Bipolar Ion Exchange Membranes Research Articles

Toward a Circular Lithium Economy with Electrodialysis: Upcycling Spent Battery Leachates with Selective and Bipolar Ion-Exchange Membranes.

Recycling spent lithium-ion batteries offers a sustainable solution to reduce ecological degradation from mining and mitigate raw material shortages and price volatility. This study investigates using electrodialysis with selective and bipolar ion-exchange membranes to establish a circular economy for lithium-ion batteries. An experimental data set of over 1700 ion concentration measurements across five current densities, two solution compositions, and three pH levels supports the techno-economic analysis. Selective electrodialysis (SED) isolates lithium ions from battery leachates, yielding a 99% Li-pure retentate with 68.8% lithium retention, achieving relative ionic fluxes up to 2.41 for Li+ over transition metal cations and a selectivity of 5.64 over monovalent cations. Bipolar membrane electrodialysis (BMED) converts LiCl into high-purity LiOH and HCl, essential for battery remanufacturing and reducing acid consumption via acid recycling. High current densities reduce ion leakage, achieving lithium leakage as low as 0.03%, though hydronium and hydroxide leakage in BMED remains high at 11-20%. Our analysis projects LiOH production costs between USD 1.1 and 3.6 per kilogram, significantly lower than current prices. Optimal SED and BMED conditions are identified, emphasizing the need to control proton transport in BMED and improve cobalt-lithium separation in SED to enhance cost efficiency.

Chromium-Modified Heterogeneous Bipolar Membrane: Structure, Characteristics, and Practical Application in Electrodialysis.

The modification of an MB-2 bipolar ion exchange membrane with chromium (III) hydroxide was carried out by a chemical method, namely, by the sequential treatment of the membrane with a solution of chromium (III) salt and alkali. Data on the morphology, phase, and chemical composition of the modified membrane were obtained using scanning electron microscopy and energy-dispersive analysis. In particular, it was shown that the modifier was distributed in a layer 30-50 microns thick at the boundary of the cation- and anion-exchange layers of the bipolar membrane. The electrochemical behavior of the modified membrane in the process of sodium sulfate conversion was studied by measurements of the following characteristics: the current efficiency of the acid and base, the energy consumption of the process, and the degree of contamination of the target products with salt ions. It was shown that the resulting membrane has an alkali and acid yield of 61% and 57%, respectively. This is higher than the same yields for the industrial unmodified MB-2 membrane (38% and 30%). The results of this study demonstrated that the modified samples allowed obtaining a higher yield of acid and base, reducing the content of salt ions in the target products and also reducing the electricity consumption for obtaining a unit of the target product. The concentration dependences of the electrical conductivity of the MK-40 heterogeneous ion-exchange membrane, which is a cation-exchange layer of MB-2, in sodium sulfate solutions before and after its modification with chromium (III) oxide were obtained. A decrease in the specific electrical conductivity of the membrane with the introduction of a modifier was established. A quantitative assessment of the influence of the modifier on the current flow, volume fraction, and spatial orientation of the conductive phases of MK-40 was carried out using an extended three-wire model for the description of the model parameters of ion-exchange materials. When a modifying additive was introduced into MK-40, the fraction of the current passing through the inner solution and the intergel phase decreased. This was due to the substitution of part of the free solution in the pore volume by the modifier. A variant of the practical application of electrodialysis with the chromium-modified bipolar ion-exchange membranes is recommended.

