Performance Of Nanofiltration Membranes Research Articles

High-rate Activated Sludge Process as a Pre-Treatment Alternative to Direct Filtration with Microfiltration/Ultrafiltration for Municipal Wastewater Reclamation to Produce Cooling Water

Industries use reclaimed water for their makeup water requirements of cooling towers to decrease their water footprints. Makeup water quality depends on the type of cooling tower design; however, total suspended solids (TSS), biological oxygen demand (BOD5), fecal coliform, pH, total dissolved solids (TDS), some ions (sulphate, chloride, ammonium) and heavy metals (aluminum, silica, manganese, iron) are important parameters to prevent contamination, scaling, and corrosion. In the first part of this study, cooling water production from municipal wastewater was experimentally investigated, in the second part of this study cost of treatment alternatives was estimated. Six different treatment configurations (C1: microfiltration (MF)+nanofiltration (NF); C2: ultrafiltration (UF)+NF; C3: high-rate activated sludge (HRAS)+NF; C4: MF+reverse osmosis (RO); S5: UF+RO; C6: HRAS+RO) were analyzed. Thanks to the high treatment performances of NF and RO membranes, reclaimed water in each scenario met the suggested cooling water quality. The effluent of the HRAS process showed the worst effluent quality in terms of turbidity (42.1±2.6 NTU of turbidity) compared to MF and UF direct filtration (turbidity of DMF permeates were below 5 NTU). However, since HRAS process is less costly than direct membrane filtration (DMF) via MF or UF membranes, the lowest treatment cost was achieved with the C3 (HRAS+NF) treatment configuration (0.52 €/m3 reclaimed water). This study demonstrates that the HRAS+NF configuration can produce water suitable for cooling tower makeup, highlighting its potential as a sustainable solution to reduce water footprints and promote water circularity in industries.

Rethinking nanofiltration membrane design for breaking the trade-off in Li/Mg separation: A comprehensive analysis based on the separation factor-lithium flux (S-JLi) framework

Nanofiltration (NF) membranes are crucial for lithium (Li) recovery from salt-lake brine, but efficient Li/magnesium (Mg) separation remains challenging. This study employs the recently proposed S-JLi (separation factor vs Li flux) framework to evaluate NF membrane performance for Li/Mg separation, addressing limitations in traditional S-A (separation factor vs water permeance) frameworks. Using the Donnan Steric Pore Model with Dielectric Exclusion (DSPM-DE), we systematically investigate how operating conditions, feedwater properties, and membrane characteristics affect Li/Mg separation. Our results reveal that positively charged membranes outperform negatively charged ones, despite experiencing performance drops in high-salinity environments. We identify a trade-off between Li/Mg selectivity and Li flux that cannot be overcome by adjusting single membrane parameters. Multi-parameter synergistic regulation, particularly minimizing effective membrane thickness while optimizing charge density and pore size, emerges as a promising strategy to enhance separation performance. Our numerical simulations align well with experimental data, providing theoretical insights for designing high-performance Li/Mg separation membranes and emphasizing the importance of considering both selectivity and Li recovery in membrane development and evaluation.

Synergistic Optimization Strategies for SA-PVA Hydrogel Nanofiltration Membrane Performance by MWCNTs and TiO2

Synergistic Optimization Strategies for SA-PVA Hydrogel Nanofiltration Membrane Performance by MWCNTs and TiO2

Nanofiltration Membrane with Enhanced Ion Selectivity Based on a Precision-Engineered Ultrathin Polyethylene Supporting Layer.

Nanofiltration (NF) technology is increasingly used in the water treatment and separation fields. However, most research has focused on refining the selective layer while overlooking the potential role of the supporting layer. With expertise in ultrathin polymer films, particularly in the production of polyethylene (PE) membranes, we explore the possibility of improving NF membrane performance by precisely controlling the structure and surface properties of the ultrathin supporting layer in this work. Here, we introduced an innovative NF membrane that used a submicrometer ultrathin PE membrane produced through a biaxial stretching process, which is significantly thinner than commercial PE membranes available on the market. The core innovations are as follows: first, we focused on precise control of the supporting layer rather than just the selective layer, achieving significant enhancements in overall NF membrane performance; second, the ultrathin PE supporting layer served as a tunable interface for interfacial polymerization, offering possibilities for structural control of the selective layer and advancing membrane performance innovations. The resulting NF membrane boasts an overall thickness of ∼630 nm, which represents the thinnest NF membrane documented to date. This ultrathin NF membrane showed an ultrahigh Cl-/SO42- selectivity of 338.03, placing it at the forefront of existing literature. This study sheds light on the important role of the supporting layer in the preparation of selective layers. We believe that this approach has the potential to contribute to the development of ultrathin, high-performance NF membranes.

