Photocatalytic activation of peroxymonosulfate using ilmenite (FeTiO3) for Enterococcus faecalis inactivation

Abstract

In this work, a raw and low cost mineral, ilmenite (FeTiO3), has been tested for the first time as a photocatalyst paired with peroxymonosulfate (HSO5-; PMS) for the inactivation of Enterococcus faecalis as an alternative to conventional treatments to disinfect wastewater for reuse. The influence of some operational parameters such as reagent dosage, catalyst concentration, initial pH, or flow rate was also studied and optimized. After several tests, the scarce pure photoactivity under UV-A was remarked by ilmenite because of its high iron content, which favors photogenerated charge recombination. However, ilmenite activity was highly promoted when combined with low concentrations of PMS and UV-A light, reaching total inactivation of Enterococcus faecalis in 120 min. Quenching tests were performed using methanol, tert-butyl alcohol, furfuryl alcohol, and Cu(II) to assess the main reactive species involved in the disinfection process determining the critical role of both HO·and SO4·- radicals in the process. Finally, the influence of the water matrix was also evaluated by studying the effect of water hardness and the presence of nutrients on the system. Overall, the PMS/Ilmenite/UV-A system yielded promising results with a total removal of Enterococcus faecalis in 120 min. However, it also showed the need for further study and understanding of the disinfection mechanism to achieve the same level of performance in real wastewater.