Fouling caused by oil and other pollutants is one of the most serious challenges for membranes used for oil/water separation. Aiming at improving the comprehensive antifouling property of membranes ...and thus achieving long‐term cyclic stability, it is reported in this work the design of a kind of zwitterionic nanosized hydrogels grafted poly(vinylidene fluoride) (PVDF) microfiltration membrane (ZNG‐g‐PVDF) with superior fouling‐tolerant property for oil‐in‐water emulsion separation. Sulfobetaine zwitterionic nanohydrogels with the diameter of ≈50 nm are synthesized by an inverse microemulsion polymerization process. They are then grafted onto the surface of PVDF microfiltration membrane, endowing the membrane a superhydrophilic and nearly zero oil adhesion property. This ZNG‐g‐PVDF membrane exhibits great tolerance and resistance to salts pH, especially an excellent antifouling property to oil‐in‐water emulsions containing various pollutants such as surfactants, proteins, and natural organic materials (e.g., humic acid). The comprehensive antifouling property of the membrane gives rise to the cyclic stability of the membrane greatly improved. A nearly 100% recovery ratio of permeating flux is achieved during several cycles of oil‐in‐water emulsion filtration. The ZNG‐g‐PVDF membrane shows great potential in treating practical oily wastewater containing complicated components in the effluent.
Zwitterionic nanosized hydrogels with the diameter of ≈50 nm, synthesized by an inverse microemulsion polymerization process, are grafted onto PVDF microfiltration membrane (ZNG‐g‐PVDF). This ZNG‐g‐PVDF membrane exhibits great tolerance and resistance to salts and a wide range of pH, an excellent antifouling property to oil‐in‐water emulsion containing various pollutants and behaves superior cyclic stability with nearly 100% recovery ratio.
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•The poly (vinylidene fluoride) (PVDF) membrane was functionalized with Cu-MOF-74.•Modified PVDF membrane held superior anti-biofouling ability.•Cu2+ played a significant role in ...inhibiting Escherichia coli. (E.coli.).•Cu-MOF-74 can release OH and reactive oxygen species (ROS) in bacteria cells.
Mitigation of membrane fouling is an important problem to be solved in the application of membrane technology. In this research, we synthesised a kind of Cu-MOF-74 by a facile and environmentally friendly method at room temperature. This kind of Cu-MOF-74 was firstly and successfully coated on poly (vinylidene fluoride) (PVDF) membranes for improving their anti-biofouling performance. The experimental results show that Cu-MOF-74 increases the hydrophilicity and roughness of the PVDF membrane surface, and the antibacterial efficiency of the modified membrane was as high as 97.7% at 4 h. Moreover, we found that the Cu-MOF-74 could sustainably release Cu2+ for one week, the maximum Cu2+ release concentration of PVDF membrane coated by 0.025 g Cu-MOF-74 reached 0.42 mg/L, and the generation of Cu2+ played a significant role in suppressing E. coli. In the meantime, this kind of Cu-MOF-74 can release OH, which will lead to the accumulation of reactive oxygen species (ROS) in bacterial cells. The ·OH can oxidise and destroy bacterial cells, which will be in favour of enhancing the anti-biofouling performance. This novel PVDF membrane surface modified by green synthetic Cu-MOF-74 has a strong antibacterial property and high application potential for water treatment.
Microplastic (MP) pollution in the aquatic environment is widespread, with a significant fraction of these particles originating from municipal wastewater treatment plant (WWTP) effluents. Whereas ...membrane filtration processes are touted as an effective MP removal strategy, the rejection of irregularly-shaped plastic particles, similar to those found in WWTPs, is poorly understood. Here, we characterize the filtration of irregularly-shaped MP particles (∼10 μm) through Durapore® microfiltration membranes (0.45 and 5 μm pore sizes). These particles were produced via ball-milling/sieving processes from a fluorescent polyethylene feedstock, enabling particle concentrations to be quantified using a standard fluorometric plate reader. Permeate samples from the 0.45 μm membrane exhibited low fluorescent intensities relative to feed samples, implying minimal MP transmission. Conversely, appreciable MP transmission through the 5 μm membrane was noted, with sizable MPs (∼2–7 μm) found in the permeate. This transmission was exacerbated at higher fluxes which emphasizes how operating conditions can govern MP retention. Post-filtration analyses demonstrated that particle capture occurred largely at the feed-membrane interface, where greater MP intrusion into the membrane was seen at the larger pore size. These results reaffirm the importance of choosing an appropriate membrane/membrane pore size and operating conditions to maximize MP retention in WWTPs.
