Types Of Ion Exchange Membranes Research Articles

Synergistic effects of various membrane and cathode electrode types in dual chamber microbial fuel cells for wastewater treatment: Investigation of the start-up phase, modeling using artificial neural networks, and cost analysis

Although various membrane and cathode electrode types have been investigated in dual chamber microbial fuel cells (DCMDCs), there is no agreement on which combination of electrodes and separator materials works best. The main objective of this study is to investigate the synergistic effects of cathode electrodes and membranes on the performance of DCMFCs during the start-up phase, to model the DCMFCs through artificial neural networks (ANN), and to determine the most cost-effective choice. Principal component analysis was used to analyze the interrelationships among various factors that influence DCMFCs. Two types of ion exchange membranes (cation exchange membrane and anion exchange membrane) and two types of cathode electrodes (carbon cloth covered with 20% Pt as catalyst and plain carbon cloth) were studied. Electrodes and membranes were analyzed using AFM, TEM, SEM, XRF, and FTIR to investigate changes in morphology and the potential of fouling. The results showed that DCMFC with cation exchange membrane (CEM) and plain carbon cloth (CC) generated the maximum power among the investigated configurations. The average voltage values and COD removal efficiency reached 748 ± 13 mV and 57.8 ± 2.5%, respectively. The maximum power density achieved was obtained when the external resistance was set at 1000 Ω and was 180 mA/m2. ANN was successful in predicting the output voltage for the examined DCMFCs. The use of DCMFC with CC and CEM can be considered optimal in terms of performance and cost.

A hybrid electrochemical system for spontaneous green‑hydrogen production with simultaneous desalination using catechol oxidation

Green hydrogen, commonly produced through water electrolysis, has attracted considerable attention owing to its energy-efficient and eco-friendly properties. However, since conventional water electrolysis system has fatal drawbacks owing to the high process cost and energy requirements, various approaches are being adopted to increase its energy efficiency. In this study, a novel hybrid system for green hydrogen production was designed by replacing the oxygen evolution reaction (OER) with electrochemical oxidation of catechol (CAT). CAT is an environmental pollutant generated by diverse industries and needs to be further treated because of its toxicity to humans and nature. Accordingly, to facilitate the degradation of CAT and increase the energy efficiency, the pH values of the anolyte (containing CAT) and catholyte were adjusted to alkali and acid, respectively. Two types of ion-exchange membranes (IEMs; anion-/cation-exchange membranes) were coupled to divide the hybrid cell into three compartments, and a buffer solution (NaCl solution) was injected between the IEMs. As a result, the hybrid system output 3.75 mW/cm2 of electricity, spontaneously produced hydrogen with 4.2 mL/h of hydrogen production rate and removed ions from the buffer solution with 0.46 mg/cm2∙min of high desalination rate.

Paired Electrosynthesis 2,5-Furandicarboxylic Acid (FDCA) and 2-Butanone in a Flow-Cell

