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 2 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 2 . Fh/B(3)NC showed excellent O 2 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 1 O 2 and H 2 O 2 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 2 C and the reductive B species, hence boosting Fe(III) reduction and 1 O 2 generation. O 2 adsorption was enhanced due to the positively charged adsorption sites (C- B + and N C + ). And 1 O 2 was generated via Fe(II) catalyzed low-efficient successive one-electron transfer (O 2  → O 2 ·−  →  1 O 2 , H 2 O 2 ), as well as biochar catalyzed high-efficient two-electron transfer (O 2  → H 2 O 2  →  1 O 2 ) that does not involve . O 2 − 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.