Photocatalytic membrane filtration and its advantages over conventional approaches in the treatment of oily wastewater: A review

Clean water supply has become one of the biggest challenges of the 21st century; therefore, water source protection is of increasing importance. Beyond environmental protection reasons, economic concerns-derived from increasing costs of processing water and wastewater discharge-also prompt industries to use advanced wastewater treatment methods, which ensure higher purification efficiency or even the recycling of water. Therefore, highly effective treatment of oily wastewaters has become an urgent necessity because they are produced in high quantities and have harmful effects on both the environment and human population. However, high purification efficiency can be difficult to achieve, because some compounds are hard to eliminate. Conventional methods are effective for the removal of floating and dispersed oil, but for finely dispersed, emulsified and dissolved oil advanced methods must be used, such as membrane filtration which exhibits several advantages. The application of this technology is restricted by fouling-the major limiting factor-which jeopardizes the membrane performance. In order to reduce fouling, in-depth research is being conducted to make the treatment of oil-contaminated water technically and economically feasible. The present work aims to review the conventional oil separation methods with their limitations and to focus on membrane filtration, which ensures significantly higher purification efficiencies, including the main problem: the flux reduction caused by fouling. This paper also discusses promising solutions, such as membrane modification methods, mostly with hydrophilic and/or photocatalytic nanoparticles and nanocomposites, overviewing the efforts that are being made to develop feasible technologies to treat oil-contaminated waters

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

In the present study, a commercial TiO2, 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 TiO2, 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 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

Enhancement of anti‐fouling properties during the treatment of paper mill effluent using functionalized zeolite and activated carbon nanomaterials based ultrafiltration

BACKGROUND: Treatment of paper mill effluent is crucial owing to its high organic constituents which necessitate the use of efficient membranes having greater anti-fouling ability. In this study, functionalized zeolite and activated carbon incorporated polyethersulfone (PES) membranes were developed to maximize the fouling resistance and rejection efficiency thereby to achieve greater reduction levels of chemical oxygen demand (COD), biological oxygen demand (BOD) and total dissolved solids (TDS) in the effluent. RESULTS: The synthesized inorganic modifiers such as functionalized copper (Cu)-zeolite, iron (Fe)-zeolite and calcium alginate functionalized activated carbon were incorporated into PES in distinct wt% of 0.25, 0.5, 0.75 and 1. The high pure water flux of 38.9 L m−2 h−1 was observed with 0.25 wt% of Cu-zeolite when compared to 24.3 L m−2 h−1 of virgin PES. The addition of 0.5 wt% of functionalized activated carbon resulted in reduction levels of about 90.2%, 92% and 80% of COD, BOD and TDS respectively. CONCLUSIONS: Facile functionalization of zeolite and activated carbon using metal salts and calcium alginate was achieved. Functionalized Cu-zeolite imparted increased hydrophilicity, anti-fouling property and increased pore size compared to that of Fe-zeolite and functionalized activated carbon

Effects of special nanoparticles on fuel cell properties of sulfonated polyethersulfone membrane

Polyethersulfone was sulfonated by changing the reaction time with sulfuric acid. The degree of sulfonation and ion exchange capacity were determined. Sulfonation of polyethersulfone was confirmed by FT-IR analysis and a new peak at 1025 cm-1. Inorganic materials such as carbon nanotubes, graphene, and kaolinite nanoparticles were synthesized. The effects of three nanoparticles on thermal stability and water uptake of sulfonated polyethersulfone were investigated. The morphology of membranes were also altered due to the addition of inorganic materials. The proton conductivity of the modified membranes increased with respect to increase in relative humidity

Enhanced performance of Mindel membranes by incorporating conductive polymer and inorganic modifier for application in direct methanol fuel cells

Sulfonated polyethersulfone (SPES), polyaniline (PANI), and Cloisite 15 A® were used as modifiers for the fabrication of Mindel composite polymer electrolyte membranes (PEMs). Pristine Mindel and Mindel composite PEMs were fabricated by the solution intercalation technique. The presence of modifiers in the Mindel membrane matrix was confirmed by Fourier transform infrared (FTIR) studies. The primary characteristics of pristine Mindel and Mindel PEMs such as water uptake, methanol uptake, proton conductivity ion-exchange capacity (IEC), and chemical and mechanical stability were evaluated. The pore size of Mindel/SPES/Cloisite 15 composite PEM was increased owing to the addition of SPES and Cloisite 15. The higher proton conductivity of 4.323 × 10−4 S cm−1, enhanced IEC of 0.482 mequiv. g−1, and maximum water uptake (%) of 38.12 were noted for Mindel/SPES/Cloisite membrane. Membrane selectivity of all Mindel PEMs was enhanced by the addition of modifiers. The results of this study indicate that Mindel composite membranes could be utilized as PEMs for direct methanol fuel cell (DMFC)