Biobased platform chemicals and energy carriers can replace conventional, fossil-based chemicals and fuels to decrease the footprint of the chemical industry in the future. Promising chemicals for this purpose are 2,5-furandicarboxylic acid (FDCA), a monomer for biobased polymers, and 2-butanone, a solvent and energy carrier. Both molecules can be synthesized in electrochemical processes: FDCA is a product of the oxidation of Hydroxymethylfurfural (HMF) and 2-butanone is a product of the reduction of acetoin. In an electrochemical reactor, the oxidation and the reduction reaction can be coupled, so that the anode and the cathode yield a value-added product. The increased efficiency is accompanied by an increased complexity. A crucial aspect is the migration of ions between anolyte and catholyte, which impacts the pH in both electrolyte compartments thereby influences the reactions. The direction of this migration is determined by the type of ion exchange membrane, the effect of which is much less pronounced when analyzing a single reaction.This work develops a coupled process for these reactions. The individual reactions have been demonstrated prior [1,2]. The oxidation takes place on an Ni-foam electrode with a Ni(OH)2/NiOOH catalyst in 0.1 mol/L KOH in a zero-gap assembly. The reduction is carried out on a lead plate electrode in a potassium phosphate buffer at pH 9 with an electrolyte gap of 3 mm. We analyze the impact of the three different ion exchange membranes on the migration of ions and the pH in the electrolyte compartments, using anion exchange membranes (AEM), cation exchange membranes (CEM), and bipolar membranes (BPM) in a flow-cell reactor (flex-E-cell). The electrode area was 25cm². No stable operation was possible with a CEM due to the acidic pH at the interface of the CEM and the anode, which deteriorated the nickel-based catalyst. With an AEM, a stable process was made possible through pH control in the electrolytes to counteract ion migration across the membrane. With a BPM, we showed the most stable process with little to no ion permeation. However, the cell-voltage was highest for the BPM.At an increased current density to 120 mA/cm2 and a reactant concentration to 0.45 mol/L of HMF and 0.9 mol/L acetoin, respectively, we were able to maintain a high yield, for FDCA on the anode side above 90 % and for 2-butanone above 60 % on the cathode side with a BPM. The combined faraday efficiency (FE) was above 150 %. The increased product concentration of FDCA required the stabilization of the alkaline pH through the redosing of base. With an AEM however, no stable process was possible at the elevated current densities due to the extensive crossover of anions, which resulted in drastically changing pH and conductivity. To increase the economic prospect of the process, we employed a background electrolyte on the cathode side (0.5 M Na2SO4) to decrease the cell voltage by 15 % and employed NaOH instead of KOH on the anode side without significantly affecting the reaction metrices. The elevated current densities in combination with the economically interesting electrolyte system moves the process towards economic competitiveness, which we will assess in the future. With this work, we hope to establish a paired electrolysis process for the efficient and economic electrochemical valorization of biomass.

Why Membranes Matter: Ion Exchange Membranes in Holistic Process Optimization of Electrochemical CO2 Reduction

AbstractReducing carbon dioxide to value‐added chemicals by electrolysis is a promising strategy to substitute fossil‐based processes. Research on CO2 electrolysis has vastly progressed, focusing on catalysis and electrode design, leaving an essential question on the central part of the electrolyzer: Which type of ion exchange membrane is best suited for CO2 electrolysis from an economic perspective? To address this question, holistic process optimization of CO2 reduction and product purification is applied. The findings demonstrate that CO2 electrolysis with an anion exchange membrane shows competitive production costs for CO of 796 €/tCO, outperforming cation exchange and bipolar membranes. Unlike often described, the CO2 pumping effect does not significantly impair the economics but offers an efficient indirect regeneration of dissociated CO2. Furthermore, the results emphasize selective reduction of CO2 rather than co‐electrolysis of CO2 and H2O. While pointing to a positive economic perspective, life‐cycle assessment highlights the need to minimize CO2 emissions related to electricity consumption and incomplete CO2 utilization.

Comparative Study of Different Ion-Exchange Membrane Types in Diffusion Dialysis for the Separation of Sulfuric Acid and Nickel Sulfate

The possibility of using various types of ion-exchange membranes in diffusion dialysis for the separation of sulfuric acid and nickel sulfate has been evaluated. The process of the dialysis separation of a real waste solution from an electroplating facility containing 252.3 g/L of sulfuric acid, 20.9 g/L of nickel ions and small amounts of zinc, iron, copper ions, etc. has been studied. Heterogeneous cation-exchange membrane containing sulfonic groups and heterogeneous anion-exchange membranes with different thicknesses (from 145 μm to 550 μm) and types of fixed groups (four samples with quaternary ammonium base and one sample with secondary and tertiary amines) have been used. The diffusion fluxes of sulfuric acid, nickel sulfate, and the total and osmotic fluxes of the solvent have been determined. The use of a cation-exchange membrane does not allow the separation of the components, since the fluxes of both components are low and comparable in magnitude. The use of anion-exchange membranes makes it possible to efficiently separate sulfuric acid and nickel sulfate. Anion-exchange membranes with quaternary ammonium groups are more effective in the diffusion dialysis process, while the thin membrane turns out to be the most effective.

