Membrane Water Permeability Research Articles

Fluoride Removal and Recovery from Water Using Reverse Osmosis and Osmotic Membrane Crystallization

Fluoride is a concern for human health at high concentrations, but it is also a valuable compound with multiple applications. Thus, having a system that gives the opportunity to remove and recover this valuable element from water is highly interesting. Reverse osmosis (RO) is a promising technology in the removal of fluoride from water. Nevertheless, the residual retentate highly concentrated in fluoride is still a concern. The aim of this study was to evaluate the performance of an integrated process consisting of RO and membrane crystallization to remove fluoride from water and to recover it as a pure fluoride salt. Pure water permeability and fluoride rejection of a commercial RO membrane was tested under different conditions. In addition, the performance of an osmotic membrane crystallization setup was evaluated, considering the effect caused by the flow rates and the concentration of both the feed and the osmotic solution on the mass transfer coefficient. The crystallization process allowed the production of pure NaF crystals with octahedral morphology with a face-centered cubic crystal system.

High-performance thin film composite nanofiltration membranes with MoS2 nanosheet interlayer

High-performance polyamide thin film composite (TFC) nanofiltration membranes have received great attention in recent years. Herein, we report the preparation of TFC nanofiltration membranes by interfacial polymerization using MoS2 nanosheets as the nanomaterial interlayer. The aqueous monomer and MoS2 nanosheets are distributed on the surface of microporous membrane substrates by a one-step method. The MoS2 interlayer improves the uniformity and smoothness of the microporous substrates, helping to form polyamide nanofilms at ultralow monomer concentration. Moreover, the hydrophilic and negatively-charged MoS2 nanosheets enhance the water permeability and negative charges of the nanofiltration membranes. The composite membranes show both high water permeance of 33.5 L m−2 h−1 bar−1 and Na2SO4 rejection of 97.5%, as well as significantly improved mono-/divalent anions selectivity and antifouling property. It is proved that the interfacial polymerization strategy assisted by the MoS2 interlayer is effective for preparing high-performance nanofiltration membranes.

Rod-like MIL-53(Fe) intercalated MXene nanosheets lamellar composite membrane for the purification of multi-component oily wastewater

The complicated oily wastewater containing hazardous organics post a great challenge to the membrane separation technology. Herein, a multilayer porous multifunctional MXene/MOF composite membrane with high permeability and photocatalytic degradation performance was prepared by embedding rod-shaped MIL-53(Fe) into layered MXene nanosheets and self-assembling them onto porous polyacrylonitrile fibrous mat. It was found that the embedment of rod-like MIL-53(Fe) with rough nanostructures could effectively avoid the dense physical stacking of MXene nanosheets and regulate the layer spacing, which was conducive to the enhancement of water channel and permeability of membrane. Moreover, the hydrophilic modification of TA could render the super-wetting feature (WCA=0°, UOCA>150°) and enhance the oil resistance of the membrane. Thence, the composite membrane exhibited favorable separation flux (904.3 ∼ 1226.5 L·m−2·h−1) and retention rate (99.06 ∼ 99.62%) for different O/W emulsions. In addition, the coupling of rod-like MIL-53(Fe) and MXene nanosheets endowed the composite membrane with efficient photocatalytic performance, which could degrade various dyes contained in oily wastewater (CV: 62.4%, MeB: 99.0%, CR: 79.5%, MO: 84.1%). Overall, this study opens up a new way for the preparation of super-wetting and multi-functional fibrous composite membrane, showing the broad application prospects in the purification of multi-component oily wastewater.

Metal-Organic-Framework-based nanofiltration membranes for selective multi-cationic recovery from seawater and brines

