Synthesis of highly crystalline BiOI thin films for the photocatalytic removal of antibiotics in tap water and secondary effluents: Assessing the potential hazard of treated water

Abstract

Pursuing sustainability in heterogeneous photocatalysis for water purification , this study focused on optimizing an eco-friendly method for obtaining BiOI thin films to degrade ciprofloxacin (CIP) and oxytetracycline (OTC) in water under visible light irradiation. The BiOI thin films were synthesized on glass substrates using the SILAR method, with water as the only solvent and relatively harmless precursors. The crystallinity was improved by overdosing KI, achieving the best morphology with a Bi:I ratio of 1:10 (1:10BiOI). The 1:10BiOI material reached 22 % degradation of CIP and 73 % for OTC, in pure water after 300 min, while mineralization rates were of 6.6 % for CIP and 51 % for OTC. Quenching tests showed that the degradation mechanism is driven by different reactive species: • OH and • O 2 - radicals for CIP and photo-holes for OTC. Activity slightly decreased for CIP in tap water and secondary effluent, while for OTC the opposite effect was observed, attributed to matrix components. Testing 1:10BiOI films over 5 cycles in tap water showed a slight decline in the catalytic conversion for CIP and a more evident decline for OTC. Stable degradation byproducts were determined by HPLC-MS/MS and their potential hazards were evaluated in silico using the ECOSAR program.