Fouling and Mitigation Behavior of Foulants on Ion Exchange Membranes with Surface Property in Reverse Electrodialysis.

In this study, two different types of ion exchange membranes are used to investigate the tendency of membrane fouling with respect to surface roughness and hydrophilicity. Commercially available membranes reinforced by electrospun nanofiber have rough and hydrophilic surfaces, and lab-made pore-filling membranes exhibit a smooth and hydrophobic surface. Three different organic surfactants (i.e., cationic, anionic and non-ionic surfactants) are chosen as foulants with similar molecular weights. It is confirmed that membrane fouling by electrical attraction mainly occurs, in which anionic and cationic foulants influence anion and cation exchange membranes, respectively. Thus, less fouling is obtained on both membranes for the non-charged foulant. The membranes with a rough surface show a higher fouling tendency than those with a smooth surface in the short-term continuous fouling tests. However, during the cyclic operations of fouling and mitigation of the commercially available membranes, the irregularities of a rough membrane surface cause a rapid increase in electrical resistance from the beginning of fouling due to excessive adsorption on the surface, but the fouling is easily mitigated due to the hydrophilic surface. On the other hand, the membranes with a smooth surface show alleviated fouling from the beginning of fouling, but the irreversible fouling occurs as foulants accumulate on the hydrophobic surface which causes membrane fouling to be favorable.

Behavior of solutes and membrane fouling in an electrodialysis to treat a side-stream: Migration of ions, dissolved organics and micropollutants

The electrodialysis (ED) is widely applied as a reliable low-energy process in which ions are transferred through selective ion-exchange membranes. The purpose of this study is to confirm the efficiency of the ED system for removing nutrient ions contained in the side-stream of actual wastewater and to identify the propensity of ion exchange membrane fouling by dissolved organic matter and micropollutants contained in the side-stream. As a result of the constant-voltage of 7 batch operation for the side-stream, 92.1 % of ammonium and 52.4 % of phosphate were removed, and it was confirmed that the ED system was particularly effective in removing ammonium. The propensity of the membrane fouling by organic solutes was compared by measuring elemental analysis and FTIR spectra of three types of ion-exchange membranes: original, fouled, and cleaned. It was confirmed that low-molecular-weight organic matter was an important cause of organic fouling, and SEM-EDS analysis showed that acid-base cleaning is effective in removing organic foulants. Among the remaining micropollutants, diclofenac, gemfibrozil, ibuprofen, ketoprofen, and naproxen can be removed by the ED system according to their ionic characteristics, but some of the diclofenac and gemfibrozil are presumed to be adsorbed on the membrane due to their hydrophobicity.

Development of Pore-Filling Anion Exchange Membranes for Anion Exchange Membrane Water Electrolysis: Enhancement of Alkaline Stability

Water electrolysis is a process that uses electricity to decompose water into oxygen and hydrogen. There are several types of ion exchange membrane can be used, anion exchange membrane, proton exchange membrane and bipolar membrane for water electrolysis. Alkaline based water electrolysis has several advantages to use non-precious electrocatalysts. However, the development of low resistance and durable anion-exchange membranes is of importance. In this study, several anion-exchange membranes were developed to enhance alkaline stability. Pore-filling anion exchange composite membranes with different contents of cross-linkers were prepared by mixing an electrolyte having good anion conducting ability. The mixture of monomers into a porous polyethylene (PE) substrate were polymerized by UV curing. The pore-filling reinforced composite membranes have been investigated in terms of good chemical stability properties, in particular, the variation of conductivity and mechanical strength in 1 M KOH at 60 oC. Characterization in terms of ion exchange capacity, water uptake, swelling ratio, and mechanical strength were also investigated. Acknowledgments This research was supported in part by "Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ016253)" Rural Development Administration, Republic of Korea, by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2022 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

