Inactivation of MS2 coliphage in sewage by solar photocatalysis using metal-doped TiO2

Abstract

The beneficial properties of metal-doped titania nanoparticles with respect to wastewater disinfection under solar irradiation were investigated. Mn-, Co- and binary Mn/Co-doped TiO2 catalysts were prepared by means of a co-precipitation method and were subsequently assessed in terms of their potential to inactivate MS2 bacteriophage in slurry reactor under simulated and natural solar irradiation. Disinfection effectiveness was evaluated in relation to influential operating parameters, like catalyst type (Mn-, Co- and Mn/Co), dopant concentration (0.02–1molwt%), artificial and natural solar light, wavelength (i.e. >420nm) and photon flux (4.93–5.8×10−7E/(Ls)). Metal doping led to considerable narrowing of the band gap and the spectral response of the catalysts extended well into the visible region. MS2 phage was readily inactivated in sewage samples under simulated solar irradiation in the presence of the prepared metal-doped catalysts. The latter proved to be superior to the commercial P25, under the current experimental conditions, resulting in an approximately 60% phage population decrease in almost 60min of simulated solar irradiation when initial MS2 concentration was 105PFU/mL. Catalysts with the binary dopant exhibited the best photocatalytic activity in all cases, as almost 99% of MS2 population was eliminated in less than 20min of irradiation highlighting the fact that composite dopants induce a synergistic effect. The effect of different dopants concentration was apparent up to a certain limit. Disinfection follows a pseudo-first order kinetic rate. Retardation of the process by a factor 1.6–3.8 was recorded under natural solar light, based on the kinetic rate constants of inactivation curves which were within the range of 0.032–0.057min−1. The corresponding range for inactivation under simulated solar irradiation was 0.053–0.221min−1. Moreover, testing the Mn-, Co-, and binary Mn/Co doped TiO2 in the absence of UV light, they were considerably sensitized making clear that they can be activated in the visible part of the spectrum.