Fe3O4 supported on water chestnut-derived biochar toward peroxymonosulfate activation for urea degradation: the key role of sulfate radical

Abstract A new type of iron-doped and porous biochar (Fe@BC) derived from a graphitized structure was systematically investigated to catalyze the organic pollutants degradation by peroxymonosulfate (PMS). In addition to Fe3O4, carbon defects also contributed to PMS activation. The effectiveness of this novel material was tested by treating excessive urea concentrations in swimming pool water. It exhibited good PMS activation capacity, achieving urea removal of 100% within 15 min. The Fe@BC/PMS system exhibited excellent resistance to common anions. Only chloride ( k Cl - / SO 4 Â · - = 3.1×108 M-1s-1) showed a small inhibitory effect, and the removal efficiency of urea decreased by 10% ([Cl−]0 = 10 mM). Quenching experiments and electron paramagnetic resonance spectroscopy analyses demonstrated that urea degradation was mainly mediated by the radical pathway, which in turn was dominated by surface-bound sulfate radicals (SO4•−). Further, reusability experiments confirmed the stability of the material. After three cycles, the degradation efficiency can still reach 86%. Therefore, the conversion of water chestnut-derived biochar into a composite catalytic material provides a novel strategy for value-added utilization of aquatic waste biomass, and it is also a promising alternative for the treatment of urea from swimming pool water.