Polymeric Nanofiltration Membranes Research Articles

Experimental Study of a Sequential Membrane Process of Ultrafiltration and Nanofiltration for Efficient Polyphenol Extraction from Wine Lees.

The wine industry is a sector of great importance in the Spanish economy, contributing substantial annual revenues. However, one challenge facing the industry is the amount of waste generated, reaching millions of tons annually. These residues consist of organic matter of industrial interest, such as polyphenols. These substances are characterised by their excellent antioxidant properties, making them ideal for use in the food, cosmetic, and pharmaceutical industries. Modern techniques, such as membrane technology, are explored for their extraction based on separating compounds according to size. This work studies a sequential filtration process using ultrafiltration (UF) and nanofiltration (NF) membranes at different operating conditions (2 bar and 9.5 bar for UF and NF, respectively, at 20 °C) to extract polyphenols from wine lees. The results show a total polyphenols rejection rate for each process of 54% for UF and 90% for NF. Pore blocking models have been studied for the UF process and an intermediate pore blocking of the membrane upon wine lees filtration has been identified. A mathematical model that justifies the behavior of a polymeric NF membrane with the filtration of pre-treated vinasse residues has been validated. This study shows a viable process for extracting polyphenols from wine lees with sequential membrane technology.

A Review of Sulfonated Polymeric Nanofiltration Membranes and their Separation Performance after Sulfonation: Emphasizing on Dye Removal from Industrial Wastewaters

A Review of Sulfonated Polymeric Nanofiltration Membranes and their Separation Performance after Sulfonation: Emphasizing on Dye Removal from Industrial Wastewaters

Recent Progress on the Development and Application of Polymeric Nanofiltration Membranes: A Mini-Review

Abstract: The inefficiency of conventional water treatment methods in terms of removing micropollutants is prompting research into other technologies. Among these, the process of separation by nanofiltration membranes is particularly promising because of the low operating cost, rapid implementation of the system, high selectivity and easy integration with other treatment processes. Studies in this area are recent and there are many avenues for future research. This mini-review describes the main characteristics of the polymeric membranes used for nanofiltration and the various methods and polymer materials under investigation. At the end, we report the result of a survey conducted on the ScienceDirect, Scopus and Web of Science platforms using different keywords, to depict a global panorama of the current research involving polymeric nanofiltration membranes. The results revealed a particular dearth of published studies involving application of these membranes to remove micropollutants with endocrine disruptive action. Furthermore, research involving nanofiltration membranes utilizing calcium alginate is very recent. This study provides an overview of the investigation of polymeric nanofiltration membranes.

In-situ interfacial synthesis of metal-organic framework/polyamide thin-film nanocomposite membranes with elevated nanofiltration performances

Incorporation of nanomaterials in the thin film polyamide (PA) is instrumental to overcome the intrinsic trade-off between permeability and selectivity of polymeric nanofiltration (NF) membranes. However, the universal method of preparing thin film nanocomposite (TFN) NF membranes by directly combining the synthesized nanofillers into PA faces a stubborn issue of poor compatibility for filler-PA, which is adverse to membrane separation. Herein, an in-situ interfacial synthetic strategy was induced in interfacial polymerization (IP) process to prepare TFN membranes with metal-organic framework (MOF) in the PA selective layer. The metal ions and ligands constituting the MOF were dissolved individually in the aqueous and organic phases. MOF particles and the PA layer were simultaneously formed at the liquid-liquid interface. The increment of cross-linking degree confirmed the good compatibility between MOF and PA. Compared with the thin film composite (TFC) membrane, the acquired TFN-1 membrane exhibited 100 % enhancement of pure water permeance (from 10.0 to 20.6 L m−2 h−1 bar−1) due to the markedly reduced thin film thickness. Meanwhile, the rejection of rhodamine B (99.9 %) and Na2SO4 (96.5 %) for TFN membrane were higher than those of TFC membrane (97.2 % and 95.6 %), respectively. The TFN membrane exhibited long-term stability without deterioration. The in-situ interfacial synthesis of the MOF/PA layer provides a new avenue in TFN membrane fabrications.

