Efficient photocatalytic disinfection of Escherichia coli by N-doped TiO2 coated on coal fly ash cenospheres

Abstract

In this study, N-doped TiO2 (TiON) coated coal fly ash cenospheres (CFACs) was synthesized for photocatalytic disinfection against Escherichia coli (E. coli). Based on the physi-chemical evaluation of the TiON coated CFACs (TiON-CFACs), the disinfection efficiencies of E. coli under three different light sources, namely, ultraviolet A (UVA), visible light (VL), and the light emitting diodes with a wavelength of 420 nm (LED-420), were investigated. Then, a three-factor, four-level orthogonal experiment was designed to evaluate the influences of dosage, pH, and light intensity on its disinfection efficiency. The TiON-CFACs were effective under UVA, LED-420, and VL irradiation, with disinfection efficiencies of 5.78 log (45 min UVA), 5.84 log (180 min LED-420) and 5.97 log (300 min VL), respectively. The optimal disinfection efficiency was achieved at an initial pH of 6 under LED-420 irradiation at 40 mW/cm2 with a dosage of 4 g/L TiON-CFACs. The mechanism of disinfection was further investigated using a range of free radical scavengers. Findings indicated that H2O2 appeared to play an indispensable role in E. coli disinfection. Moreover, the TiON-CFACs showed a stable disinfection efficiency of 5 log, even when the substance was recycled for four times, indicating the reliability and stability of the material. The results showed that the TiON-CFACs are promising in water treatment for photocatalytic disinfection of E. coli.