Highly stable WO3-Ag-AgCl films for continuous water treatment synthesized using a new low-cost ultrasonic spray pyrolysis/photoreduction approach

This study reports on the successful synthesis of WO3-Ag-AgCl films on glass substrates using a simple and cost-effective ultrasonic spray-pyrolysis/photoreduction method, intended for use in continuous flat plate photochemical reactors. A central composite design was used to optimize the amounts of WO3 and AgCl deposited on the substrate. The films synthesized under varying conditions exhibited heterojunctions of WO3 and AgCl, whose photocatalytic efficiency, assessed by the removal of the model contaminant acetaminophen (ACT) under continuous flow, was greatly influenced by the amount of AgCl deposited on the substrate, while that of WO3 had a minimal impact on ACT removal. The film with WO3:AgCl molar ratio of 1.84 showed exceptional stability over 20h of continuous operation, with only a 4% reduction in contaminant removal. Additional tests using a real pharmaceutical effluent spiked with ACT confirmed the high (>92%) ACT removal of this film formulation and its stability; further tests indicated •OH and O2•− as the primary reactive species involved in the photodegradation reaction. Overall, these findings offer promising and cost-effective alternatives for synthesizing highly stable WO3-Ag-AgCl films that are efficient in treating real pharmaceutical effluents containing emerging contaminants using sunlight.