Membrane Ion Research Articles

Solvent-Responsive Reversible and Controllable Conversion between a Polyimine Membrane and an Organic Molecule Cage.

Adaptive bionic self-correcting behavior offers an attractive property for chemical systems. Here, based on the dynamic feature of imine formation, we propose a solvent-responsive strategy for smart switching between an amorphous ionic polyimine membrane and a crystalline organic molecule cage without the addition of other building blocks. To adapt to solvent environmental constraints, the aldehyde and amine components undergo self-correction to form a polymer network or a molecular cage. Studies have shown that the amorphous film can be switched in acetonitrile to generate a discrete cage with bright birefringence under polarized light. Conversely, the membrane from the cage crystal conversion can be regained in ethanol. Such a membrane-cage interconversion can be cycled continuously at least 5 times by switching the two solvents. This work builds a bridge between the polymer network and crystalline molecules and offers prospects for smart dynamic materials.

Flexible sugarcane juice based ionic polymer membrane

Flexible sugarcane juice based ionic polymer membrane

Mid-Infrared Electrochromics Enabled by Intraband Modulation in Carbon Nanotube Networks.

Tuneable infrared properties, such as transparency and emissivity, are highly desirable for a range of applications, including thermal windows and emissive cooling. Here, we demonstrate the use of carbon nanotube networks spray-deposited onto an ionic liquid-infused membrane to fabricate devices with electrochromic modulation in the mid-infrared spectrum, facilitating control of emissivity and apparent temperature. Such modulation is enabled by intraband transitions in unsorted single-walled carbon nanotube networks, allowing the use of scalable nanotube inks for printed devices. These devices are optimized by varying film thickness and sheet resistance, demonstrating the emissivity modulation (from ∼0.5 to ∼0.2). These devices and the understanding thereof open the door to selection criteria for infrared electrochromic materials based on the relationship between band structure, electrochemistry, and optothermal properties to enable the development of solution-processable large-area coatings for widespread thermal management applications.

Pressure Sensors Combining Porous Electrodes and Electrospun Nanofiber-Based Ionic Membranes

It is one of the most urgent development directions and crucial challenges for flexible pressure sensors to have both characteristics of high sensitivity and wide measuring range. To address this challenging problem, this paper proposes an innovative, convenient, and industrially scalable capacitive pressure sensor that combines porous electrodes and electrospun nano ionic membranes with surface microstructure. The advantage of this sensor is that nano ionic nanofiber membranes are directly prepared on porous conductive fabrics by electrospinning with high reliability and good repeatability. The prepared dielectric layer of the sensor is in complete contact with the electrode, which effectively eliminates the uncertainty of air gap interference in traditional packaging methods. The sensing mechanism of the designed sensor is also persuasively revealed by finite-element and theoretical analysis in this paper. First, the porosity of both the conductive fabric and dielectric layer expands the measurement range. Second, the surface microstructure of the nano ion membrane increases the effective contact area between the dielectric layers when external pressure is applied to the sensor, thus increasing the conduction path of the ions. The increase of the ionizing degree under pressure leads to the change of the interface capacitance. These make the sensor have high sensitivity in the wide measurement range. The designed sensor exhibits a sensitivity of up to 1254.5 kPa–1 over a low-pressure measurement range of 0–10 kPa, providing an amazingly wide measurement range of 0–800 kPa, with an extremely high sensitivity of 128.1 kPa–1 over the entire measurement range. The designed sensor illustrates both a fairly fast response time of 10 ms and a relaxation time of 16 ms, in addition to the durability of up to 3000 cycles. The above exceptional performance demonstrates its remarkable potential applications in smart wearable devices and pneumatic pressure monitoring.

Construction of Clostridium tyrobutyricum strain and ionic membrane technology combination pattern for refinery final molasses recovery and butyric acid production.

