Airbrush-sprayed TiO2 layers for the photocatalytic degradation of endocrine disruptors: Performance, stability and applicability

Abstract

Heterogeneous TiO₂ photocatalysis is an efficient process to be added after standard wastewater treatment to ensure the complete removal of endocrine disruptors, toxic to humans and animals. To address the challenges of industrial-scale operation, an airbrush spraying immobilization method was developed, which provided layers with high stability, reusability, and repeatability. On these layers, an over 50 % conversion after 5 h was achieved for two structurally differing endocrine disrupting chemicals under standardized conditions. The experimental conditions were further optimized; for TiO₂ areal density above 0.8 mg cm⁻², the photocatalytic activity was independent on the used thickness range and proportional to the layer area. The optimization enabled 70 % conversion of 17α-ethinylestradiol after 5 h even when greywater was used as a matrix, with theoretical complete conversion within 24 h. Based on concentrations of identified transformation products of 17α-ethinylestradiol under different experimental conditions, an alternative to the dominant reaction mechanism is proposed.