Photocatalytic disinfection of wastewater using peroxymonosulfate activated by pyrite, chalcopyrite and marcasite under solar irradiation

Resumen

This study investigates the photocatalytic potential of three natural iron-based minerals: pyrite, marcasite, and chalcopyrite for the inactivation of Enterococcus faecalis in simulated and real wastewater. Pyrite and marcasite (0.5 g/L) achieved complete bacterial inactivation within 90 and 30 min, respectively, while chalcopyrite only reached a 2.06 log10 reduction value (LRV) under the same conditions. The introduction of peroxymonosulfate (PMS) as an oxidant significantly improved disinfection kinetics, allowing a halving of the required mineral dosage. PMS activation by Fe2+ on mineral surfaces under solar irradiation generated highly reactive radicals (SO4 center dot-, center dot OH, and O2 center dot-), enhancing the overall oxidative capacity. Under optimized conditions (PMS/Pyrite/Solar and PMS/Marcasite/Solar), simultaneous removal of E. faecalis and tetracycline (TC) was demonstrated. TC removal efficiencies reached 98.99 and 88.90 % within 30 min, while complete bacterial inactivation occurred in 120 and 90 min, respectively. pH played a crucial role in system performance, since disinfection efficiency decreased at higher pH levels, though this effect was less severe in the pyrite-based system. The natural catalysts also showed a degree of pH self-regulation, reducing the need for chemical adjustment beneficial for practical deployment. Validation in real wastewater from a treatment plant near Madrid confirmed the systems' applicability, especially the PMS/Marcasite/Solar setup, which achieved full E. faecalis inactivation within 60 min along with a notable COD reduction. These results highlight the potential of solar-driven PMS activation using natural minerals for efficient, sustainable and low-cost wastewater disinfection.