Immobilization of solar light-active photocatalyst Cr-TiO2 into the polyurethane/polycaprolactone electrospun membrane for the photocatalytic oxidation of Acid Orange 7

Abstract

The considerable presence of organic pollutants, such as Acid Orange 7 (AO7) dye, in wastewater poses significant environmental challenges, necessitating the development of efficient and sustainable purification methods. In this study, we investigated the use of photocatalytic polymeric membranes (PPMs) based on the use of polyurethane (PU)/polycaprolactone (PCL) for the oxidation of AO7 under solar light irradiation on a sol-gel chromium-doped TiO₂ visible active photocatalyst. Our objective was to realize a directly separable and easily recyclable photocatalyst. The photocatalyst was embedded into PU/PCL fibres via electrospinning, with catalyst loadings of 5 %, 10 %, and 20 % (w/w). The good dispersion of the photocatalyst within the fibrous membrane was evidenced by SEM-EDX, Raman, UV–Vis DRS, TGA-DTG and SSA measurements. The effect of catalyst load, pH of the solution, and initial concentration of dye was examined in AO7 photooxidation. Photocatalytic efficiency markedly increases up to 20 % w/w. The greater photocatalytic activity was recorded by treating the solution with 5 ppm of dye and pH = 2, leading to a conversion of 99 % after 3 h. A statistical approach was used to model the AO7 photodegradation by adopting a polynomial equation while scavenger studies suggested a photocatalytic mechanism primarily driven by hydroxyl, hydroperoxyl and superoxide radicals. Additionally, a comparison of the electrical energy consumption (EE/O) under the optimal operating demonstrates a substantial reduction in EE/O with the application of electrospun composite. This result highlights the superior energy efficiency of the easily recoverable photocatalytic system implemented in this work. These findings underscore the potential of PPMs as a sustainable technology for self-cleaning applications within hybrid wastewater treatment systems and underline the valuable role of electrospinning in the development of efficient, solar-active photocatalytic processes.