Efficient activation of N and S co-doped magnetic biochar for peroxomonosulfate degradation of tetracycline

N-S co-doped magnetic biochar (NSMBC) was synthesized by a two-step pyrolysis technique and used for the degradation of tetracycline (TC) by activated persulfate (peroxomonosulfate [PMS]). Batch experiments showed that the pyrolysis temperature and doping ratio affected the catalytic performance of NSMBC. The degradation rate of TC in the NSMBC/PMS system prepared at 350°C with a doping ratio of 33% was up to 94.50%, and the system exhibited strong pH adaptability and resistance to environmental interference. The results of free radical burst and electron paramagnetic resonance (EPR) spectroscopy experiments indicated the free radical pathway (SO₄^•−) for TC degradation. In addition, NSMBC has good stability and excellent magnetic properties favorable for separation and recovery. This study not only provides a new idea for the synthesis of efficient and stable catalysts but also provides a green pathway for the resourceization of pomelo peel waste.