Enhancing in-situ tetracycline degradation in urine environment using boron-modified sewage sludge biochar: Mechanism of carbonate radical promotion.

[Display omitted] • B-SSBC is used to activate peroxymonosulfate and degrade tetracycline in urine. • HCO 3 −/CO 3 2− in urine contributes to the degradation of tetracycline. • DFT calculations reveal the mechanism of tetracycline degradation in urine. • The B-SSBC/PDS system removed up to 77.35 % of tetracycline in urine at pH = 7. In this work, we reveal the influencing factors and mechanisms of tetracycline removal by peroxydisulfate activated with boron-modified sewage sludge biochar in urine. Advanced characterization techniques showed that the introduced BCO 2 and BC 2 O were the main activation sites for peroxydisulfate, which maintained a high removal rate of tetracycline in synthetic and actual urine (86.48% and 77.35%). HCO 3 −/CO 3 2− and some organic matter in the urine contributed to the degradation of the tetracycline. Theoretical calculations showed that CO 3 2− in urine could be efficiently adsorbed by the introduced B atoms and converted to CO 3 ·− by peroxydisulfate to assist the degradation of tetracycline, which was attributed to the special electronic structure of the B atoms as well as the strong electron-enrichment ability of the neighboring O atoms. The potential toxicity of tetracycline and its degradation intermediates was further explored, revealing a significant reduction in toxicity during boron-modified sewage sludge biochar/ peroxydisulfate treatment. [ABSTRACT FROM AUTHOR]