Highly-efficient photocatalytic disinfection of Escherichia coli under visible light using carbon supported Vanadium Tetrasulfide nanocomposites

Reliable and effective water disinfectants are of paramount importance to address mounting health concerns in drinking water. Herein, Vanadium Tetrasulfide (VS4) nanocomposites supported by different carbon materials, including VS4/CP (carbon powder), VS4/rGO (reduced graphene oxides), VS4/CF (carbon fiber), and VS4/CNT (carbon nanotube), were synthesized, comprehensively characterized, and investigated as photocatalytic disinfectants. Among them, the cost-effective and lattice-structure VS4/CP exhibited the best disinfection performance for removing E. coil (Gram-negative) under both simulated visible light and sunlight, with a maximum inactivation rate of 9.7 log at 0.1 g L-1 in 30 min. However, it was not very effective to eliminate S. aureus (Gram-positive bacteria) with a disinfection rate of 1.7 log inactivation in 30 min. Consistent disinfection performance was confirmed with four successive stability tests and over a wide range of E. coil density (6 log to 9 log CFU ml(-1)). The potential disinfection mechanism was studied on a subcellular level, indicating that membrane damage (via mineralization, lipid peroxidation and collapsed membrane potential) and penetration-induced intracellular damage including DNA degradation and decreased ATP level could be the main inactivation principles. Further photochemical investigation suggested that center dot O-2(-), h(+) and e(-) were crucial active species, and an acidic/neutral environment would favor the photocatalytic disinfection. These results have demonstrated effectiveness and potential applications of the developed VS4/CP nanocomposites in water disinfection.