INFLUENCE OF A HYDROPHOBIZER ON THE PROPERTIES OF EXPERIMENTAL BENTONITE-CONTAINING BIPOLAR MEMBRANES

Experimental samples of bipolar ion-exchange membranes were obtained by applying liquid sulfocation exchanger LF-4SK containing bentonite clays treated with stearic acid to an anion-exchange membrane-substrate with quaternary ammonium groups MA-41. The effect of the amount of added bentonite (1, 2, 3 wt%) on the characteristics of membranes was studied. Silicon and hydroxyl of the included bentonite accelerate the dissociation of water molecules, which leads to increasing the concentration of hydrogen and hydroxyl ions during bipolar electrodialysis. Surface modification of bentonite particles with stearic acid improves the dispersion of the clay in the polymer solution. The physico-mechanical characteristics of experimental ion-exchange membranes containing bentonite treated with stearic acid are compared with a membrane containing natural untreated bentonite. The total exchange capacity, density, moisture capacity, as well as tensile strength and relative elongation were determined. The injection of a hydrophobizer into the membrane leads to a decrease in moisture content, an increase in the total exchange capacity and density of the cation-exchange layer compared to a membrane containing bentonite in its original form. The conversion of sodium sulfate (concentration 0.5 mol/dm3) was carried out with experimental bipolar ion-exchange membranes. The use of a bipolar membrane containing bentonite treated with stearic acid (3%) in the cation-exchange layer leads to an increase in the productivity of the process and a decrease in energy costs compared to a commercially available heterogeneous ion-exchange membrane with similar functional groups and not containing catalytic additives. A scheme for obtaining experimental bipolar membranes is proposed, which consists of the following stages: preparation of bentonite; treatment of bentonitewith stearic acid; preparation of anion-exchange membrane-substrate MA-41; coating the membrane-substrate with of a cation-exchange layer.

Preparation of RBPM-Ru based on FPSu and its characterization through image segmentation

A membrane technology is one of the basic categories of water purification technologies that are used to treat wide range of salinity water from brackish to sea water. Bipolar membrane (BPM) is a special type of catalytic ion exchange membrane (IEM) which involves water dissociation reaction in intermediate layer. Here monopolar and bipolar IEMs with Ru (water dissociation catalyst) as intermediate layer (IL) are prepared with resin and glass fiber reinforcements using functionalized polysulfone polymer (RBPM-Ru). The prepared RBPM-Ru was characterized using universal testing machine, thermo gravimetric analysis, contact angle and chemical stability through conductivity and water absorption studies. In addition the present study highlights the new method of characterizing RBPM-Ru especially through image segmentation technique as one of the prior characteristic technique before SEM analysis to confirm its bi-layer formation in a single membrane because of its advantages like no cost requirement and less time consumption method with the same quality of accuracy. The performance of RBPM-Ru in a two-compartment electrodialytic cell was evaluated using correlated parameters such as pH, concentration and conductivity studies in both compartments. By using current voltage graph (I-V) the importance of incorporating catalytic material in IL for enhancing BPM water dissociation reaction were identified. Finaly it can be concluded that RBPM-Ru was expected to have better process efficiency due to lower co-ion leakage capacity when compared with results of polystyrene–divinylbenzene (PSDVB) based BPM under similar experimental conditions.

Factors Affecting Hydroxide Ion Concentrations in Bipolar Membranes

The useful lifetime of bipolar ion exchange membranes is often limited by nucleophilic attack by hydroxide ions on the ionic groups and polymer backbone in the anion exchange layers (AELs). This is especially problematic in water treatment applications for making acid and base from salt solutions. This research investigated the effect of bulk electrolyte composition, current density, membrane thickness, ion exchange capacity, and bulk solution pH value on hydroxide ion concentrations inside the AELs of a bipolar membrane. Onedimensional Nernst-Plank equations were solved for the species Na+, Cl-, OH- and H+ within 20-100 μm thick anion and cation exchange layers with fixed charged densities ranging from 0.5-2.0 eq/L. In 1 M NaCl solutions at neutral pH values, hydroxide concentrations in the AEL reached as high as 2.2 M at a current density of 100 mA/cm2. In 1 M NaOH solutions, hydroxide ion concentrations reached as high as 3.77 M. Hydroxide concentrations in the AEL were significantly affected by the ratio of Cl- to hydroxide ions in the bulk electrolyte. Where hydroxide concentrations in the bulk electrolyte were an order of magnitude lower than chloride concentrations, membrane hydroxide concentrations were nearly proportional to the current density. Increases in ion exchange capacity and AEL thickness resulted in increased membrane hydroxide ion concentrations. Membrane concentrations of hydroxide ions can be minimized by operation at low current densities, with high background electrolyte concentrations using thin membranes with low ion exchange capacities and producing base concentrations less than 0.1 M.

Turning water into a protonic diode and solar cell via doping and dye sensitization

<h2>Summary</h2> The key advance that led to the digital revolution was the invention of the solid-state diode, due to its ability to effectively rectify electronic current. Analogous, water-based diodes were invented around the same time, yet their ability to rectify protonic current paled in comparison. A suitable platform to fabricate water-based diodes is the bipolar ion-exchange membrane, which serves as a scaffold for dopants that ionize when infiltrated with protonically semiconducting water. Herein, by fashioning bipolar membranes into membrane-electrode assemblies and characterizing them like fuel cells, we report high-quality protonic diodes that, when sensitized to visible light using photoacids, exhibit "reverse" photovoltaic action. These demonstrations will spur innovations in the fields of iontronics, neuromorphic computing, and brain-machine interfaces, among others.

