Polyacrylonitrile Ultrafiltration Membrane Research Articles

Potential oscillation enhanced lithium ion pump membrane for lithium ion extraction

In this work, a novel electrochemically switched ion permselective membrane (ESIPM) has been applied to the recovery of lithium from brine in the electrochemically switched ion permselective (ESIP) membrane separation system. This ESIPM was prepared by multi-layer assembly, with polyacrylonitrile ultrafiltration membrane (PAN) as the base membrane, and CNTs/CS membranes pressed and filtered on the base membrane as the current collector, crosslinking a lithium manganate/carbon black/polyvinyl alcohol/polyacrylic acid (LiMn2O4/C/PVA/PAA) composite material, which coated on a polyacrylonitrile ultrafiltration membrane/carbon nanotubes (PAN/CNTs) composite membrane as the electroactive lithium ion exchange layer. In the ESIP system, by alternately applying oscillation potentials between the ESIPM membrane and counter-electrodes to regulate the placement and release of the target ions on the membrane, Meanwhile the target ions are driven by the electric field to be enriched in the ESIPM and directionally transported through the ESIPM. As a result, it was found that compared with the electrodialysis (ED) system, the flux of Li+ in ESIPM in the ESIP system increased by 12 times and the selectivity factor for Li+/Mg2+ increased by 1.4 times for the brine with Mg2+/Li+=1. Besides, the selectivity factor for Li+/Mg2+ reaches 4.4 for the brine with Mg2+/Li+=20 in ESIPM in the ESIP system, which was 2.2 times higher than that of the commercial ion exchange membrane CIMS in the ED system.

Enhanced anti-biochemical fouling properties of the polyacrylonitrile membranes assisted by the d-amino acid surface-modified halloysite nanotubes

Membrane fouling has always been one of the key problems to be solved in the liquid–liquid separation process of biomacromolecules, proteins, bacteria, etc. Here, halloysite nanotubes (HNTs) surface-modified with D-Amino acid (D-Aa) is synthesized in one step and introduced into the polyacrylonitrile (PAN) ultrafiltration membrane matrix to obtain a PAN mixed matrix membrane (MMM). D-Aas with three different R groups are selected to modify the HNTs. The results show that the carboxyl and amino groups of the D-Aa molecules interact with the surface of HNTs through hydrogen bonds, while the R groups are oriented towards the outside of the tube, thereby becoming the main factor affecting the surface chemical structure of the HNTs. Therefore, due to the low polarity of isobutyl and the good affinity with PAN and DMAc molecules, D-leucine-modified halloysite nanotubes (D-Leu@HNTs) can be evenly dispersed in the PAN membrane matrix and segregate to the membrane top-surface and pore wall during the non-solvent induced phase separation (NIPS) process with the solvent exchange between water and DMAc, thereby significantly improving the pore structure and hydrophilicity of the polyacrylonitrile membrane, and ultimately giving the PAN/D-Leu membrane ultra-high pure water permeability (PWP) of 1334 L·m−2·h−1·bar−1, rejection of 100 %, and excellent anti-biochemical fouling performances. The prepared PAN/D-Leu membrane maintains stable and efficient filtration performances in the 300-hour cross-flow experiment, and the membrane after testing still has excellent anti-biofilm fouling performance, showing a promising industrial application prospect.

Positively charged loose nanofiltration membranes via the assembly of amino-quinone networks for efficient dye/salt separation

Nanofiltration (NF) membranes with superior permeability and selectivity are highly desirable for the applications. The development of non-polyamide loose NF membranes with high permeability and dye/salt selectivity has aroused great attention in recent years. In this work, 2-hydroxy-1,4-naphthoquinone, a natural compound commonly existed in plants, was chosen to prepare loose NF membranes via the co-deposition with polyethyleneimine (PEI). By optimizing the deposition conditions, we successfully fabricated amine-quinone network coatings on the surface of polyacrylonitrile (PAN) ultrafiltration membranes, and further cross-linked the coatings with glutaraldehyde to improve the compactness and stability. For this kind of loose NF membrane, the rejections to dyes with a molecular weight larger than 600 Da reach 98 %, and the water permeance keeps above 10 L·m−2·h−1·bar−1. In contrast, the rejections to inorganic salts (NaCl, Na2SO4, MgCl2, and MgSO4) are only about 10 %, and the selectivity of the dye molecule alcian blue against NaCl can reach 430. These results prove that this novel composite membrane can realize effective separation for dyes with different molecular weights and desalination for dye solutions. The present work will open up an avenue for designing loose NF membranes with novel separation layers.

