In Situ Synthesis of Z-Scheme AgI/Ag3PO4/SPS Photocatalyst with Enhanced Photocatalytic Activity

Ion exchange resin is used to treat heavy metal ions efficiently in wastewater. However, the disposal of as-used resin is a difficulty. The resin containing Ag+ was transformed into AgI/Ag3PO4/SPS (Sulfonated polystyrene microspheres) photocatalyst by in situ chemical precipitation in this study, which will help as-used resin for the effective regeneration and utilization. Scanning electron microscopy, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy have been used to study the morphology, phase composition and optical absorption properties of the AgI/Ag3PO4/SPS composite. The photocatalytic activity of the AgI/Ag3PO4/SPS composite has been investigated by the degradation of Rhodamine B (RhB) under visible-light irradiation. 99.5% of RhB was degraded within 3 h in the AgI/Ag3PO4/SPS system. Moreover, the photocatalytic activity of AgI/Ag3PO4/SPS remained at 95% after five runs. The evaluation results show that the AgI/Ag3PO4/SPS composite exhibited significantly photocatalytic activity and stability. The enhanced photocatalytic performance of the AgI/Ag3PO4/SPS composite should be attributed to highly effective charge separation through the synergy of AgI and Ag3PO4, and the plasma effect of Ag nanoparticles. Free radical and hole trapping experiments show that ·O2− and h+ are the main active species in the photocatalytic process. Finally, a possible plasmonic mechanism can be proposed for the AgI/Ag3PO4/SPS photocatalytic system.