Activation of peroxymonosulfate by(sunlight)FeCl3-modified biochar for efficient degradation of contaminants of emerging concern: Comparison with H2O2 and effect of microplastics

Coexistence of microplastics (MPs) and biochar (BC) in the removal of contaminants of emerging concern (CECs) from urban wastewater has been rarely investigated in the scientific literature. Accordingly, this study investigated the effects of MPs on the degradation of four target CECs (carbamazepine, diclofenac, sulfamethoxazole and trimethoprim) by iron-modified biochar/peroxymonosulfate (Fe-BC/PMS) system under dark and sunlight. Field emission scanning electron microscopy (FeSEM) analysis showed surface erosion of MPs due to heterogeneous interaction of Fe-BC and MPs, and MPs adsorption on the Fe-BC surface. Experimental results showed that 80 % of total CECs were degraded within 10 min by Fe-BC/PMS under sunlight at Fe-BC and PMS dose of 0.25 g/L and 0.1 mM, respectively. A lower removal of CECs (50 %, 180 min) by sunlight/Fe-BC/PMS treatment was observed in secondary treated urban wastewater. Lower performance of Fe-BC/H2O2 was obtained under the same experimental conditions. Coexistence of Fe-BC with polyvinyl chloride MPs (0.5 g/L and 1.0 g/L) increased CECs degradation efficiency (up to 25 % under sunlight) compared to no MPs condition which could be possibly due to release of dissolved organic carbon (DOC) and production of environmental persistent free radicals (EPFRs), thereby generating additional hydroxyl radicals and sulfate radicals for effective CECs removal. These findings suggested that the potential interactions between MPs and BC should not be undermined when treating urban wastewater.