Recovery of ammonia nitrogen from landfill leachate using a biopolar membrane equipped electrodialysis system.

In this paper, a laboratory-scale electrodialysis reactor with five compartment cells separated by a bipolar membrane and ion exchange membrane was assembled to remove ammonia nitrogen from landfill leachate as a pretreatment process. The effects of humic acid, magnesium ions (Mg2+) and calcium ions (Ca2+) existing in leachate on the removal efficiency of ammonium (NH4 +) were investigated by using simulated wastewater. The results indicate that humic acid has little impact on ammonium in the presence of an electric field. High concentrations of Mg2+ and Ca2+ in solution have a substantial impact on the removal efficiency of ammonium, but the average migration rate of the three ions is NH4 + > Mg2+ > Ca2+ under the same current intensity, and NH4 + plays a major role in electromigration for mixture electrodialysis. Therefore, ammonia nitrogen can be separated from leachate and accumulated effectively. Meanwhile, the bipolar membrane near the cathode produces alkali that is released into the base cell to promote ammonia nitrogen transformation from accumulated ammonium, which creates in-site alkaline condition for ammonia nitrogen recovery by a further stripping process. When the actual leachate collected from a local municipal sanitary landfill was employed, the reactor reached 86.17% of ammonia nitrogen removal after 3.0 h reaction. Analysis of membrane scale suggests the inhibitory effect of Mg2+ on Ca2+ migration during the initial working period of the reaction can potentially slow down the membrane scaling of the cation exchange membrane. This study provides a promising technology for the removal and recovery of ammonia nitrogen from landfill leachate.

A comprehensive mathematical model of water splitting in bipolar membranes: Impact of the spatial distribution of fixed charges and catalyst at bipolar junction

Bipolar ion-exchange membranes (BPM) have a long history and many uses. Still, the number of applications continues to grow every year, as does the interest in a better understanding of the mechanisms of ion transport and water splitting. We reconsider the existing theoretical background for the BPMs and propose a one-dimensional stationary model. For the first time, the Nernst-Planck-Poisson equations are coupled with the equations, which locally describe the water splitting kinetics. The catalytic effects exerted by the functional groups and the catalyst (if present), the protonation-deprotonation reactions of these groups as well as the effect of strong electric field (the second Wien effect) are taken into account when describing the reverse-bias mode. The effective rate constant of water splitting occurring in the absence of electric field is determined from the acid dissociation constants (Ka). The concentration profiles, the thickness of the reaction zone and space charge region (SCR) are simulated and analyzed. The results of numerical computation are compared with the known analytical estimations. Thus, the basic assumptions of the theory of BPMs are examined, and the conditions under which these assumptions are valid or not are found. Current-voltage curves and partial currents are calculated and compared with experimental data. The occurrence of two limiting currents at pKa close to 7 is predicted due to current-induced membrane discharge. According to simulations, any increase in the SCR thickness leads to a decrease of the water spitting rate at a fixed voltage due to a decrease in the second Wien effect. A very thin (about 4 nm) catalytic layer within the bipolar junction is sufficient to obtain 100 mA cm−2 current density at 1 V even when the anion-exchange and cation-exchange membrane layers do not contain catalytically active functional groups.

Aqueous based dual-electrolyte rechargeable Pb–Zn battery with a 2.8 V operating voltage

Abstract A novel rechargeable PbO2-Zn battery system using Zn as negative and PbO2 as positive electrodes in a KOH-H2SO4 dual-electrolyte is developed. Using a bi-polar ion exchange membrane that effectively prevents the H+ and OH− from neutralization, the positive and negative electrodes operate in the respective electrolytes with different pH. The Zn electrode provides a low potential of −1.3 V in KOH solution and the PbO2 has a high potential of +1.5 V in H2SO4 solution. This resulted in a cell operating voltage of 2.8 V in an aqueous electrolyte. The system also demonstrated a high rate performance and good rechargeability. This simple, low-cost system not only overcomes the thermodynamic limit of water decomposition and achieves a high voltage aqueous based battery, but also provides a new approach in design of future electrochemical devices.

