Enhanced photocatalytic degradation of tetracycline hydrochloride by Zr-doped Bi₂₄O₃₁Cl₁₀: Synthesis, characterization, and reaction mechanism

This study addresses antibiotic water pollution by synthesizing Zr-doped Bi₂₄O₃₁Cl₁₀ (Bi₂₄(₁₋ₓ)Zr₁₈ₓO₃₁Cl₁₀) photocatalysts via hydrothermal method for tetracycline hydrochloride (TC-HCl) removal. Zr doping ratios (6–14%) were systematically investigated, with the optimal BZOC4 (12% Zr) degrading 91.24% of 20 mg/L TC-HCl within 120 min under 500 W xenon lamp irradiation (pH = 9). Its reaction rate constant (0.0239 min −1 ) is triple that of pristine Bi₂₄O₃₁Cl₁₀. Zr doping reduces the band gap from 3.12 eV to 2.8 eV, improves visible light utilization (absorption edge red-shifted to 525 nm), accelerates electron transfer, and reduces e − /h + recombination—supported by UV –Vis DRS, PL, and electrochemical tests. Superoxide radicals (O₂ − ·) and holes (h + ) are primary active species, confirmed by radical trapping and ESR. TOC analysis confirms 32.4% mineralization of TC-HCl to CO₂ and H₂O.This work offers new design strategies for bismuth halide-based photocatalysts in antibiotic remediation by integrating structural regulation and electronic modulation via Zr doping.