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.

In the present study, additive-free, pH-driven, hydrothermal crystallization was used to obtain shape-tailored monoclinic BiVO₄ photocatalysts. The as-prepared BiVO₄ products were systematically characterized, uncovering their crystallographic, morphologic and optical properties, while their applicability was verified in the visible light-driven photodegradation of oxalic acid and rhodamine B. Monoclinic clinobisvanite was obtained in most cases, with their band gap values located between 2.1 and 2.4 eV. The morphology varied from large, aggregated crystals, individual microcrystals to hierarchical microstructures. It was found that the degradation efficiency values obtained in the case of oxalic acid were directly related to the presence of (040) crystallographic plane, while the degradation of rhodamine B was partially independent by the presence of this structural feature. The importance of (040) crystallographic plane was also demonstrated via the reduction of Cu²⁺ to Cu, by analyzing the Raman spectra of the Cu containing samples, the mean primary crystallite size of Cu and Cu content. Furthermore, the presence of (040) crystallographic plane was directly proportional with the hydrodynamic properties of the powders as well.

In the present work, visible light active bismuth oxyiodide (BiOI) was immobilized on a commercial, non-conductive support (an Al₂O₃ based ceramic paper) using a novel two-step spray coating technique and investigated with different characterization methods (e.g., SEM, Raman, XPS). Our main goal was to eliminate the separation costs after the photocatalytic measurement and investigate the chemical relevance and opportunity to use this technique in the industry. Our as-prepared uniform BiOI layer had similar properties to the well-known reference BiOI powder. The Raman and XPS measurements confirmed that the enriched amount of the surface iodine defined the color and as well the band gap of the BiOI layer. The durable BiOI layers have prominent photocatalytic activity under UV and visible light irradiation as well. The scale-up procedure proved that the designed BiOI coated paper was reusable and potentially applicable in the industry by straightforward scale-up, which is due to the elaborated non-conventional BiOI coverage estimation method. This immobilization technique could open several opportunities for immobilizing many other visible light active photocatalysts with simple materials and low cost.