A self-contained catalytic sponge for point-of-use solar driven persulfate oxidation and photothermal evaporation

Abstract

Persulfate-enabled advanced oxidation processes (PS-AOPs) show great promise in next-generation environmental remediation. This work presents a self-contained catalytic sponge as point-of-use (POU) water purification devices by co-encapsulating zero-valent iron nanoparticles (nZVI) and sodium persulfate (PS) within a polyvinyl alcohol (PVA) aerogel, which turns into a composite hydrogel upon contact with water. The POU device, SP + PVA@PS@Fe, allows solar driven photocatalytic degradation and thermal evaporation for dual functional wastewater treatment. This device is stable for long-term preservation, and when submerged in water, enables direct PS-AOPs without additional introduction of chemical reagents. Results demonstrate the exceptional capability of the sponge in pollutant removal, with degradation rates of methyl orange, tetracycline hydrochlorid, and methylene blue reaching 73 %, 92 %, and 82 % respectively within 2 h and maintaining high efficiencies of 73 %, 91 %, and 80 % after three cycles. The device achieves a maximum evaporation rate of 4.91 kg m h⁻¹ for dual functional solar driven interfacial evaporation. Density functional theory (DFT) calculations indicate that incorporating nZVI can reduce the activation energy barrier for PS, enhancing the generation of reactive species such as SO₄⁻, OH, O₂⁻, and ¹O₂, which synergistically contribute to pollutant degradation. This work innovates the design of self-contained catalytic devices for environmental remediation, expected to advance PS-AOPs toward outdoor and even industrial applications.