Efficient tetracycline degradation via peroxymonosulfate activation by magnetic Co/N co-doped biochar: Emphasizing the important role of biochar graphitization

The accumulation of tetracycline (TC) in aquatic environments raised the risk to ecosystems and human health due to its potential biological toxicity. The development of carbon-based materials with features of low cost, easy isolation and excellent performance for activating peroxymonosulfate (PMS) to generate reactive oxygen species toward TC degradation is essential but remains a grand challenge. Herein, sustainable biomass kelp-derived self-nitrogen doped biochar (KC)-stabilized Co nanoparticles were developed for PMS activation toward TC degradation. The influences of calcination temperature on the microstructure were studied to further optimize the degradation performance for TC. The Co-N/KC-900 exhibited an optimal performance for activating PMS to degrade TC with a removal efficiency of 99 % within 15 min. Additionally, the magnetic Co-N/KC-900 had robust recycling stability because of the enhanced interaction between the Co nanoparticles and graphitized biochar. Characterization results indicated that Co nanoparticles, graphite nitrogen, and direct electron transfer process participate in the PMS activation. Quenching experiments and electron paramagnetic resonance analyses revealed the combined radical and non-radical pathways for TC degradation, and the non-radical pathway plays a dominant role. The possible degradation pathways of tetracycline were proposed, and the toxicity of intermediates in the degradation process was evaluated. This study offers a facile and low-cost strategy to prepare an efficient PMS activator for antibiotic wastewater remediation.