Photolysis and TiO(2)Photocatalytic Treatment under UVC/VUV Irradiation for Simultaneous Degradation of Pesticides and Microorganisms

Abstract

Efficiencies of various treatments for UVC photolysis (ultraviolet light-C at 254 nm), VUV photolysis (vacuum ultraviolet light at 254 nm and 185 nm), UVC-assisted titanium dioxide photocatalysis (UVC-TiO2), and VUV-assisted titanium dioxide photocatalysis (VUV-TiO2) were investigated for the degradation of pesticides including pyraclostrobin, boscalid, fludioxonil, and azoxystrobin and inactivation of microorganismsEscherichia coliK12 as a surrogate forE. coliO157:H7 andSaccharomyces cerevisiaein aqueous solutions and on the surface of fresh cut carrots. The degradation efficiencies of VUV were higher than for UVC on pesticides in aqueous solutions. However, there was no significant difference between degradation efficiencies for UVC and UVC-TiO(2)treatments, and between VUV and VUV-TiO(2)treatments. UVC, VUV, UVC-TiO2, and VUV-TiO(2)showed similar inactivation effects againstE. coliK12 andS. cerevisiaein aqueous solutions. The combined use of UVC and VUV treatments (combined UV) and combined use of UVC-TiO(2)and VUV-TiO(2)treatments (combined UV-TiO2) showed higher efficiencies (72-94% removal) for the removal of residual pesticides on fresh cut carrots than bubble water washing (53-73% removal). However, there was no significant difference in removal efficiency between combined UV and combined UV-TiO(2)treatments. ForE. coliK12 andS. cerevisiaeon fresh cut carrots, the combined UV-TiO(2)treatment (1.5 log and 1.6 log reduction, respectively) showed slightly higher inactivation effects than combined UV (1.3 log and 1.2 log reduction, respectively). Photolysis and TiO(2)photocatalytic treatments under UV irradiation, including VUV as a light source, showed potential for the simultaneous degradation of pesticides and microorganisms as a non-chemical and residue-free technique for surface disinfection of fresh produce.