Selective Composite Membranes Research Articles

Flexible lithium selective composite membrane for direct lithium extraction from high Na/Li ratio brine

Monovalent selective ion-exchange membranes have been widely used for lithium extraction from brine with a high Mg/Li ratio. However, extracting Li+ directly from raw brine with high Na/Li ratio remains a significant challenge. This study introduces a flexible lithium selective composite membrane by incorporating lithium-ion conductor with a quaternized polymer. The lithium-ion conductor provides pathways for lithium transmission, while the quaternized polymer effectively hinders the leakage of impurity cations. As a result, with the applied voltage of 2.0 V, the membrane achieved a high Li+/Na+ separation coefficient of 35.48 with a Li+ flux of 8.33 × 10−10 mol cm−2 s−1 in the simulated Yiliping brine, which are 56.3 and 2.8 times higher than that of commercial monovalent selective cation exchange membrane (CIMS). We proposed a lithium transport mechanism involving an adsorption-dehydration-diffusion process through the membrane. Theoretical calculations indicate that the combined effects of significant adsorption energy (−0.47 eV), low dehydration energy (515 kJ mol−1), and low diffusion barrier (0.37 eV) leads to the high selectivity for lithium. These findings provide promising prospects for the large-scale preparation of lithium ion-selective membranes, enabling the direct lithium extraction from raw brine.

Rapid hollow fiber-coating device for thin film composite membrane preparation.

Aligned with the recent trend and imperative to reduce separation layer thickness in gas separation membranes to the nanometer scale in order to raise permeance to levels that can render them competitive with respect to other gas separation technologies, a novel approach and device for fabricating defect-free composite hollow fiber (HF) membranes by dip-coating is described. The presented method avoids the fundamental drawbacks of state-of-the-art techniques for applying a thin gas separation layer onto a porous HF substrate, providing a safe but, at the same time, easily up-scalable way of producing HF membranes at a relatively high production rate. As a basic concept, hanging HF substrates are coated by allowing the coating solution to flow and drip along their external surface. The adaptability of this method, stemming from the array of available coating solutions (a plethora of dispersed nanofillers) and the multitude of substrate options, holds great promise for the fabrication of highly selective and defect-free composite HF membranes.

Preparation of highly selective nanofiltration composite membranes based on a novel soluble rigidly contorted monomer

AbstractNanofiltration composite membranes with high selectivity are one of the most critical cores in water treatment, and regulating the surface charge and pore structure of active separation layers in thin film composite membranes is one of the most effective means to improve the selectivity of composite membranes. This article synthesized a novel monomer with positive charge and a rigid twisted Tröger's base structure (named TBDA‐SO3), which was manipulated to improve the microporous structure and surface charge of the composite membrane. By interfacial polymerization, TBDA‐SO3, and piperazine were co‐reacted with trimesoyl chloride to successfully prepare positively charged, highly selective, and strongly microporous polyamide composite nanofiltration membranes. The best‐performing composite nanofiltration membrane in this article has a permeability similar to that of the control group's poly(piperazine amide) (PPA) membrane (pure water flux, 7.8 L m−2 h−1 bar−1), but has excellent divalent cation selectivity (52.57), which is 4.4 times that of the control group's PPA membrane.

A highly-selective layer-by-layer membrane modified with polyethylenimine and graphene oxide for vanadium redox flow battery

ABSTRACT A selective composite membrane for vanadium redox flow battery (VRFB) was successfully prepared by layer-by-layer (LbL) technique using a perfluorosulfonic sulfonic acid or Nafion 117 (N117). The composite membrane referred as N117-(PEI/GO)n, was obtained by depositing alternating layers of positively charged polyethylenimine (PEI) and negatively charged graphene oxide (GO) as polyelectrolytes. The physicochemical properties and performance of the pristine and composite membranes were investigated. The membrane showed an enhancement in proton conductivity and simultaneously exhibited a notable 90% reduction in vanadium permeability. This, in turn, results in a well-balanced ratio of proton conductivity to vanadium permeability, leading to high selectivity. The highest selectivity of the LbL membranes was found to be 19.2 × 104 S.min/cm3, which is 13 times higher than the N117 membrane (n = 0). This was translated into an improvement in the battery performance, with the n = 1 membrane showing a 4–6% improvement in coulombic efficiency and a 7–15% improvement in voltage efficiency at current densities ranging from 40 to 80 mA/cm2. Furthermore, the membrane displays stable operation over a long-term stability at around 88% at a current density of 40 mA/cm2, making it an attractive option for VRFB applications using the LbL technique. The use of PEI/GO bilayers maintains high proton conductivity and VE of the battery, opening up possibilities for further optimization and improvement of VRFBs.

