Electrochemical enhancement of sulfite-induced phosphate release from iron phosphate with concurrent micropollutant degradation in water.

Phosphorus (P) recovery from iron phosphate (FePO4, FP) residues offers a sustainable route for resource reuse but is hindered by strong Fe-P bonding and surface passivation. Here, we propose an electrochemically mediated FP-sulfite (E-FP-S(IV)) system that couples controlled phosphate release with simultaneous micropollutant degradation. Electrochemical stimulation accelerates early-stage P mobilization and sustains long-term release by promoting sulfite activation to SO3•- and its conversion to SO5•-/SO4•-. The electrochemical and radical-mediated process enhanced Fe(II)/Fe(III) redox cycling and suppressed secondary Fe(III) re-adsorption or reprecipitation on the FP surface to promote P release. Under optimal conditions (pH 4.0, [S(IV)] = 2 mM, current = 100 A m⁻2), cumulative phosphate release reached 27.1 μM-2.2 times higher than the FP-S(IV) system-while achieving >90% acetaminophen (APAP) removal. Mechanistic investigations confirmed SO5•- and SO4•- as dominant oxidants, with minimal changes in FP crystallinity, indicating a controlled-release process suitable for direct reuse. This integrated approach addresses two critical challenges in wastewater treatment: phosphorus recovery and micropollutant abatement. The E-FP-S(IV) system demonstrates a scalable, energy-efficient strategy for coupling resource recovery with water purification, offering practical implications for circular water management.