Enhancing the performance of polymeric membranes by nanomaterials has become of great interest in the field of membrane technology. The present work aimed to fabricate polyvinylidene fluoride (PVDF)-hybrid nanocomposite membranes and modify them with TiO₂ and/or BiVO₄ nanoparticles and/or carbon nanotubes (CNTs) in various ratios. Their photocatalytic performance under visible light was also investigated. All modified PVDF membranes exhibited higher hydrophilicity (lower contact angle of water droplets) than that of the neat membrane used as a reference. The membranes were characterized by using bovine serum albumin (BSA) as model dairy wastewater. The hybrid membranes had better antifouling properties as they had lower irreversible filtration resistance than that of the neat membrane. Hybrid PVDF membranes containing TiO₂/CNT/BiVO₄ showed the highest flux and lowest irreversible resistance during the filtration of the BSA solution. PVDF-TiO₂/BiVO₄ had the highest flux recovery ratio under visible light (70% for the PVDF mixed with 0.5% TiO₂ and 0.5% BiVO₄). The hydrophilicity of membrane surfaces increased with the incorporation of nanoparticles, preventing BSA to bind to the surface. This resulted in a slight decrease in BSA and chemical oxygen demand rejections, which were still above 97% in all cases.

Membrane filtration is an effective technique for separating micro- and nano-sized oil droplets from harmful oil-contaminated waters produced by numerous industrial activities. However, significant flux reduction discourages the extensive application of this technology; therefore, developing antifouling membranes is necessary. For this purpose, various titanium dioxide/carbon nanotube (TiO₂/CNT) nanocomposites (containing 1, 2, and 5 wt.% multi-walled CNTs) were used for the modification of polyvinylidene fluoride (PVDF) ultrafilter (250 kDa) membrane surfaces. The effects of surface modifications were compared in relation to the flux, the filtration resistance, the flux recovery ratio, and the purification efficiency. TiO₂/CNT_2% composite modification reduced both irreversible and total filtration resistances the most during the filtration of 100 ppm oil emulsions. The fluxes were approximately 4–7 times higher compared to the unmodified PVDF membrane, depending on the used transmembrane pressure (510, 900, and 1340 L/m²h fluxes were measured at 0.1, 0.2, and 0.3 MPa pressures, respectively). Moreover, the flux recovery ratio (up to 68%) and the purification efficiency (95.1–99.8%) were also significantly higher because of the surface modification, and the beneficial effects were more dominant at higher transmembrane pressures. TiO₂/CNT_2% nanocomposites are promising to be applied to modify membranes used for oil–water separation and achieve outstanding flux, cleanability, and purification efficiency.

In the present study, a commercial TiO₂, several BiVO₄ photocatalysts, a WO₃ nanomaterial, and their composites were used to prepare photocatalytic polyvinylidene fluoride (PVDF) ultrafilter membranes. Their photocatalytic activities and the effects of coatings on the filtration of oil‐in‐water emulsion (crude oil; c_oil = 100 mg L⁻¹) were investigated. Fluxes, filtration resistances, purification efficiencies, and fouling resistance abilities—like flux decay ratios (FDRs) and flux recovery ratios (FRRs)—were compared. The solar light‐induced photocatalytic decomposition of the foulants was also investigated. WO₃ was used as a composite component to suppress the electron–hole recombination with the goal of achieving higher photocatalytic activity, but the presence of WO₃ was not beneficial concerning the filtration properties. However, the application of TiO₂, one of the investigated BiVO₄ photocatalysts, and their composites was also beneficial. In the case of the neat membrane, only 87 L m⁻² h⁻¹ flux was measured, whereas with the most beneficial BiVO₄ coating, 464 L m⁻² h⁻¹ flux was achieved. Pure BiVO₄ coating was more beneficial in terms of filtration properties, whereas pure TiO₂ coating proved to be more beneficial concerning the photocatalytic regeneration of the membrane. The TiO₂(80%)/BiVO₄(20%) composite was estimated to be the most beneficial combination taking into account both the aspects of photocatalytic activity and filtration properties.

This study aimed to investigate the performance of composite photocatalytic membranes fabricated by incorporating multiple nanoparticles (TiO₂, carbon nanotubes, BiVO₄) into polyvinylidene fluoride membrane material for real dairy wastewater treatment. The composite photocatalytic membranes exhibited superior antifouling behavior, lower filtration resistance, better flux, and higher flux recovery ratio than the pristine membrane. Salinity, pH, and lactose concentration are determinant factors that affect filtration resistance and rejection performance during the ultrafiltration of dairy wastewater. Generally, higher irreversible and total resistances and slightly lower chemical oxygen demand (COD) rejections were found at higher salinity (expressed by electric conductivity values of >4 mS/cm) than lower salinity (<4 mS/cm) levels. The presence of lactose in dairy wastewater increased irreversible resistance and severely reduced COD rejection during ultrafiltration due to the ability of lactose to pass through the membranes. It was ascertained that membranes require further treatment after filtrating such wastewater. Lower resistances and slightly better COD rejections were observed at pH 7.5 and pH 9.5 compared to those observed at pH 4. Photocatalytic membranes fouled during the ultrafiltration of real dairy wastewater were regenerated by visible light irradiation. The membrane containing all constituents (i.e., TiO₂, carbon nanotubes, and BiVO₄) showed the best regeneration performance, exceeding that of the pristine membrane by 30%.

Regardless of changes of ZnO NPs after interaction with the soil solutions, it remains active!