A novel approach for water disinfection by enhanced photoanode oxidation using in-situ generated hydrogen peroxide

Abstract

To improve disinfection efficiency in distributed water treatment systems using clean energy, a novel photoelectrochemical process was adopted. This process couples photoanodic oxidation with in-situ generated H2O2 (PEC/E-H2O2) and was used for the inactivation of Escherichia coli (E. coli) under simulated solar conditions. In a low-concentration 5 mM Na2SO4 electrolyte, the PEC/E-H2O2 process consumed only 2.14 KJ/L-log of energy and eliminated 106 CFU/mL of E. coli within 50 min. The 0.61 mM H2O2 in-situ generated enhanced the oxidation of the photoelectrochemical system due to the formation of •OH. Compared with traditional electrochemically generated H2O2 (E-H2O2) and photoelectrochemical (PEC) processes, the specific rate constant of E. coli inactivated by the PEC/E-H2O2 process increased by 2.19 and 2.11 times, respectively. The mechanism and the contribution of active species to the process were investigated through a series of competition experiments, fluorescence probes, and EPR measurements. It was verified that the generated radicals, especially h+, •OH, and •O2−, played a significant role in bacterial inactivation. Additionally, the electron transfer mechanism of the PEC/E-H2O2 system and the possible inactivation mechanism of E. coli were proposed. SEM comparisons, potassium ion leakage, and the β-GAL activity decreasing of targeted cells indicated the destruction of the inner and outer cellular membranes, thus causing the inactivation of E. coli. In summary, the study provides a promising alternative disinfection process for drinking water treatment.