Clostridium tyrobutyricum has considerable prospect in the production of organic acids. Globally, refinery final molasses is rich in sugar and reported to have high levels of accumulation and high emission costs, recognized as an excellent substrate for C. tyrobutyricum fermentation, but there is no suitable method available at present. In this study, an acid-base treatment combined with a new green membrane treatment technology - a dynamic ion-exchange membrane -was used to pretreat refinery final molasses, so that it could be used for C. tyrobutyricum to produce butyric acid. A high-performance liquid chromatography method was established to determine the conversion of a large amount of sucrose into fermentable sugars (71.88 g/L glucose and 38.06 g/L fructose) in the treated refinery final molasses. The process of sequential filtration with 3, 1, and 0.45 μm-pore diameter dynamic ion-exchange membranes could remove impurities, pigments, and harmful substances from the refinery final molasses, and retain the fermentable sugar. This means that refinery final molasses from the sugar industry could be utilized as a high-value by-product and used for the growth of C. tyrobutyricum, with industrial feasibility and economic competitiveness. Using the treated refinery final molasses as a carbon source, C. tyrobutyricum was screened by the method of adaptive evolution. The strain with butyric acid yielded 52.54 g/L, and the yield of the six carbon sugar was increased from 0.240 to 0.478 g/g. The results showed that combination of C. tyrobutyricum and ionic membrane technology broke through the bottleneck of its utilization of refinery final molasses. This study provided an innovative idea for the C. tyrobutyricum fermentation to produce butyric acid.

Enhancement of flame retardancy of solid polymer electrolyte based on phosphorus-containing ionic liquid polyurethane membrane for safe lithium batteries

The inherent defects such as flammable and inadequate cycle performance of polyurethane solid electrolytes impede their practical application in lithium batteries. Herein, phosphorus-containing flame retardant ionic liquid polyurethane (FR-ILPU) membrane is regard as an effective approach for overcoming the potential deficiencies. The FR-ILPU is fabricated by grafting phosphorus-containing diols and ionic liquids to polyurethane molecular segments. The FR-ILPU membrane exhibits benign flame retardancy, accompanying by the limiting oxygen index (LOI) value increases from 17.2% to 32.3%, while the total heat release (THR) and total smoke release (TSR) decrease 54.8% and 73.7%, respectively. Moreover, the SPE(15,5) electrolyte composed of FR-ILPU membrane, 15 wt% Li1.4Al0.4Ti1.6(PO4)3 (LATP) along with 5 wt% lithium bis-(trifluoromethanesulfonyl)imide) (LiTFSI) displays a wide electrochemical window of 4.84 V (vs. Li+/Li). In addition, an all-solid-state battery which assembled with lithium iron phosphate (LiFePO4), SPE(15,5), and Li anodes presents excellent cycling performance (157.3 mAhg−1, 0.2 C) and coulombic efficiency (99.1%) after 140 cycles at 70 °C, illustrating an enhancement of cycling performance than the cell assembled by R–PU(15,5) electrolyte. Thus, FR-ILPU is argued to provide potential for the practical application with high safety lithium batteries.

Ionization of Tröger's base polymer of intrinsic microporosity for high-performance membrane-mediated helium recovery

Tröger's base (TB) polymer of intrinsic microporosity has aroused increasing attention in various membrane-mediated gas separations. Herein we report macromolecular engineering to tune the microporosity of Tröger's base polymer of intrinsic microporosity (TB-PIM) via ionization for highly permselective helium recovery from natural gas. We reveal that the ionization of TB-PIM tightens polymer chain-packing, leading to dramatic enhancement of gas selectivities. Consequently, the ionic ITB-PIM membranes display the He/CH4 selectivity increments in the range of 34–158% and impressively high gas selectivities for helium recovery (i.e., α(He/CH4) = 246; α(He/N2) = 229). Due to the enhancement of inter-chain interactions induced by electrostatic interaction, the ITB-PIM membranes exhibit enhanced plasticization resistance compared to the pristine TB-PIM membranes. Notably, the ITB-Trip membrane showed excellent low-temperature gas separation performance with a He permeance of 3162 Barrer and He/CH4 selectivity of 38.5 at −30 °C, far beyond the 2008 upper bound. It is also proved that the microporosity and gas separation performance of ITB-PIM membranes is highly tailorable by adjusting the TB monomer structure. The facile functionalization method, highly diverse tunability, and excellent gas separation performance render the ITB-PIM membranes promising for helium recovery from natural gas.

