Electromembrane Processes Research Articles

How peptide migration and fraction bioactivity are modulated by applied electrical current conditions during electromembrane process separation: A comprehensive machine learning-based peptidomic approach

Industrial wastewaters are significant global concerns due to their environmental impact. Yet, protein-rich wastewaters can be valorized by enzymatic hydrolysis to release bioactive peptides. However, achieving selective molecular differentiation and eventually enhancing peptide bioactivities require costly cascades of membranes. In this study, a complex porcine cruor hydrolysate, containing 150 well-characterized peptides and demonstrating only an antifungal activity, was used as a model solution to evaluate the impact of current modes (continuous electrical current (CC), pulsed electric field (PEF) and polarity reversal (PR)) and the combination of pulse/pause-reversal pulse duration (10 s/1 s and 1 s/1 s) during peptides separation by an electromembrane process. The data analysis was assisted by a machine learning (ML)-based peptidomic approach to identify which of the 45 physicochemical characteristics of the peptides explain migration, or lack thereof, during electrodialysis with filtration membrane, a generic electromembrane process. The results demonstrated, for the first time, that electric current conditions modulate the population of recovered peptides and their associated fraction bioactivities. ML models identified the main features correlated to peptide migration, allowing tentative explanations of the underlying peptide selective migration phenomena. For CC-PEF 10 s/1 s-PR 10 s/1 s, isoelectric point (pI) (importance of 63.1 %) and molecular weight (MW) (17.7 %) were most important. For PEF 1 s/1 s, pI (53.9 %), MW (23 %) and GRAVY score (6.2 %) played major roles. Finally, for PR 1 s/1 s, MW (82.5 %), GRAVY score (5.5 %) and tyrosine content (1.1 %) were the key features. In addition, CC, PEF 10 s/1 s and PR 10 s/1 s allowed the production of two reusable fractions, an antibacterial recovery fraction and a feed fraction retaining antifungal activity, which aligns with the concept of circular economy.

Hydrogen-Electrodialysis with Bipolar Membrane (H-EDBM): First experiments and preliminary economic evaluation

In the present work Electrodialysis with Bipolar Membranes (EDBM) for brine valorisation is for the first time investigated for the simultaneous production of hydrogen and chemicals. EDBM allows current densities one order of magnitude higher than ED and RED electro-membrane processes, making the technology more attractive to the hydrogen market. In this work, an experimental campaign with the Hydrogen-EDBM (H-EDBM) was conducted for the first time, investigating different configurations consisting of different end-membranes for the electrode compartments. The results showed 98 % ±2 % faradic efficiency for hydrogen production, with a productivity of up to 18.4 mol h−1 m−2 at the current density of 1000 A m−2. In addition, the Bipolar Membranes allow the simultaneous production of chemicals such as NaOH, for which a Current Efficiency of 96 % and a Specific Energy Consumptions (SECs) of 1.78 kWh kgNaOH−1 were obtained. Eventually, the research was completed with a preliminary economic analysis combining the different operations and costs of the tested configurations in order to identify the optimum of the process. The Levelized Costs Of Hydrogen (LCOH) and of NaOH (LCONaOH) were used as performance parameters. The minimum LCONaOH of 0.13 € kgNaOH−1 and LCOH of 2.4 € kgH2−1 were found when bipolar membranes are used as end-membranes and the unit is coupled with onshore wind plant, identifying this configuration as the most promising. Collected results show a great potential for the H-EDBM, thus fully justifying future more in-depth analyses.

The green resource recovery process of a new type of selective bipolar membrane electrodialysis system for saline wastewater treatment

The selective electrodialysis with bipolar membrane (BMSED) is an advanced electro-membrane process that combines monovalent perm-selective ion exchange membrane and a bipolar membrane, and presented significant potential in high salinity wastewater treatment and reclamation. Herein, we accomplished an in-depth assessment of the external-integration and internal-integration systems for the treatment of high-salinity mining wastewater and seawater desalination concentrate brine. The issues surrounding their cycling performance during batch operation, their anti-fouling potential in the presence of Mg2+/Ca2+ ions, and its specific operational cost were thoroughly investigated. The results suggest that the internal integration system demonstrates suitable stability during long-term operation under batch (cycling) mode. Nevertheless, the membrane exhibited inorganic scaling due to co-ion leakage at high current density. A highly pure NaOH was obtained through an internal integration process at a cost of 0.68 $/kg, outperforming the external integration system (98.96 %, 1.85 $/kg). The findings presented in this study offer valuable insights for the industrial application of BMSED technology in managing high salinity wastewaters.

