Separation Performance Of Membranes Research Articles

2D Vermiculite Nanolaminated Membranes for Efficient Organic Solvent Nanofiltration

AbstractMembrane separation technology has found widespread application in molecular sieving and water reclamation. Its use in organic solvent nanofiltration (OSN) has been limited by the modest permeation rates and stability of existing membranes. In this study, 2D clay nanolaminated membranes are engineered, derived from the stacking of exfoliated vermiculite nanosheets, as a potential solution for OSN. The as‐synthesized clay membrane displayed limited stability in both water and solvents due to rapid hydration or solvation of the nanosheets. To enhance the membrane's stability and sieving capabilities, cations of various valences (K+, Na+, Mg2+, Ca2+, Fe3+) are intercalated into the interlayer of the clay nanosheets. The resulting cation‐treated clay membranes display considerable enhancement in structural stability in both aqueous and organic media. Subsequently, the solvent transport behavior and separation performance of these clay membranes are evaluated and described by molecular dynamic simulation and experiments. It is identified that Fe‐intercalated nanolaminates demonstrate controllable stacking order, resulting in enhanced sieving performance with a rejection rate of over 95% for Methyl Orange and a methanol permeation rate of ≈165 L m−2 h−1 bar−1 [LMHB]. The findings of this work pave the way for the practical applications of 2D nanolaminated clay membranes in OSN.

Development of a Negatively Charged Polyether Sulfone Membrane Enriched with MIL-101(Cr)-Modified Magnetic Activated Pyrolytic Coke for Enhanced Dye Removal, Permeability, and Antifouling Properties

Developing high-performance nanofiltration membranes for effectively treating wastewater contaminated with organic pollutants has become increasingly important. Given the hazardous nature of these contaminants, proper treatment of wastewater is crucial before it is released into natural water bodies. This study synthesized a novel composite membrane by incorporating Fe3O4@APC@MIL-101(Cr) nanocomposites into a polyether sulfone (PES) matrix using a phase inversion technique. The inclusion of 0.5wt.% Fe3O4@APC@MIL-101(Cr) significantly enhanced the membrane's hydrophilicity, porosity, and surface characteristics. The optimized membrane achieved an impressive pure water flux (PWF) of 90.24L/m²h, reflecting a 400% improvement over pristine PES membranes. Moreover, it exhibited excellent rejection rates of 97.21% for crystal violet (CV) and 99.43% for methylene blue (MB), alongside a rejection efficiency of 57.73% for the anionic dye methyl orange (MO). The antifouling performance was notably improved, as evidenced by an increase in the flux recovery ratio (FRR) from 46% for bare PES membranes to 81.11% for hybrid membranes. Additionally, the effects of various salt types on the membrane's separation performance were investigated. The Fe3O4@APC@MIL-101(Cr) modified PES membranes demonstrate significant potential as effective candidates for treating wastewater contaminated with dye pollutants.

Construction of stable triazine porous organic polymer nanofiltration membrane for selective separation: The role of substrate on the membrane formation and separation performance

Porous organic polymers (POPs) have been regarded as potential candidates for high-performance membrane building blocks ascribed to their robust structure, tunable pore size, and high surface area. Normally, the POPs membrane possesses a POPs selective layer on the porous substrate for its real application. Numerous efforts have been paid to manipulate the POPs selective layer to enhance the separation performance, however, except from providing mechanical strength, the role of substrates in the formation and separation performance of POPs membrane receives less attention. In this work, we employed a systematic study to reveal the role of substrates in the governing POPs membrane formation by choosing substrates with diverse properties. The relationship between the properties of substrate (e.g., pore size, porosity, roughness, hydrophilicity, and surface functional groups) and the assembly structure of POPs membranes was in-detail analyzed. We found that the hydrolyzed polyacrylonitrile substrate induced a better assembly of POPs nanoparticles. Its rough surface and carboxylic functional groups created Van der Waals interactions and hydrogen bonding interactions to reinforce interfacial adhesion between the substrate and POPs selective layer, which facilitated the formation of intact and defect-free POPs membranes. The resulting POPs membrane displayed a high water permeance of 121.3 L m-2h−1 bar−1 with a congo red rejection of 98.9 %. Moreover, benefiting from the robust interfacial interactions between POPs selective layer and the substrate, the POPs membrane enabled itself to maintain structure stability under harsh environments, such as acidic, alkaline, and organic solvents. This work gives new insights to producing robust and high-performance POPs membranes.