Low temperature pyrolysis of thin film composite polyphosphazene membranes for hot gas separation

Highly selective thin-film composite membranes for hot hydrogen sieving are prepared via the pyrolysis of thin cyclomatric polyphenoxy phosphazene films that are prepared via a non-conventional interfacial polymerization of hexachlorocyclotriphosphazene with 1,3,5-trihydroxybenzene or m-dihydroxybenzene. The presence of the cyclic phosphazene ring within the weakly branched polymer films gives rise to a distinct thermal degradation evolution, with an onset temperature of around 200 °C. For the trihydroxybenzene derived material, the hydrogen permselectivity of the films shows a maximum pyrolysis temperature of around 450 °C. At this temperature a compact atomic structure is obtained that comprises mostly disordered carbon and accommodates P–O–C and P–O–P bonds. During thermal treatment, these films reveal molecular sieving with permselectivities exceeding 100 for H2/N2, H2/CH4, and H2/CO2, and a hydrogen permeance of 2 × 10−10 to 1.5 × 10−8 mol/m2/s/Pa (0.6-44.8GPU), at 200 °C. At ambient temperatures, thin films are very effective barriers for small gas molecules. Because of the inexpensive facile synthesis and low- temperature pyrolysis, the polyphosphazene films have the potential for use in high-temperature industrial gas separations, as well as for use as barriers such as liners in high- pressure hydrogen storage vessels at ambient temperature.

Using Cu-TCPP Nanosheets as Interlayers for High-Performance Organic Solvent Nanofiltration Membranes

The development of highly permeable and selective thin-film composite (TFC) membranes is essential for organic solvent nanofiltration (OSN) applications. However, overcoming the permeability–selectivity trade-off in polymer membranes remains highly challenging owing to the difficulty in controlling the thickness and nanostructures of the selective layers. In this study, TFC OSN membranes with sandwich-like structures were developed via interfacial polymerization on Cu-TCPP nanosheet-modified microporous polyvinylidene fluoride (PVDF) substrate surface. The interfacial polymerization was done by using mixed amine (polyethyleneimine and piperazine) in the aqueous phase and the 1,3,5-benzenetricarbonyl trichloride in the hydrophobic ionic liquid phase as monomers. It was found that the Cu-TCPP nanosheets of micrometer lateral dimensions and nanometer thickness (1.5 ± 0.6 nm) can be deposited on the PVDF substrate as an interlayer to facilitate the following interfacial polymerization reaction. The Cu-TCPP interlayer also can be served as a binder between the polyamide selective layer and the microporous PVDF substrate to enhance their mechanical strength. As compared with the PVDF/PA membrane, the PVDF/t-Cu-TCPP/PA membrane exhibited higher elongation (8.0 vs. 4.6%) while ensuring slightly lower tensile strength (36.0 vs. 48.6 MPa). Under optimal synthetic conditions, the TFC membranes could achieve 2.7 L m–2 h–1 bar–1, and 98.9% and 95.0% rejection to Brilliant Blue R (826 Da) and Congo red (697 Da), respectively, in ethanol. Furthermore, the membranes showed steady performance throughout the 36 h nanofiltration of the Rose bengal/ethanol mixture and exhibited good performance in the concentration of lecithin in methanol. Accordingly, this work highlights the potential of using thin metal–organic framework nanosheets as interlayers to develop high-performance TFC membranes for OSN applications.

Thin film poly(vinyl alcohol)-polysulfone composite membranes based on recycled polysulfone: salt separation performances.