Vilsmeier Complex Promotes Polycondensation of Imidodisulfuryl Chloride with Diols: Preparation of Ionic Oligomer Electrolytes

We report polycondensation of imidodisulfuryl chloride with diol monomers in the presence of catalysts. The method proceeds via stabilization of imidodisulfuryl chloride by the formation of a complex with N,N-dimethylformamide. This compound is well known as a Vilsmeier complex. The method is versatile and permits the incorporation of alkyl monomers in the oligomer backbone, and a maximum of 17 repeating units is reported. Linear ionic oligomers with protons, lithium ions, and BF4– incorporated into the main chain are successfully produced to fabricate self-standing composite single-ion ionic membranes that exhibited good ionic conductivity and stability at high voltages. Pulsed-field gradient nuclear magnetic resonance (PFG NMR) has been utilized to investigate ion diffusion in membranes.

A review of transport models in charged porous electrodes

There is increased interest in many different processes based upon interactions between a charged solid surface and a liquid electrolyte. Energy storage in capacitive porous materials, ionic membranes, capacitive deionization (CDI) for water desalination, capacitive energy generation, removal of heavy ions from wastewater streams, and geophysical applications are some examples of these processes. Process development is driven by the production of porous materials with increasing surface area. Understanding of the physical phenomena occurring at the charged solid-electrolyte interface will significantly improve the design and development of more effective applied processes. The goal of this work is to critically review the current knowledge in the field. The focus is on concepts behind different models. We start by briefly presenting the classical electrical double layer (EDL) models in flat surfaces. Then, we discuss models for porous materials containing macro-, meso-, and micro-pores. Some of the current models for systems comprising two different pore sizes are also included. Finally, we discuss the concepts behind the most common models used for ionic transport and Faradaic processes in porous media. The latter models are used for simulation of electrosorption processes in porous media.

High rate lithium slurry flow batteries enabled by an ionic exchange Nafion composite membrane incorporated with LLZTO fillers

Lithium slurry flow batteries (LSFBs) possessing decoupled energy/power density feature and high energy density are considered as the most promising next-generation energy storage devices. However, their cycling stability is depressed by the high permeability of active components through porous separator and low conductivity of lithium ion in non-porous membrane. Herein, a novel Nafion/PVDF/LLZTO ion exchange membrane (IEM) with high ion conductivity and mechanical properties is proposed. As-optimized IEM possesses an ionic conductivity of 0.29 mS cm−1. Both experimental and density functional theory (DFT) calculation studies suggest that the complementary effect between inorganic ceramic fillers LLZTO and polymer materials favor the generation of new Li+ migration expressway and dehydrofluorination. The H-bonding interactions can successfully address the poor mechanical strength issues. Moreover, the sandwich-like structure by commercialized PE buffer layer will be beneficial to the improved stability and can effectively suppress the swelling effect of membrane in organic electrolyte. Consequently, LFP//LTO slurry cells containing PE/NPL3/PE membrane exhibit extraordinary performance under 0.3 C. Assembled slurry pouch cells could be cycled stably for more than 270 h at room temperature. This ingenious strategy of introducing inorganic ceramic fillers into the composite membrane will pave a novel promising direction to the development of LSFBs.

Ionic liquid-based pore-filling anion-exchange membranes enable fast large-sized metallic anion migration in electrodialysis