Leveraging molecular scale free volume generation to improve gas separation performance of carbon molecular sieve membranes

Carbon molecular sieve (CMS) membranes have proven to be promising candidates for next-generation gas separations. Modification of polymeric precursors is a critical tool that permits fine-tuning of CMS structure and performance for a wide variety of gas mixtures. Here, we make a targeted alteration to a polyimide CMS precursor through substitution of free-volume-generating trifluoromethyl groups for aliphatic methyl groups on the polymer backbone. Gas separation performance shows a vast improvement, demonstrated by up to an eightfold increase in gas permeability as well as higher mixed gas separation factors in some cases. We investigate these properties, and their dependence on pyrolysis temperature, with detailed measurements of gas sorption and permeation in CMS dense film membranes with additional analysis through classical materials characterization methods. Our observations indicate that addition of free-volume-generating groups into polymeric precursors is a powerful tool for developing state-of-the-art CMS membranes, especially in cases when high permeability is an important design parameter.

Nanofoamed Polyamide Membranes: Mechanisms, Developments, and Environmental Implications.

Thin film composite (TFC) polyamide membranes have been widely applied for environmental applications, such as desalination and water reuse. The separation performance of TFC polyamide membranes strongly depends on their nanovoid-containing roughness morphology. These nanovoids not only influence the effective filtration area of the polyamide film but also regulate the water transport pathways through the film. Although there have been ongoing debates on the formation mechanisms of nanovoids, a nanofoaming theory─stipulating the shaping of polyamide roughness morphology by nanobubbles of degassed CO2 and the vapor of volatile solvents─has gained much attention in recent years. In this review, we provide a comprehensive summary of the nanofoaming mechanism, including related fundamental principles and strategies to tailor nanovoid formation for improved membrane separation performance. The effects of nanovoids on the fouling behaviors of TFC membranes are also discussed. In addition, numerical models on the role of nanovoids in regulating the water transport pathways toward improved water permeance and antifouling ability are highlighted. The comprehensive summary on the nanofoaming mechanism in this review provides insightful guidelines for the future design and optimization of TFC polyamide membranes toward various environmental applications.

Twinned Metal-Organic Framework Nanoplates for Hydrocarbon Separation Membranes.

Filler morphology control is critical for enhancing the gas separation performance of mixed matrix membranes (MMMs). A vertical transport channel using the crystal twinning phenomenon is designed on the zeolitic imidazolate framework (ZIF) nanoplate. Twinned ZIF-8 (TZIF-8) nanoplate is prepared by controlling the shape of ZIF-L from nanosheet to twinned flake, followed by conversion into the ZIF-8 phase. With the addition of TZIF-8 in 6FDA-DAM polymer, propylene/propane selectivity is dramatically enhanced, showing propylene permeability of 40 Barrer and propylene/propane selectivity of 82. The separation performance surpasses the performance of MMMs reported so far, and the selectivity is comparable to that of polycrystalline ZIF-8 membranes. A transport mechanism study using mathematical models implies that the percolated twin fillers create rapid and selective gas channels for desired molecules and substantial tortuous pathways for undesired molecules.

Effect of Addition Amount of Ethylenediamine on Interlayer Nanochannels and the Separation Performance of Graphene Oxide Membranes.

