Removal of bisphenol a from water via visible light-driven photocatalytic dual layer hollow fiber membrane

Abstract

In recent years, the level of bisphenol A (BPA) detected in various water sources, foods and beverages has gained media attention. The presence of BPA in the environment is highly potential to contaminate the environment and can cause various adverse affects to human and aquatic life. Photocatalysis in the presence of titanium dioxide (TiO2) is one of the promising options which offer complete degradation of organic contaminants even at low concentrations. However, TiO2 only displays its photocatalytic effect under ultraviolet (UV) light irradiation and is associated with difficulties of recovery after treatment process. Therefore, the present study is conducted to investigate the efficiency of visible light-driven photocatalytic dual layer hollow fiber (DLHF) ultrafiltration (UF) membrane for the removal of BPA from contaminated water and its detrimental effects by using an in-vivo model. Visible light-active (VLA) nitrogen-doping TiO2 (N-doped TiO2) was successfully prepared via simple, energy and cost saving sol-gel method. Then, N-doped TiO2 was further incorporated into DLHF membrane with different N-doped TiO2/ polyvinylidene fluoride (PVDF) weight ratio (0.2, 0.5 and 0.7) via co-extrusion spinning method. The photocatalytic membranes were characterized for their morphology, particles distribution, surface roughness, crytallinity and light absorption spectra. The photocatalytic activity was measured by photocatalytic degradation of BPA in contaminated water under visible and UV light irradiations in comparison with the commercial TiO2. This is followed by investigating the effects of untreated-BPA and treated- BPA water on the tight junction protein. The expressions of Claudin-2, -3 and -4 were measured quantitatively and qualitatively via western blotting (WB), haematoxylin and eosin (H&E) and immunohistochemistry (IHC) staining. Excellent photocatalytic activity with more than 90% of BPA removal was achieved in the presence of N-doped TiO2 DLHF under visible and UV light irradiation. The removal of BPA was 80% higher in comparison with the commercial TiO2. In-vivo study showed that the BPA exposure altered the morphology of finger-like projections of villi and changed expression level of Claudin 2, 3 and 4 proteins in the jejunum and ileum of both pregnant rats and their foetuses. Interestingly, villi and Claudins expressions were undisrupted in treated-BPA water exposed-group. The presence of VLA element in N-doped TiO2 DLHF significantly improved the absorbance capability under visible irradiation, thus increases the photocatalytic degradation activity under visible light irradiation and effectively mitigated the effect on BPA on the ileum and jejunum of gastrointestinal tract. Altogether, successfully fabricated photocatalytic DLHF membrane using co-extrusion method has a promising potential in removing BPA to fulfill the public focus on the safety of water and their need to consume clean water.