Nanofiltration membrane performance in recirculating aquaculture systems: modeling permeate concentration with diverse pre-treatment configurations

Nanofiltration membrane performance in recirculating aquaculture systems: modeling permeate concentration with diverse pre-treatment configurations

Stereochemical tuning, post-synthesis crosslinking and quaternizing to tune the membrane performance of ultra-stable polyamine nanofiltration membranes

Solvent resistant and pH-stable nanofiltration membranes play a crucial role in solvent or water reuse across various industries, including pharma, chemical, dairy and mining, where stringent pH conditions and chemical stability are imperative. Previous research introduced a chlorine-resistant top-layer for nanofiltration membranes, using 1,2,4,5-tetra(bromomethyl)benzene and 1,2-diaminocyclohexane, with also exceptional stability at extreme pH values and a broad solvent resistance thanks to its crosslinked nature. To further optimize this remarkably stable and versatile membrane material, the unique property of 1,2-diaminocyclohexane, i.e. its stereochemistry, is employed here to manipulate membrane properties through diastereomerism and enantiomeric excess. Filtration experiments employing different 1,2-diaminocyclohexane isomers revealed significant variations in membrane performance, emphasizing the impact of stereochemistry on separation performance. Adjusting the enantiomeric excess of 1,2-diaminocyclohexane resulted in notable changes in membrane permeability and rejection, highlighting the general power of stereochemical control in membrane synthesis. Additionally, post-synthesis modifications, including further crosslinking and quaternization, allowed to tune the membrane structure and performance in both aqueous and solvent media, offering opportunities for optimization towards specific applications. SEM and XPS providing insights into membrane morphology and composition, confirmed the influence of stereochemistry and post-synthesis modifications on membrane properties. These findings demonstrate the efficacy of stereochemistry manipulation and post-synthesis techniques in tailoring pH-stable and solvent resistant nanofiltration membranes for specific applications, paving the way for advanced membrane design.

Synthesis and modification of nanofiltration membranes with dendrimer-modified graphene oxide to remove lead and cadmium ions from aqueous solutions

This study explored the use of graphene oxide modified with dendrimer (GO/MDA) to enhance the hydrophilicity and reduce the clogging of nanofiltration membranes, aiming to remove lead and cadmium from aqueous solutions. The synthesis involved multiple steps for creating graphene oxide (GO) nanoparticles and dendrimer (MDA), with FT-IR and EDX tests confirming the successful fabrication of GO/MDA and its application in nanofiltration membranes. Four types of membranes were designated based on the concentration of GO/MDA used: nanofiltration without nanoparticles (NF), nanofiltration with 0.25% weight of nanoparticles (NF-0.25), nanofiltration with 0.5% weight of nanoparticles (NF-0.5), and nanofiltration with 1% weight of nanoparticles (NF-1). The results showed a significant decrease in contact angle from 68.2° to 51.6° with the increase of GO/MDA concentration from 0.25% to 1%, illustrating improved hydrophilicity. Moreover, the pure water flow rate increased, with the NF-1 membrane achieving the highest flow rate of 121 L/m2.h, compared to 86 L/m2.h for the standard NF membrane. The study also established that the removal efficiencies for lead and cadmium improved with rising pH levels, peaking at pH 6, where the NF-0.5 membrane achieved optimal removal rates of 89.45% for Pb2⁺ and 92.58% for Cd2⁺. Additionally, the incorporation of GO/MDA nanoparticles effectively reduced irreversible fouling, with the NF-0.5 membrane displaying a remarkable flux recovery percentage of 97.21%. Overall, the findings confirm that the incorporation of GO/MDA nanoparticles successfully enhanced the performance of nanofiltration membranes in removing heavy metals.