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•Irregular fluorescent microplastics (∼10 μm) were created by ball-milling/sieving.•Little evidence of particle transmission was seen through a 0.45 μm membrane.•Microplastics approaching 5 μm could transmit through a 5 μm membrane's pores.•Higher permeate fluxes induced greater transmission of microplastics.•Microplastics intruded deeper into the pore structure of the 5 μm membrane.
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•MF membranes were hydrophilized by pyrogallol (PG)/ε-polylysine (EPL) coating.•PG/EPL coating solutions produced crosslinked macromolecular PG/EPL complexes.•PG/EPL complexes were ...densely and uniformly deposited throughout MF membranes.•Modified membranes showed enhanced permeance and organic antifouling performance.•Modified membranes showed superior oil–water separation and antifouling performance.
Microfiltration (MF) membranes need to be hydrophilized to enhance their fouling resistance and applicability. Previous modification strategies are somewhat ineffective and rely on harmful synthetic chemicals. Here, we propose a versatile and ecofriendly strategy to hydrophilize MF membranes via simple coating with the natural compounds, pyrogallol (PG) and ε-polylysine (EPL). The PG/EPL aqueous coating solution produced crosslinked macromolecular PG/EPL complexes via the auto-oxidation of PG and its subsequent reactions with numerous EPL amines. The PG/EPL complexes were densely coated on MF membranes via collective hydrophobic interactions between their abundant PG moieties and membrane surfaces, achieving the excellent hydrodynamic and pH stabilities of the PG/EPL coating. The PG/EPL coating also significantly and uniformly improved the hydrophilicity of the poly(vinylidene fluoride) (PVDF) membrane with no distinct deformation of the membrane pore structure. Hence, the PG/EPL-coated PVDF membrane exhibited remarkably higher organic fouling resistance and water permeance (∼22% enhancement) than its pristine control. Furthermore, the PG/EPL-coated PVDF membrane demonstrated dramatic improvements in oil–water separation (∼27% higher oil rejection) and oil antifouling performance compared with its pristine counterpart. The PG/EPL coating was further extended to hydrophilize other polytetrafluoroethylene and polyethylene MF membranes. The proposed coating strategy provides a versatile and ecofriendly platform for hydrophilizing various membranes.
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•Extended DLVO modeling can predict virus removal by microfiltration (MF) membrane.•The negative secondary minima can remove viruses even with hydrophilic repulsion.•Hydrophobic ...membranes can remove viruses even with weak electrostatic repulsion.•The electrostatic interactions have a negative correlation with virus removal values.•The hydrophobic interaction defines whether viruses can attach to a membrane surface.
Virus removal by membrane filtration is challenging due to the small size of these microorganisms. For microfiltration (MF) membranes, which have pore sizes above 100 nm (i.e., larger than most viruses), surface interactions are of critical importance in determining virus removal. The present study aims to evaluate the impact of surface interactions on virus removal by MF membranes wherein predictions by extended DLVO (XDLVO) modeling are compared with experimental data on virus clearance. The study employed four viruses (MS2, Qβ, phiX174, phi6), two MF cartridge membranes (nylon and PTFE), and several solution chemistry conditions to cover a range of virus-membrane surface interaction scenarios. For the hydrophilic nylon membrane, the highest log removal values (LRVs) were observed at the pH when the filter carried a slightly positive charge. For the hydrophobic PTFE membrane, higher LRVs were attained for high ionic strength solutions, wherein the electric double layer was compressed, even at pH values where the filter was negatively charged. We conclude that the electrostatic interaction determines whether viruses can approach the membrane and hydrophobic interactions are a critical factor in retaining viruses near the membrane surface, preventing viral leakage into the filtrate. The surface interactions have to be considered in virus membrane filtration.
