Iron-Rich Slag from Lithium Iron Phosphate as an Efficient Heterogeneous Fenton Catalyst for Organic Pollutant Degradation

The fabrication of efficient Fenton catalysts from solid waste offers a sustainable strategy for achieving waste valorization and wastewater remediation. In this work, after selective separation of valuable Li from spent lithium iron phosphate (LFP), the generated iron-rich slag (IRS) was employed as a Fenton catalyst for the degradation of organic pollutants. IRS catalysts consist of lumpy particles with abundant active sites, enabling efficient H2O2 activation. Under optimal conditions, 99.62% of doxorubicin hydrochloride (DOX) can be degraded within 30 min with a rate constant of 0.30 min−1. In the continuous-flow degradation experiment, the catalyst maintains a DOX removal efficiency of over 90% at an effluent volume of 1400 mL. The IRS catalyst exhibits efficient DOX degradation over a wide pH range (2.0–8.0), and it also potentially removes different pollutants, including amodiaquine, tetracycline, methyl orange, and methylene blue. Quenching tests and characterizations reveal the dominant contribution of ·OH radicals as reactive species, while the Fe2+/Fe3+ cycle facilitates continuous H2O2 activation. This work establishes an integrated strategy coupling lithium recovery from spent LFP with catalyst production for advanced wastewater treatment.