Development of High-Performance Bipolar Membranes with Optimal Junction Properties for Efficient Electro-Membrane Processes

A bipolar membrane (BPM) is a special type of ion-exchange membrane in which an anion-exchange layer (AEL) and a cation-exchange layer (CEL) are combined. Water molecules can be easily dissociated at the interface of the BPM by the strong electric field generated when a reverse bias voltage is applied through the membrane. Such dissociation leads to the generation of proton and hydroxide ions, which are then transported through the CEL and AEL, respectively, resulting in the production of acid and base solutions. Under a forward bias, these ions are drawn back to the bipolar interface, where they neutralize each other. The energy derived from this neutralization process, represented as a junction potential (JP) value, is a key factor in the BPM's efficiency. BPMs with ideal JP values are critical for achieving high separation and energy efficiencies in electro-membrane processes. Furthermore, for the prolonged operation of these processes, BPMs must possess a highly adhesive bipolar junction. Our work includes the development of a novel BPM with an ideal JP and a highly adhesive bipolar junction. This BPM has been applied to various electro-membrane processes, including an acid-base flow battery and direct seawater electrolysis. The BPMs are fabricated using poly(phenylene oxide) (PPO)-based ionomers, and incorporates an iron-based catalyst and a reinforcing material. These additions enhance the water-splitting performance and the durability of the interface between the ion-exchange layers. The prepared BPMs not only demonstrated excellent interfacial adhesiveness and mechanical properties but also achieved a water-splitting efficiency of 98% or higher. In comparison to commercial BPM, the electro-membrane processes utilizing the prepared BPM exhibited superior performance. This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Korean government (MEST) (NRF-2022M3C1A3081178 & NRF-2022M3H4A4097521).

Composite Ion-Exchange Membranes with High Specific Ion Selectivity for Efficient Electro-Membrane Processes

The advancement of ion-exchange membranes (IEMs) with heightened permselectivity for specific ions is pivotal for improving electro-membrane processes. Achieving targeted ion selectivity necessitates precise control over membrane surface characteristics, including electrostatic forces, ion transport channel size, and hydrophobicity. Utilization of diverse nanostructured materials, particularly metal-organic frameworks (MOFs), offers a pathway to modify these surface properties. MOFs, known for their structural diversity, adjustable pore sizes, and customizable frameworks, are widely applied in separation, catalysis, electrochemical, and biomedical fields. This study presents novel composite membranes, enhanced with various nanostructured materials including MOFs, demonstrating improved specific ion selectivity, robust physical strength, and superior electrochemical properties compared to standard commercial membranes. Notably, these membranes exhibit augmented performance in water-splitting electrodialysis for LiOH production, attributed to enhanced proton-blocking and monovalent ion permeability. This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Korea government (MEST) (NRF-2022M3C1A3081178 and NRF-2022M3H4A4097521).

Green electromembrane extraction of morphine by sodium alginate-g-polyacrylamide/agarose interpenetrating polymer network as a membrane

The isolation and pre-concentration of drugs from complex biological matrices prior to analysis remains a significant challenge. This study introduces a novel method for the extraction and determination of morphine from biological fluids utilizing a sodium alginate-g-polyacrylamide/agarose hydrogel electromembrane (EME) coupled with square wave voltammetry (SWV) at a glassy carbon electrode. This innovative approach eliminates the need for organic solvents, promoting a greener analytical methodology. The EME process involves the application of a direct current potential across the hydrogel membrane, facilitating the transport of charged morphine molecules from a donor solution (pH 7.0) to an acceptor solution (pH 3.0) under optimized conditions. Following extraction (70 V, 25 min), the acceptor solution is subjected to SWV analysis in a phosphate buffer solution (pH 6.0). This approach successfully extracts morphine, a highly polar compound (log P = 0.43), without requiring ion-pairing or carrier reagents. The method exhibits impressive limits of detection (LOD) and quantification (LOQ) of 0.036 μg/mL and 0.109 μg/mL, respectively. This work demonstrates the potential of the sodium alginate-g-polyacrylamide/agarose hydrogel EME coupled with SWV for the sensitive determination of morphine in urine and wastewater samples.

