Small concentrations, big results: μM addition of photoactive iron oxides with PMS, PDS, or H2O2, leads to enhanced removal of viruses at near-neutral pH

The photo-Fenton process is effective for pathogen removal, and its low-cost versions can be applied in resourcepoor contexts. Herein, a photo-Fenton-like system was proposed using low concentrations of iron oxides (hematite and magnetite) and persulfates (peroxymonosulfate – PMS, and peroxydisulfate - PDS), which exhibited excellent inactivation performance towards MS2 bacteriophages. In the presence of bacteria, MS2 inactivation was inhibited in H2O2 and PDS systems but promoted in PMS-involved systems. The inactivation efficacy of all the proposed systems for mixed bacteria and viruses was greater than that of the sole bacteria, showing potential practical applications. The inactivation performance of humic acid-incorporated iron oxides mediating photo-Fenton-like processes was also studied; except for the PMS-involved system, the inactivation efficacy of the H2O2- and PDS-involved systems was inhibited, but the PDS-involved system was still acceptable (< 2 h). Reactive species exploration experiments indicated that ⋅OH was the main radical in the H2O2 and PDS systems, whereas 1O2 played a key role in the PMS-involved system. In summary, hematite- and magnetite-mediated persulfate-assisted photo-Fenton-like systems at low concentrations can be used as alternatives to the photo-Fenton process for virus inactivation in sunny areas, providing more possibilities for point-of-use drinking water treatment in developing countries.