Rice hull-derived biochar with photocatalytic activity for efficient degradation of oxytetracycline in water under sunlight

Photocatalytic degradation is an effective strategy for the removal of environmental pollutants. However, the development of low-cost and high-efficiency photocatalysts continues to present a significant challenge. This work reported the fabrication of a composite photocatalyst directly from waste biomass (rice hulls) in a single step, which efficiently degraded oxytetracycline (OTCs) under sunlight. The morphology, microstructures and photoelectric features of the fabricated materials were subjected to comprehensive investigation using characterization techniques. The results found that the improved photocatalytic activity in sunlight was attributed to the complexation of rice hull-derived biochar and nano-ZnO generated in the preparation, which exhibited favourable adsorption, conductivity characteristics and small bandgap. The photocatalytic efficiency was observed to reach 72.6 % in 120 min under the irradiation of a 100 W xenon lamp. The effect of natural waters, degradation kinetics and degradation TOC analysis were also examined. The dominant agent responsible for the degradation of OTCs was the •O2− radical. Furthermore, the principal photocatalytic degradation pathway of OTCs was identified with the assistance of UHPLC/MS.