Evaluation Study of Ammonium Removal from Groundwater by Electrodialysis: Case Study of Real Groundwater from the City of Kenitra in Morocco.

In this work, we investigated the feasibility of ammonium removal by electrodialysis (ED), a well-known electro-membrane process, based on the selective migration of anions and cations through anion exchange membranes (AEMs) and cation exchange membranes (CEMs). ED experiments are performed using a laboratory pilot. The ion exchange membranes (IEMs) pair used is AXE/CMX, AXE as an AEMs and CMX as a CEMs. The first tests are performed with real groundwater solutions from Kenitra city (Morocco), spiked with an initial concentration of 3 mg/L NH4Cl. The results gave a specific demineralization (SD) to NH4 + ions of 84.60 %; for a demineralization rate (DR) of 80 % and a time of 60 min. The multivariate principal component analysis (PCA) presents a total inertia of 99.23 %, the majority of the variables of which are positively correlated on the C1 axis with a variance of 95.5 % than that of C2 of 3.78 %. The quality of the diluted water determined by the Legrand-Poirier method showed that the water was aggressive and that the addition of 4.54 mg/L Ca2+ was necessary to balance the water and make it fit for human consumption.

Elevated caproic acid production from one-stage anaerobic fermentation of organic waste and its selective recovery by electro-membrane process

A constructed microbial consortia-based strategy to enhance caproic acid production from one-stage mixed-fermentation of glucose was developed, which incubated with acidogens (Clostridium sensu stricto 1, 11 dominated) and chain elongators (including Clostridium sensu stricto 12, Sporanaerobacter, and Caproiciproducens) acclimated from anaerobic sludge. Significant product upgrading toward caproic acid (8.31 g‧L−1) and improved substrate degradation was achieved, which can be greatly attributed to the lactic acid platform. Whereas, a small amount of caproic acid was observed in the control incubating with acidogens, with an average concentration of 2.09 g‧L−1. The strategy accelerated the shape and cooperation of the specific microbial community dominated by Clostridium sensu stricto and Caproiciproducens, which thereby contributed to caproic acid production via the fatty acid biosynthesis pathway. Moreover, the tailored electrodialysis with bipolar membrane enabled progressive up-concentration and acidification, allowing selective separation of caproic acid as an immiscible product with a purity of 82.58 % from the mixture.

The development and validation of a novel, parameter-free, modelling strategy for electromembrane processes: Electrodialysis

As the global water crisis worsens and natural resources of strategic inorganic elements dwindle, the need for efficient and effective salt separation methods is becoming ever more important. Electromembrane processes, and in particular electrodialysis, are emerging as efficient and effective separation technologies that use an electric field to drive the transport of ions against a concentration gradient. Modelling electromembrane processes allows for process design and optimisation, as well as the identification of what technological improvements would have the greatest effect. However, the wide use of empirical fitting parameters in most existing models greatly limits their globality. The presence of complex and confounding phenomena within electromembrane processes greatly exacerbates this. In this work, a novel, circuit-based modelling strategy for electromembrane processes is presented, avoiding the use of any fitting parameters. Conventional electrodialysis is adopted as a case study. The implementation of a novel transport number model and membrane resistance model are crucial for model accuracy over a wide range of process conditions. The model was experimentally validated and showed excellent agreement with experimental data across a range of concentrations and voltages. Consequently, this model will prove to be an excellent tool for researchers and process designers.

Modeling non-linear ion transport phenomena in ion-selective membranes: Three simplified models

