| Summary: | The occurrence of bisphenol A (BPA) residues in the environment has become a growing concern as the BPA is extensively used in various product in the market. This BPA is often incompletely eliminated by the conventional wastewater treatment plant and released into the environment mainly through the industrial effluents, posing a serious impact towards humans and the ecosystem. Consequently, an improved method for eliminating BPA needs to be devised. Recently, semiconductor-based photocatalysis has been proven to be an effective treatment method to degrade BPA from surface water. Despite the fact that photocatalysts have become a great alternative, several reports on TiO2/g-C3N4 composites have used different concentrations of g-C3N4 in the composite, which makes it difficult to find the ideal mass ratio of TiO2/g-C3N4 for BPA degradation. It has also been reported that the TiO2/g-C3N4 composites exhibit slow electron mobility, which is due to the inability of TiO2 to generate photogenerated electron-hole pairs when irradiated with visible light. In addition, the use of photocatalysis for wastewater treatment is limited due to the difficulty of recovering the spent photocatalyst once it has been used. Therefore, the main focus of this study was to determine the optimal mass ratio of TiO2 and g-C3N4 and the optimal loading Ag. Then the optimized Ag/N-TiO2/g-C3N4 photocatalyst was utilized as a nanofiller to fabricate a photocatalytic dual layer hollow fiber membrane (DLHFM) for BPA removal in water. Immobilization of Ag/N-TiO2/g-C3N4 photocatalyst into the outer layer of DLHFM matrix would allow the membrane to simultaneously exhibit photocatalytic activity while separating the clean water from the degraded products. The mass ratio of TiO2 and g-C3N4 was manipulated between 2:1 (TGN-0.5), 1:1 (TGN-1), 1:2 (TGN-2), 1:4 (TGN-4), and 1:8 (TGN-8) by a two-step calcination method, and later the optimized binary photocatalyst was modified with different Ag loadings of 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 5 wt.% by the chemically assisted photoreduction method. The X-ray photoelectron spectroscopy analysis showed the presence of TiN peak in N 1s spectra which confirms the successful formation of nitrogen-doped TiO2 using g-C3N4 precursor via two step calcination method. The prepared photocatalysts were tested for their photocatalytic activity under visible light irradiation for the degradation of BPA. It was found that 4 wt.% AgTGN exhibited the best photocatalytic performance for the degradation of BPA in 150 min. 4 wt.% AgTGN was then used as a photocatalyst to produce PVDF DLHFM via dry-wet spinning method with different photocatalyst loading (1 wt.%, 3 wt.% and 5 wt.%) in the outer layer of the membrane. Based on morphological characterization, the middle structure of the photocatalytic DLHFM has a more porous sponge-like structure compared to the pure DLHFM, which could significantly improve the water permeability of the membrane. The photocatalyst with 1 wt.% loading showed the highest flux (13.62 L/m2h) and 92% BPA removal when tested in the submerged membrane photocatalytic reactor. The DLHFM incorporated with Ag/N-TiO2/g-C3N4 holds good promise in the field of wastewater treatment for BPA removal.
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