N-doped TiO2 photocatalysts for bacterial inactivation in water

BACKGROUNDThe elimination of diverse and pathogenic microbial loads in water imposes the exploration of effective disinfection techniques. The current study focused on the synthesis of N-TiO2 photocatalysts and the investigation of their disinfection potential, in terms of Escherichia coli, Pseudomonas aeruginosa and Bacillus cereus inactivation in aqueous samples under artificial sunlight. RESULTSN-TiO2 photocatalysts were synthesized using various nitrogen precursors [urea, triethylamine-(TEA) and NH3], exhibiting narrow band gaps and improved visible light response. The relative bactericidal activity of the catalysts followed the order N-TiO2 (UREA)>N-TiO2 (NH3)approximate to N-TiO2 (TEA)>synthesized TiO2>TiO2-P25. The Gram-negative indicators E.coli and P.aeruginosa, were readily inactivated, reaching reduction rates up to 6 log(10) within 60min of treatment at an initial bacterial concentration of 10(6)CFUmL(-1) and a catalyst concentration of 50mgL(-1). The activity discrepancies among the catalysts were more pronounced in the case of B.cereus, which showed higher resistance, thus exhibiting slower inactivation rates. Complete elimination was achieved only with N-TiO2 (TEA) within 60min of irradiation at a loading of 100mgL(-1). Increasing the TEA concentration for the preparation of this catalyst from 25 to 89v/v% did not enhance significantly the process. Operating conditions, including catalyst concentration, nitrogen precursor and, especially, bacterial species defined the disinfection efficiency up to a certain extent. CONCLUSIONSolar photocatalysis with N-TiO2 catalysts may be an effective disinfection technology if the operational conditions are established in relation to the microbial content in water, which includes opportunistic pathogens such as P.aeruginosa and B.cereus. (c) 2018 Society of Chemical Industry