Development of Pore-Filling Anion Exchange Membranes for Anion Exchange Membrane Water Electrolysis: Enhancement of Resistance

Water electrolysis is a process that uses electricity to decompose water into oxygen and hydrogen. There are several types of ion exchange membrane can be used, anion exchange membrane, proton exchange membrane and bipolar membrane for water electrolysis. Alkaline based water electrolysis has several advantages to use non-precious electrocatalysts. However, the development of low resistance and durable anion-exchange membranes is of importance. In this study, several anion-exchange membranes were developed to enhance areal resistance, in other words, to minimize areal resistance. Pore-filling anion exchange composite membranes with different contents of cross-linkers were prepared by mixing an electrolyte having good anion conducting ability. The mixture of monomers into a porous polyethylene (PE) substrate were polymerized by UV curing. The pore-filling reinforced composite membranes have been investigated in terms of good electrochemical properties, in particular, areal resistance. The conductivity and areal specific resistance were measured in both in-plane cell and through-plane cell at 80 ℃ and at room temperature, respectively. Characterization in terms of ion exchange capacity, water uptake, swelling ratio, and mechanical strength were also investigated. Acknowledgments This research was supported in part by "Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ016253)" Rural Development Administration, Republic of Korea, by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2022 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

Investigation on various types of ion-exchange membranes in vanadium redox flow batteries: Experiment and modeling

Choosing the appropriate ion exchange membrane in vanadium redox flow batteries plays an important role in achieving optimal system performance. In this article, the implementation of commercial cation exchange membranes (Nafion 115, Nafion 117, and Nafion 212), anion exchange membranes (FAP 450 and QA-PFE), and the combination of them are investigated. In this regard, the effects of membrane type, thickness, electrical conductivity, and the transfer of vanadium species at different current densities are examined carefully. In addition, the influences of the flow rate and the concentration of electrolytes are investigated using a comprehensive developed model. The model predictions are validated against the experimental data of a charge and discharge cycle of cation and anion exchange membranes with a mean relative error of 2.06 %. It is found that FAP 450, despite the relatively low thickness, provides the highest capacity retention (91.19 %) after twenty working cycles. This can be attributed to the anion exchange nature and having the lowest diffusion coefficients of vanadium species. In addition, Nafion 212 provides the highest power density (256 mW cm−2) among the examined membranes. It can be attributed to the inverse relation between system power density and membrane ohmic resistance. Moreover, charging and discharging time, efficiency, maximum power density, and capacity fade of the system are functions of net transfer rate of vanadium species, thickness, and electrical conductivity of the membrane combination. Furthermore, the maximum and minimum values of the peak power densities of the system are 244 and 210 mW cm−2, which are obtained for the combination of Nafion 212-Nafion 212 and Nafion 117-Nafion 117, respectively. Finally, the maximum and minimum values of the capacity retention of the system after twenty working cycles are 93.39 % and 75.25 % for combinations of FAP 450-FAP 450 and Nafion 212-Nafion 212, respectively.

Correlations between Properties of Pore-Filling Ion Exchange Membranes and Performance of a Reverse Electrodialysis Stack for High Power Density.

The reverse electrodialysis (RED) stack-harnessing salinity gradient power mainly consists of ion exchange membranes (IEMs). Among the various types of IEMs used in RED stacks, pore-filling ion exchange membranes (PIEMs) have been considered promising IEMs to improve the power density of RED stacks. The compositions of PIEMs affect the electrical resistance and permselectivity of PIEMs; however, their effect on the performance of large RED stacks have not yet been considered. In this study, PIEMs of various compositions with respect to the RED stack were adopted to evaluate the performance of the RED stack according to stack size (electrode area: 5 × 5 cm2 vs. 15 × 15 cm2). By increasing the stack size, the gross power per membrane area decreased despite the increase in gross power on a single RED stack. The electrical resistance of the PIEMs was the most important factor for enhancing the power production of the RED stack. Moreover, power production was less sensitive to permselectivities over 90%. By increasing the RED stack size, the contributions of non-ohmic resistances were significantly increased. Thus, we determined that reducing the salinity gradients across PIEMs by ion transport increased the non-ohmic resistance of large RED stacks. These results will aid in designing pilot-scale RED stacks.

