Integration of tailored Co3O4@G with porous biochars for efficient degradation of tetracycline

Graphitic-carbon-coated metallic-catalyst-loaded porous carrier composites are widely used to degrade antibiotics by activating peroxymonosulfate (PMS). Integration of the defect sites within the graphitic shell, core–shell interface, and catalyst/carrier could enhance the “1 + 1 > 2” catalytic effect. In this work, graphitic-carbon-coated cobaltosic oxide (Co3O4@G) having a tailored nanostructure (23.3–29.7 nm for the core and 2.35–1.29 nm for the shell) was first synthesized by pulsed laser ablation. Then, porous Co3O4@G/biochars (Co3O4@G/Bs; 18.5–134.8 m2/g) were synthesized by crosslinking nitrogen-modified Co3O4@G with waste bamboo-pyrolyzed biochars. The degradation behaviors were evaluated as functions of the composite species, catalyst dosage, PMS concentration, tetracycline concentration, solution pH, and coexisting anions. The Co3O4@G/Bs presented high catalytic k values (0.159–0.449 min–1) that were 15.5–40.8 times higher than those of the individual biochars; furthermore, excellent recycling performance (92.5% remaining k value) and promising stability (8.31–2.77 μg/L of Co leakage) were observed after recycling 10 times. The favorable catalytic versatility of the Co3O4@G/Bs was verified by the efficient degradations of levofloxacin (88.6%), oxytetracycline (95.4%), and norfloxacin (92.5%). The degradation mechanism was governed by the radical-based degradation pathways involving •OH, SO4•–, and 1O2 via Co3+ and Co2+ recycling. The present study is expected to provide a valuable reference for degrading antibiotics by integrating tailored laser-ablated core/shell nanoparticles with biochars.