Green nanoparticles blending with polyacrylonitrile ultrafiltration membrane for antifouling oily wastewater treatment

This work prepares novel polyacrylonitrile (PAN) membranes by incorporating eggplant waste (EGW) as eco-friendly green nanoparticles (NPs) with PAN membranes to enhance the antifouling of PAN membranes to separate oil from oily wastewater (OWW). The modified PAN membranes are characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM), and measurements of the contact angle, porosity, and mechanical properties. The effect of EGW NPs content on membrane properties and morphology, its entire performance, and its antifouling characteristics is investigated. The performance of the PAN-EGW membranes is evaluated by pure water flux and oil rejection. The PAN membrane incorporated with 0.1 wt% EGW NPs enhances a pure water flux to 204.71 L/m2 h, exceeding that of the pristine PAN membrane (136.51 L/m2 h). This can be attributed to the low contact angle (39.66◦), high surface membrane porosity (91%), and good tensile strength (8.2 MPa) for PAN-EGW membranes compared to the contact angle (68.56◦), surface membrane porosity (69%), and tensile strength (5.1 MPa) for the pristine PAN membrane. Another significant improvement noticed is the excellent oil rejection by the modified membranes (about 99.95%, 95.50%, and 90.00% at oil concentrations of 1000, 100, and 10 ppm, respectively, and a transmembrane pressure (TMP) of 2 bar); treated-wastewater oil content that complies with the World Health Organization (WHO) environmental discharge standards (< 5 ppm) is achieved. Also, the antifouling performance is improved; a higher flux recovery ratio (FRR) is obtained (about 94.43%). In addition, the oil separation efficiency remains stable with a minor decrease in permeate flux after four cycles. This study demonstrates that the novel PAN-EGW membranes have great promise and potential for purifying OWW, particularly at low oil concentrations (10 ppm) compared to pristine PAN membranes, attributable to their high separation efficiency, oil-fouling resistance, and excellent environmental durability.

Hydrophilic membranes for effective removal of PFAS from water: Anti-fouling, durability, and reusability

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants in natural water. The polyacrylonitrile ultrafiltration membrane with an average pore size of 10.9 nm, grafted with tertiary amino groups, and subsequently quaternized, was developed to effectively adsorb PFAS in the presence of co-existing competitors. It achieved over 98 % removal of perfluorooctane sulfonic acid (PFOS) at neutral pH. Over 90 % removal efficiency was recovered within four cycles through eluent regeneration. The removal mechanism was determined, through advanced characterization and theoretical analysis, as a synergistic process of electrostatic, hydrophobic, and dipole-dipole interactions. To address potential competition in adsorption caused by natural organic matter (NOM), membrane pores were regulated to achieve selective interception of humic acid (HA, a representative NOM). Effective PFOS removal (98.4 %) maintained in the presence of abundant competitors. Furthermore, the mild regeneration method led to a flux recovery rate of 99.0 %, underscoring its resistance to contamination. The effects of versatile NOM and surfactants were also evaluated, that insignificant reduction in removal efficiency was observed. After 144th regeneration cycles (equivalent), <15 % changed in grafting moieties and <13.5 % decreased in HA removal were observed, suggesting the durability on chemical composition and interception ability. Overall, the adsorptive membranes, with reusability, anti-fouling, and durability, showed great potential for remediation of PFAS from natural water.

