Solar photocatalysis: A green technology for E. coli contaminated water disinfection. Effect of concentration and different types of suspended catalyst

• A positive effect of the solar heating on bacteria inactivation was observed.
• E. coli solar inactivation is enhanced by the presence of photocatalysts.
• More absorption of solar light of Rutile and Bi2WO6 do not induced higher efficiency.
• Optimal concentration of Rutile is lower than this one of the other photocatalysts.
• Formation of NH4+ and release of K+ during solar photocatalytic desinfection.

Photocatalytic and photolytic disinfection of Escherichia coli in water was studied under natural sunlight using different types of photocatalyst (TiO2 P-25, PC500, Ruana and Bi2WO6) at different concentrations.The solar photo-inactivation yielded complete inactivation results, which varied with the solar light intensity. Meanwhile, dark control samples in the lab (temperature constant at 25 °C) remained at constant concentration and dark samples outside laboratory showed a decrease due to the mild solar heating occurred during the experiments.The adding of any kind of photo-catalyst to the water accelerated the bactericidal action of solar irradiation and led to complete disinfection (until detection limit). The photocatalytic disinfection efficiency was not enhanced by the increase of catalyst concentration above 0.5 g/L for P-25, PC500 and Bi2WO6, where about 106 CFU/mL were completely inactivated within 5 min, 30 min and more than 150 min of solar exposure under clear sky, respectively. An increase of the concentration to 1 g/L slightly decreased the total inactivation time. Rutile (Ruana) catalyst behaves differently, optimal concentration was lower than for the other titania materials; agglomeration of particles occurred as the concentration of catalyst increases. Durability of photocatalytic treatment and chemicals analyses of inorganic anions and cations have also been investigated.

Effect of the natural solar UV intensity on E. coli inactivation as a function of Local time. C0 ∼106 CFU/mL. Open symbols are dark controls. DL is the detection limit for the experiments; 4 CFU/mL.Figure optionsDownload as PowerPoint slide