Synergistic photothermal/photocatalytic activation of peroxymonosulfate using $SrFe_{12}O_{19}$@Ni-P core@shell microparticles for energy efficient water remediation

Abstract

The urgent need for more efficient water remediation systems requires the development of new low cost and low energy strategies to remove persistent organic pollutants. This work investigates the activation of peroxymonosulfate (PMS) using Ni-P-coated SrFe12O19 (SFO@Ni-P) microparticles under thermal, photothermal and photocatalytic conditions by either conventional heating or near-infrared (NIR; 915 nm) or blue (450 nm) light activation. The synergistic photothermal/photocatalytic activation using blue light (i.e., above the SFO bandgap) outperformed conventional thermal treatments or photothermal NIR activation, enhancing the PMS decomposition at moderate temperatures. The outstanding performance of SFO@Ni-P was due the combination of Ni2+/Ni3+ redox cycling and the highly damped plasmonic behavior or the Ni-P shell, and the photothermal/photocatalytic activation offered by the semiconducting SFO core, leading to >99.9% degradation and 99.9–100.0% mineralization of tetracycline after 90 min under blue-light (combined photothermal/photocatalytic) activation. Moreover, the dual photothermal/photocatalytic effects under blue light enabled up to 87.4% mineralization of a 120 ppm multi-pollutant mixture in 90 min, with markedly lower electrical energy per order (EE/O) (≈4-fold) than conventional thermal activation. The catalysts maintained high activity over multiple cycles with negligible metal leaching. Remarkably, under sunlight the catalyst achieved nearly complete multi-pollutant mineralization (≈99%) within 40 min without external electrical input for heating/irradiation (excluding ancillary power). Importantly, seed germination/root elongation assays confirmed strong detoxification of the treated effluents (GI > 80%). These findings highlight the potential of SFO@Ni-P microparticles for efficient, reusable, and low-energy advanced oxidation processes, and solar-compatible wastewater treatment applications.