Investigation of the applicability of TiO₂, BiVO₄, and WO₃ nanomaterials for advanced photocatalytic membranes used for oil‐in‐water emulsion separation

Abstract

In the present study, a commercial TiO 2 , several BiVO 4 photocatalysts, a WO 3 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. WO 3 was used as a composite component to suppress the electron-hole recombination with the goal of achieving higher photocatalytic activity, but the presence of WO 3 was not beneficial concerning the filtration properties. However, the application of TiO 2 , one of the investigated BiVO 4 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 BiVO 4 coating, 464 L m −2 h −1 flux was achieved. Pure BiVO 4 coating was more beneficial in terms of filtration properties, whereas pure TiO 2 coating proved to be more beneficial concerning the photocatalytic regeneration of the membrane. The TiO 2 (80%)/BiVO 4 (20%) composite was estimated to be the most beneficial combination taking into account both the aspects of photocatalytic activity and filtration properties.

Outstanding Separation Performance of Oil-in-Water Emulsions with TiO2/CNT Nanocomposite-Modified PVDF Membranes

“…In accordance with the literature [ 18 , 20 , 23 , 25 , 28 ], a significantly higher flux value (185 L/m 2 h at VRR = 5) was achieved for the pure TiO 2 -coated membrane, while TiO 2 /CNT composite modifications (at lower CNT concentrations: 1% and 2%) were more beneficial by providing ~2.4 times higher (310 L/m 2 h) and almost 4 times higher (510 L/m 2 h) fluxes than the commercial membrane, respectively. These positive effects on fluxes can be associated with the more negative surface zeta potential of the carbon nanotube (compared to that of pure TiO 2 ; Figure 3 ).…”

“…Among the nanoparticles, titanium dioxide (TiO 2 ) is one of the most investigated materials [ 6 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] due to its hydrophilic nature, chemical stability, availability, and photocatalytic activity (which provides the possibility of preparing self-cleaning membrane surfaces). The beneficial effects of TiO 2 -based membrane modification have been proved in relation to both surface coating [ 18 , 19 , 21 , 22 , 23 , 25 ] and blending [ 17 , 20 , 28 , 29 ] methods. Carbon nanotubes (CNTs) also have a growing interest in the field of advanced membranes, which exhibit high flux, selectivity, and low-fouling properties even against biofouling [ 30 , 31 ].…”

Statistical Analysis of Synthesis Parameters to Fabricate PVDF/PVP/TiO2 Membranes via Phase-Inversion with Enhanced Filtration Performance and Photocatalytic Properties

“…The addition of TiO 2 did not significantly change the pore size of the membranes. It is widely known that hydrophilic nanoparticles can enhance pure water flux compared to that for neat PVDF membranes [ 26 , 54 , 75 ]. However, hydrophilic polymer additives (such as PVP) have a greater influence on pore size and the enhancement of pure water flux due to their “pore former” characteristic [ 30 , 72 ].…”

Investigation of Photocatalytic PVDF Membranes Containing Inorganic Nanoparticles for Model Dairy Wastewater Treatment

“…BiVO 4 nanoparticles, referred to as “BiVO 4 -I sample” in the earlier study of Nascimben et al (2020), were synthesized with a hydrothermal method. These BiVO4 nanoparticles proved stable, and had a narrow band gap of 2.35 eV [ 26 ]. XRD measurements proved that TiO 2 and CNT are stable too [ 22 ].…”