The Processing of Titanium Production Effluents in an Electrodialysis Cell with Monopolar and Bipolar Membranes

Results of research on the processing of spent acid etching solution (SAES) produced during manufacturing of titanium products by their etching in hydrochloric acid are presented in this paper. The processing technology consists of neutralizing SAES with alkali, filtering, drying and calcining of titanium hydroxide precipitate, and also processing of filtrate by electrodialysis in a cell with ion-exchange membranes. Anion-, cation- and bipolar ion exchange membranes were used. It is shown that the processing of SAES formed during etching of titanium products makes it possible to purify effluents to remove NaCl in an electrodialysis cell with monopolar and bipolar membranes. Transfer of Na+ and Cl– ions through the bipolar membrane MB-1 was observed. Thus, solutions generated in acid and alkali concentration chambers contain significant amounts of NaCl. It is obvious that the introduction of buffer chambers is necessary to obtain acid and alkali solutions free from NaCl when using bipolar membranes.

Flow battery based on reverse electrodialysis with bipolar membranes: Single cell experiments

The efficient storage of electrical energy is a key issue for a sustainable electrical energy supply from fluctuating sources such as windmills or photovoltaic devices. In addition to traditional electrical energy storage devices, flow batteries have become a subject of intensive research and development activities. This publication is concentrated on a flow battery type, based on the neutralization of an acid and a base by reverse electrodialysis with bipolar membranes. The fundamental aspects of the process will be discussed and experiments at laboratory scale in a single repeating cell unit will be presented, using HCl as acid, NaOH as base and NaCl as neutral salt solution. The components and process parameters which determine the performance of this battery, such as the monopolar and bipolar membranes, the concentrations of acid and base, and the operating temperature, have been investigated and their effect on the overall efficiency of the battery will be discussed. In a following second part, experimental results for stacks with 5–20 repeating cell units will be presented by Xia et al., in preparation [13]. Key issues for a successful implementation of a flow battery based on acid/base neutralization are the membrane permselectivities, depending on the fixed charge density, the ionic resistances of the mono- and bipolar ion-exchange membranes and the water permeability of the bipolar membrane.

Aqueous Based Asymmetrical-Bipolar Electrochemical Capacitor with a 2.4 V Operating Voltage

A novel aqueous-based asymmetrical-bipolar electrochemical capacitor (EC) was developed. The EC device has leveraged the contributions from a Zn-CNT asymmetrical electrode and a KOH-H2SO4 dual-pH electrolyte. The positive and the negative electrodes operate in their respective electrolytes that have different pH values, leading to a cell voltage of 2.4 V. The potential tracking of both electrodes reveals that the Zn negative electrode maintains a potential of -1.2 V, while the CNT positive electrode is charged and discharged reversible up to +1.2 V. A bipolar ion exchange membrane effectively separates the acid and the alkaline from neutralizing. As a result, the aqueous-based asymmetrical-bipolar EC device has shown stable performance with a capacitance retention of 94 % and a coulombic efficiency of 99% over 10,000 cycles. The asymmetrical-bipolar design overcomes the thermodynamic limitation of water decomposition of the aqueous-based electrolyte, paving a new avenue towards aqueous-based ECs and energy storage systems with both high energy and power density. Figure 1

Aqueous based asymmetrical-bipolar electrochemical capacitor with a 2.4 V operating voltage

A novel asymmetrical-bipolar electrochemical capacitor system leveraging the contributions of a Zn-CNT asymmetrical electrode and a KOH-H2SO4 dual-pH electrolyte was developed. The positive and negative electrodes operated in electrolytes with different pH, exploiting the maximum potential of both electrodes, which led to a cell voltage of 2.4 V. The potential tracking of both electrodes revealed that the Zn negative electrode could maintain a potential at −1.2 V, while the CNT positive electrode can be charged to +1.2 V without significant irreversible reactions. A bipolar ion exchange membrane has effectively separated the acid and alkaline from neutralization, which resulted in stable performance of the device with capacitance retention of 94% and coulombic efficiency of 99% over 10,000 cycles. This asymmetrical-bipolar design overcomes the thermodynamic limit of water decomposition, opening a new avenue towards high energy and high power density aqueous-based ECs.