In electromembrane processes employing the ion concentration polarization phenomenon, such as electrodialysis (ED), ion concentration polarization (ICP) desalination, and reverse electrodialysis, the ion-selective membrane (ISM) has been modeled with an assumption of an ideal ISM permits only the passage of counter-ions with all the co-ions blocked. However, in the works that study the effects of co-ion flux on the response of system, this assumption has been questioned about the adequate answer to the simulation of the characteristic properties of the membrane. In this work, we evaluate the three models which are used widely in modeling ISM including surface-charged, space-charged and nanochannel array model. The results show that the nanochannel array and space-charged models, the alternative model for the model ISM in the case of the studies which consider the effects of co-ion leakage on the performance of the system, sufficiently mimic the key characteristic of the membrane. Their current–voltage response (I-V) curve conforms to a typical one, yet they differ due to the varying co-ion fluxes. The nanochannel array model, which is the direct model of the actual ISM, closely mimics the seed electroconvection vortices near the membrane, which does not appear in the surface-charged and space-charged model. This model is computationally expensive because of resolving the nonlinearity of the variables near the entrance of nanochannels, so it is not the appropriate model to employ in a study that considers the micrometer or millimeter order scale system. Finally, the space-charged model is more appropriate to mimic the ISM but requires more careful consideration of the simplification condition. By investigating the volume charge density of the membrane in the space-charged model, we suggest a value that brings the most similar I-V curve to that of the nanochannel array model.

Kinetic Transport Coefficients Through a Bilayer Ion Exchange Membrane during Electrodiffusion

Analytical expressions for the specific coefficients of electrical conductivity and electrodiffusion through a bilayer ion exchange membrane during the electrodiffusion process are obtained within the framework of thermodynamics of irreversible processes and a homogeneous model of a fine-porous membrane. The influence of physicochemical characteristics of the modifying layer and electrolyte concentration on the values of the obtained coefficients at fixed physicochemical characteristics of the substrate has been investigated by the method of mathematical modelling. It is shown that electrical conductivity and electrodiffusion of the modified membrane at coincidence of signs of volume charges of the membrane layers increase with an increase of density of volume charge of the modifying layer and decrease at their difference or an increase of thickness of the modifying layer. With increasing electrolyte concentration, the abovementioned characteristics of the modified membrane increase regardless of the sign of the charges of the membrane layers. The obtained analytical expressions can be used in modelling electromembrane processes and predicting the parameters of new surface modified ion exchange membranes.

Analyzing the pressure drop in spacer stacks for electrodialytic processes considering the effect of mechanical compression: Experimental vs. free and porous flow model prediction

There is a growing interest in using electromembrane processes in sustainable applications. However, it involves designing efficient cells with low pressure drops, which is particularly important in processes requiring high energy efficiency. In order to analyze the fluid dynamics in spacer-filled channels, manifolds and stacks used primarily in acid base flow batteries a free and porous flow model was developed. The predictive model composed by Navier-Stokes equations and Brinkman Forchheimer extended Darcy model closely follows the experimental pressure drop in a single spacer-filled channel. According to the model results, the entrance and exit zones of the spacer produce the highest pressure drop per axial longitude, highlighting the strong effect of the design of spacer in these zones. In the case of stacks the mechanical compression among spacers as revealed by measurement with compression film suggests some spacer deformation on entrance and exit zones that intensified the inlet and outlet effects.

Lithium recovery from brines by lithium membrane flow capacitive deionization (Li-MFCDI) – A proof of concept

The demand of lithium for electric vehicles and energy storage devices is increasing rapidly, thus new sources of lithium (such as seawater and natural or industrial brines), as well as sustainable methods for its recovery, will need to be explored/developed soon. This work presents a novel electromembrane process, called Lithium Membrane Flow Capacitive Deionization (Li-MFCDI), which was tested to recover lithium from a synthetic geothermal brine containing a much higher mass concentration of sodium than lithium (more than 650 times). Specifically, a ceramic lithium-selective membrane was integrated into a flow capacitive deionization (FCDI) cell, which was specifically designed, and 3D printed, to allow simultaneous charging and regeneration of the employed flow electrodes. Despite the extremely high Na+/Li+ mass ratio in the feed stream, 99.98% of the sodium was rejected and the process selectivity for lithium over other monovalent cations was 141 ± 5.85 for Li+/Na+ and 46 ± 1.46 for Li+/K+. The Li-MFCDI process exhibited a stable behaviour over a 7-day test period, and the estimated energy consumption was 16.70 ± 1.63 kWh/kg of Li+ recovered in the draw solution. These results demonstrate promising potential of the Li-MFCDI for the sustainable lithium recovery from saline streams.