Flexible layered double hydroxides array composite membrane for efficient pervaporation desalination

Pervaporation has been considered a promising technique in seawater desalination. Developing new and efficient pervaporation membrane material remains the main challenge. In this study, the layered double hydroxides (LDH) nanosheet array composite membranes were prepared on a commercial polyacrylonitrile ultrafiltration membrane through the hydrothermal method. The structure and morphology of the LDH array was regulated by the hydrolysis of the substrate and the hydrothermal conditions. The obtained LDH composite membrane had a good pervaporation desalination performance due to its unique water molecular transport channel and high hydrophilicity. When the salt concentration in the feed solution increased from 3 to 10 wt%, the rejection of the composite membrane could maintain at 99.8 %. The real seawater was also used to evaluate the membrane. The results indicated the LDH composite membrane had a good desalination performance in a relatively wide range. Moreover, the LDH composite membrane exhibited excellent flexibility and stability. We anticipated that the membrane may have great potential in pervaporation desalination.

PAN/TiO2 Ultrafiltration Membrane for Enhanced BSA Removal and Antifouling Performance

Membrane separation has been widely utilized to eliminate pollutants from wastewater. Among them, a polyacrylonitrile (PAN) ultrafiltration (UF) membrane has presented outstanding stability, and distinguished chemical and thermal properties. However, UF membranes inevitably incur fouling issues during their operation procedure caused by contaminant adhesion on the membrane surface, which would restrict the operational efficiency and increase the maintenance cost. The conventional physical and chemical cleaning is not an effective technique to reduce the fouling due to the additional chemical addition and inevitable structure damage. Recently, UF membranes combined with photocatalytic materials are suggested to be a useful approach to conquer the membrane fouling issues. Herein, TiO2 nanoparticles were utilized to blend with a PAN casting solution for fabricating a composite UF membrane via a phase inversion method. With a certain TiO2 addition, the obtained membranes presented an enhancement of hydrophilicity, which could promote the water permeability and antifouling performance. The optimized M3 membrane prepared with 15.0 wt% PAN and 0.6 wt% TiO2 exhibited an excellent water permeability up to 207.0 L m−2 h−1 bar−1 with an outstanding 99.0% BSA rejection and superior antifouling property. In addition, the photocatalytic TiO2 nanoparticles endowed the M3 membrane with a remarkable self-cleaning ability under the UV irradiation. This facile construction method offered new insight to enhance the UF membrane separation performance with an enhanced antifouling ability.

Polyacrylonitrile ultrafiltration membranes incorporating graphene oxide fillers modified with Zeolitic Imidazolate Framework-8 and 3-aminopropyltriethoxysilane for dye and salt removal in real textile wastewater

Chemical grafting of graphene oxide (GO) with 3-aminopropyltriethoxysilane (APTES) reduced GO-sheet aggregation, improved their dispersion and interaction with the polymer matrix. Zeolitic Imidazolate Framework (0.1–1.5 wt%) were grown on GO-APTES forming ZIF-8 @GO-APTES nanocomposites. The incorporation of these composites into polyacrylonitrile (PAN) ultrafiltration (UF) membranes resulted in increased hydrophilicity (contact angle decreasing from 69.5° to 25.9°), and pure water flux (increasing from 31.3 L.m-2 h−1 to 101.3 L.m-2 h−1). The dye rejection in synthetic and colour removal in real textile wastewater increased in the composite membranes. Methyl orange rejection increased from 61 % to above 75 % whilst for methylene blue it increased from 33 % to 40 %. Colour removal in real textile wastewater increased with the increasing loading of ZIF-8 @GO-APTES in the membranes, increasing from 63 % for PAN membrane to 96 % in the composite membrane with high loading of ZIF-8 @GO-APTES. Relatively high metal ions (Pb, Zn, Ca, Cr, and Mg) rejection was also observed, increasing from 40 % in PAN and GO@PAN membranes to between 60 % and 80 % as filler content was increased. The difference in solute rejection with filler loading was attributed to electrostatic interactions due the presence of the functional nanocomposites embedded in the membrane surface layer. The rejection fractionally increased as the ZIF-8 component in the filler increased within the same series and generally more as the overall loading of ZIF-8 @GO-APTES in the PAN membranes was increased, further confirmation the electrostatic-based rejection mechanism. The ZIF-8 @GO-APTES/PAN membranes showed high antifouling properties with FRR of 93.4 % compared to 43.5 % for pristine PAN membranes.

