Virus removal and inactivation by iron (hydr)oxide-mediated Fenton-like processes under sunlight and in the dark

Advanced oxidation processes (AOPs) have emerged as a promising alternative to conventional disinfection methods to control microbial water quality, yet little is known about the fate of viruses in AOPs. In this study, we investigated the fate of MS2 coliphage in AOPs that rely on heterogeneous Fenton-like processes catalyzed by iron (hydr)oxide particles. Both physical removal of viruses from solution via adsorption onto particles as well as true inactivation were considered. Virus fate was studied in batch reactors at circumneutral pH, containing 200 mg L(-1) of four different commercial iron (hydr)oxide particles of similar mesh sizes: hematite (α-Fe2O3), goethite (α-FeOOH), magnetite (Fe3O4) and amorphous iron(iii) hydroxide (Fe(OH)3). The effect of adsorption and sunlight exposure on the survival of MS2 was considered. On a mass basis, all particles exhibited a similar virus adsorption capacity, whereas the rate of adsorption followed the order FeOOH > Fe2O3 > Fe3O4 ≈ Fe(OH)3. This adsorption behavior could not be explained by electrostatic considerations; instead, adsorption must be governed by other factors, such as hydrophobic interactions or van der Waals forces. Adsorption to three of the particles investigated (α-FeOOH, Fe3O4, Fe(OH)3) caused virus inactivation of 7%, 22%, and 14%, respectively. Exposure of particle-adsorbed viruses to sunlight and H2O2 resulted in efficient additional inactivation, whereas inactivation was negligible for suspended viruses. The observed first-order inactivation rate constants were 6.6 × 10(-2), 8.7 × 10(-2), 0.55 and 1.5 min(-1) for α-FeOOH, α-Fe2O3, Fe3O4 and Fe(OH)3 respectively. In the absence of sunlight or H2O2, no inactivation was observed beyond that caused by adsorption alone, except for Fe3O4, which caused virus inactivation via a dark Fenton-like process. Overall our results demonstrate that heterogeneous Fenton-like processes can both physically remove viruses from water as well as inactivate them via adsorption and via a particle-mediated (photo-)Fenton-like process.