Accelerating of Fe2+ regeneration in Fenton reaction by biochar: Pivotal roles of carbon defects as electron donor and shuttle

Accelerating Fe regeneration emerges as a promising approach to boost Fenton reaction. However, most co-catalysts to accelerate Fe regeneration embrace drawbacks including cumbersome synthesis, expensive precursors and metal leaching. Herein, we report an approach to remarkably accelerate Fe regeneration by metal-free biochar. Quantitatively, the overall reaction rate constant for Fe regeneration by biochar was 9.68 × 10, and correspondingly the concentration of OH generated in biochar/Fe/HO system was 2.08 times higher than that in Fe/HO. Favored by this, satisfying performance on both mineralization and detoxification on sulfamethoxazole was achieved. Moreover, 99.6 % of Chemical Oxygen Demand (COD) was removed from medical wastewater in a biochar-packed fixed-bed column, while comparably the traditional Fenton process achieved only 14.6 %. Distinguished with traditional knowledge, surface carboxyl groups on the surface of biochar were identified as reactive sites to capture Fe, while, carbon defects played multifunctional roles as electron donors and shuttle to reduce Fe. Besides, advantages including negligible metal leaching, low interferences from water matrixes and suppression of toxic BrO generation suggested the strategy promising. The achievements shed light on the acceleration of Fe regeneration in Fenton processes in an economic and environmentally-friendly way, and also the modulation of the reactivity of biochar