Ferrihydrite/B, N co-doped biochar composites enhancing tetracycline degradation: The crucial role of boron incorporation in Fe(III) reduction and oxygen activation.

Harnessing the redox potential of biochar to activate airborne O for contaminant removal is challenging. In this study, ferrihydrite (Fh) modified the boron (B), nitrogen (N) co-doped biochars (BCs) composites (Fh/B(n)NC) were developed for enhancing the degradation of a model pollutant, tetracycline (TC), merely by airborne O. Fh/B(3)NC showed excellent O activation activity for efficient TC degradation with a apparent TC degradation rate of 5.54, 6.88, and 22.15 times that of B(3)NC, Fh, and raw BCs, respectively, where O and HO were identified as the dominant ROS for TC degradation. The B incorporation into the carbon lattice of Fh/B(3)NC promoted the generation of electron donors, sp C and the reductive B species, hence boosting Fe(III) reduction and O generation. O adsorption was enhanced due to the positively charged adsorption sites (C-Band NC). And O was generated via Fe(II) catalyzed low-efficient successive one-electron transfer (O → O → O, HO), as well as biochar catalyzed high-efficient two-electron transfer (O → HO → O) that does not involve O as the intermediate. Moreover, Fh/B, N co-doped biochar showed a wide pH range, remarkable anti-interference capabilities, and effective detoxification. These findings shed new light on the development of environmentally benign BCs materials capable of degradading organic pollutants.