Comparative studies of photocatalytic and photoelectrocatalytic inactivation of E. coli in presence of halides

Abstract

The bactericidal performances of photocatalytic and photoelectrocatalytic systems in absence and presence of low concentrations of X− (X=Br, Cl) were quantitatively studied and meaningfully compared under identical experimental conditions. The photoelectrocatalytic system in presence of low concentration of Br− was found to be the most effective bactericidal system amongst all systems investigated, capable of inactivating 100% of 9.0x106CFU/mL Escherichia coli within 1.57s. The photocatalytically generated active oxygen species are important attributes to the bactericidal performance of all cases investigated except the case of photoelectrocatalytic inactivation in presence of Br− for which the bactericidal performance is dominated by the photoelectrocatalytically generated Br−/Br2−. The results revealed that in a photocatalysis or photoelectrocatalysis bactericidal process, X− acts as an electron mediator that does not change its chemical form before and after bactericidal process, and a high bactericidal performance photoelectrocatalytic system can be established with Br− concentration as low as 50μM. The findings of this work confirm that new forms of effective bactericides such as X−/X2− can be generated in situ via a photocatalysis or photoelectrocatalysis process for high performance bactericidal system.Keywords: Biohazards; Disinfection; Br−/Br2−; Photocatalysis; Photoelectrocatalysis