A novel way for hydroxyl radicals generation: Biochar-supported zero-valent iron composite activates oxygen to generate hydroxyl radicals

As the cheapest oxidant, it is significant to investigate how to use oxygen to generate hydroxyl radicals (·OH) effectively. Though the oxidation of zero-valent iron (ZVI) by O2 can generate ·OH, the yield is too low for application. Here, we successfully prepared the biochar-supported zero-valent iron composites (BC-ZVI) and applied them to generate ·OH. The ·OH quantitative experiments presented that the BC-ZVI (1:1) has the strongest ability to activate oxygen to generate ·OH among the different mass ratios of BC-ZVI, which can reach 20.19 μM at the concentration of 1.0 g/L. Materials characterization results demonstrated that the uniform dispersion of ZVI particles and the catalytic capacity of biochar led to the superior performance of BC-ZVI (1:1) in ·OH generation. The O2·- and H2O2 are proved to be the intermediate reactive oxygen species in the generation of ·OH through reactive oxygen species (ROS) capture experiments. Our findings presented that the BC-ZVI (1:1) exhibited high performance in TC removal (186.26 mg/g) and the role of ·OH was demonstrated by quenching experiments. Overall, those results indicated that BC-ZVI (1:1) composite could be a promising material to generate ·OH and remove pollutants.