Conversion of Visible Light into Ionic Power Using Photoacid-Dye-Sensitized Bipolar Ion-Exchange Membranes

Summary For over half a century, it has been recognized that the classical physics that dictates the behavior of hydrated ion-exchange membranes, such as Nafion, and semiconductors, such as doped silicon, are similar. However, no demonstrations of photovoltaic action from ion-exchange materials existed. We recently reported a synthetic light-driven proton pump derived from an ion-exchange membrane. Absorption of light by covalently bound photoacid molecules resulted in photovoltaic action. This design lacked a second permselective membrane contact, which limited its performance. Here, we report a ∼60-fold increase in the photovoltage through use of a bipolar membrane structure consisting of a cation-exchange membrane affixed to an anion-exchange membrane. The junction between the layers was characterized in detail using electrochemistry, scanning electron microscopy, spectroscopy, and thermal gravimetric analysis. Our results represent considerable progress toward a device that directly converts sunlight into ionic electricity, which has implications for direct solar desalination of salt water.

Solar Generation of Ion Gradients Using Dye-Sensitized Ion-Exchange Membranes

Most solar energy conversion technologies generate power through transport of energized electron particles; however, the physics that describes these technologies only requires that the particles be charged and not specifically that they are electrons. My research group studies solar energy conversion technologies that generate power from sunlight through ion transport. In my presentation I will report on my research group’s recent demonstration of ion transport against concentration gradients driven by solar illumination of dye-sensitized ion-exchange materials. Mechanistically, visible light was used to drive endergonic excited-state proton transfer from a covalent photoacid-functionalized polymer membrane. Photoacid molecules convert the energy in light into a change in the chemical potential of protons via a weakening of protic functional groups on the photoacid, i.e. a drop in its pK a. As a model system for ion-channels in polymer-electrolyte ion-exchange membranes, dye-sensitized conical nanopores in poly(ethylene terephthalate) (1 – 108 pores/cm2) were investigated. Remarkably, in a region occupied by ~20 zeptoliters (~2 x 10-20 L) of aqueous electrolyte, electrochemistry was used to determine the number of binding groups of the dyes and the ground-state pK a of the dyes, and fluorescence microscopy was used to determine the conditions where excited-state proton transfer occurred. These data were consistent with a hypothesis that pK a values of the photoacids in the ground-state and excited-state were significantly smaller than those measured for dye molecules in solution, likely due to incomplete screening of surface charges in the confined nanopores. Dye-sensitized Nafion monopolar ion-exchange membranes and bipolar ion-exchange membranes were also investigated. Under sunlight-simulated illumination these materials were found to exhibit photovoltaic action, i.e. generation of a photocurrent and a photovoltage. Bipolar membranes are a class of polymeric ion-exchange materials that consist of a monopolar cation-exchange membrane that is in intimate contact with a monopolar anion-exchange membrane. They are unique among the ion-exchange membranes in that they that separate and maintain pH differences across the membrane even during passage of ionic current. Moreover, the physics of ion equilibration processes within these membranes resembles that which occurs during equilibration of semiconductor pn-junctions. This body of work represents an underexplored solar energy conversion process that is being pioneered by my research group to operate via a mechanism similar to that in semiconductor pn-junctions. The applicability and practicality of these materials as standalone ionic photoelectrochemical devices will also be presented.

Monopolar and Platinum Interfaced Bipolar Membrane Electrodialysis: Experimental Assessment Using Synthetic Salt Solution Heterogeneous Cation Exchange Membranes

In this study, polystyrene ethylene butylene polystyrene (PSEBS) was functionalized to prepare mono and bipolar ion exchange membranes. In the case of the bipolar membrane, platinum was used as the intermediate layer. NaCl solution of concentration ranging from 5 g/L to 25 g/L was used as the feed solution. A commercially procured ion exchange membrane made of polystyrene divinyl benzene was also evaluated for the purpose of comparison. The BPMED performance reached the highest current efficiency of 69.54% and 53.6% with the energy consumption of 0.37 Wh and 1.39 Wh for the synthesized and commercial membranes, respectively. Also the performance of the fabricated unit was assessed in terms of electrical conductivity, salinity and ion (sodium and chloride) concentrations for the feed solution after 8-hour duration. The reproducibility performance of the membranes was also analyzed for the synthetic salt solution.