Poly(vinyl alcohol) (PVA)-coated membranes on polysulfone (Ps) (Memb-Pv) were cross-linked using the dibasic maleic acid. The tailoring of membrane properties (viz. hydrophilicity, permeability) develops through the ester linkage due to cross-linking of PVA and maleic acid (MA). Series of Ps asymmetric membranes were prepared using the successive stages of phase inversion of Ps materials. The recyclability approaches of polysulfone (Ps) pertained. The characteristics and transport properties of all the membranes are evaluated. FTIR-ATR, scanning electron (SEM), and atomic force microscopy (AFM) are used for the structural characterization of the membranes. The salient features of Memb-Pv composite membranes support promising results in desalination. The work aimed to highlight the trade-off between the flux and selectivity of composite membranes' salts (bi-/monovalent) through the recycled Ps matrix. The number of recycling stages influences the salt separation performance. The sulfate rejection differs from Memb-IPv (93.26%) to Memb-IVPv (86.70%) for water-I matrix using 2500mg/L. The defluoridation potential of the membranes is also convincing. The defluoridation performance of Memb-IPv is 87% for 10mg/L. A significant dimension is added regarding salt separation performance's dependence on the water matrices' nature. The decrease in fluoride separation is ~ 1-3% for the water-2 matrix as the TDS increases.

Highly selective Pd composite membrane on porous metal support for high-purity hydrogen production through effective ammonia decomposition

In this study, an alumina sol assisted pretreatment method for porous metal supports was investigated for a highly selective Pd composite membrane for ammonia decomposition. Alumina sol made of boehmite was applied to an yttria-stabilized zirconia (YSZ) filled porous Inconel support. Additionally, a vacuum-assisted, two-step electroless plating of Pd drastically increased the hydrogen selectivity. The hydrogen permeation flux and selectivity (H2/N2) measured at 723 K and a transmembrane pressure difference of 100 kPa were 3.40 × 10−1 mol m−2 s−1 and 8,050, respectively. A highly selective Pd composite membrane was applied to a membrane reactor combined with a Ru/Al2O3 catalyst to efficiently produce high-purity hydrogen by ammonia decomposition. The ammonia decomposition test showed that the membrane reactor was able to achieve a high ammonia conversion (99.6%) and a high hydrogen purity (99.99%) with a hydrogen production rate of 0.25 Nm3 h−1 at 745 K and a gauge pressure of 500 kPa. The Pd composite membrane reactor has the advantage of being able to selectively removing hydrogen, increasing the ammonia conversion rate and high-purity hydrogen production via a one-step reaction combined with purification.

Enhancing the Permselectivity of Thin-Film Composite Membranes Interlayered with MoS2 Nanosheets via Precise Thickness Control.

The demand for highly permeable and selective thin-film composite (TFC) nanofiltration membranes, which are essential for seawater and brackish water softening and resource recovery, is growing rapidly. However, improving and tuning membrane permeability and selectivity simultaneously remain highly challenging owing to the lack of thickness control in polyamide films. In this study, we fabricated a high-performance interlayered TFC membrane through classical interfacial polymerization on a MoS2-coated polyethersulfone substrate. Due to the enhanced confinement effect on the interface degassing and the improved adsorption of the amine monomer by the MoS2 interlayer, the MoS2-interlayered TFC membrane exhibited enhanced roughness and crosslinking. Compared to the control TFC membrane, MoS2-interlayered TFC membranes have a thinner polyamide layer, with thickness ranging from 60 to 85 nm, which can be tuned by altering the MoS2 interlayer thickness. A multilayer permeation model was developed to delineate and analyze the transport resistance and permeability of the MoS2 interlayer and polyamide film through the regression of experimental data. The optimized MoS2-interlayered TFC membrane (0.3-inter) had a 96.8% Na2SO4 rejection combined with an excellent permeability of 15.9 L m-2 h-1 bar-1 (LMH/bar), approximately 2.4 times that of the control membrane (6.6 LMH/bar). This research provides a feasible strategy for the rational design of tunable, high-performance NF membranes for environmental applications.