Integration of efficient LaSrCoO4 perovskite and polyacrylonitrile membrane to enhance mass transfer for rapid contaminant degradation

A2BO4-type perovskite with Ruddlesden-Popper structure performed favorable catalytic activity in the activation of peroxymonosulfate (PMS) for the degradation of organic pollutants than ABO3, but the higher forming temperature limits its further application. In this work, a series of A-site Sr doped La2CoO4-δ perovskites were prepared and used for the degradation of tetracycline hydrochloride (TC). The introduction of Sr lowered the formation temperature of the perovskite and improved the catalytic capability. The LaSrCoO4 perovskite with 50 % Sr doping possessed the best TC degradation efficiency (complete degradation in 14 min). Besides, to overcome the mass transfer limitation caused by catalyst powder agglomeration and the difficulty of recovery, perovskite powder catalysts were embedded in polyacrylonitrile (PAN) ultrafiltration membrane by phase conversion method. The resulting PAN/LSC catalytic separation membranes achieved efficient degradation of TC due to the partial increase in the concentration of contaminants inside the membrane pores. The membrane embedded with 5 wt% LaSrCoO4 perovskite degraded 94 % TC in 3 min, which improved over 24 % compared to the perovskite powder. The catalytic degradation mechanism of TC and the toxicity of the intermediates were then analyzed. The effectiveness of catalytic membranes in practical applications was also evaluated. Overall, PAN/LSC membranes provide the potential for rapid purification of organic wastewater.

Highly ordered mesostructured flexible silica-based nanofiltration membrane with satisfactory acid, chlorine, and fouling resistances

In this report, a highly ordered mesostructured flexible silica-based nanofiltration membrane is fabricated using tetraethyl orthosilicate (TEOS) as a silica source and Pluronic F127 copolymer as a structure directing agent, and hydrolyzed polyacrylonitrile ultrafiltration membrane as a substrate by an evaporation induced self-assembly approach. The results show the fabricated silica/F127 (SF) composite membrane possesses ordered mesostructures with different space groups depending on the mass ratios of TEOS/F127. The membrane is negatively charged with an isoelectric point at pH 2.9, and it also has a very hydrophilic surface. The pure water permeability of the membrane is 32 Lm−2h−1bar−1. The membrane also has high rejections to methyl blue (100%) and multivalent salts (> 95%), and moderate rejection to divalent salt (78.5% for Na2SO4). The ordering of the mesostructure enhances the membrane compactness, favoring the improvement of the separation performance. Additionally, the membrane possesses satisfactory resistances to humic acid (HA) and bull serum albumin (BSA) fouling, and bacteria adhesion due to the smooth and hydrophilic surface. Additionally, the salt rejection is stable in 0.5 M HCl for 11 h and/or active chlorine solution (pH = 5) with 9000 ppm·h chlorination strength accompanied by an obvious increase in permeate flux. The membrane also exhibits satisfactory performance stability in a long-term (168 h) running.

Effect of tea polyphenols on the structure and properties of polyacrylonitrile ultrafiltration membrane

Effect of tea polyphenols on the structure and properties of polyacrylonitrile ultrafiltration membrane

Facile and effectual surface modification of polyacrylonitrile (PAN)-based ultrafiltration membranes via manipulating the synergistic interaction of dopamine and enzymes