The development of low-resistance ion-exchange membranes enabling fast transport of large-sized metallic anions is extremely desirable for the treatment of metal containing effluents using electrodialysis (ED). Herein, mechanically stable ionic liquid-based pore-filling anion-exchange membranes (PFAEMs) with excellent transport performance for large-sized metallic anions were fabricated by impregnating porous polytetrafluoroethylene with ionic liquid (IL) tricapryl(methyl) ammonium chloride, poly(ethylene glycol) dimethacrylate and poly(vinylidene fluoride-co-hexafluoropropylene). The superior compatibility between the ILs and polymeric chains ensured the stable existence of quaternary ammonium groups, thus enabling fast metallic anion migration along the continuous pathway in the membrane matrix at a low current density. The prepared PFAEM exhibited a dramatically greater flux of HCrO4− (90.7 μmol m−2 s−1), which was 9.5 and 4.4 times higher than the flagship commercial Neosepta@ASE and Neosepta@AMX membranes, respectively. The area resistance of PFAEM (3.4 Ω cm2) was found to be 3.4 and 2.0 times lower than those of the Neosepta@ASE and Neosepta@AMX membranes, respectively. Besides, the preeminent transport performance of PFAEM to other metal coordination anions revealed the universality of the prepared membrane. Moreover, the extremely high limiting current density and satisfactory long-term stability of PFAEM manifested bright prospects for realizing efficient metal separation in industrial-scale applications.

PEG promoted anti-fouling adsorptive membranes with excellent adsorption performance for removal of pharmaceuticals from water

Rapid and effective removal of pharmaceutical contaminants (PhCs) from water through adsorptive approach remains a huge challenge due to the multiple ionization sites and lipophilic property of most PhCs. Another issue for adsorptive media is the tough trade-off problem between adsorption enhancement and fouling-resistance. Adsorptive membranes have the advantages of convenient post-treatment and huge promise in removing PhCs compared with conventional adsorbents. Herein, two types of PEG-coupled ionic grafting adsorption membranes (NVFM-H-PEG and PPM-PMA-PEG) with outstanding adsorption and antifouling performance are developed for PhCs removal. The membranes obtained shows ultra-high water flux (up to ca. 45,000 L/(m2h) at a pressure drop of 15 cm water gravity) and outstanding protein repulsion. According to the Langmuir model, the adsorption capacity of NVFM-H-PEG toward ibuprofen (IBU) reaches at 81.3 mg/g at 45 ℃. The large negative ΔG value (−22.0 kJ/mol) reveals the strong affinity of the positively charged NVFM-H-PEG to adsorb negative PhCs at environmental concentrations (10 µg/L). A mechanism for the excellent adsorption performance of the membranes is proposed based on the synergy of hydrophobic interactions and electrostatic interaction. After ten adsorption/eluting cycles, no detectable decrease was observed in the removal efficiency (>96%) of IBU from the river contaminated with IBU. Furthermore, high removal efficiency (totally 90.8%) could be achieved from river water multi-contaminated with five PhCs using a complex of positively charged (NVFM-H-PEG) and negatively charged (PPM-PMA-PEG) membranes. This study provides a new design strategy for effective removing PhCs from contaminated water using adsorptive membrane technique.

A novel system integrating electrolysis and ionic membranes (EIMs) enables artificial carbon concentration and alleviation of metal cation stress in microalgae cultivation

An EIM system that enables carbon concentration artificially and alleviation of metal cation stress by integrating electrolysis and ionic membranes for microalgae cultivation.

An Electrolyte with Elevated Average Valence for Suppressing the Capacity Decay of Vanadium Redox Flow Batteries.

Nafion series membranes are widely used in vanadium redox flow batteries (VRFBs). However, the poor ion selectivity of the membranes to vanadium ions, especially for V2+, results in a rapid capacity decay during cycling. Although tremendous efforts have been made to improve the membrane's ion selectivity, increasing the ion selectivity without sacrificing the proton conductivity is still a challenging issue. In this work, instead of focusing on enhancing the membranes' ion selectivity, we develop an efficient valence regulation strategy to suppress the capacity decay caused by the crossover of V2+ in VRFBs. Despite the discharge capacity of the VRFB with the elevated average valence electrolytes (V3.68+) being slightly lower than that with commercial electrolytes (V3.50+) in the first 35 cycles, the accumulated discharge capacity in 400 cycles is improved by 52.33%. Moreover, this method is efficient, is easy to scale up, and provides deep insights into the capacity decay mechanism of VRFBs.