(Invited) Sunlight-Driven Ionic Power Generation from Bipolar Ion-Exchange Membranes Functionalized with Photoacids

Bipolar membranes are a class of polymeric ion-exchange materials that consist of a cation-exchange membrane that is in intimate contact with an anion-exchange membrane. They are unique among the ion-exchange membranes in that they that separate and maintain pH differences across the membrane even during passage of ionic current. Moreover, the physics of ion equilibration processes within these membranes resembles that which occurs during equilibration of semiconductor pn-junctions. In my presentation I will report on my research group’s recent results from measurements of the electrochemical behavior of bipolar membranes under conditions relevant to solar fuels devices. We identified a condition where the energy required to electrolyze water was seemingly less than 1.23 V, which we showed was due to transport of ions other than protons and hydroxide ions. This subtlety will be explained in great detail to clarify misunderstandings in the interpretation of current–voltage behavior of bipolar membranes. My research group has also recently successfully demonstrated ionic power generation through solar light harvesting in dye-sensitized ion-exchange membranes. Visible light illumination of photoacid-functionalized Nafion membranes drove endergonic excited-state proton transfer and a photovoltage and photocurrent resulted. Photoacid molecules convert the energy in light into a change in the chemical potential of protons via a weakening of protic functional groups on the photoacid, i.e. a drop in its pK a. Many photoacids absorb visible light poorly and so a secondary research thrust on this project is to develop new visible-light-absorbing photoacids. Toward this, we have developed the first Ir-based inorganic coordination compound photoacids and quantum dot photoacids. Visible-light excitation of these molecules resulted in clear observation of effective photoacid behavior. Calculation of the excited-state pK a and ongoing work to comprehend the analysis of photoacid behavior in complex systems will be covered. The applicability and practicality of bipolar membranes in solar fuels devices and as standalone ionic photoelectrochemical devices will also be discussed. As most of these materials, techniques, and analyses are new to the artificial photosynthesis community, we plan to carefully present the results of our studies and provide ample explanations. Collectively, this body of work represents several new directions in artificial photosynthesis research and development that are being pioneered by my research group.

Development of monopolar and platinum intermediate bipolar membranes: application in desalting brine solution

The desalination process parameters like current efficiency (CE), energy consumption, and acid–base production for the fabricated bipolar membrane (BPM) electrodialysis unit (five compartments of 120 cm2 active areas) were investigated in this paper using monopolar- and bipolar-based ion-exchange membranes (IEMs). Also, the performance of the fabricated unit in removing NaCl was assessed in terms of salinity. Polystyrene–ethylene–butylene–polystyrene was functionalized to prepare the monopolar and bipolar IEMs. In the case of BPM, platinum was used as the intermediate layer. The synthesized IEMs were characterized thermally and by contact angle measurements. A commercially procured monopolar and bipolar ion-exchange membrane made of polystyrene–divinylbenzene was also evaluated for the purpose of comparison. The electrodialysis process using these IEMs reached the highest CE of 66 and 38% with the lowest energy consumption of 0.24 Wh and 1.60 Wh for the synthesized and commercial membrane, respectively.

Acid and base recovery from brine solution using PVP intermediate-based bipolar membrane through water splitting technology

Potable water has become a scarce resource in many countries. In fact, the world is not running out of water, but rather, the relatively fixed quantity is becoming too contaminated for many applications. Hence, the present work was designed to evaluate the desalination efficiency of resin and glass fiber-reinforced Polysulfone polymer-based monopolar and bipolar (BPM) ion exchange membranes (with polyvinyl pyrrolidone as the intermediate layer) on a real sample brine solution for 8 h duration. The prepared ion exchange membranes (IEMs) were characterized using FTIR, SEM, TGA, water absorption, and contact angle measurements. The BPM efficiency, electrical conductivity, salinity, sodium, and chloride ion concentration were evaluated for both prepared and commercial-based IEM systems. The current efficiency and energy consumption values obtained during BPMED process were found to be 45 % and 0.41 Wh for RPSu-PVP-based IEM system and 38 % and 1.60 Wh for PSDVB-based IEM system, respectively.

Influence of water content on properties of a heterogeneous bipolar membrane

The heterogeneous ion-exchange membranes consist of polymer matrix and ion-exchange resin powder. The goal of this work was to compare two types of the heterogeneous bipolar membranes made of powdered ion-exchange resin with different water content. The water content influences the resistance of layers and the kinetics of water dissociation. The properties of heterogeneous bipolar ion-exchange membranes were compared due to the current–voltage curve. The evaluated parameters are the limiting current density, the efficiency of the water dissociation, and the resistance below the potential for water splitting. Finally, the bipolar membranes were tested in the electrodialysis stack. The membranes with higher water content had about 25% higher performance at the stack.