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

Abstract

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.