In the sulfadiazine (SDZ) degradation experiment, the degradation rate of HRP/C3/CN reached 71.21 % within 60 min, which was much higher than that of HRP (2.33 %), CN (49.78 %) and C3/CN (58.85 %). In addition, under the degradation of HRP/C/CN, the total organic carbon (TOC) removal rate of SDZ reached 53.14 %, which was 6.47 and 1.74 times that of CN and C3/CN, respectively. This study shows that the introduction of biochar is of great significance to the photo-enzyme cascade coupling system and provides a new strategy for the application of HRP&g-C3N4 system in wastewater treatment.