Different inactivation behaviors and mechanisms of representative pathogens (Escherichia coli bacteria, human adenoviruses and Bacillus subtilis spores) in g-C3N4-based metal-free visible-light-enabled photocatalytic disinfection

Continuous economic loss and even human death caused by various microbial pathogens in drinking water call for the development of water disinfection systems with the features of environmentally friendly nature, high inactivation efficacy without pathogen regrowth, facile disinfection operation and low energy consumption. Alternatively, g-CN-based visible-light-enabled photocatalytic disinfection can meet the above requirements and thus has attracted increasing interest in recent years. Here, we explored for the first time the antimicrobial ability and mechanisms of a wide spectrum of representative pathogens ranging from bacteria (Escherichia coli), to viruses (human adenoviruses) and spores (Bacillus subtilis spores) by g-CN/Vis system with the assistance of two common oxidants (HO and PMS), especially in a comparative perspective. Pristine g-CN could achieve a complete inactivation of bacteria (5-log) within 150 min, but displayed negligible antimicrobial activity against human viruses and spores (< 0.5-log). Fortunately, simple addition of oxidants into the system could greatly enhance the inactivation of bacteria (5-log with PMS within 120 min) and human viruses (2.6-log with HO within 150 min). Roles of reactive oxygen species were found to be quite different in the disinfection processes, depending on both types of chemical oxidants and microbial pathogens. Additionally, disinfection efficiency could be facilely and effectively improved by statistical optimization of two important operating factors (i.e., catalyst loading and oxidant addition). Selection of added oxidants was determined by not only the target pathogen but also the water matrix. As a proof of concept, this work can provide some meaningful and useful information for advancing the field of green and sustainable water disinfection.