Highly Selective Pd Composite Membrane on Porous Metal Support for High-Purity Hydrogen Production Through Effective Ammonia Decompositionhighly Selective Pd Composite Membrane on Porous Metal Support for High-Purity Hydrogen Production Through Effective Ammonia Decomposition

Highly Selective Pd Composite Membrane on Porous Metal Support for High-Purity Hydrogen Production Through Effective Ammonia Decompositionhighly Selective Pd Composite Membrane on Porous Metal Support for High-Purity Hydrogen Production Through Effective Ammonia Decomposition

Sandwich Structure Organic Selective Composite Membrane with Anti-Swelling and Anti-Mechanical Damage for Bioethanol Separation by Pervaporation

Sandwich Structure Organic Selective Composite Membrane with Anti-Swelling and Anti-Mechanical Damage for Bioethanol Separation by Pervaporation

A highly selective porous composite membrane with bromine capturing ability for a bromine-based flow battery

Bromine-based flow batteries (Br-FBs) are receiving more and more attention because of the high potential, high solubility, and low cost of the Br2/Br− redox couple. However, the self-discharge reaction caused by the bromine diffusion leads to serious and irreversible capacity decay of Br-FBs. Herein, a porous composite membrane is designed for Br-FBs, upon which a highly selective separation layer is constructed by introducing a bromine complexing agent. Apart from the intrinsically high selectivity on bromine, the complexing agent in the non-porous selective layer can complex with diffused bromine. Therefore, diffused bromine is captured by the separation layer, consequently suppressing the self-discharging of the battery. The zinc–bromine single flow battery (ZBSFB) assembled with the prepared porous composite membrane demonstrates a Coulombic efficiency of 97.42% and an energy efficiency of 85.31% at 40 mA/cm2. Moreover, this battery can operate stably at a high current density of 140 mA/cm2, much higher than that of the pristine membrane matrix (only 40 mA/cm2), enabling a higher-power density ZBSFB. Most importantly, this ZBSFB exhibits a much higher capacity retention rate after resting for 24 h than that based on a pristine membrane matrix (69.3% vs. 35.7%), suggesting a dramatically improved membrane selectivity. Therefore, the designed porous composite membranes can be a very promising prospect for Br-FB applications.

A defect-free MOF composite membrane prepared via in-situ binder-controlled restrained second-growth method for energy storage device

Composite membranes with high selectivity and permeability are always essential in diverse fields including batteries and separation. Ultrathin highly-selective layers with well-defined porous structures are deemed as the priority for the composite membranes to break the trade-off effect between selectivity and permeability. Here, we report a binder-controlled restrained second-growth method (BRSM), which directly introduces continuous and uniform metal organic frameworks selective layers (UiO-66/-67) on porous polymer substrates (Daramic) to achieve defect-free composite membranes. In this method, the nucleation and growth of MOF can be well-tuned via controlling MOF nucleation density and the dissolution rates of binders. Composite membranes with UiO-66/-67 layers demonstrate well-controlled selectivities on different ions, confirming the key role of well-ordered pores of MOF. This is further highlighted by the coulombic efficiency (CE) enhanced from 88.4% to 94.5% at a current density of 80 mA cm−2 in zinc-iodine flow battery (ZIFB) demonstration. Additionally, a more even deposition of zinc is induced by MOF surface layer with uniformly pore size distribution, which can suppress the zinc dendrites effectively. This work demonstrates an effective and controllable way to introduce defect-free MOF selective layers on polymer substrates via tuning the MOF nucleation and growth, creating highly selective composite membranes.

Development of highly selective composite polymeric membranes for Li+/Mg2+ separation

