Water-borne virus pollution has caused great harm and attracted widespread attention in many countries. Visible-light-driven photocatalysis is considered as a promising process for disinfection. In this study, Ag₃PO₄/g-C₃N₄ (AgCN) composites were synthesized by hydrothermal method. The photocatalytic disinfection was investigated using bacteriophage f2 as the model virus. Moreover, the effects of pH and humic acid on photocatalytic disinfection were studied. Meanwhile, the mechanism of enhanced disinfection by Ag₃PO₄/g-C₃N₄ was systematically investigated by radical scavenger experiments. The results show that Ag₃PO₄ particles were uniformly distributed on g-C₃N₄ sheets. By means of photoluminescence spectrometer analysis, it is confirmed that a lower carrier recombination rate for Ag₃PO₄/g-C₃N₄ was achieved compared with Ag₃PO₃ and g-C₃N₄. Meanwhile, complete inactivation of f2 with concentration of 3 × 10⁶ PFU/mL was reached within 80 min in the presence of Ag₃PO₄/g-C₃N₄ composite. The pH had little effect on removal efficiency overall, while the existence of humic acid resulted in a significant negative effect on the inactivation of f2 due to the optical shielding and absorption of humic acid. Recycling tests of Ag₃PO₄/g-C₃N₄ confirmed that Ag₃PO₄/g-C₃N₄ presented superior stability. The results from radical scavenger experiments indicated that holes (h⁺) and hydroxyl radicals (·OH) played important roles in photocatalytic disinfection process.

In the actual water environment, the health risk of waterborne viruses is evaluated to be 10¹–10⁴ times higher at a similar level of exposure compared with bacteria and has aroused strong concern in many countries in the world. Photocatalytic membrane reactor (PMR), a new process for virus inactivation in water, has gradually become one of the main tools to inactivate pathogenic organisms in water. However, there is relatively little attention to the effect of natural organic matters (NOMs) on the PMR system, which actually exists in the water environment. In this paper, the TiO₂-P25, a common type in sales and marketing, was selected as the photocatalyst, and humic acid was regarded as the representative substance of NOMs for investigating thoroughly the influence of humic acid on virus removal by the PMR system. It was found that competitive adsorption between the virus and humic acid occurred, which markedly reduced the amount of virus adsorbed on the surface of the photocatalyst. Moreover, with humic acid, the direct contact behavior between the virus and the photocatalyst was blocked to some extent, and the disinfection of phage f2 by the active free radicals produced by photocatalysis was furthermore badly affected. Meanwhile, the special structure of humic acid, which made humic acid be able to absorb light of 270–500 nm, led to the reduction of photocatalytic efficiency. Further experiments showed that when there was a certain concentration of humic acid in water, intermittent operation mode or higher membrane flux (>40 L/(m²·h)) was selected to partly alleviate the adverse effects of humic acid.