A novel P/Ag/Ag2O/Ag3PO4/TiO2 composite film for water purification and antibacterial application under solar light irradiation

Abstract

TiO₂-based thin films have been intensively studied in recent years to develop efficient photocatalyst films to degrade refractory organics and inactivate bacteria for wastewater treatment. In the present work, P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films on the inner-surface of glass tube were successfully prepared via sol-gel approach. P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films with 3 coating layers, synthesized at 400°C for 2h, showed the optimal photocatalytic performance for rhodamine B (Rh B) degradation. The results indicated that degradation ratio of Rh B by P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite film reached 99.9% after 60min under simulated solar light, while just 67.9% of Rh B was degraded by pure TiO₂ film. Moreover, repeatability experiments indicated that even after five recycling runs, the photodegradation ratio of Rh B over composite film maintained at 99.9%, demonstrating its high stability. Photocatalytic inactivation of E. coli with initial concentration of 10⁷CFU/mL also showed around 100% of sterilization ratio under simulated solar light irradiation in 5min by the composite film. The radical trapping experiments implied that the major active species of P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films were photo-generated holes and O₂^- radicals. The proposed photocatalytic mechanism shows that the transfer of photo-induced electrons and holes may reduce the recombination efficiency of electron-hole pairs and potential photodecomposition of composite film, resulting in enhanced photocatalytic ability of P/Ag/Ag₂O/Ag₃PO₄/TiO₂ composite films.

Keywords: Bacterial inactivation; P/Ag/Ag(2)O/Ag(3)PO(4)/TiO(2) composite film; Photocatalytic mechanism; Rh B photodegradation; Simulated solar light irradiation.