Spent rather than pristine LiFePO4 cathode materials can catalytically activate sulfite for organic pollutants decontamination

Abstract

Lab-prepared Fe-bearing materials have demonstrated their ability to activate sulfite (S(IV)) to generate reactive radicals, which is however limited by their costs and inefficiencies for practical application. Here we report that spent LiFePO4 (SLFP) cathode materials can function as a robust catalyst for S(IV) activation and consequent decontamination of organic pollutants like 4,4′-sulfonyldiphenol (BPS). Unexpectedly, SLFP materials with lithium defects and oxygen vacancies (Ov) are significantly effective than pristine LiFePO4. BPS degradation undergoes an induction period when rapid adsorption of O2 and HSO3− in water occurs, followed by a slow release of HSO5−, as evidenced by the same depletion trends of BPS and sulfite, and confirmed by theoretical calculations. The HSO5− is activated by Fe(II) on the SLFP surface, with •OH being the main reactive species via a multi-step reaction. The potential environmental application of this SLFP/S(IV) process are evaluated ultimately.