Characterization and Performance Nanofiltration Membranes in Water Quality for Goldfish (Carassius auratus) Aquaculture

Water quality is an important factor in aquaculture activities, including goldfish (Carassius auratus) farming. One approach to improving water quality is the use of nanofilters. This study aims to evaluate the performance of nanofilters made from Sargassum sp. with the addition of copper oxide nanoparticles. The method used involves the fermentation of bacterial cellulose from Acetobacter xylinum using Sargassum sp. extract as a medium, followed by homogenization and the addition of CuO-NPs at concentrations of 0.5%, 1%, and 1.5%, and subsequent oven drying. The nanofilter membrane will then be analyzed using SEM, XRD, and FTIR to characterize its properties. Performance tests will assess the quality of water used in goldfish farming, including pH, TOM, TDS, and TSS after treatment with the nanofilter. Morphological results show a rougher and denser surface with dispersed CuO-NPs. Characterization reveals cellulose I with crystallinity values ranging from 86.80% to 90.20%, with functional group peaks at 3145, 2927, and 1735 cm⁻¹ indicating cellulose characteristics, and a peak at 424 cm⁻¹ indicating Cu-O bonds. Statistical analysis of performance tests on the water quality of goldfish farming in the F-test shows significant differences (p

The investigation of adhesion force of support membrane on the structure and performance of nanofiltration membrane

The surface properties of non-porous areas (>90 %) of support membranes were often overlooked to influence the performance of nanofiltration (NF) membranes. In this work, the role of the support membrane in interfacial polymerization (IP) during synthesis of NF membrane and consequently on its performance were quantitatively investigated from the perspective of adhesion force for the first time. The support membranes with considerable pore structures and different surface sulfonate (-SO3-) contents were prepared from different concentrations of polyethersulfone/sulfonated polysulfone (PES/SPSf) solutions. The adhesion forces of different support membranes were measured by atomic force microscope (AFM). The IP process between piperazine (PIP) and trimethylbenzoyl chloride (TMC) and the obtained polyamide (PA) layer on the support membranes were monitored by Quartz crystal microbalance with dissipation (QCM-D). The results indicated that the contents of sulfonic groups on the surface of the support membranes decreased as the casting-solution concentration increased (from 16 % to 28 %) due to a negative segregation phenomenon, which resulted in a decrease in the adhesion force (from 17.9 to 2.6 nN) between the support membranes and PIP monomers. The reduced adhesion force between the support membrane and PIP monomers led to an increase in the PA layer thickness (from 0.8 to 18 nm). Interestingly, the time to reach PA layer thickness equilibrium decreased (from 91 to 23 s). The obtained NF membranes (from PA@PES/SPSf16 to PA@PES/SPSf28) achieved the pure water permeance from 51.2 to 26.2 L m−2 h−1·bar−1 while the salt (Na2SO4) rejection from 97.5 to 99.5 %, respectively, was noted. It was demonstrated that controlling the adhesion force between the support membranes and PIP monomers could effectively regulate the structure and the performance of NF membranes. This work would provide valuable insights for designing high-performance NF membranes in practical applications.

Enhanced anti-fouling and selective performance of GO-modified nanofiltration membranes for lithium extraction from salt lake brine

Nanofiltration (NF) is a promising method in lithium extraction from salt lake brine with a high Mg2+/Li+ mass ratio. However, membrane fouling challenges its applicability and productivity. This study incorporated graphene oxide (GO) into the polyamide (PA) selective layer of NF membranes to enhance anti-fouling properties and improve lithium extraction from brine. Membrane structure analyses revealed that 0.002 wt% and 0.01 wt% GO facilitated the interfacial polymerization reaction. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results indicated that the PA selective layers in the GO-0.002 % and GO-0.01 % membranes were denser, smoother, and thinner. In contrast, the addition of 0.05 wt% GO resulted in the Turing structures on the membrane surface. Adsorption kinetics indicated pollutant adhesion in the following order: GO-0.05 % > GO-0 % > GO-0.002 % > GO-0.01 %, which was attributed to calcium-carboxyl complexation, as directly measured by AFM and consistent with carboxyl density. The GO-0.002 % and GO-0.01 % NF membranes demonstrated excellent anti-fouling properties in brines, with lower initial fouling rates and higher flux recovery after cleaning, underscoring the significant role of calcium-carboxyl complexation in membrane fouling. The retention of Mg2+ increased to 95 %, while that of Li+ decreased to below −28 % for GO-0.002 % and GO-0.01 % membranes, indicating promising potential for Mg and Li separation. This study provides valuable insights into developing NF membranes with high Mg/Li selectivity and anti-fouling capabilities for lithium extraction from salt lake brine.