A drastic improvement in the overall permeability and antifouling performance was observed for the polyacrylonitrile (PAN) ultrafiltration (UF) membrane by the co-incorporation of dopamine (DA), protease (E1), and lipase (E2) in a facile multi-step synthetic scheme. SEM was utilized to indicate the successful formation of modifying layers on the membrane surface, whereas ATR-FTIR and zeta potential were used to provide deeper insight into the membrane surface chemistry. AFM and contact angle were used to assess the membrane's surface roughness and hydrophilicity, respectively. The optimally modified membrane surface was found to be quite hydrophilic, as indicated by the water contact angle value (39.8 ± 0.8°), and water flux across the membrane of 78.09 ± 1.6 kg/m2·h. Simultaneously, natural organic matter (NOM), including milk powder (MP), bovine serum albumin (BSA), and humic acid (HA), were efficiently removed, resulting in 99.9, 92.5, and 80.5 % removal efficiencies, respectively. Notably, the enzyme-immobilized membrane demonstrated outstanding antifouling performance as well as long-term stability. The dynamic anti-NOM fouling studies indicated that the surface modification was potentially capable of overcoming the tradeoff between membrane permeability and selectivity, resulting in FRR values of >90 %. The antibacterial properties of the surface-modified membranes against E. coli and S. aureus were also explored, and the optimal enzyme-immobilized membrane was found to be substantially antibacterial. Overall, this study aims to pave the way for the development of sustainable chemistry in designing innovative and highly efficient membranes.

Preparation of high-performance nanofiltration membranes with quaternized cross-linked microgels as intermediate layer

The high-performance nanofiltration (NF) membranes were fabricated by using hydrolyzed polyacrylonitrile (HPAN) ultrafiltration (UF) membranes with negatively surface charges as the substrate membranes, quaternized crosslinked microgels (PNI6) with positive charges as the intermediate layer, piperazine (PIP) and trimesoyl chloride (TMC) as the monomers for the formation of polyamide selective layer via interfacial polymerization (IP). The introduction of positively charged PNI6 microgels as the intermediate layer improved the hydrophilicity of resultant NF membranes and rendered the NF membranes with surface positive charges. The obtained NF membranes (MG-NF) with PNI6 microgel interlayer simultaneously achieved excellent water flux and the rejection of salts including Na2SO4, MgSO4, MgCl2, and CaCl2. Increasing the deposition time of PNI6 microgels on the HPAN UF substrate membranes increased the water flux and rejection of MgCl2 of the resultant MG-NF series NF membranes. The nanofiltration performance of obtained MG-NF series NF membranes exhibited thermo-sensitivity and long-term stability. For MG-NF-6 NF membrane, the water flux and rejection of MgCl2 reached 10.1 L·m−2·h−1·bar−1 and 93.4 % at 25 °C, respectively. With increase of temperature, the water flux of MG-NF-6 membrane was significantly enhanced to be 13.4 L·m−2·h−1·bar−1 at 45 °C, while the rejection of MgCl2 slightly decreased to be 90 %.

Positively-charged nanofiltration membrane constructed by polyethyleneimine/layered double hydroxide for Mg2+/Li+ separation

As an important resource, lithium is abundant in Salt Lake. The high Mg2+/Li+ ratio is the main obstacle to lithium extraction. Positively-charged nanofiltration membrane has shown great potential in the separation of Mg2+/Li+. Herein, we report a facile method to construct positively-charged nanofiltration membrane by polyethyleneimine (PEI) and layered double hydroxide (LDH) nanosheets on hydrolyzed polyacrylonitrile ultrafiltration membrane. Subsequently, the PEI-LDH composite membrane was crosslinked with glutaraldehyde (GA) to improve its stability. The incorporation of LDH could improve the positive charge of the membrane. Then, the obtained PEI-LDH/GA membrane showed an enhanced separation performance for separating Mg2+/Li+ in an aqueous solution. When the Mg2+/Li+ ratio was 10, the membrane showed a separation factor (SMg2+/Li+) of 18.7. Moreover, the membrane could maintain the separation performance for 100 h, which exhibited a potential application in Mg2+/Li+ separation.