Efficient separation of Li+/Mg2+ via positively charged TFN membrane based on the PEI interlayer

Nanofiltration (NF) technology has exceptional mono/divalent ion separation performance, providing considerable application potential for lithium extraction. However, polymeric NF membranes provided only restricted amounts of practical applications since of their low permeability and limited selectivity. Herein, a positively charged membrane designed for Li+/Mg2+ separation was developed, this achievement was accomplished by incorporating NH2-MIL-101(Cr) nanoparticles (NPs) into the polyamide (PA) layer situated atop the polyethyleneimine (PEI) interlayer. The PEI interlayer controlled the amine monomer distribution, regulated the PA nanofilm morphology, and improved the membrane positively charged properties. Meanwhile, the NH2-MIL-101(Cr) could provide Li+ with fast transport paths to further enhance the membrane Li+/Mg2+ separation capability. The improved membrane possessed MgCl2 rejection of 96.1 %, LiCl rejection of 42.3 %, and Li+/Mg2+ separation factor of 102 with outstanding permeance of 17.0 L m-2h−1 bar−1. This research made a valuable contribution to applying NF membranes in lithium extraction processes.

Highly tunable structure-by-design polymer brush membranes for organic solvent nanofiltration

Synthetic polymeric nanofiltration membrane processes offer an alternate low-energy option to energy-intensive distillation to fractionate similar size organic solvents for chemical, petroleum, food and biotechnology industries. Here, we synthesize and test a new class of structure-by-design hydrophilic polymeric brush membranes, that address the limitations of commercial polymer membranes, are tunable and exhibit commercially relevant filtration performance. Because these brush membranes are grafted by Single Electron Transfer-Living Radical Polymerization (SET-LRP) and replace statistically random phase inversion or interfacial polymerization used for synthesizing commercial polymer membranes, their porous structure can be remodeled by varying their morphology and chemistry. We graft hydroxyethyl methacrylate (HEMA) brush structures with short and long crosslinkers, demonstrate two competing phenomena - pore stiffening and opening - and obtain high selectivity at reasonable permeability for commercially relevant methanol/toluene separation. This new class of stable, tunable, and scalable membranes offers exciting opportunities to reduce energy for separation of organic solvents.

Performance of polymeric nanofiltration membranes for non-aqueous systems: experimental results and modeling

Performance of polymeric nanofiltration membranes for non-aqueous systems: experimental results and modeling

Pore Size in the Removal of Phosphorus and Nitrogen from Poultry Slaughterhouse Wastewater Using Polymeric Nanofiltration Membranes

Nutrients (nitrogen and phosphorus) are among the water quality parameters that cannot be easily removed from wastewater. Unfortunately, the excessive accumulation of nutrients in water can lead to numerous health issues for humans and the environment in general (including aquatic life). This study looked into the potential use of polymeric nanofiltration membranes to remove total phosphorus, ammonia, nitrate, and nitrite from poultry slaughterhouse wastewater. The wastewater samples were subjected to three different treatment systems determined by pore sizes (0.4, 0.6, and 0.8 nm) as well as an integrated system composed of ultrafiltration and nanofiltration as the main units. The results of the study showed that pore size can significantly affect a nanofiltration system’s overall performance for removing nutrients from poultry slaughterhouse wastewater. The phenomenon was supported by the analysis of variance (ANOVA) results, which showed that the treated effluent’s concentrations of the investigated water quality parameters at different pore sizes produced p-values that were less than 0.01 (statistically significant). According to the results of the removal efficiency analysis, the combination of ammonia and a 0.8 nm pore size demonstrated the lowest removal efficiency, with a removal rate of around 54.57%. However, the combination of nitrate and a 0.4 nm pore size showed the best removal efficiency of about 90.5%. On the other hand, the integrated treatment was observed to be highly effective in the removal of the investigated parameters with a removal efficiency ranging from 97.8 to 99.71%. The study’s findings offer useful information about the potential use of nanofiltration treatment systems for wastewater from poultry slaughterhouses.

Performance-based comparative study of commercial polymeric nanofiltration membranes for ionic retention from synthetic water

Performance-based comparative study of commercial polymeric nanofiltration membranes for ionic retention from synthetic water

CoFe2O4-peroxymonosulfate based catalytic UF and NF polymeric membranes for naproxen removal: The role of residence time