Advanced lithium extraction nanofiltration membrane with fast transport channels via competitive diffusion and reaction of rigid electropositive phenylbiguanide molecules

The utilization of nanofiltration membranes for lithium extraction from Salt-Lake holds the potential to address lithium resource scarcity and drive energy transformation. Nevertheless, the trade-off effect between water permeability and Mg2+/Li+ separation selectivity poses a challenge in the application of these membranes. In this work, rigid-flexible interpenetration and competitive diffusion reaction strategies were proposed to regulate the pore structure and charge density of the functional layer, thus enhancing the overall separation performance of nanofiltration membrane. Phenylbiguanide (PBG) possessing rigid structure, high positive charge density, and low energy transfer barrier was embedded into flexible polyethyleneimine-based polyamide network. This integration facilitated the formation of continuous and semi-permanent microcavities with rigid-flexible coupled structure, and meanwhile, elevated the density of positive charges. Consequently, the modification extended the water molecular transport channels within the functional layer, leading to a notable enhancement in pure water flux, from 7.40 to 26.43 L m−2h−1. In addition, due to the faster diffusion of PBG than polyethyleneimine with high molecular weight (70000 Da, as aqueous monomer in this work), it could react with excess 1,3,5-trimesoyl chloride (TMC) on the surface of initial membrane to form a new polyamide layer, which repaired the defects in the functional layer and also enhanced the charge density inside pore channels. Therefore, Mg2+/Li+ separation selectivity factor increased from 3.79 of TFC membrane to 22.98 of PBG membrane, i.e., by about 6 times. This study provided an effective strategy to develop nanofiltration membranes with both good water permeability and Mg2+/Li+ selectivity.

The performance of nanofiltration membranes in seawater and desalination brine applications: Saudi Water Authority experience

The process of dual brine concentration employs an NF-RO-MBC configuration as its fundamental setup. Understanding the ion rejection capabilities of NF in seawater is crucial within this framework. Testing of fourteen commercial NF membranes using Jubail seawater revealed variations in ion rejection capabilities. Twelve membranes operated at a consistent feed pressure of 17.7 bar. The results categorized membranes based on their TDS rejection into high (≥ 45 %), medium (25–45 %), and low (< 25 %) rejection membranes. When concentrating the NF-treated SWRO brine, NF membranes can be utilized in the MBC system. Eight commercial NF membranes were evaluated with SWRO brine, where Na and Cl constituted over 96 % of the TDS. The investigation assessed the concentration performance and secured solid quantity in the reject relative to the feed by applying pressures of up to 40 bar for the conventional NF membranes and up to 65 bar for the newly introduced HPNF membranes. Among these membranes, two conventional and two HPNF membranes exhibited promise for concentrating SWRO brine. In addition, the ion rejection performance of five commercial NF membranes on SWRO brine was examined for a potential RO-NF-MBC configuration, suggesting suitable NF membranes for SWRO brine separation. Lastly, the ion rejection performance was studied in a multistage NF system with varying feed compositions at each stage and compared with projected performance. The accumulated NF membrane performance database will be utilized to optimize the overall membrane system configuration for seawater and brine separation and concentration.

Electro-coagulation pretreatment for improving nanofiltration membrane performance during reclamation of microplastic-contaminated secondary effluent: unexpectedly enhanced membrane fouling and mechanism analysis by MD-DFT simulation

The residue of microplastic in secondary effluent was inevitable with continuous aggravation on nanofiltration membrane fouling. Thus, this study aimed to further evaluate the applicability of electro-coagulation as pretreatment for improving the performance of a nanofiltration-oriented hybrid process during the reclamation of microplastic-contaminated secondary effluent. The electro-coagulation parameters were skillfully optimized and designed for following dynamic nanofiltration experiments. The potential influence of coagulants in different forms as well as their combined effects of microplastics on membrane fouling behaviors and pollutant rejection efficiency was distinguished. Specifically, terminal membrane permeability was reduced by 19% after 0.05 A electro-coagulation, while 0.2 A electro-coagulation almost eliminated the negative effects of microplastics. Mass transfer model analysis excluded the dominance of organic accumulation in the concentration polarization layer on membrane fouling development. Molecular dynamic (MD) simulation and egg-box model demonstrated that humic-Fe network possessed stronger bridging effects and greater porosity. This structure favored the co-deposition of other unlinked bacteria metabolites, which secretion was also facilitated by microplastics as immobilized carriers, on membrane surface. Additionally, density functional theory (DFT) calculation further confirmed that the greater demand for dehydration energy for ferric ions (1124 kcal/mol) inspired the formation of stronger humic-Fe complexes. Besides, residual microplastics in electro-coagulation effluent had different impacts on membrane rejection towards organic and inorganic pollutants, and it depended on the influenced cake-enhanced concentration polarization (CECP) by microplastic affinity with different pollutants.

