In situ observation of Co3O4−α–OH formation on optimized biochar for peroxymonosulfate activation and ultrafast antibiotics degradation

Biochar optimized with oxygen-containing functional groups is believed to be beneficial for peroxymonosulfate (PMS) activation, and biochar-loaded Co 3 O 4 -based catalysts are expected to be one of the most promising PMS activators for the efficient removal of organic pollutants. Nevertheless, the real active sites on Co 3 O 4 catalysts are still in debate due to insufficient experimental evidence. Herein, Co 3 O 4 growing on the oxygen-containing functional groups optimized rice husk biochar (RHBA) was synthesized (RHBA@Co 3 O 4 ), and RHBA800@25Co 3 O 4 + PMS system achieved complete degradation (100%) of refractory levofloxacin (LFX) within 4 min. The superior catalytic performance was suggested to be attributed not only to the uniform dispersion of Co 3 O 4 , but also to the transformation of lattice oxygen in Co 3 O 4 , which was found to play an important role in the catalytic process by inducing the formation of Co 3 O 4−α –OH. Meanwhile, density functional theory (DFT) calculations indicated that the adsorption energy ( E ads ) of PMS on Co 3 O 4−α –OH was far lower than that on Co 3 O 4 . Moreover, both radical and non-radical pathways were indicated to be involved during the degradation process. Additionally, the practical application of RHBA@Co 3 O 4 was investigated using various antibiotics, actual water environments, and fixed-bed reactors. The results showed that it possessed good practical degradation performance and significantly reduced the toxicity of intermediate products. This work provides a fresh insight into the catalytic mechanism of RHBA800@25Co 3 O 4 for PMS activation and wastewater treatment, offering a new perspective on the catalytic mechanism of Co 3 O 4 -based materials. Highlights RHBA800@25Co 3 O 4 exhibited ultrafast antibiotics degradation via peroxymonosulfate activation. Inspired formation of Co 3 O 4−α –OH by lattice oxygen induction was explored. Ecological safety of levofloxacin degradation products was verified through antibacterial experiments.