Nanofiltration (NF) is gaining a role of increasing importance in Zero Liquid Discharge (ZLD)/Minimal Liquid Discharge (MLD) systems, enhancing the efficiency of downstream technologies to recover valuable minerals from seawater and brines. However, often the purity of the recovered minerals does not meet market specifications, making ZLD/MLD currently economically unfeasible. To such end, in this study, a novel positively charged NF membrane was developed to enhance magnesium and calcium selectivity. The membrane comprised: (i) an ultrafiltration substrate and (ii) an active layer that incorporated NH2-MIL-101(Al) and ZnO nanoparticles in a chitosan matrix. The influence of different loadings of NH2-MIL-101(Al) and ZnO on membrane structure, selectivity and water permeability was investigated. Initial filtration tests with single-salt solutions at 1000 ppm (NaCl, Na2SO4, MgCl2, CaCl2) showed that the membrane with 35%wt of ZnO presented the highest rejections of MgCl2 (90.10%) and CaCl2 (86.49%). Selectivity towards MgCl2 and CaCl2 was higher than those of commercial membranes (NF90 and NF270) and the positively charged membranes introduced in recent literature. The novel synthesized membrane in this work was also tested with synthetic seawater and brine at a trans-membrane pressure of 30 bar. Results highlighted the intriguing competitiveness of the novel membrane in terms of magnesium and calcium selectivity with NF90 and NF270 within the field of both seawater and brine valorization.

Dual regulation of graphene oxide membrane by crosslinker and hydrophilic promoter for dye separation

Graphene oxide (GO)-based membranes have shown considerable promise in the field of water treatment. However, the structural swelling of GO membranes in water has hindered their further development. A single regulatory approach seems difficult to simultaneously improve permeability, selectivity, and stability. In this study, we present a dual regulation strategy for GO membranes employing the 1,4-Diaminobutane crosslinker to prevent swelling and maintain an interlayer spacing of 1.34 nm, resulting in effective dye rejection, and employing the hydrophilic EMT-type zeolite promoter to improve the membrane's water permeability. The obtained NH2-GO/10EMT composite membrane exhibited enhanced pure water flux (from 9.0 to 20.8 L/m2 h bar) and anionic dye rejection (from 87.2% to 97.6%) with promising structure stability (at least 20 h), while greatly improving the membrane's fouling resistance (the water recovery ratio increased from 46.5% to 86.2%). Our findings provide a straightforward and efficient approach to the development of high-performance GO membranes for selective water separation.

A machine learning approach for prediction of reverse solute flux in forward osmosis

This study introduces a novel approach using a supervised machine learning model to accurately predict reverse solute flux (RSF) in the forward osmosis process. This study employed feature engineering techniques to identify significant process parameters that influence RSF. Notably, the results demonstrate the high effectiveness of the Categorical boosting (CatBoost) machine learning algorithm in RSF prediction, achieving an R-square value of 0.94 and a root mean square error of 0.44 when comparing the actual and predicted data. Furthermore, the model underwent simulation using real experimental data, revealing a minimal percentage error ranging from 0 to 2 % compared to the experimental reverse solute flux. The result showcases the potential of machine learning to save valuable time typically spent on experimental data while offering accurate predictions of reverse solute flux. The implications are particularly valuable in various applications involving reverse salt flux, where precise predictions can be achieved solely based on input parameters related to the forward osmosis process, membrane water permeability, and salt permeability.

Impact of Silver-Decorated Graphene Oxide (Ag-GO) towards Improving the Characteristics of Nanohybrid Polysulfone Membranes.

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver-graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm-1 of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe2+) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10-100 mg L-1 towards purification of groundwater for safe drinking water.

Constructing low-friction mass transfer channel in laminar graphene oxide membrane for efficient molecular separation with enhanced permeability

In recent years, graphene oxide (GO) has attracted increasing interest in fabricating next-generation separation membranes. The perm-selectivity of laminar GO membrane is generally determined by their interlayer nanochannel structure. Herein, we used a new molecule called 5, 5′-diamine-2, 2′-biphenol (BIPOL-NH2) as the intercalator of laminar GO-based membrane to construct low-friction interlayer mass transfer channels. The aromatic BIPOL-NH2 molecules act as hydrophobic side walls of the mass transfer channels between adjacent GO nanosheets, reducing the interaction between water molecules and channel structure, thereby enhancing water permeability of GO membranes. This was confirmed by the further molecular dynamics simulation. Compared with pristine GO membrane, the BIPOL-GO membrane showed a water permeability increase by a factor of about 3 (up to 72.4 L m-2h−1 bar−1), which was consistent with our simulation results. Also, it represented excellent dye/salt separation performance (the selectivity of NaCl/CR is more than 117.2) and good structural stability. Overall, our work provides a novel and efficient approach to modify GO-based membranes for enhanced permeability.

