Nitrogen-phosphorus codoped biochar prepared from tannic acid for degradation of trace antibiotics in wastewater.

This study was designed to develop a one-step pyrolysis process that could efficiently activate peroxymonosulfate (PMS) and degrade tetracycline hydrochloride (TCH) by producing N, and P codoped carbon materials (NPTC-800). Furthermore, it exhibited a high specific surface area (658 cm), a larger pore volume (0.3 cm), and a certain content of heteroatoms (nitrogen and phosphorus). PMS-activated NPTC-800 attained a TCH removal efficiency of over 90% within 40 min, with an observed rate constant (k) of 0.0307 min. Similarly, the materials exhibited strong resistance to ionic interferences and showed broad applicability across various water bodies. Mobility experiments were conducted to further assess the stability of catalyst (92%, 40 h). Non-radical oxidation pathways, particularly including the singlet oxygen (O), were evidenced to play dominant roles in TCH degradation, as demonstrated by electron paramagnetic resonance (EPR) observations and experiments with free radical quenching. Theoretical calculations demonstrated that the N and P codoped domains substantially improve TCH removal compared to pure biochar. Finally, the proposed degradation pathways for TCH were identified, and the resulting degradation products demonstrated reduced biological toxicity.