An innovative AgI/MIL-100(Fe) Z-scheme heterojunction for simultaneously enhanced photoreduction of Cr(VI) and antibacterial activity

Designing photocatalysts with excellent photocatalytic performance and strong redox properties is a challenging task. In this study, a novel Z-scheme heterojunction AgI/MIL-100 nanocomposite with retaining redox properties was successfully fabricated by a simple precipitation method. According to the experimental results, the Z-scheme heterostructure can significantly improve the charge transfer efficiency between interfaces of heterojunction. In addition, it could generate reactive oxygen species (ROS) and had excellent photocatalytic effects on E. coli and S. aureus inactivation and Cr(VI) reduction. Furthermore, the ROS enhancement process was further confirmed by nitroblue tetrazolium (NBT) and terephthalic acid (TA) conversion experiments. When the mass ratio of AgI to MIL-100(Fe) was 1:10 (named AM-10), it displayed optimal photocatalytic activity toward Cr(VI) reduction. The Cr(VI) could be completely reduced within 75 min under LED light irradiation. The reduction rate of Cr(VI) by AM-10 was 15.3-fold and 2.6-fold of that by AgI and MIL-100(Fe), respectively. Moreover, after 5 cycles of Cr(VI) reduction, it could still achieve good stability. Furthermore, it could completely kill E. coli and S. aureus at 107 CFU/mL within 45 min. Capture experiments confirmed that the main antibacterial active species were h+ and O2-. Therefore, this study can provide an environmentally friendly photocatalytic process using Z-scheme heterojunction nanocomposites with dual purification functions.