Improved separation performance, anti-fouling property and durability of polyamide-based RO membrane by constructing a polyvinyl alcohol/polyquaternium-10 surface coating layer

In this work, a novel coating layer of polyvinyl alcohol (PVA)/polyquaternium-10 (PQ10) was constructed onto the surface of polyamide-based RO membrane via the method of surface coating followed by cross-linking. Permeation tests demonstrated that the incorporation of PQ10 into PVA could efficiently improve the water permeation ability of surface coating layer, showing a significant decrease of hydraulic resistance from 5.9 × 1012 m−1 of the PVA-1.0 coating layer to 2.5 × 1012 m−1 of the PVA-1.0/PQ10-0.2 coating layer. Anti-fouling performance evaluation revealed that the PVA/PQ10-coated membrane not only possessed the good anti-fouling property of the PVA-coated membrane to negatively charged foulants and protein but also exhibited more excellent anti-fouling performance to positively charged foulant due to its relatively lower surface charge density and pseudo-zwitterionic surface character. Long-term filtration tests with dye wastewater illustrated that although the initial water permeability of membrane coated with PVA-1.0/PQ10-0.2 surface layer was lower than that of the virgin RO membrane under the same operation condition, the PVA-1.0/PQ10-0.2-coated membrane exhibited a higher salt rejection, lower flux decline rate and larger cumulative volume of permeated water during a filtration period of 48.0 h. Soaking tests further demonstrated the improvement of membrane chemical durability against acid, alkaline and chlorine by the PVA/PQ10 coating layer.

Ultrafast seawater desalination with phosphorene oxide nanochannel based membrane: Nonmonotonic relationship between oxidation degree and water permeability

Previous studies have demonstrated the efficacy of phosphorene membranes for seawater desalination. However, these membranes are susceptible to oxidation in water, albeit at a slower rate compared to exposure to air. This study investigates the desalination performance of phosphorene oxide (PO) nanochannel-based membranes using molecular dynamics simulations. Our results reveal that PO membranes with varying oxidation degrees (ranging from 0 % to 10 %) exhibit exceptional performance, surpassing traditional commercial membranes by two orders of magnitude in terms of water permeability. Notably, the water permeability of PO membranes with large interlayer spacings does not exhibit a linear decrease with increasing oxidation, since the high oxidation degree elicits the steric hindrance as well as the strong interactions (hydrogen bond and Coulomb energies) between these oxidation groups and water molecules. These findings not only confirms the superior performance of phosphorene oxide membranes in desalination but also uncovers the non-monotonic relationship between oxidation degree and water permeability.

In situ assembly of graphitic carbon nitride/polypyrrole in a thin-film nanocomposite membrane with highly enhanced permeability and durability

Although thin-film nanocomposite (TFN) membranes have been proposed as a competitive approach for improved reverse osmosis performance within the last decade, their intrinsically poor organic-inorganic interfacial compatibility and low durability still hinder further upscaling. In this study, a new in situ assembly strategy is proposed to solve this dilemma by using polypyrrole (PPy) to build a bridge between polyamide matrix and nanomaterial (graphitic carbon nitride, g-C3N4) and further fabricate g-C3N4/PPy-incorporated TFN membrane. The synthesized g-C3N4/PPy nanocomposites are hybridized into the interfacial polymerization process, which endows the TFN membrane with a smaller “ridge-valley”, higher hydrophilic and thinner polyamide layer. With 0.005 wt% of g-C3N4/PPy, the water permeability of TFN membrane is increased to 377 % (4.0 L·m−2·h−1·bar−1), while keeping a similar NaCl rejection (99.1 %) to pure polyamide membrane. Importantly, the resulting TFN membrane exhibits high chlorine resistance in acidic, neutral and alkaline environments. Moreover, the TFN membrane has superior antifouling performance for organic, inorganic and mixed organic-inorganic foulants, which is of vital importance for the long service life of TFN membranes. This study offers a facile avenue to solve the application needs of advanced TFN membranes for efficient desalination with stable high-quality water.

