Morphology-tailored CoFe2O4/biochar from powder to granule: mechanistic insights into PMS activation and continuous-flow treatment of imidacloprid-containing wastewater.

Notwithstanding the widespread application of advanced oxidation processes (AOP) for degradation of emerging pollutants, the persistent challenges of high buoyancy and difficult recovery associated with powdered materials remain to be addressed. To address this bottleneck, this study synthesized self-supporting granular-form CoFe2O4/Biochar (GCB) using powder-form CoFe2O4/Biochar (PCB) materials, which demonstrated as a recyclable catalyst for PMS activation. The optimized PCB can effectively activate peroxymonosulfate (PMS) to degrade Imidacloprid (IMI). Specifically, it achieves an optimal degradation efficiency of 95.2%, which is 119 times higher than that of pristine biochar (0.8%). Additionally, good stability and repeatability of PCB maintaining an 87.1% removal efficiency even after five reuse times. The radicals (SO4·- and ·OH) and non-radicals (1O2 and electron transfer) pathways were responsible for IMI oxidation. The GCB exhibits enhanced practicality for water treatment applications compared to its PCB, owing to its favorable separation and low buoyancy properties. The GCB demonstrated excellent mechanical stability and catalytic activity in AOP, the GCB maintained outstanding dye pollutants removal efficiency with a near-quantitative degradation rate (>99%) throughout 12 h of continuous operation without significant deactivation. This investigation is expected to provide valuable insights for the future advancement of practical PMS activation strategies utilizing recyclable granular catalysts.