Converting softening nanofiltration brine into high-solubility liquid salts (HSLS) via electrodialysis metathesis: Effect of membrane type

A fundamental aspect of developing electrodialysis-metathesis (EDM) process involves the selection of an appropriate membrane for converting softening nanofiltration (SNF) brine into high-solubility liquid salts (HSLS). Three types of ion-exchange membranes (heterogeneous, Ss; semi-homogeneous, Lh; and homogeneous, Yl, Tb, Aj) were investigated herein by assessing the overall performances (running resistance, salt removal ratio, energy consumption, etc.) and the transport of ions and water during the EDM process. The results showed that increasing the fixed ion density promoted counter-ions migration, while decreasing the permselectivity or increasing the water uptake or ion-exchange capacity enhanced the co-ion flux. The membrane thickness constitutes an efficient barrier for water osmosis, which could lead to more concentrated HSLS. As a result, the investigated membranes could be ranked using the flux of counter-ions and water as indices: Aj > Tb > Yl ≈ Lh > Ss. The Lh membrane exhibited similar energy consumption characteristics to the Yl and Tb membranes. Regardless of the membrane type, the Cl-type HSLS obtained had higher purity, while the Na-type HSLS had higher concentration. Overall, the membranes with higher fixed ion density and permselectivity, and lower resistance and water uptake, were best suited for the zero liquid discharge desalination of typical high-hardness brine using the described EDM process. Finally, considering the performance and cost of the semi-homogeneous Lh membrane, this membrane type is recommended for application in EDM to convert SNF brine into HSLS.

Evaluation of Electrodialysis Desalination Performance of Novel Bioinspired and Conventional Ion Exchange Membranes with Sodium Chloride Feed Solutions.

Electrodialysis (ED) desalination performance of different conventional and laboratory-scale ion exchange membranes (IEMs) has been evaluated by many researchers, but most of these studies used their own sets of experimental parameters such as feed solution compositions and concentrations, superficial velocities of the process streams (diluate, concentrate, and electrode rinse), applied electrical voltages, and types of IEMs. Thus, direct comparison of ED desalination performance of different IEMs is virtually impossible. While the use of different conventional IEMs in ED has been reported, the use of bioinspired ion exchange membrane has not been reported yet. The goal of this study was to evaluate the ED desalination performance differences between novel laboratory‑scale bioinspired IEM and conventional IEMs by determining (i) limiting current density, (ii) current density, (iii) current efficiency, (iv) salinity reduction in diluate stream, (v) normalized specific energy consumption, and (vi) water flux by osmosis as a function of (a) initial concentration of NaCl feed solution (diluate and concentrate streams), (b) superficial velocity of feed solution, and (c) applied stack voltage per cell-pair of membranes. A laboratory‑scale single stage batch-recycle electrodialysis experimental apparatus was assembled with five cell‑pairs of IEMs with an active cross-sectional area of 7.84 cm2. In this study, seven combinations of IEMs (commercial and laboratory-made) were compared: (i) Neosepta AMX/CMX, (ii) PCA PCSA/PCSK, (iii) Fujifilm Type 1 AEM/CEM, (iv) SUEZ AR204SZRA/CR67HMR, (v) Ralex AMH-PES/CMH-PES, (vi) Neosepta AMX/Bare Polycarbonate membrane (Polycarb), and (vii) Neosepta AMX/Sandia novel bioinspired cation exchange membrane (SandiaCEM). ED desalination performance with the Sandia novel bioinspired cation exchange membrane (SandiaCEM) was found to be competitive with commercial Neosepta CMX cation exchange membrane.

Ion Transport Characteristics in Membranes for Direct Formate Fuel Cells.