Micropollutants pose a significant threat to water quality, aquatic life, and public health. A catalytic polymeric membrane, combining membrane filtration and peroxymonosulfate (PMS) activation provides an alternative option to their treatment. In this work, CoFe 2 O 4 based catalytic particles were blended with polyethersulfone (PES) polymer and catalytic UF (ultrafiltration) membranes were fabricated by non-solvent induced phase inversion. The catalytic UF membrane with 2.0% CoFe 2 O 4 concentration can effectively degrade 70% naproxen in a batch experiment. Additionally, a stable selective layer was built by the layer-by-layer assembly of PDADMAC (poly(diallyldimethylammonium chloride)) and PSS (poly(styrenesulfonate)) on the surface of the catalytic UF membrane. Both the catalytic UF and NF (nanofiltration) membranes were measured in full-recycling mode and single-pass mode. In the full-recycling mode, the naproxen rejection of catalytic UF and NF membranes both increased after adding PMS due to the activation of PMS and increased adsorption. Naproxen removal at different fluxes indicates that longer residence time (i.e. lower flux) can effectively decrease the naproxen concentration in the permeate. The same effect of residence time was also observed in the single-pass mode. By prolonging the residence time of UF membranes to the same level of the NF membranes, the catalytic UF membrane exhibited 87.7% naproxen rejection which is comparable to that of the NF membranes. Significantly, the pressure used in the UF membrane was only 0.1 bar, showing a great advantage of reduced energy cost. These results reveal the important role of residence time on the treatment efficiency of micropollutants by catalytic membranes. Moreover, the application of catalytic UF membranes under low pressure provides an energy-friendly way of removing micropollutants. • Catalytic polymeric UF and NF membranes are successfully prepared incorporating CoFe 2 O 4 particles. • Naproxen removal efficacy is dependent on the filtration flux during operation. • UF membranes obtain similar removal rates as NF membranes, but at significantly lower operating pressures.

Ultrafiltration system of an MFI-type zeolite-coated membrane in N,N-dimethylformamide solvent

Resistance to polar organic solvents is a desirable characteristic of membranes which needs further development for membrane separation systems. Inorganic membranes are one type of material with the potential to confer the desired resistance. In the present work, an MFI-type zeolite-coated tubular membrane was therefore prepared and evaluated for application to an ultrafiltration system using a polar organic solvent. The membrane was successfully prepared by a secondary growth method on an α-alumina membrane continuously with thickness of ca. 100 µm. The ultrafiltration of gold nanoparticles, as a model solute, in N,N-dimethylformamide (DMF) was achieved by the membrane under investigation, although the pure DMF permeability was 1.56 ( ± 0.41) × 10−7 m3/m2·s·MPa which is lower than conventional polymeric nanofiltration membranes. Real rejection of the gold nanoparticles was calculated based on concentration polarization model and was obtained as 1.00. The MFI-type zeolite-coated membrane maintained a stable effective rejection level over a long-term operation of 80 h, which indicates that the membrane possesses sufficient resistance to polar organic solvents.

An engineering model for solute transport in semi-aromatic polymeric nanofiltration membranes: Extension of Solution-Electro-Diffusion model to complex mixtures

Pressure-driven membrane processes, such as reverse osmosis (RO) and nanofiltration (NF), are preferred solutions for salinity reduction in ground, surface and sea waters as well as in mining and urban wastewaters. Interest in NF is increasing because it enables a more cost-efficient operation than RO. However, predictive projection tools for NF applications are still lacking. Whereas in RO the solute rejections are usually above 95% and approximately independent of feed composition, the performance of NF membranes is highly influenced by the feed-solution composition. Moreover, in both processes, concentration polarisation (CP) affects the transport of species and membrane scaling. This study presents an extended Solution-Electro-Diffusion model for the description of the transport of solutes through NF membranes in complex multi electrolytes (strong and weak) taking into account CP, namely “Solution-Electro-Diffusion-Film coupled with Reactive Transport” (SEDFRT) model. The model is first validated by using a semi-aromatic polymeric membrane (NF270) and electrolyte mixtures containing two dominant (MgSO4 and MgCl2) and two minor salts (NH4Cl and NaBr). The membrane permeances to all the species are determined as key parameters to be used in design projections. Finally, the model is applied for the description of the performance of NF270 membrane with model brackish surface water, influenced by urban, industrial and agriculture discharges.

Confining the motion of enzymes in nanofiltration membrane for efficient and stable removal of micropollutants

Enzymes in living cells are highly dynamic but at the same time regularly confined for achieving efficient metabolism. Inspired by this phenomenon, we have prepared a novel biocatalytic membrane with high enzyme activity and stability by tuning the confinement strength of the membrane to enzyme, which was achieved via modifying the support layer of a polymeric nanofiltration (NF) membrane and reversely filtrating enzyme. A mussel-inspired coating was used to modify the support interior of the NF membrane to enhance charge and steric effects on enzyme, thus stabilizing enzyme in the membrane with little increment in mass transfer resistance for substrate and products (only 20% permeability loss with a high enzyme loading of 1.34 mg/cm2). A suitable confinement strength of the membrane to enzyme could delay the enzyme leakage and endow enzyme with certain mobility for efficient reaction. Thus, the obtained biocatalytic membrane exhibited a negligible decline in BPA removal efficiency for 7 reuse cycles (<3.5%) or 36 h continuous operation (<1%) in flow through mode, resulting in a long-term stability adequate for micropollutant removal. For the first time, enzyme mobility was defined and calculated to quantify the confinement strength of the membrane, which could be used to optimize the microenvironment for enzyme immobilization and predict the performance of the biocatalytic membrane. This work concluded that rationally regulating the enzyme mobility in the membrane and a periodic back-flushing operation for redistribution of enzymes could achieve a long-term stable removal of micropollutant in water by a biocatalytic membrane.