In recent years, graphene oxide (GO)-based two-dimensional (2D) laminar membranes have attracted considerable attention because of their unique well-defined nanochannels and deliver a wide range of molecular separation properties and fundamentals. However, the practical application of 2D GO layered membranes suffers from instability in aqueous solutions as the interlayer d-spacing of GO membranes is prone to expansion caused by the hydration effect. In this study, the effects of the ethylenediamine (EDA) addition amount on the structure, crosslinking mechanism and separation performance of GO membranes were investigated systematically, and membrane performance was evaluated using water permeability and dye/salt rejection tests. The experimental results show that the amine groups of EDA chemically bond with the hydroxyl functional group (O=C-OH) of GO after intercalation, as evident from Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). By further controlling the amount of the intercalated EDA, the as-prepared GO composite membranes show nanoscale-tuned d-spacing promising for downstream applications. In the demonstrated dye/salt nanofiltration scenario, the EDA intercalated and crosslinked GO membrane has enhanced permeability by over five times and a better dye rejection rate of over 96% compared with pure GO membranes. These findings highlight a facile strategy for controlling nanochannels by tuning the amounts of reactive intercalants.

Nanosized SiO2-enhanced PDMS membrane for efficient isopropanol–butanol–ethanol (IBE) separation by pervaporation

Pervaporation separation of isopropanol–butanol–ethanol (IBE) aqueous mixture was carried out using polydimethylsiloxane (PMDS) membranes containing 5, 10, and 15 wt.% of nanosized SiO2. PDMS/SiO2 membranes prepared by solution-casting technique were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). Sorption experiments were performed at 30 °C, 40 °C, and 50 °C, and the interaction parameters between the pure components and the membrane were calculated. Further, the activity coefficients, excess Gibbs energies, and binary interaction parameters of organic-water binary systems at different temperatures were estimated using the UNIFAC method. A single-component permeation through pristine PDMS and nanocomposite PDMS membranes, as well as the pervaporation separation performance of PDMS-based membranes at different temperatures for a model IBE mixture with a concentration of 20 g·L−1, were investigated. The pervaporation results showed that the highest butanol permeability (15514 Barrer) and selectivity (102.6) values were obtained for 5 wt.% and 15 wt.% SiO2-filled PDMS membranes at 30 °C, respectively.

Polydopamine-incorporated MOF membrane with hydrophilicity for effective oil/water separation and fouling-resistant model analysis and prediction

A large number of oil spills and oily wastewater are discharged, in the modern industrial production process, resulting in serious water pollution. Oily wastewater can be extremely harmful to ecosystems and human health. Oil-water separation has become a major challenge at present, and membrane separation has aroused more and more concern in recent years due to its high economic efficiency. This paper fabricated PES filtration membranes using the novel nanoparticlesbased on both metal–organic frameworks-5 (MOF-5) and polydopamine (PDA) layers as dopants, and then adequately explored the porosity, morphology, separation, hydrophilicity, and fouling-resistant performance of the resultant membranes. In addition, the prepared membranes were used for oil–water separation, including soybean-in-water, petroleum ether-in-water, and gasoline-in-water emulsions. MOF@PDA membranes exhibit high separation efficiency of up to 99.8%. Subsequently, membrane fouling mechanisms were investigated using the Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, and the molecular mode of interaction with the three oil–water emulsions with the membrane was compared. Newly prepared MOF@PDA membranes have better stability, fouling-resistant, and self-cleaning properties. Finally, an optimal machine learning model for oil–water separation efficiency was developed with a high prediction accuracy of 98%. The obtained results indicate that mixed matrix membranes exhibit excellent oil–water separation performance, demonstrating great application prospects in the remediation of oily wastewater.