To meet the exponentially rising demand for lithium, it becomes vital to develop environmentally friendly processes for its recovery from brines, salt lakes and/or seawater. In this work, novel composite lithium transport selective polymeric membranes were developed to separate lithium and magnesium ions. Hydrogen manganese oxide (HMO) (at weight percentage from 0 to 25%), polystyrene sulfonate sodium salt (PSS–Na) and lithium triflate (LiCF3SO3) were added into the sulfonated polyethersulfone (SPES) matrix to prepare composite membranes. The developed membranes showed high mechanical stability and a homogeneous distribution of HMO. The most promising membrane, containing 20% (w/w) of HMO, showed an almost 13 times higher Li+ ionic conductivity (8.28 mS/cm) compared to the control composite membrane (without HMO) and an average ideal selectivity of 11.75 for the Li+/Mg2+ pair. The composite-20% membrane had the lowest intermolecular distance between the polymer chains (according to X-ray diffraction (XRD) analysis), the most flexible structure (lowest Tg) and showed the homogeneous dispersion of HMO (SEM images), which explains its highest Li+/Mg2+ selectivity among the tested membranes. The lithium ion transport performance and separation efficiency were investigated through diffusion dialysis experiments, under different operating conditions. A binary separation factor of 9.10 for Li+/Mg2+ and Li+ molar flux of 0.026 mol/(m2.h) was achieved without applying any external potential difference. When an external potential difference of 0.2 V was applied, the binary separation factor of Li+/Mg2+ pair was 5, while the Li+ molar flux increased almost 5 times. The obtained results provide the basis to design and develop composite lithium transport selective polymeric membranes, thus representing a promising step for future implementation of such membranes to recover lithium from saline streams.

Preparation of thin-film composite membranes supported with electrospun nanofibers for desalination by forward osmosis

Abstract. The forward osmosis (FO) process has been considered to be a viable option for water desalination in comparison to the traditional processes like reverse osmosis, regarding energy consumption and economical operation. In this work, a polyacrylonitrile (PAN) nanofiber support layer was prepared using the electrospinning process as a modern method. Then, an interfacial polymerization reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) was carried out to generate a polyamide selective thin-film composite (TFC) membrane on the support layer. The TFC membrane was tested in FO mode (feed solution facing the active layer) using the standard methodology and compared to a commercially available cellulose triacetate membrane (CTA). The synthesized membrane showed a high performance in terms of water flux (16 Lm −2 h−1) but traded the salt rejection (4 gm−2 h−1) compared with the commercial CTA membrane (water flux = 13 Lm−2 h−1 and salt rejection = 3 gm−2 h−1) at no applied pressure and room temperature. Scanning electron microscopy (SEM), contact angle, mechanical properties, porosity, and performance characterizations were conducted to examine the membrane.

Enhancing hydrogen gas separation performance of thin film composite membrane through facilely blended polyvinyl alcohol and PEBAX

Polymeric membranes offer economic separation processes but are less explored for H2 separation application. This work aims to unveil the H2 separation potential of polymeric membrane by developing PVA-based reverse selective composite membrane. CO2-selective PEBAX was blended at different PVA:PEBAX ratio. The effect of PEBAX blending on membrane morphology, crystallinity and gas separation behavior was studied. Incorporation of PEBAX at <50 wt% resulted in composite with improved CO2 permeability but selectivity loss. Blending of >60 wt% PEBAX enhanced both permeance and selectivity of the resulted composite as the host matrix was dominated by this PEO containing material thus greatly enhancing polymer chain mobility and promoting CO2-solubility. The best composite which contains 60 wt% PEBAX exhibited CO2 permeability of 20.0 Barrer and CO2/H2 selectivity of 7.6. This performance surpasses the Robeson's boundary and unleashes the potential of tailoring the properties of polymeric nanocomposite membrane for H2 separation application through facile PVA/PEBAX blending.

Sulfonated poly (ether ether ketone) composite cation exchange membrane for selective recovery of lithium by electrodialysis

Lithium is in demand since decades due to high applicability in batteries for electronic devices, which is expected to increase by 8 to 11% every year and Lithium ion battery market is estimated to grow to € 180 billion by 2024. Land deposits and seawater are two major sources of lithium but availability in sea water is higher than land. So an efficient technology is required to recover the lithium from sea water. Electrodialysis (ED) may be an alternate approach to recover the lithium from sea by selective ion exchange membranes. Here, Lithium selective ion exchange membranes have been synthesized by modification of sulfonated poly (ether ether ketone) (SPEEK) with lithium selective nanomaterial. Synthesized membranes were characterized for their chemical, structural and morphological structures and uniform dispersion of lithium selective nanomaterials. Composite membrane shows better lithium exchange capacity with excellent lithium conductivity as compared to SPEEK membrane. The adsorption of lithium (15.2 mg/g) found to be five times higher than that of Mg while recovery of lithium was 64% using electrodialysis process by NC-4 composite membrane. Selectivity factor for composite membrane were 4.82, 3.0 and 2.17 for Li/Mg, Li/K and Li/Na, respectively. The selective composite membranes can be suitable for Li-ion recovery from sea brine/bittern on large scale.

