Abstract: In order to improve the degradation rate of  norfloxacin residues in the environment, we prepared a rice husk biochar based graphite phase nitrogen doped carbon (g-C₃N₄) composite photocatalyst through a one-step calcination method. We characterized its structure by using various methods, substituting the bridging nitrogen atoms in the g-C₃N₄ lattice with carbon atoms to effectively construct a delocalized π-bond system, significantly enhancing its photocatalytic degradation performance of norfloxacin. Experimental results show  that the photocatalytic degradation rate constant of the optimized biochar g-C₃N₄ composite photocatalyst can reach up to  0.029 4 min^-1, and the degradation rate of norfloxacin can be increased to 85.45% within 2 h, which is 1.46 times  that of pure g-C₃N₄ material. This article provides novel design concept for developing highly efficient and stable photocatalysts for water treatment, demonstrating the application potential of biochar g-C₃N₄ composite materials  in the field of environmental remediation.

Key words: graphitic carbon g-C₃N₄, biochar, antibiotic, degradation, norfloxacin