Oxygen plasma-assisted contra-diffusion self-assembly of covalent organic framework pervaporation membranes for organic-solvent dehydration

Pervaporation is considered to have great potential for application in the field of organic-solvent dehydration. In this study, a type of keto-enamine-linked covalent organic framework TpPa (synthesized using the Schiff-base reaction of 1,3,5-triformylphloroglucinol [Tp] with p-phenylenediamine [Pa]), was fabricated on commercial polyacrylonitrile (PAN) ultrafiltration membranes through an oxygen-plasma assisted contra-diffusion self-assembly strategy for organic-solvent dehydration. The PAN membranes with a glycerol exhibited a better separation factor for dehydration of organic solvents than those without a glycerol layer. The influence of oxygen plasma and glycerol on the formation of the TpPa membrane was investigated. The best plasma treatment condition and optimum glycerol impregnation concentration were determined as a device power of 60 W and 30 wt%, respectively. Defect-free TpPa membrane formation took only 24 h. The as-prepared TpPa membrane exhibited a separation factor of 1491 and a high permeation flux of 2530 g m−2 h−1 for a 90 wt% isopropanol–water mixture. The separation performance of the TpPa membrane was stable for >100 h, exhibiting great potential in organic-solvent dehydration.

Effect of Acetone as Co-Solvent on Fabrication of Polyacrylonitrile Ultrafiltration Membranes by Non-Solvent Induced Phase Separation.

For the first time, the presence of acetone in the casting solutions of polyacrylonitrile (PAN) in dimethylsulfoxide or N-methyl-2-pyrrolidone was studied with regards to thermodynamical aspects of phase separation of polymeric solutions induced by contact with non-solvent (water), formation and performance of porous membranes of ultrafiltration range. The positions of the liquid equilibrium binodals on the phase diagrams of these three-component and pseudo-three-component mixtures were determined. For PAN-N-methyl-2-pyrrolidone-water glass transition curve on a ternary phase diagram was plotted experimentally for the first time. The real-time evolution of the structure of mixtures of PAN with solvents (co-solvents) upon contact with a non-solvent (water) has been studied. The thermodynamic analysis of the phase diagrams of these mixtures, together with optical data, made it possible to propose a mechanism of structure formation during non-solvent induced phase separation of different mixtures. The addition of acetone promotes the formation of a spongy layer on the membrane surface, which decreases the probability of defect formation on the membrane surface and keeps finger-like macrovoids from the underlying layers of the membrane. It was shown that the molecular weight cut-off (MWCO) of the membranes can be improved from 58 down to 1.8 kg/mol by changing the acetone content, while polymer concentration remained the same.

Poly(caffeic acid) as interlayer to enhance nanofiltration performance of polyamide composite membrane

It is a challenge to develop nanofiltration (NF) membranes with simultaneously high permeability and excellent selectivity for water desalination. In this work, a composite NF membrane with an interlayer was prepared in order to overcome the upper bound of permeability-selectivity. Poly(caffeic acid) (PCA) was first deposited on the surface of polyacrylonitrile (PAN) ultrafiltration membrane to construct an interlayer, and then polyamide (PA) layer was formed on the PCA interlayer to fabricate the composite membrane (PAN-PCAn-PA). The chemical structure, morphology and surface properties of the composite membranes with and without the interlayer were compared. In addition, the preparation conditions and separation properties of the composite membranes were investigated. The results suggested that a loose “gutter” interlayer and a nanoscale Turing structure on the membrane surface were constructed due to the hydrophilic and electronegative PCA, which optimized the transport channels of water molecules. Hence, the water permeance of PAN-PCA2-PA membrane was 17.7 L·m−2·h−1·bar−1, which was 86% higher than that of PAN-PA membrane. Meanwhile, the PAN-PCA2-PA membrane exhibited high rejection ratio of Na2SO4 (98.9%), excellent selectivity for Cl‐/SO42‐ (75.9) and long-term filtration stability, which showed its potential for practical applications in water desalination.