Enhanced removal of fluoride ions using lanthanum-doped coconut shell biochar in PVDF ultrafiltration membranes

Fluoride contamination in surface and ground water poses significant health risks, necessitating a low-energy, cost-effective removal method. Herein, an ultrafiltration (UF) adsorptive membrane doped with lanthanum (La)-based coconut shell biochar was synthesized to effectively remove fluoride ions. Based on the results of adsorption and membrane separation performance, it was found that La-based biochar showed a significantly higher adsorption capacity (126.7 mg F/g) compared to bare biochar (27.41 mg F/g), due to the oxygen-containing functional groups from La2O2CO3 that enhance binding sites and electrostatic attraction for fluoride ions. Furthermore, the addition of La-modified adsorbent to the polyvinylidene fluoride (PVDF) UF membrane markedly altered its structure and surface properties, changing the pore structure to porous, narrowing pore size, increasing active adsorption sites, and improving hydrophilicity. These changes boosted fluoride ion rejection from 9.53 % to 62.07 % with tiny effect on membrane permeability. More important, this UF adsorptive membrane exhibited excellent antifouling ability with the lowest flux decline (J/J0 =0.450) compared to pristine PVDF membrane (J/J0 =0.142), which was owing to the better improved surface properties. In all, this study provides a novel strategy for efficient, economic and selective separation of fluoride ions and further extends the application of UF to the field of ion removal.

Enhancing permeability of CA/MoS2 pervaporation membrane via electric field-induced orientation of MoS2 nanosheets

The formation of a mixed matrix membrane by incorporating nanofillers into a polymer matrix is a potential strategy to improve the separation performance of polymer membranes. However, agglomeration and random arrangement of nanofillers in the mixed matrix membrane result in lower permeation flux increase than expected. In this work, mixed matrix membranes composed of cellulose acetate polymer and varying amounts of Molybdenum disulfide (MoS2) nanosheets as nanofillers were prepared, and an electric field was applied to induce the alignment of MoS2 nanosheets in the membrane thickness direction. The effects of solution parameters including solvent type, MoS2 content, and polymer concentration as well as electric field parameters i.e., frequency, strength, and action time on MoS2 orientation were investigated using a stereoscopic microscope. The pervaporation desalination performance of mixed matrix membranes with randomly arranged MoS2 and orientally arranged MoS2 was assessed. At 2 wt% MoS2 content, the mixed matrix membrane with orientally arranged MoS2 exhibited a flux of 5.44 kg/(m2·h), representing a 25.9 % increase over the mixed matrix membrane with randomly arranged MoS2, while maintaining a salt rejection rate of over 99.9 %. The mixed matrix membrane demonstrated good long-term stability with consistent water flux and salt rejection during 120 h of operation.

Fabrication and separation performances of composite membranes containing copper ferrite photocatalysts on graphene oxide nanosheets

An innovative approach thatintegrates photocatalysis, adsorption, and membrane separation processes was presented to degrade pollutants simultaneously during the filtration process. Firstly, a one-pot method was employed to prepare 3D graphene oxide/carbon quantum dot/copper ferrite (G/CFQ) photocatalysts. Then, the M−G/CFQ membrane was fabricated by intercalating 3D G/CFQ photocatalysts between 2D graphene oxide (GO) nanosheets using a negative pressure filtration technique. The time-dependent flux and MB residual rate results revealed that the M−G/CFQ membrane exhibited superior photocatalytic capabilities, particularly in alkaline environments. Furthermore, M−G/CFQ, when used without reaching adsorption saturation and under illumination, displayed outstanding long-term operational catalytic degradation capabilities. For a 5 ppm methylene blue (MB) solution at pH of 7, 10, and 12, the filtrate residue rates were only 8.63 %, 4.44 %, and 1.61 % respectively within 6 h. The versatility, stability, and exceptional properties of M−G/CFQ make it a promising candidate for large-scale water treatment applications, contributing significantly to the conservation of clean water resources and environmental sustainability.

