Enhanced visible-light-driven peroxymonosulfate activation for antibiotic mineralization using electrosynthesized nanostructured bismuth oxyiodides thin films

The search for non-specific catalysts capable of removing a wide range of organic contaminants remains a key challenge given their increasing presence in aquatic environments. In this ongoing exploration, this work proposes the use of bismuth oxyiodides as activators of ecological oxidative radicals, wherein raw substances like peroxymonosulfate (PMS) gain prominence due to the valuable efficiency of the radicals they can generate. For BiOI, serving as a precursor to the photocatalysts, the effect of the electroactive solution components on its electrochemical preparation was analyzed using the voltamperometric technique. The compositional and structural characterization confirmed successful formation. Deposit annealing treatments result in new species such as Bi7O9I3 at 250ºC and, primarily, Bi5O7I at 420 or 520ºC—species that also exhibit visible light absorption, paving the way for their use under sunlight. Initially, a single tetracycline (TC) solution was employed to test the degradation and mineralization capability of the prepared films, assessing the impact of the solution's pH, the presence of PMS, light irradiation, and annealing temperature. The annealing temperature increases the catalytic effect. It is noteworthy that for all bismuth iodide films, the highest catalytic activity was observed when combining PMS and visible light irradiation, showcasing a synergistic improvement. This trend holds for multipollutant solutions as well. In a crucial role for the material's application, the results demonstrate that annealing temperatures below 450ºC promote films that reasonably maintain their activity and chemical stability after continuous reuse. [Display omitted] •BiOI film is formed via electroprecipitation, not classical electrodeposition.•Film morphology shifts from nanoplates to spongy as the potential becomes more negative.•Less iodine and more oxygen in the Bi5O7I structure alter the bandgap, minimizing recombination.•Light boosts peroxymonosulfate (PMS) activation, proving more effective radicals.•Visible light improves tetracycline (TC) degradation and mineralization, activating sulphate radicals.