Dual-skin layer nanofiltration membranes for highly selective Li+/Mg2+ separation

The wide application of lithium batteries in consumer electronics and electric vehicles bring about ever-rising demand of lithium resources globally. Nanofiltration (NF) membranes with high Mg2+/Li+ selectivity could achieve highly efficient separation of lithium from natural brines, which provides a good alternative for steady lithium supply. In this work, we developed a dual-skin layer nanofiltration membrane comprised of a polyethylene-imine (PEI) layer grafted on a polyamide layer. The polyamide layer was prepared via interfacial polymerization to endow the NF membrane with sub-nm pores, while the PEI layer was grafted on the polyamide surface via amidation reaction to further equip the membrane with enhanced positive charge. With the synergistic effect of size sieving from the polyamide layer and electrostatic exclusion from the PEI layer, the dual-skin layer NF membrane exhibits a high rejection of 98.5% to MgCl2 and a low rejection of 46.2% to LiCl, suggesting a high Mg2+/Li+ selectivity. As using this dual-skin layer NF membrane for separating Li+ from a simulated brine, a high Mg2+/Li+ separation factor (SMg,Li) up to 33.4 was achieved, which is the highest value among the pressure-driven polymeric nanofiltration membranes reported so far.

PVDF-CaAlg nanofiltration membranes with dual thin-film-composite (TFC) structure and high permeation flux for dye removal

Novel polyvinylidene fluoride-calcium alginate (PVDF-CaAlg) nanofiltration (NF) membranes were prepared by impregnating electrospun PVDF substrates with sodium alginate solution and crosslinking with CaCl2 solution. The NF membranes were characterized via field emission scanning electron microscopy (FESEM) equipped with an energy-dispersive spectrometry (EDS), attenuated total reflectance Fourier transform infrared spectra (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The results show that the prepared PVDF-CaAlg NF membranes exhibit dual thin-film-composite (TFC) structure and superior surface hydrophilicity. The highest pure water flux can achieve 63.8 L·m−2·h−1·bar−1 accompanied with a 98.5% rejection rate for methyl blue (MB), which is superior to many polymeric NF membranes. The prepared PVDF-CaAlg NF membranes exhibit much higher rejections for seven typical dyes, and the rejection slightly rises with the increase of impregnating time. In the long-term filtration process, the permeation flux for dye solution remains stable. PVDF-CaAlg NF membranes show good anti-fouling performance to BSA protein and lactobacillus.

Desalination of Groundwater from a Well in Puglia Region (Italy) by Al2O3-Doped Silica and Polymeric Nanofiltration Membranes.

Some of the groundwater aquifers in the Puglia Region, Italy, suffer from high salinity and potential micropollutant contamination due to seawater infiltration and chemical discharge. The objective of this study is twofold: to evaluate the performance of the recently reported alumina-doped silica nanofiltration membranes for water potabilization, and to provide a possible solution to improve the groundwater quality in the Puglia Region while maintaining a low energy-footprint. Two lab-made alumina-doped silica membranes with different pore structures, namely S/O = 0.5 and S/O = 2, were tested with real groundwater samples and their performances were compared with those of a commercial polymeric membrane (Dow NF90). Moreover, groundwater samples were sparked with acetamiprid, imidacloprid, and thiacloprid to test the membrane performance in the presence of potential contamination by pesticides. At a trans-membrane pressure of 5 bar, NF90 could reduce the groundwater conductivity from 4.6 to around 1.3 mS·cm−1 and reject 56–85% of the model pesticides, with a permeate flux of 14.2 L·m−2·h−1. The two inorganic membranes S/O = 2 and S/O = 0.5 reduced the permeate conductivity to 3.8 and 2.4 mS·cm−1, respectively. The specific energy consumption for all three membranes was below 0.2 kWh·m−3 which indicates that the potabilization of this groundwater by nanofiltration is commercially feasible.

A comparative study on the monovalent and divalent cation separation of polymeric films and membranes from salt solutions under diffusion-dialysis.