Boron and lithium recovery from aqueous solutions by ion-exchange resin stuffed electro-electrodialysis process with hydrogen production

A considerable amount of lithium is released in the wastes generated during the boron mineral enrichment process. Hence, there is a need to develop systems or processes to recover lithium and boron minerals from the waste of mining industries. In this context, electro-membrane processes have gained importance in literature recently. This study proposes a novel electro-membrane process to recover lithium and boron from an aqueous solution and simultaneous hydrogen production using an electro-electrodialysis stack composed of monovalent-anion and monovalent-cation-exchange membranes filled with ion-exchange resins. The effect of the operating parameters, such as current density, flow rate, pH type of ion-exchange resins, and initial conductivity value of the aqueous solution, on the system efficiencies are investigated. Finally, the proposed electrochemical stack's energy consumption and hydrogen production rates are calculated based on the measurements. The results reflect that maximum conductivity removal efficiency is achieved at 90% by the electro-electrodialysis process with ion-exchange resins. The highest removal efficiency of boron and lithium ions are achieved via electro-electrodialysis with ion-exchange resin as 95.1% and 99.5%, respectively. The hydrogen gas production rate is calculated as 13.55 mmol/h with the same configuration and adding ion-exchange resins to the electro-electrodialysis process improves hydrogen production by 8.6%. Finally, the net energy consumption is calculated as 6.1 kWh/m3 of synthetic wastewater. This study presents a promising method to produce hydrogen and recover valuable minerals of boron and lithium from the aqueous waste solutions.

A cascade electro-dehydration process for simultaneous extraction and enrichment of uranium from simulated seawater

Uranium extraction from seawater has become a crucial issue that has raised tremendous attention. The transport of water molecules along with salt ions through an ion-exchange membrane is a common phenomenon for typical electro-membrane processes such as selective electrodialysis (SED). In this study, a cascade electro-dehydration process was proposed for the simultaneous extraction and enrichment of uranium from simulated seawater by taking advantage of water transport through ion-exchange membranes and the high permselectivity of membranes for monovalent ions against uranate ions. The results indicated that the electro-dehydration effect in SED allowed 1.8 times the concentration of uranium with a loose structure CJMC-5 cation-exchange membrane at a current density of 4 mA/cm2. Thereafter, a cascade electro-dehydration by a combination of SED with conventional electrodialysis (CED) enabled approximately 7.5 times uranium concentration with the extraction yield rate reaching over 80% and simultaneously desalting the majority of salts. Overall, a cascade electro-dehydration is a viable approach, creating a novel route for highly effective uranium extraction and enrichment from seawater.

Selective recovery and re-utilization of lithium: prospects for the use of membrane methods

In recent years, due to the sharp increase in lithium demand, the interest in the problem of lithium recovery/extraction has increased dramatically: according to the Scopus database, about 3000 scientific publications on this issue appeared in 2021. The efforts of many specialists are directed towards the development of new, more economical and environmentally safe membrane technologies for lithium recovery to replace the existing reagent-based methods. This review integrates up-to-date data about the traditional and prospective methods for lithium recovery from natural solutions and leachates resulting from the disposal of spent batteries. The attention is focused on membrane methods. Known approaches are classified and analyzed, experimental and theoretical aspects of membrane-based ion separation are described; separation mechanisms and mathematical models are discussed. The review addresses pressure-driven and electromembrane processes, relatively well-developed at a laboratory level, which are used to extract lithium and other singly charged ions from mixed solutions containing large amounts of magnesium and calcium. The results of application of commercial and laboratory-made membranes are compared. Novel and emerging approaches suitable for effective separation of lithium ions from a mixture of singly charged cations, including hybrid electrobaromembrane methods, are considered.<br> The bibliography includes 295 references

Modeling and Validation of a LiOH Production Process by Bipolar Membrane Electrodialysis from Concentrated LiCl.

Electromembrane processes for LiOH production from lithium brines obtained from solar evaporation ponds in production processes of the Salar de Atacama are considered. In order to analyze high concentrations' effect on ion exchange membranes, the use of concentrated LiCl aqueous solutions in a bipolar membrane electrodialysis process to produce LiOH solutions higher than 3.0% by mass is initially investigated. For this purpose, a mathematical model based on the Nernst-Planck equation is developed and validated, and a parametric study is simulated considering as input variables electrolyte concentrations, applied current density, stack design, process design and membrane characteristics. As a novelty, this mathematical model allows estimating LiOH production in a wide concentration range of LiCl, HCl and LiOH solutions and its effect on the process, providing data on final LiOH solution purity, current efficiency, specific electricity consumption and membrane performance. Among the main results, a concentration of 4.0% to 4.5% by LiOH mass is achieved, with a solution purity higher than 95% by mass and specific electrical energy consumption close to 4.0 kWh/kg. The work performed provides key information on process sensitivity to operating conditions and process design characteristics. These results serve as a guide in the application of this technology to lithium hydroxide production.