Retarded Interfacial Formation of Polyamine-Based Nanofiltration Membranes with Pyromellitic Acid: Separation, Acid Stability, and Antifouling Performance

Crosslinked and additive-added polyamide thin-film composite (TFC) nanofiltration (NF) membranes formed by the conventional interfacial polymerization (IP) process have shown good performances. However, studies on polyamine TFC NF membrane prepared via an adjusted IP process with low-cost acid ligands as an interfacial additive for improved liquid-based separation are still lagging. In this regard, a polyamine-based TFC NF membrane synthesized by retarding the interfacial polymerization (IP) process with pyromellitic acid (PMA) (a polycarboxylate acid ligand) is herein reported. The PMA-adjusted membrane displayed a superb range of pure water fluxes from 9.8 to 20.4 L m–2 h–1 bar–1, with the best-performed membrane achieving up to 95.1% for Na2SO4 rejection. Thus, the water permeability of the PMA-TFC membrane is ∼2.4 times as high as the control TFC membrane. The best-performed PMA-TFC membrane showed good hydrophilicity, pressure resistance, and long-term filtration stability. In addition, the membrane structural stability was maintained with ∼3.9% declination in salt rejection after 30 days of immersion in 0.1 M HNO3 solution. Also, an impressive fouling resistance was achieved after three-cycle of bovine serum albumin fouling tests. This work, therefore, offers a more feasible way of designing polyamine-based NF membranes with good prospects in water reuse and nitric acid-generating wastewater treatment application.

Enhanced water permeability of hollow fiber composite reverse osmosis membrane using porous α-cellulose/polysulfone hollow fiber membrane as the substrate

The hollow fiber composite (HFC) reverse osmosis (RO) membrane with a special self-supporting structure has attracted a great deal of attention in the fields of separation and purification. However, low permeability is an urgent problem restricting its wide application. A porous polysulfone (PSF) hollow fiber support membrane was fabricated through the dry–wet spinning technique and hydrophilic α-cellulose © powder was incorporated in the PSF membrane matrix to improve the membrane’s water permeability. The HFC RO membrane was prepared via the interfacial polymerization process on the inner surface of the C/PSF support membrane. The membrane morphology and surface hydrophilicity were evaluated through scanning electron microscopy observation and dynamic water contact angle (WCA) measurement. The effects of α-cellulose incorporation on the separation performance of PSF hollow fiber membranes and HFC RO membranes were investigated. The results showed that the surface hydrophilicity and water permeability of the PSF membrane were significantly improved after the introduction of α-cellulose. The WCA of the modified PSF support membrane decreased from 84.6° for the neat PSF membrane to 70.25°, and the pure water flux can reach a maximum value of 102.1 L/(m2 · h) (0.1 Mpa), which was 1.3 times that of the pristine membrane. The HFC RO membrane using the hydrophilic modified PSF membrane as the substrate exhibited an enhanced water flux of 15.6 L/(m2 · h) and, meanwhile, the membrane salt rejection remained above 97.6% (1.0 wt% NaCl aqueous solution, 0.7 Mpa). The HFC RO membrane showed extremely high rejection rates (99%) for different dyes (congo red and methylene blue). No obvious performance deterioration was observed for the HFC RO membrane during continuous vacuum membrane distillation (VMD) experiments for 60 h.

Improving permselectivity of the polyamide reverse osmosis membrane by a controlled-release sulfate radical modification

The sulfate radical (SO4.-) is an effective reactive oxidative species that can improve the permselectivity of polyamide membranes. However, the coexistence of hydroxyl radicals, which have been previously reported in a thermal-activated persulfate (PDS) system, have detrimental effects on membrane integrity and salt rejection. In this study, we adopted a facile citric acid chelated Fe(II)/PDS modification method to generate a controlled-release SO4.- oxidation condition at room temperature, which enhanced membrane performance. The rapid oxidation by Fe(II)/PDS significantly increased membrane water permeability. However, ferric oxyhydroxides were formed and deposited on the membrane surface, reducing surface hydrophilicity and negative charge. Citric acid was then introduced into the modification as a chelating agent to control the release of Fe(II) and improve the modification efficiency. The modified membrane showed further increased water permeability (from 26.0 to 53.0 L m−2h−1) and maintained a salt rejection of 98.4%. The optimized membrane enhanced surface hydrophilicity and negative charge, slightly improving anti-fouling ability. The membrane chemical composition characterization using ATR-FTIR and XPS indicated the formation of excess oxygenous groups. Furthermore, SO4.- oxidized the chlorine-sensitive sites, endowing the modified membrane with significantly improved chlorine resistance. The results from this study provide a facile SO4.--based modification method for comprehensively improving permselectivity, surface properties, and anti-fouling/anti-chlorine resistances of the polyamide membranes.