A new method for tailoring the surface pore size and internal pore structure of ultrafiltration membranes without using additives—Atomization-assisted nonsolvent induced phase separation method

It is highly desired to improve the safety and stability of ultrafiltration (UF) membranes for biotechnology, medicine and food processing by eliminating the use of chemical additives during the membrane preparation process. In this work, a series of high-performance polyacrylonitrile (PAN) UF membranes were prepared continuously by the atomization-assisted nonsolvent induced phase separation (AA-NIPS) method. The pore structure and surface properties of the membranes can be precisely tailored, requiring no chemical additives. The prepared UF membranes are composed of a sublayer of highly interconnected three-dimensional (3D) network structure and a smooth surface layer of uniform small pore structure with a narrow pore size distribution. Compared to UF membranes prepared by the NIPS method, the PAN UF membranes exhibit enhanced water flux and antifouling properties as well as a well-preserved high rejection to bovine serum albumin (BSA). With different atomization pretreatment times, the pure water fluxes of the UF membranes increased by 41 %∼100 %. The AA-NIPS method employed in the present work can effectively modify the porous structure of the membranes without introducing pore-forming additives. The good separation performance, structural controllability, and easy functionalization of the UF membranes make them a promising candidate to be applied in many fields, especially in biotechnology, medicine, and food processing.

Preparation and characterization of PVA‐g‐GO/PVA/PAN composite membrane for pervaporation desalination

AbstractGraphene oxide (GO) has extensive applications in membrane‐based separations, but its dispersion in the membrane has always been a problem due to the presence of π–π interactions in GO nanosheets. In this study, a grafting reaction was designed by using poly (vinyl alcohol) (PVA) for GO grafting modification and poly (vinyl alcohol)‐g‐graphene oxide (PVA‐g‐GO) nanocomposites were synthesized. The grafting material to GO was the same as the basic separation polymer material. PVA‐g‐GO showed better dispersibility and hydrophilicity than GO, and a series of composite membranes were prepared using a polyacrylonitrile (PAN) ultrafiltration (UF) membrane as a substrate. PVA‐g‐GO nanocomposites and membranes were characterized by using X‐ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier‐transform infrared spectroscopy (FTIR), water contact angle, scanning electron microscopy (SEM), etc. The addition of PVA‐g‐GO improved both the separation performance and anti‐swelling property of the composite membrane, and the PVA‐g‐GO/PVA/PAN composite membrane loaded with 2 wt.% PVA‐g‐GO obtained a high flux of 4.46 kg/m2 · h and a high rejection of 99.99% when dehydrating 3.5 wt.% NaCl solution at 30°C by pervaporation.

A novel nanofibrous PAN ultrafiltration membrane embedded with ZIF-8 nanoparticles for effective removal of Congo red, Pb(II), and Cu(II) in industrial wastewater treatment.

A novel Polyacrylonitrile (PAN) composite membrane involving ZIF-8 nanoparticles, named as ZIF-8/PAN membrane, was obtained via electrospinning to remove the Congo red (CR), Pb(II) and Cu(II) ions in industrial wastewaters, during which the adsorption mechanisms were examined in this study. The adsorption efficiency of the electrospun ZIF-8/PAN membrane was as high as 89%, 92% and 76% for CR, Pb(II) and Cu(II), respectively. Comparative analysis showed that ZIF-8 nanoparticles embedded in the ZIF-8/PAN membrane accounted for these enhanced adsorption capabilities. The adsorption behaviors of the ZIF-8 nanoparticles were investigated through experiments and theoretical analysis, and the results unraveled that the adsorption for CR by the ZIF-8 was mainly including electrostatic interaction, hydrogen bonding and π-π interaction, while those for Pb(II) and Cu(II) were mainly caused by ion-exchange and chemical adsorption. Parametric studies were conducted to optimize the conditions for removing CR, Pb(II), and Cu(II) by ZIF-8 nanoparticles, during which all of pollutants showed different reactions to the solution pH. This work not only develops a novel ZIF-8/PAN composite membrane for effective removals of pollutants, but also reveals the underlying mechanisms of pollutants adsorption in terms of molecular interactions, providing important understandings on fibrous materials design for efficient heavy metals and dyes removals in industrial wastewater treatment.