Enhanced Mg2+/Li+ separation performance of polyelectrolyte multilayers nanofiltration membranes modified by trimethylamine N-oxide zwitterions

Polyelectrolyte multilayer nanofiltration (NF) membranes have garnered attention for their potential in Mg2⁺/Li⁺ separation applications, particularly due to their positively charged nature and the versatility offered by the layer-by-layer (LbL) self-assembly technique. However, these membranes often face significant challenges in balancing high ion selectivity with adequate water permeability. Addressing these limitations, this study introduces a novel approach by grafting a zwitterionic material, trimethylamine N-oxide (TMAO), onto polyacrylamide hydrochloride (PAH), creating a new cationic polyelectrolyte (TPAH). By cyclically depositing sodium polystyrene sulfonate (PSS) and TPAH onto a polyethersulfone (PES) substrate, we have successfully fabricated a high-performance NF membrane (i.e., (PSS/TPAH)n) that demonstrates enhanced Mg2⁺/Li⁺ selectivity with high water permeability. TMAO features shorter distances between its positive and negative charge groups and smaller dipoles compared to other zwitterions. These characteristics enhance its ability to resistance to salt effects and transfer charge from amine oxide to water molecule. Furthermore, the grafting of TMAO enhanced the hydrophilicity of TPAH and regulated the charge distribution of the polyelectrolyte. Compared to the control membrane (PSS/PAH)n, the optimized membrane (PSS/TPAH)n showed reduced rejection of LiCl from 60.9 ± 2.7 % to 35.9 ± 1.5 %, while that of MgCl2 increased from 94.3 ± 1.6 % to 96.1 ± 0.7 %. Additionally, water permeability improved from 9.2 ± 0.9 LMH/bar to 16.1 ± 0.5 LMH/bar. Notably, the membranes exhibited an improved selectivity for Mg2+/Li+ ions in synthetic saline, reaching a maximum of 30.5 ± 1.5, highlighting its potential for practical separation applications. Density functional theory simulations indicate that TMAO not only enhances Donnan effect and intensify ion dehydration of polyelectrolyte multilayers NF membranes but also increases their hydrophilicity. In general, these polyelectrolyte multilayers NF membranes exhibit considerable promise for multiple applications, such as seawater pretreatment, groundwater softening and lithium extraction.

Performances of Nanofiltration and Reverse Osmosis Membranes in Desalination of Tagounite Brackish Water, Morocco

Performances of Nanofiltration and Reverse Osmosis Membranes in Desalination of Tagounite Brackish Water, Morocco

Optimizing dual-layer composite membranes with functionalized CNT loadings using response surface methodology

ABSTRACT In this study, we optimized double-layer composite membranes comprising polyethersulfone (PES) and polyamide (PA) using response surface methodology (RSM). We assessed the impact of PES, piperazine (PIP), and trimesoyl chloride (TMC) concentrations, and interfacial polymerization (IP) reaction time on nanofiltration (NF) membrane performance, aiming to enhance pure water flux (PWF) and salt rejection. Optimal parameters for maximum PWF and salt rejection were determined: PES concentration at 14.0 wt%, PIP concentration at 1.5 w/v%, TMC concentration at 0.2 w/v%, and reaction time at 45 s. In addition, we improved membrane performance by incorporating functionalized multi-walled carbon nanotubes (f-MWCNTs) into the PES ultrafiltration substrate, enhancing hydrophilicity and porosity. The resulting PA NF membrane developed on a substrate containing 0.15 wt% f-MWCNT (TFNC) exhibited a PWF of 11.84 LMH/bar, surpassing the PWF of the same NF membrane on an unloaded substrate (TFC) by approximately 20%, while maintaining nearly identical salt rejection levels. Salt rejection followed the order: Na2SO4 &amp;gt; MgSO4 &amp;gt; NaCl, suggesting Donnan-exclusion mechanisms primarily governed the separation process due to repulsion forces between the negatively charged membrane surface and anions.

Distinct Efficacies of Interlayers in Tailoring Polyamide Nanofiltration Membrane Performance for Organic Micropollutant Removal: Dependent on Substrate Characteristics.