Intensifying the CO2/N2 separation performance of PVAm membrane by amine-functionalized porous montmorillonite

Multilayered montmorillonite (MMT) exhibits the building block stacking in polymer matrix, which has tortuous transport passageways and a few CO2 affinity sites, thus mixed matrix membranes incorporated with MMT have low molecular recognition ability for CO2. Herein, the porous MMT (p-MMT) was initially prepared through the solid-phase desilication reaction, and then amine-functionalized p-MMT (P3.2@p-MMT) was synthesized by the electrostatic interaction between positively charged polyethyleneimine (PEI) and negatively charged p-MMT, in which PEI was confined within the pore. Subsequently, mixed matrix composite membranes (MMCMs) were developed by the dispersion of polyvinylamine (PVAm) and P3.2@p-MMT, as well as hydrophilic-modified polysulfone as a support. It was observed that P3.2@p-MMT was uniformly dispersed in polymer matrix, and two phases had good interfacial compatibility due to hydrogen bonding. As a result, the gas separation performance of as-prepared MMCMs achieved a CO2 permeance of 217 GPU with a CO2/N2 selectivity of 112.3, which were 2.97 and 2.45 times that of the pristine PVAm membrane, and 1.57 and 2.49 times that of MMCMs incorporated with p-MMT respectively. The excellent gas separation performance is attributed to the relatively straight transport passageways, which originates from P3.2@p-MMT. Moreover, the amine groups within the pore of P3.2@p-MMT facilitate CO2 transport in the MMCMs. In addition, as-prepared MMCMs had high stability during over 360 h-testing, which displayed an average CO2 permeance of 238 GPU with the CO2/N2 selectivity of 124.1 utilizing a gas mixture as the feed gas.

Improving CO2 separation performances of Styrene-Butadiene-Styrene Triblock Copolymer Membranes by tunning its Microstructure via varying solvents and/or non-solvents

Microstructure in block copolymers has a critical impact on CO2 separation performances. In this work, styrene-butadiene-styrene (SBS) triblock copolymer membranes were made using various solvent/non-solvent combinations. It was found that the solvents changed their microstructure thus the CO2 separation performances were changed accordingly. CO2 permeability in the range of 203.4 to 282, and CO2/N2 selectivity in the range of 15.8 to 22.7. The highest CO2 separation performance (PCO2 282 Barrer with CO2/N2 selectivity of 20.5) was obtained using cyclohexane (CYH) as solvent. Furthermore, the CO2 separation performances of the membrane can be further improved by DI water-induced microstructure rearrangement (PCO2 343.5 Barrer and CO2/N2 selectivity 17.9). In addition, it was found that the rearranged membrane demonstrated stable gas separation performance after the membrane was stored under ambient conditions for about 120 days, clearly denoting that the CO2 separation performances of block copolymeric membranes can be tuned by varying the solvents/non-solvents.

Preparation of PDMS permeation membrane by emulsion dilution method and its separation performance for aromatics

Natural aroma compounds are a kind of important food additive. Taking bis(2-ethylhexyl) sodium sulfosuccinate (AOT) as the surfactant, water-in-n-heptane emulsions were prepared. Then, the emulsions were adopted as the diluter to prepare polydimethylsiloxane (PDMS) pervaporation membranes using the emulsion templating method (ePDMS), of which the separation layer was controlled by the template action of emulsion drops. The ePDMS membranes were utilized to separate aroma compounds. Field-emission scanning electron microscope (FESEM) analysis revealed that the surface of the ePDMS membrane remained smooth, and white light interferometry confirmed the membrane’s surface smoothness. FESEM cross-sectional analysis exposed the voids left by the evaporation of the emulsion, rendering the separation layer of the ePDMS membrane more porous. Water contact angle measurements demonstrated the hydrophobicity of the ePDMS membrane, which is advantageous for the pervaporation of aromatic compounds. Fourier transform infrared spectrometry analysis confirmed the evaporation and separation of the emulsion, retaining the original chemical properties of the PDMS membrane. In an ethanol–water system, the permeation flux of ethanol in ePDMS membranes prepared with 1 emulsion (Vwater:Vn-heptane = 1:9; mass concentration of AOT of 1.0 mg/ml) is 90.6% higher than that in PDMS membranes, while the separation factor does not change obviously. The separation performance of ePDMS membranes for linalool in water was further studied. Results show that the permeation flux and separation factor of linalool in ePDMS composite membranes at 50 °C are 786 g m−2 h−1 and 17.69, which separately increase by 84.7% and 27.1% compared with those in PDMS membranes. This indicates that adding ethanol exerts a significant synergistic effect on the separation of linalool.