Novel lithium selective composite membranes: synthesis, characterization and validation tests in dialysis

With the general growing demand for Lithium compounds, notably for use in Lithium ion batteries, the selective extraction of this metal from various different sources is generating a lot of attention. A number of different methods have been used to recover and/or separate this element, often involving membranes technologies. In an attempt to overcome issues raised by the high rigidity of ceramic membranes and the poor selectivity performance of polymer membranes, we have tried to combine the Li selectivity of Lithium Ion Conducting Glass Ceramic (LICGC) and the flexibility of polymers. We are therefore proposing new malleable composite membranes made using a blending technique where the LICGC powder is incorporated into a flexible copolymerized anion-exchange membrane. We have attempted to demonstrate the homogeneity of the inorganic particle dispersion in the six prepared Lithium Composite Membranes (LCMs) as well as their thermal stability and mechanical properties. We have also investigated the effects of membrane composition on the physicochemical characteristics (water sorption, contact angle and conductivity) of the membranes. The selectivity of these LCMs for Li+ was tested under dialysis conditions using Na+ and K+ as the competitive cations, and the results were compared to those obtained with control membranes containing no LICGC particles. For the best membrane LCM5, the Li+/Na+ selectivity coefficient reaches 376 when using only Na+ as competitive ion. Whilst, when using both Na+ and K+, this selectivity (Li+/Na+) decrease to 278 and the Li+/K+ selectivity coefficient is found to be 364.

High Selective Composite Polyalkylmethylsiloxane Membranes for Pervaporative Removal of MTBE from Water: Effect of Polymer Side-chain.

For the first time, the effect of the side-chain in polyalkylmethylsiloxane towards pervaporative removal of methyl tert-butyl ether (MTBE) from water was studied. The noticeable enhancement of separation factor during the pervaporation of 1 wt.% MTBE solution in water through the dense film (40–50 µm) can be achieved by substitution of a methyl group (separation factor 111) for heptyl (161), octyl (169) or decyl (180) one in polyalkylmethylsiloxane. Composite membrane with the selective layer (~8 µm) made of polydecylmethylsiloxane (M10) on top of microfiltration support (MFFK membrane) demonstrated MTBE/water separation factor of 310, which was 72% greater than for the dense film (180). A high separation factor together with an overall flux of 0.82 kg·m−2·h−1 allowed this M10/MFFK composite membrane to outperform the commercial composite membranes. The analysis of the concentration polarization modulus and the boundary layer thickness revealed that the feed flow velocity should be gradually increased from 5 cm·s−1 for an initial solution (1 wt.% of MTBE in water) to 13 cm·s−1 for a depleted solution (0.2 wt.% of MTBE in water) to overcome the concentration polarization phenomena in case of composite membrane M10/MFFK (Texp = 50 °C).

Membrane materials for energy production and storage

Abstract Ion exchange membranes are widely used in chemical power sources, including fuel cells, redox batteries, reverse electrodialysis devices and lithium-ion batteries. The general requirements for them are high ionic conductivity and selectivity of transport processes. Heterogeneous membranes are much cheaper but less selective due to the secondary porosity with large pore size. The composition of grafted membranes is almost identical to heterogeneous ones. But they are more selective due to the lack of secondary porosity. The conductivity of ion exchange membranes can be improved by their modification via nanoparticle incorporation. Hybrid membranes exhibit suppressed transport of co-ions and fuel gases. Highly selective composite membranes can be synthesized by incorporating nanoparticles with modified surface. Furthermore, the increase in the conductivity of hybrid membranes at low humidity is a significant advantage for fuel cell application. Proton-conducting membranes in the lithium form intercalated with aprotic solvents can be used in lithium-ion batteries and make them more safe. In this review, we summarize recent progress in the synthesis, and modification and transport properties of ion exchange membranes, their transport properties, methods of preparation and modification. Their application in fuel cells, reverse electrodialysis devices and lithium-ion batteries is also reviewed.