Interlayered thin-film nanocomposite (TFN) membranes have shown the potential to boost nanofiltration performance for water treatment applications including the removal of organic micropollutants (OMPs). However, the effects of substrates have been overlooked when exploiting and evaluating the efficacy of certain kinds of interlayers in tailoring membrane performance. Herein, a series of TFN membranes were synthesized on different porous substrates with identical interlayers of metal-organic framework nanosheets. It was revealed that the interlayer introduction could narrow but not fully eliminate the difference in the properties among the polyamide layers formed on different substrates, and the membrane performance variation was prominent in distinct aspects. For substrates with small pore sizes exerting severe water transport hindrance, the introduced interlayer mainly enhanced membrane water permeance by affording the gutter effect, while it could be more effective in reducing membrane pore size by improving the interfacial polymerization platform and avoiding PA defects when using a large-pore-size substrate. By matching the selected substrates and interlayers well, superior TFN membranes were obtained with simultaneously higher water permeance and OMP rejections compared to three commercial membranes. This study helps us to objectively understand interlayer efficacies and attain performance breakthroughs of TFN membranes for more efficient water treatment.

Machine learning-assisted performance prediction from the synthesis conditions of nanofiltration membranes

Optimizing membrane fabrication conditions, including monomer and catalyst concentrations, reaction time, etc., is crucial for achieving high-performance membranes. However, the multitude of variables involved can result in a complex and laborious permutation process, making trial-and-error optimization challenging. To address this issue, we developed a conventional multiple linear regression model and machine learning (ML) models, specifically random forest (RF) and multi-layer perceptron (MLP), to predict the performance of nanofiltration membranes in terms of key parameters such as pure water permeance or PWP (LMH/bar), Na2SO4 rejection (%), and NaCl rejection (%), based on specified input variable ranges. The input variables utilized to construct the models are the concentration of piperazine (PIP) (0.01–2 wt%), the concentration of trimesoyl chloride (TMC) (0.05–0.15 wt%), the concentration of sodium lauryl sulfate (SLS) (0–10 mM), and reaction time (5–1200 s). The conventional regression model failed to predict the membrane performance. The RF model exhibited the best prediction capability for PWP and NaCl rejection with the R2 of 0.9806 and 0.9812 for training, and 0.9669 and 0.9082 for testing, respectively. Similarly, the MLP model outperformed the RF model in predicting Na2SO4 rejection with an R2 of 0.9972 for testing and 0.9844 for training. The best membrane exhibited permeance ranging from 16 to 20 LMH/bar and selectivity between NaCl and Na2SO4 of over 4000, was facilitated by specific conditions. These conditions included lower concentrations of PIP (0.05–0.1 wt%), intermediate concentration of TMC (0.1 wt%), lower concentration of SLS (1 mM), and shorter reaction times (5–30 s). The best-performing ML-based models have been used to provide insights into the relative importance of these input variables in determining membrane performance, thereby aiding in correlating model predictions with fundamental principles of membrane fabrication processes.

PH controllably induced PPTA/PEMs composite nanofiltration membranes for long-term acid-resistant separation

In this study, we deposited polyelectrolyte multilayers (PEMs) on Poly (p-phenylene terephthamide) (PPTA) ultrafiltration (UF) substrates with strong polyelectrolytes (PEs): polystyrene sulfonic acid (PSS) and poly (diallyldimethylammonium chloride) (PDADMAC). The growth pattern of PEMs was shifted from linear to exponential by changing substrate potential, which was attributed to synergism and antagonism of dispersion of PEs on hydrophilic substrates and electrostatic interaction between PEs and substrates. Eventually, PEMs of layer-dominated and pore-dominated regimes were successfully obtained. We focused on the transition from the pore-dominated to the layer-dominated regime of PEMs. The PEMs nanofiltration (NF) membranes in this situation showed a better separation performance due to the together work of the interface and in-pore energy barriers. The retention rate of Na2SO4 and MgSO4 was 98 % and 91 %. The eosin Y retention rate was 99.9 % and only declined 2 % after 100 h. The hindered deposition of pore-dominated regimes led to denser and thinner layers, which achieved long-term acid resistance. It maintained a stable salt retention after 185 h cross-filtration of 0.1 M H2SO4 feed solution. The performance of PEMs NF membrane was improved from a new perspective, and excellent acid-resistant nanofiltration membranes were obtained, which are expected to be used to treat industrial acidic wastewater.

The Effect of GO on TiO2-doped PVDF Nanofiltration Membrane Performance: Synergistic Filtration of Large and Small Molecules Facilitated the Removal of Small Molecule Contaminants

The Effect of GO on TiO2-doped PVDF Nanofiltration Membrane Performance: Synergistic Filtration of Large and Small Molecules Facilitated the Removal of Small Molecule Contaminants