Pervaporation dehydration of ethylene glycol/water mixture via hydrophilic polymer of intrinsic microporosity (PIM) derivatives

The chemical process for manufacturing raw materials requires a substantial amount of organic solvent, and it is important to recover the solvent overused during the reaction. This work uses membrane pervaporation to recover ethylene glycol by dehydrating water from a mixture of ethylene glycol (EG) and water. As a feasible membrane material suitable for the dehydration of lean-EG/water (with a water content of 70–95 wt%), we suggest two hydrophilic derivatives from the polymer of intrinsic microporosity (PIM-1). Two PIM-derivatives, amidoxime-functionalized PIM (AO-PIM) and 2,4-diamino-1,3,5-triazine-functionalized PIM (DAT-PIM), were effectively produced through hydrophilic functional group modification and retained their intrinsic microporosity based on a rigid and highly twisted polymer backbone. The PIM-derivatives showed increased water sorption capacity, resulting in tenfold greater water permeability of both PIM-derivative membranes than pure PIM-1. In addition, the modified membranes retained a water content of 99.9% in the permeate. This study demonstrated a simple method for modifying suitable dehydration materials while maintaining the original polymer's structural quality.

Electrochemical and hydraulic analysis of thin-film composite and cellulose triacetate membranes for seawater electrolysis applications

Polymeric filtration membranes could be a cost-effective alternative to cation exchange membranes (CEMs) in electrolysis with a contained anolyte and saltwater catholyte because they size selectively hinder salt ion transport between compartments while facilitating proton and hydroxide transport. Optimizing membrane performance requires a better understanding of membrane properties that impact electrical resistances and ion retention. Twelve reverse osmosis (RO) membranes, one nanofiltration (NF) membrane, and one cellulose triacetate forward osmosis (FO) membrane were examined for their electrical resistances under conditions typically used for characterization of CEMs. Resistances measured at low current densities (0.07–0.3 mA cm−2) varied between different membranes by over an order of magnitude in 1 M NaCl at neutral pH, from 6.1 ± 0.1 Ω cm2 to 70 ± 30 Ω cm2. There was no significant correlation between membrane resistance and applied potential during saltwater electrolysis at 20 mA cm−2 (p = 0.44), or between membrane resistance and water permeability (p = 0.35). These results indicate that traditional CEM resistance characterization methods do not predict polymeric filtration membrane electrolysis performance because proton and hydroxide transport, which is important during electrolysis when large pH gradients develop, must be considered separately from salt ion and water molecule transport through size selective RO, NF, and FO membranes during water electrolysis.

Removal of arsenic from water using a CuBTC incorporated thin film nanocomposite hollow fiber membrane by interfacial polymerization on lumen side

A thin film nanocomposite (TFN) low-pressure driven hollow fiber (HF) nanofiltration (NF) membrane of CuBTC incorporated in polyamide layer was developed via interfacial polymerization (IP) of m-phenylenediamine (MPD) and CuBTC/trimesoyl chloride (TMC). The inner surface of the polysulfone (PSF) hollow fiber substrate was covered with a thin polyamide coating. During the IP process, a small quantity of CuBTC (0.2 wt%) was mixed into the TMC solution, which significantly enhanced the pure water permeate flux of the developed TFN hollow fiber membrane. The characteristics of developed HF membranes were studied using the scanning electron microscope (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM), molecular weight cut-off (MWCO), pure water permeability, X-ray photoelectron spectroscopy (XPS), contact angle, Fourier transform infrared spectroscopy (FTIR) and surface zeta potential. As CuBTC was included in the polyamide layer, the pure water permeability of the TFN membrane increased from 4.4 l/m2h.bar (TFC) to 16.6 l/m2h.bar, as supported by an increment in average pore radius from 6.9 Å to 10.6 Å and MWCO from 693 Da to 1723 Da. The TFN hollow fiber membrane exhibits 85.8 % rejection of arsenate with enhanced permeated flux compared to the nascent thin film composite membrane. Thus, the developed low-pressure driven TFN HF membrane was capable of arsenate rejection. Performance of the developed TFN HF membrane was tested for artificially arsenic-contaminated groundwater with a rejection of 79.7–84.5 % arsenate, 41.6 % TDS, 41.2 iron and 42.8 % hardness at 1 bar transmembrane pressure (TMP) with 12.5 l/m2h permeate flux.