Application of Membrane Processes for Nitrate (NO3-) Removal

Background: The primary sources of nitrate contamination in groundwater resources are excessive fertilizer use and unregulated land discharges of treated wastewater. Due to its harmful nature to human health and its contribution to eutrophication, the removal of nitrate from water has been of great interest in the last decades. Various techniques, such as adsorption, ion exchange, catalytic and biological denitrification, and membrane processes, have been applied for NO3 - removal. Objective: In this review study, the removal of NO3 - by membrane processes, including electrodialysis (ED), electrodeionization (EDI), reverse osmosis (RO), and ultrafiltration, has been reviewed. Method: The pressure-driven membrane and electro-membrane processes applications to NO3 - removal have been reviewed. Results: The effects of process parameters, interferences, and limitations of membrane processes have been summarized. Conclusion: Membrane processes could be a promising alternative for NO3 - removal. After suitable membrane preparation/modification, the nitrate removal rate could reach >99%.

Bipolar Membranes Containing Iron-Based Catalysts for Efficient Water-Splitting Electrodialysis.

Water-splitting electrodialysis (WSED) process using bipolar membranes (BPMs) is attracting attention as an eco-friendly and efficient electro-membrane process that can produce acids and bases from salt solutions. BPMs are a key component of the WSED process and should satisfy the requirements of high water-splitting capability, physicochemical stability, low membrane cost, etc. The water-splitting performance of BPMs can be determined by the catalytic materials introduced at the bipolar junction. Therefore, in this study, several kinds of iron metal compounds (i.e., Fe(OH)3, Fe(OH)3@Fe3O4, Fe(OH)2EDTA, and Fe3O4@ZIF-8) were prepared and the catalytic activities for water-splitting reactions in BPMs were systematically analyzed. In addition, the pore-filling method was applied to fabricate low-cost/high-performance BPMs, and the 50 μm-thick BPMs prepared on the basis of PE porous support showed several times superior toughness compared to Fumatech FBM membrane. Through various electrochemical analyses, it was proven that Fe(OH)2EDTA has the highest catalytic activity for water-splitting reactions and the best physical and electrochemical stabilities among the considered metal compounds. This is the result of stable complex formation between Fe and EDTA ligand, increase in hydrophilicity, and catalytic water-splitting reactions by weak acid and base groups included in EDTA as well as iron hydroxide. It was also confirmed that the hydrophilicity of the catalyst materials introduced to the bipolar junction plays a critical role in the water-splitting reactions of BPM.

Investigation of Transport Processes through Ion-Exchange Membranes Used in the Production of Amines from Their Salts Using Bipolar Electrodialysis.

The influence of the nature of amine solutions on the frequency spectrum of the electrochemical impedance of the bipolar membrane aMB-2m is investigated. Moreover, the effect of the circulation rate of solutions in the electrodialyzer chambers on the volt-ampere characteristics of the Ralex AMH and MA-40L anion-exchange membranes and the aMB-2m bipolar membrane has been investigated. The diffusion characteristics of various types of anion-exchange membranes in a system containing dimethylammonium sulfate ((DEA)2H2SO4), as well as the diffusion characteristics of the Ralex AMH membrane in systems with methylammonium sulfate, dimethylammonium sulfate, diethylammonium sulfate, and ethylenediammonium sulfate ((MA)2H2SO4, (DMA)2H2SO4, (DEA)2H2SO4, EDAH2SO4) have been studied. It is shown that diffusion permeability depends on the structure and composition of anion-exchange membranes, as well as on the nature of amines. The technical and economic characteristics of the electromembrane processes for the production of amines and sulfuric acid from amine salts are determined. It is shown that when using Ralex AMH anion-exchange membranes in an electrodialyzer together with bipolar aMB-2m membranes, higher concentrations of diethylamine and sulfuric acid are achieved, compared with the use of MA-40L anion-exchange membranes.