In this study, permeate quality, membrane performance, and microbial community in a gravity-driven microfiltration (GDM) reactor and a biofiltration (BF) + GDM reactor for seawater reverse osmosis ...(RO) desalination pretreatment were compared at both lab-scale and pilot-scale. The presence of BF column was more efficient in removing soluble organic substances by biosorption/biodegradation, leading to superior permeate quality from BF + GDM and subsequently lower RO fouling than GDM. Compared to the biofilm-saturated anthracite media, the granular activated carbon media in BF improved the assimilable organic substances removal in BF + GDM. Although less organic substances and microbial cells were accumulated on the membrane in BF + GDM, its permeate flux was 10–20% lower than GDM. Furthermore, BF lowered the amounts and diversity of prokaryotes (due to less organic substances) and eukaryotes (due to BF media rejection and lacking of prokaryotic preys) in the membrane biofilm of BF + GDM, but did not cause significant shifts of predominant species. Thus, the lower flux in BF + GDM was attributed to the limited predation and movement of eukaryotes in membrane biofilm, which may result in the formation of less porous and compact biofilm layer. The cost analysis indicated that BF + GDM-RO requires 5.2% less operating cost and 1.5% less water production cost than GDM-RO.
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•Integration of BF with GDM reactor improved permeate quality.•Lower permeate flux was observed in BF + GDM reactor.•Improved quality of BF + GDM permeate led to less RO fouling.•BF column influenced microbial community composition in GDM biofilm.•BF + GDM-RO system cost less than GDM-RO system for seawater desalination.
Our objective was to determine the impact of simultaneous removal of lactose plus low molecular weight solutes and milk serum proteins from skim milk by microfiltration (MF) on the chemical, physical ...and sensory properties of 3.4, 7.5, and 10.5% milk protein-based beverages before and after a direct steam injection thermal process. Skim milk was microfiltered at 50°C using 0.1 micron ceramic membranes with a diafiltration ratio of water to milk of about 2.5. Milk lactose, serum proteins, and soluble minerals were removed simultaneously to produce protein beverages containing from 3.4 to 10.5% true protein from skim milk and this process was replicated twice with different skim milks. The soluble mineral plus lactose content was very low and the aqueous phase of the beverages had a freezing point very close to water (i.e., −0.02°C). Beverage pH ranged from 7.19 to 7.41, with pH decreasing with increasing protein concentration. Overall, the beverages were whiter and blander than skim milk. When UHT processed with direct steam injection at a holding temp of 140°C for 2 to 3 s, there was some protein aggregation detected by particle size analysis (volume mean diameter of protein particles was 0.16 micron before and 22 microns after UHT). No sulfur/eggy flavor was detected and no browning was observed due to the UHT thermal treatment. Both apparent viscosity and sensory viscosity increased with increasing protein concentration and heat treatment.
Membrane-based operations, especially pressure-driven membrane operations, are today well-established procedures for various applications in the wine industry thanks to their intrinsic properties and ...undoubted advantages over traditional methods. Emerging membrane processes, such as pervaporation, electrodialysis and osmotic distillation, forward osmosis, membrane contactors, offer new and interesting perspectives to improve quality and develop new products without compromising organoleptic properties.
This review provides a comprehensive overview on the use of membrane operations in wine processing. A bibliometric and scientometric analysis has been done to provide the current advances dealing with the application of these operations in different steps of wine manufacture, including clarification, stabilization, concentration, acidification, deacidification and dealcoholization. The current challenges and perspectives are highlighted to guide further advancements of membrane technology in this field.
The use of conventional and emerging membrane systems offers interesting opportunities to improve and optimize current practices of the wine processing industry. Considerable progress has been done concerning the development of low-fouling materials, identification of wine molecules responsible for membrane fouling and methods to mitigate such phenomenon in the clarification of wines by microfiltration membranes. Technological progress in electrodialysis makes this process a very attractive method for tartrate stabilization, acidification and deacidification of wines. Different conventional and emerging membrane processes offer valid post-fermentation strategies to remove ethanol in wines while preserving their original characteristics. The global results provide interesting perspectives for a wider implementation of membrane processes in the winemaking industry and to redesign the traditional vinification process under the process intensification strategy.
•An overview of membrane technology in wine processing is presented.•Bibliometric and scientometric analysis provide current advances of membrane technology in the field.•Conventional and emerging membrane processes are analyzed.•Current challenges and perspectives are highlighted to guide further advancements.•Interesting perspectives of global results for redesigning the traditional vinification process.
