Synergy effect between adsorption and heterogeneous photo-Fenton-like catalysis on LaFeO₃/lignin-biochar composites for high efficiency degradation of ofloxacin under visible light

The perovskite-type LaFeO₃ serves as a promising photo-Fenton-like catalyst, but its low adsorption ability and catalytic activity inhibit the effective removal of ofloxacin. Herein, the LaFeO₃ and lignin-biochar composites were fabricated by a facile sol–gel pyrolysis route. As compared with LaFeO₃ nanoparticles, the LaFeO₃/lignin-biochar composites showed better adsorption and degradation ability due to the synergistic effect between LaFeO₃ nanoparticles and lignin-biochar. Compared with LaFeO₃, the adsorption capacity of LaFeO₃/lignin-biochar for ofloxacin increased from 0.72 to 30.4 mg·g⁻¹. Importantly, this catalyst exhibited the improved degradation efficiency of ofloxacin during 75 min (95.6 % for LaFeO₃/lignin-biochar Vs 53.4 % for LaFeO₃) as the adsorption process was combined with the photo-Fenton-like process. Notably, the lignin-biochar in the LaFeO₃/lignin-biochar composites decreased the bandgap of LaFeO₃ nanoparticles from 2.10 eV to 1.79 eV due to the interface interaction between LaFeO₃ and lignin-biochar, facilitating the enhanced photo-Fenton-like activity. The hydroxyl radicals that were generated in the photo-Fenton-like process effectively induced the oxidative degradation of ofloxacin, which was confirmed by free radical capture experiments and ESR characterization. Moreover, the photo-Fenton-like degradation pathway of ofloxacin was proposed according to LC-MS analyses, and the toxicity analysis of degradation intermediates was further carried out. Hence, the LaFeO₃/lignin-biochar composite was a promising photo-Fenton-like catalyst to eliminate ofloxacin via coupling of adsorption and photo-Fenton-like processes.