Graphene oxide membranes intercalated with titanium dioxide nanorods for fast infiltration and dye separation

Membrane technology has brought new developments in the field of water treatment. Membranes with ultrafast solvent transport and precise molecular separation to reduce energy consumption during separation. Graphene oxide (GO) shows great potential in the field of membrane separation. However, the low water permeability of GO membranes is the main reason limiting the development of GO membranes. This working material prepared TiO2 nanorods by one-step hydrothermal method and embedded them in GO nanosheets to achieve the enlargement of the interlayer spacing. XRD, BET and SEM were used to characterize the physical and chemical properties (interlayer spacing, specific surface area, pore size distribution, surface morphology and cross-section morphology) of the membranes. The obtained membrane has a water permeability of 420.2 L·m−2·h−1·bar−1 and more than 97% rejection for the four dyes (EB, MB, RB, MO). The water contact angle indicated that the membrane had good wettability (CA < 47°). The separation mechanism depends on the synergy of steric hindrance and electrostatic repulsion. Their high water permeability and excellent molecular separation performance can provide promising candidates for the preparation of nanofiltration membranes with high permeation flux and excellent separation performance.

Multiscale Analysis of Permeable and Impermeable Wall Models for Seawater Reverse Osmosis Desalination

In recent years, high permeability membranes (HPMs) have attracted wide attention in seawater reverse osmosis (SWRO) desalination. However, the limitation of hydrodynamics and mass transfer characteristics for conventional spiral wound modules defeats the advantage of HPMs. Feed spacer design is one of the effective ways to improve module performance by enhancing permeation flux and mitigating membrane fouling. Herein, we propose a multiscale modeling framework that integrates a three-dimensional multi-physics model with a permeable wall and an impermeable wall, respectively, at a sub-millimeter scale and a system-level model at a meter scale. Using the proposed solution framework, a thorough quantitative analysis at different scales is conducted and it indicates that the average errors of the friction coefficient and the Sherwood number using the impermeable wall model are less than 2% and 9%, respectively, for commercial SWRO membrane (water permeability 1 L m−2 h−1 bar−1) and HPMs (3 L m−2 h−1 bar−1, 5 L m−2 h−1 bar−1 and 10 L m−2 h−1 bar−1) systems, compared to the predictions using the permeable wall model. Using both the permeable and impermeable wall models, the system-level simulations, e.g., specific energy consumption, average permeation flux, and the maximum concentration polarization factor at the system inlet are basically the same (error &lt; 2%), while the impermeable wall model has a significant advantage in computational efficiency. The multiscale framework coupling the impermeable wall model can be used to guide the efficient and accurate optimal spacer design and system design for HPMs using, e.g., a machine learning approach.

Understanding the desalination performance of seawater passing through the lamellar BN membranes: Effect of interlayer spacing and concentration

Due to its smaller surface tension and greater wetting degree, BN-based membranes have exhibited promising application prospect in water treatment and seawater desalination. In this work, boron nitride nanosheets were employed to establish lamellar BN membranes layer by layer. By using non-equilibrium molecular dynamics simulations (NEMD), we evaluated the influence of interlayer spacing on the desalination performance of BN membranes. We also evaluated the relationship between the water permeability and the concentration of the feed solution. The simulation results showed that the water permeability of BN membrane first decreased and then increased with the interlayer spacing, it reached the minimum at the interlayer spacing of 1.1 nm, with a turning point at the same time. This is due to the strong interaction between water molecules and BN. What’s more, with the increase of the concentration of the feed solution, the hindering effect of ions on the transport of water molecules gradually decreases, the difference between water permeability in systems with different interlayer spacing decreases gradually.