Abstract
The growing interest in mixed matrix membranes (MMMs) for developing photocatalytic membranes has provided a new direction in the search for efficient methods to concurrently separate and degrade contaminants. In this study, a visible light-responsive photocatalyst was blended into a polyvinylidene fluoride (PVDF) membrane casting solution to prepare PVDF-ZnO/Ag2CO3/Ag2O MMMs using the wet phase inversion method. The potential of ZnO/Ag2CO3/Ag2O as a photocatalytic component that is incorporated into the membrane was explored in detail under various loadings (0.5–2.91 wt%). The membranes were tested under ibuprofen (IBF) aqueous solution to analyze the membrane behavior in the synergistic combination of membrane filtration and photodegradation. The resulting PVDF-ZnO/Ag2CO3/Ag2O membrane with a rougher membrane surface area and excellent light harvesting capability showed higher photocatalytic filtration activity in removing IBF under visible light irradiations. The MMM fluxes demonstrated higher IBF fluxes than their initial fluxes at certain durations. This indicates that the membrane actively responds to light irradiation. The increase in the positive flux could be attributed to the photoinduced hydrophilicity generated by the ZnO/Ag2CO3/Ag2O photocatalyst, resulting in easier water layer formation and rapid transport through membranes. The highest IBF removal was demonstrated by the PVDF-ZAA2 membrane (1.96 wt% loading), with 49.96% of IBF removal within 180 min upon visible light irradiation. The reason for this lower IBF removal is that the UF membrane pores exceed the size of IBF molecules, thereby preventing the size exclusion mechanism. Thus, charge repulsion, hydrophobic adsorption, and photocatalytic activity were considered along with the IBF removal of the photocatalytic membranes. However, the recyclability of the PVDF-ZAA2 photocatalytic membrane showed a great improvement, with 99.01% of IBF removal recovery after three cycles. These results highlight the potential of such hybrid membranes in mitigating membrane fouling by providing a platform for photocatalysts to continuously degrade pollutants present in such wastewaters. Therefore, the hybridization of a photocatalyst and membrane provides insight that could be utilized to improve and retrofit current water effluent treatment methods.
Highlights
In recent decades, emerging contaminants found in aqueous streams, such as hormones, pesticides, pharmaceuticals, and personal care products, have received widespread public attention because of their adverse effects on human health, plants, soils, and aquatic systems [1,2]
ZnO/Ag2CO3/Ag2O was successfully incorporated into the polyvinylidene fluoride (PVDF) membrane for advanced membrane antifouling and photocatalytic water purification
Water contact angle measurements showed that the matrix membranes (MMMs) had a lower water contact angle, which implies improved membrane hydrophilicity
Summary
In recent decades, emerging contaminants found in aqueous streams, such as hormones, pesticides, pharmaceuticals, and personal care products, have received widespread public attention because of their adverse effects on human health, plants, soils, and aquatic systems [1,2]. A number of studies have demonstrated the persistence of their toxicological effects, even at low concentrations of nanograms per liter; these contaminants become more complex when they are mixed [3,4]. The compounds in this class are mostly found in prescription medicines, over-the-counter therapeutic drugs, cosmetics, plastic additives, and other industrial products [5]. The water must, be treated several times in order to remove IBF and its derivatives before it is discharged, for example, by introducing a membrane technology at the polishing stage
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