Visible-light-driven photocatalytic disinfection by S-scheme alpha-Fe2O3/g-C3N4 heterojunction: Bactericidal performance and mechanism insight

High-performance photocatalytic applications require to develop heterostructures between two semiconductors with matched band energy levels to facilitate charge-carrier separation. The S-scheme photocatalytic system has great potential to be explored, in terms of the improvement of charge separation, however, small efforts have been made in photocatalytic disinfection application. In this study, a non-toxic and low-cost S-scheme photocatalytic system composed of alpha-Fe2O3 and g-C3N4 was fabricated by in-suit production of g-C3N4 and firstly applied into water disinfection. The alpha-Fe2O3/g-C3N4 junction demonstrated an enhanced activity for photocatalytic bacterial inactivation, with the complete inactivation of 7 log10 cfu.mL(-1) of Escherichia coli K-12 cells within 120 min under visible light irradiation. Its logarithmic bacterial inactivation efficiency was nearly 7 times better than that of single g-C3N4. The experimental results suggested that the effective prevention of charge-carrier recombination led to an improved generation of reactive oxygen species (ROSs), resulting in impressive disinfection performance. Moreover, the DNA gel electrophoresis experiments validated the reason for the irreversible death of bacteria, which was the leakage and destruction of chromosomal DNA. In addition, this S-scheme heterojunction also showed excellent photocatalytic disinfection performance in authentic water matrices (including tap water, secondary treated sewage effluent, and surface water) under visible light irradiation. Hence, the alpha-Fe2O3/g-C3N4 composite has great potential for sustainable and efficient photocatalytic disinfection applications.