Dual-activation interfacial polymerization based anionic covalent organic framework nanofiltration membrane for high-flux dye separation

Covalent organic frameworks (COFs) hold great promise in constructing a new-generation of molecular separation membranes. Significantly, ionic COF membranes endow novel functions distinct from those of neutral membranes. However, ionic COF membranes generally suffer from extremely slow reaction rates and low yields, limiting their widespread application. In this work, a self-standing anionic COF membrane was prepared by a dual-activation interfacial polymerization strategy. And the obtained anionic COF membrane possessed a unique ordered pore structure, superhydrophilicity, as well as good chemical stability. Meanwhile, the as-prepared membrane provided the high-efficiency water transport pathways with effective rejection for dye molecules. As expected, the anionic COF membrane exhibited an excellent water permeability of about 270 L m−2 h−1 bar−1, which was much higher than those of commercial nanofiltration membranes, and also approximately 2–15 times significantly higher than those reported for polymer- or neutral COF-based nanofiltration membranes with similar rejection. Owing to the electrostatic attraction between positively charged dyes and anionic COF channels, the rejection rates of cationic dyes were above 96 %. In addition, the size-exclusion effect dominated rejection efficiency of dyes with molecular sizes larger than COF channels. These findings provided a new candidate membrane for efficient dye wastewater treatment.

INVESTIGATION OF THE MECHANISM OF SELECTIVE EXTRACTION OF IONS OF VARIOUS SALTS FROM WATER, USING POLYAMIDE MEMBRANES

The processes of membrane separation and concentration belong to the category of critical technologies for obtaining and processing structural and functional materials for desalination of water. The prospects and advantages of polyamides membranes are determined based on the analysis of the kinetics of membrane separation, the polyamides membrane has resistance to the studied salt solutions. The purpose of this work is to study the features and regularities of the mechanism of selective extraction of salt ions from water by polyamide membranes. Great importance are the methods of water purification in the selective extraction of salt ions from water using polyamide membranes. Methodology. Polyamides have a high selectivity with respect to salts, but the flow of water through them is slightly lower. At a pH range 2.0 – 10 polyamides, they withstand processing temperatures up to 100 0C without significant changes in the porous structure, allow multiple regeneration, and are resistant to most acids, depending on the pH of the medium. Results. According to the results of pilot tests in the extraction of salt ions from water using polyamide membranes, it was found that in the pH region = 6-7, the joint presence of the main charged forms of salt ions is assumed. Conclusion. Thus, based on the results, it follows that the values of the diffusion coefficients of salt ions in membranes with pore radii from 5 to 8 nm at pH =6.5–7.5 are generally comparable for salt ions.

Optogenetic polymerization and assembly of electrically functional polymers for modulation of single-neuron excitability.

Ionic conductivity and membrane capacitance are two foundational parameters that govern neuron excitability. Conventional optogenetics has emerged as a powerful tool to temporarily manipulate membrane ionic conductivity in intact biological systems. However, no analogous method exists for precisely manipulating cell membrane capacitance to enable long-lasting modulation of neuronal excitability. Genetically targetable chemical assembly of conductive and insulating polymers can modulate cell membrane capacitance, but further development of this technique has been hindered by poor spatiotemporal control of the polymer deposition and cytotoxicity from the widely diffused peroxide. We address these issues by harnessing genetically targetable photosensitizer proteins to assemble electrically functional polymers in neurons with precise spatiotemporal control. Using whole-cell patch-clamp recordings, we demonstrate that this optogenetic polymerization can achieve stepwise modulation of both neuron membrane capacitance and intrinsic excitability. Furthermore, cytotoxicity can be limited by controlling light exposure, demonstrating a promising new method for precisely modulating cell excitability.

Efficiency Analysis of Fuel Cell Components with Ionic Poly-Arylether Composite Membrane.