This study deals with selective separation of mono- and divalent cations from aqueous salt solutions using polymeric films based on polyethylene (PE) and polyamide6 (PA6), and two different commercial nanofiltration (NF) membranes. The diffusion rates (D) of ions (Na+ and Ca2+), separation factors (α) and ion rejections (R) of the films and NF membranes are examined comparatively as well as their surface morphology and hydrophilicity. It is observed that the diffusion rates of Na+ are in the range of 0.7–1.8 × 10−8cm2 .s−1 in the decreasing order of PE > NF90 > NF270 > PA6 while Ca2+ shows diffusion rates of 7.4–18.4 × 10−8 cm2 .s−1 in the increasing order of NF270 > NF90 ≈ PA6 > PE. Rejection values of the polymeric films and NF membranes against to Na+ and Ca2+ vary between 90% and 99.6%.The highest α(Ca2+/Na+) is found to be 20 for PA6 film. D, α, and R value of both polymeric films and NF membranes are strongly affected by the existence of osmosis during diffusion-dialysis and the sizes of hydrated sodiu and calcium ions. In conclusion, the film based on PA6 may be a good alternative for selective separation of mono- an divalent cations.

Inkjet printing of graphene oxide and dopamine on nanofiltration membranes for improved anti-fouling properties and chlorine resistance

Anti-fouling properties and chlorine resistance nature are highly desirable features for membranes used in nanofiltration (NF). Conventional polymeric NF membranes often suffer from fouling issues and poor stability under chlorine based chemicals. Therefore, in this work, a thin film composite (TFC) NF membrane was modified by coating a binding agent polydopamine (PDA) and graphene oxide (GO) using a simple and scalable inkjet printing process where the GO deposition was controlled by the number of printing cycles. The NF test results revealed the PDA-GO printed NF membranes exhibited higher salt rejection while achieving slightly lower permeate flux compared to control membrane. Moreover, the PDA-GO printed membrane exhibited enhanced anti-fouling properties where only 20% of permeate flux reduction was observed while the control membrane displayed significant reduction in flux up to 48%. Furthermore, chlorine resistance of the PDA-GO printed membrane showed reduction in salt rejection was effectively suppressed compared to the control membrane for the chlorination time of 1 and 3 h. Our work demonstrates an effective strategy to mitigate fouling and chlorine stability issues in NF membranes as well as validate inkjet printing as a versatile technique for the formation of advanced nanomaterial based membranes with high controllability of membrane properties.

Antibiotics Separation with MXene Membranes Based on Regularly Stacked High-Aspect-Ratio Nanosheets.

The uncontrolled release of antibiotics and pharmaceuticals into the environment is a worldwide increasing problem. Thus, highly efficient treatment technologies for wastewater are urgently needed. In this work, seven kinds of typical antibiotics (including water and alcohol soluble ones) are successfully separated from the corresponding aqueous and ethanolic solutions using highly regular laminated membranes. Our membranes are assembled with 2-4 μm titanium carbide nanosheets. The solvent permeance through such titanium carbide membrane is one order of magnitude higher than that through most polymeric nanofiltration membranes with similar antibiotics rejection. This high flux is due to the regular two-dimensional (2D) structure resulting from the large aspect ratio of titanium carbide nanosheets. Moreover, the electrostatic interaction between the surface terminations and the antibiotics also affects the rejection and enhances the antifouling property. Such 2D titanium carbide membranes further broaden the application scope of laminated materials for separation and purification of high value added drugs in academia and industry.

Antibiotics Separation with MXene Membranes Based on Regularly Stacked High‐Aspect‐Ratio Nanosheets

AbstractThe uncontrolled release of antibiotics and pharmaceuticals into the environment is a worldwide increasing problem. Thus, highly efficient treatment technologies for wastewater are urgently needed. In this work, seven kinds of typical antibiotics (including water and alcohol soluble ones) are successfully separated from the corresponding aqueous and ethanolic solutions using highly regular laminated membranes. Our membranes are assembled with 2–4 μm titanium carbide nanosheets. The solvent permeance through such titanium carbide membrane is one order of magnitude higher than that through most polymeric nanofiltration membranes with similar antibiotics rejection. This high flux is due to the regular two‐dimensional (2D) structure resulting from the large aspect ratio of titanium carbide nanosheets. Moreover, the electrostatic interaction between the surface terminations and the antibiotics also affects the rejection and enhances the antifouling property. Such 2D titanium carbide membranes further broaden the application scope of laminated materials for separation and purification of high value added drugs in academia and industry.