Modifying polysulfone dual-layer hollow fiber membrane with amine-functionalized bimetallic MOF (PEI@HKUST-1(Cu, Mg)) for improved mechanical stability and CO2/CH4separation performance

As the demand for cleaner energy sources and carbon dioxide (CO2) capture technologies increases, membrane-based separation is increasingly seen as a viable, scalable, and eco-friendly option. However, fabricating mechanically stable membranes with high permeance and selectivity remains a significant challenge, owing to the limited CO2 affinity sites and transport channels inside the membrane. This study investigates integrating the unique properties of metal-organic frameworks (MOFs) with the structural benefits of dual-layer hollow fiber (DLHF) membranes. Herein, a polyethyleneimine (PEI) functionalized bimetallic MOF (PEI@HKUST-1(Cu, Mg)) as filler was blended to polysulfone(PSf) matrix to fabricate MOF/PSf mixed matrix membrane (MMM) through co-extrusion and dry-jet wetting spinning process. The open metal sites (Cu2+ and Mg2+), high porosity, and the CO2-philicity of the amine groups of the PEI-functionalized MOF could create additional CO2 binding sites and transport channels, thus promoting the rapid permeation of CO2 molecules through the membrane. The improved affinity among the organic linker, amines group, and polymer chains facilitated the formation of defect-free hollow fibers. Notably, the tensile strength increases from 4.51MPa to 8.78MPa for pure membranes to 10wt% MOF-loaded membranes, showing a direct correlation between fiber strength and MOF loadings. The optimized membrane containing 5wt% PEI@HKUST-1(Cu, Mg) exhibited a CO2 permeance of 28 GPU and a CO2/CH4 selectivity of 51, displaying an increase of 75% and 85.45%, respectively, over the pure PSf membrane. These findings suggest that incorporating amine-functionalized MOFs can enhance the CO2 separation performance and mechanical stability of hollow fiber membranes used in natural gas purification.

Membrane fouling behavior and cleaning control of a dual-charged nanofiltration membrane in treating acid mine drainage after neutralization

The study evaluated the membrane fouling behavior of a dual-charged nanofiltration (NF) membrane in treating acid mine drainage (AMD) after neutralization. After 10hours of fouling, the membrane demonstrated an 89.52% recovery rate and exhibited excellent retention ability for divalent ions (91.21% Mg2+, 89.24% Ca2+, 91.51% Mn2+, 93.72% SO42-), as well as outstanding anti-pollution performance. Membrane fouling characterization revealed that the primary cause of membrane fouling was inorganic salt fouling from CaSO4 and MgSO4. In the initial stage of NF separation, when the inorganic salt fouling was close to the membrane surface, the adhesion-free energy between the membrane and the inorganic salt fouling was dominant, causing the inorganic salt fouling to be deposited on the membrane surface. As time progressed, the deposited inorganic salt fouling gradually covered the membrane surface, with agglomeration-free energy between the inorganic salt fouling dominating subsequent stages of membrane fouling. The fitting of the membrane plugging model revealed that, in addition to the deposition of inorganic salt fouling on the membrane surface, some inorganic salt fouling would also penetrate the membrane pores and obstruct them, leading to a rapid decline in membrane flux and subsequently reducing the membrane separation performance. Following cleaning with deionized (DI) water, citric acid (CA), NaOH, and EDTA, it was observed that the CA cleaning agent achieved the highest membrane flux recovery rate at 91.84%. The EDTA cleaning agent demonstrated superior retention effects on bivalent ions (94.21% Mg2+, 93.21% Ca2+, 96.74% Mn2+, 97.45% SO42-). This work provides a reference direction and theoretical guidance for the behavior and control strategy of membrane fouling in neutralized AMD treated by the dual-charged NF membrane.