We use polyethylene glycol as an additive to explore how the hydrogen bonding of this additive changes the properties of SA8 blended sulfonated polyetheretherketone (SPEEK) composite films. We mixed a 5%wt polyethylene glycol solution into a 12.5%wt SA8 solution, and then prepared a film with a total weight of 40 g at a ratio of 1:99. The SA8 (PEG) solution was prepared and then mixed with 5%wt SPEEK solution, and a film-forming solution with a total weight of 8g in different mixing ratios was created. Polyethylene glycol (PEG) was mixed into the sulfonated polyarylether polymer SA8 to form physical cross-linking. Therefore, the sulfonated polyether ether ketone SPEEK was mixed in, and it exhibited good thermal stability and dimensional stability. However, there was some decrease in proton conductivity as the proportion of SPEEK increased. Although SPEEK mixed with sulfonated polymer reduces the proton conductivity, the physical cross-linking of PEG can improve the proton conductivity of the composite membrane, and adding SPEEK can not only solve the problem of the high sulfonation film swelling phenomenon, it can also improve the dimensional stability of the film through the hydrogen bonding force of PEG and obtain a composite film with excellent properties.

Technological advancements in the use of ionic liquid- membrane systems for CO2 capture from biogas/flue gas - A review

Carbon capture has become a very important method for curbing the problems associated with the release of carbon dioxide into the atmosphere, which in turn has detrimental effects on the planet and its inhabitants. Ionic liquids and membrane separation have been explored in this review paper as effective means of capturing carbon dioxide. An innovative approach to CO2 capture is the use of Ionic liquids (ILs) since they exhibit certain significant traits such as good stability (thermal, mechanical and chemical), inflammability and high absorptive capacities. Ionic liquids (ILs) are widely regarded as nontoxic substances. Viscosity and thermal degradation of ILs at temperatures slightly above 100 °C are the major disadvantages of ILs. Membrane separation is a technique used for the effective separation of substances by materials bearing holes in a continuous structure. Membrane technology has gained significant improvements, over the years. Several ILs and membrane systems were considered in this work. Their weaknesses, strengths, permeability, selectivity, operating conditions and carbon capture efficiencies, were all highlighted in order to gain a good perspective on ways by which the individual systems can be improved upon. The study considered several polymer-Ionic liquid hybrid materials as viable options for CO2 capture from a post-combustion process. Different ILs were scrutinized for possible integration in membranes by taking full advantage of their individual properties and harnessing their tune-able characteristics in order to improve the overall carbon capture performance of the system. Several options for improving the mechanical, chemical, and thermal stabilities of the hybrid systems were considered including the use of cellulose acetate membrane, nanoparticles (graphene oxide powder) alongside potential ionic liquids. Doping membranes with ILs and nanoparticulates such as graphene oxide serves as a potential method for enhancing the CO2 capture of membranes and this review provides several evidences that serve as proofs for this concept.

Multifunctional Flexible Ionic Skin with Dual-Modal Output Based on Fibrous Structure.

Flexible wearable electronic devices with multiple sensing functions that simulate human skin in all aspects have become a popular research topic. However, the current expensive and time-consuming means of integration and the complex decoupling process are hampering the further development of multifunctional sensors. Here, an ultraflexible ionic fiber membrane (IFM) prepared by a simple electrospinning technique is reported, which exhibits pressure and humidity sensing properties. With the help of different electrode structures, the IFM-based multifunctional sensor achieved pressure and humidity detection with different sensing mechanisms. Pressure sensing with high sensitivity (49.7 kPa-1 at 0-30 kPa) and wide detection range (0-220 kPa) was indicated by the capacitive signal. Humidity sensing with high linearity (1.086% per percent relative humidity (RH)) in the range 15%-90% RH was indicated by the resistance signal. In particular, the multimodal output of capacitance/resistance corresponding to pressure/humidity in this study directly addresses the problem of accurately distinguishing the two stimuli. Furthermore, we have demonstrated that the impact between pressure and humidity is negligible when measured simultaneously and independently. Because of the excellent pressure/humidity sensing performance, we have fabricated a smart bracelet and mask for pulse, skin moisture, and breathe monitoring, which indicates the promising future of multifunctional flexible sensors based on IFM in the healthcare field.