Boosting lithium/magnesium separation performance of selective electrodialysis membranes regulated by enamine reaction

Monovalent cation exchange membranes (MCEMs) have progressively played an important role in the field of ion separation. However, according to transition state theory (TST), synchronously tuning the enthalpy barrier (△H) and entropy barrier (△S) for cation transport to improve ion separation performance is challenging. Here, the enamine reaction between the -NH- and -CHO groups is applied to regulate the subsequent Schiff-base reaction between the -CHO and -NH2 groups, which reduces the positive charges of the selective layer but increases the steric hindrance. The increased -T△S (△S term) for cation transport plays an important role in improving Li+/Mg2+ separation performance. The optimal positively-charged glutaraldehyde@piperazine/polyethyleneimine assembled membrane (M-Glu@PIP/PEI) has a perm-selectivity (Li+/Mg2+) of 31.83 with a Li+ flux of 1.87 mol·m-2·h-1, surpassing the Li+/Mg2+ separation performance of state-of-the-art monovalent ion selective membranes (MISMs). Most importantly, the selective electrodialysis (S-ED) process with M-Glu@PIP/PEI can be directly applied to treat simulated salt-lake brines (SLBs), and its superior Li+/Mg2+ separation performance and operational stability enables 74.44 % of the lithium resources with a Li+ purity of 34.02 % to be recovered. This study presents new insights into the design of high-performance MCEMs for energy-efficient resource recovery.

PFSA-g-ZIF-L/CS-PVA mixed-matrix membrane for pervaporation desalination

In this work, perfluorosulfonic acid (PFSA)-g-ZIF-L nanocomposites were prepared by grafting PFSA onto NH2-Co/Zn-ZIF-L at different mass ratios via substitution reaction. A series of PFSA-g-ZIF-L/chitosan (CS)-polyvinyl alcohol (PVA) composite membranes were prepared by solution coating method using different contents of PFSA-g-ZIF-L nanocomposites as nanofillers and polyacrylonitrile (PAN) membrane as the substrate. PFSA-g-ZIF-L nanocomposites and PFSA-g-ZIF-L/CS-PVA membrane were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle. The application of composite membrane for pervaporation desalination was explored. The incorporation of PFSA-g-ZIF-L into the polymers introduced more water transport channels and hydrophilic groups, which improved the separation performance of membrane. The PFSA-g-ZIF-L/CS-PVA composite membrane loaded with 5 wt% PFSA-g-ZIF-L (PFSA:ZIF-L mass ratio of 5:1) showed excellent structural stability under continuous pervaporation desalination for 55 h. The water flux was about 15.4 kg·m−2·h−1 (2.3 times higher than that of CS-PVA membrane), and the rejection was as high as 99.99 % at 35 °C for 3.5 wt% aqueous NaCl solution.

The Impact of Adsorption Property Modification by Crosslinkers on Graphene Oxide Membrane Separation Performance

The health risks associated with the presence of heavy metals in drinking water can be severe. To address this issue, membrane separation technology is one of the consolidated alternatives. Inorganic, porous membranes were found in applications where low energy consumption is highly desirable. The selectivity of these membranes is attained by functionalisation. Graphene oxide functionalised membrane technology is promising for removing heavy metal ions. This work summarises, discusses and presents the relationship between adsorption and overall membrane separation process performance for heavy metal ions removal from wastewater when a graphene oxide-functionalised membrane is used. The separation performance depends on the hydrophobic interactions of the membrane and the solute. The electrostatic interaction between the negatively charged membrane surface and positively charged metal ions facilitates the adsorption, leading to the rejection of these metal ions. The influences of the chemical nature of the modifiers of graphene oxide layers are highlighted.