Ion exchange membranes are widely used in fuel cells to physically separate two electrodes and functionally conduct charge-carrier ions, such as anion exchange membranes and cation exchange membranes. The physiochemical characteristics of ion exchange membranes can affect the ion transport processes through the membrane and thus the fuel cell performance. This work aims to understand the ion transport characteristics through different types of ion exchange membrane in direct formate fuel cells. A one-dimensional model is developed and applied to predict the polarization curves, concentration distributions of reactants/products, distributions of three potentials (electric potential, electrolyte potential, and electrode potential) and the local current density in direct formate fuel cells. The effects of the membrane type and membrane thickness on the ion transport process and thus fuel cell performance are numerically investigated. In addition, particular attention is paid to the effect of the anion-cation conducting ratio of the membrane, i.e., the ratio of the anionic current to the cationic current through the membrane, on the fuel cell performance. The modeling results show that, when using an anion exchange membrane, both formate and hydroxide concentrations in the anode catalyst layer are higher than those achieved by using a cation exchange membrane. Although a thicker membrane better alleviates the fuel crossover phenomenon, increasing the membrane thickness will increase the ohmic loss, due to the enlarged ion-transport distance through the membrane. It is further found that increasing the anion-cation conducting ratio will upgrade the fuel cell performance via three mechanisms: (i) providing a higher ionic conductivity and thus reducing the ohmic loss; (ii) enabling more OH− ions to transport from the cathode to the anode and thus increasing the OH− concentration in the anode catalyst layer; and (iii) accumulating more cations in the anode and thus enhancing the formate-ion migration to the anode catalyst layer for the anodic reaction.

Effect of ion exchange capacity and water uptake on hydroxide transport in PSU-TMA membranes: A DFT and molecular dynamics study

Anion Exchange Membranes (AEMs) are nowadays used in a very wide range of different applications, from electrodialytic systems for water treatment, to Fuel Cells for energy generation. In many of these cases, the AEM is in contact with water molecules, either in aqueous or gas phase, which can strongly interact with the AEM polymer, thus affecting membrane properties. The role of water in fully swollen AEM and its effect on the diffusion of hydroxide is the focus of this work. Density Functional Theory (DFT) based calculations were merged with Molecular Dynamics (MD) simulations coming to a more accurate description of the ionic exchange capacity effect on the hydroxide ion diffusion in AEM. Hydration of the polysulfone-tetramethylammonium (PSU-TMA), one of the most studied systems in Alkaline anion exchange Membrane Fuel Cells (AMFC), was determined by DFT developing an efficient algorithm. The ab-initio calculations predicted water uptake, at different Ion Exchange Capacity (IEC), resulted in good agreement with the experimental data. The theory-experiment comparison identified a threshold range of 1.2–1.7 meq/g as critical IEC at which over-swelling of functionalized polymer matrix occurs. From this comparison, three IEC values were chosen to perform MD simulations in order to evaluate the hydroxyl diffusion coefficients as a function of the different IEC where the ab-initio water uptake and partial charges, utilized in the force-field, were adopted. Diffusion coefficients in the bulk of the membrane were calculated through the Mean Square Displacement (MSD) over 100 ns MD trajectories, and then compared with the values obtained by the analytical Mackie-Meares's model, finding good agreement between the two computational methodologies. In addition, the computed diffusion coefficients were compared with the experimental conductivity data with a fair agreement. It is worth noting that, thanks to the minimization of adjustable parameters, the present work can be easily adapted to study any type of Ion Exchange Membrane (IEM) and counter-ions diffusion.

Electricity Production from Marine Water by Sulfide-Driven Fuel Cell

While there is a universal trend to replace fossil fuels at least partially, renewable fuels seem to impose new solutions. Hydrogen sulfide, typical for closed water ponds such as the Black Sea, seems to offer one namely, a new sulfide-driven fuel cell providing for exchange of OH− anions across the membrane by use of hydrogen sulfide in natural marine water. When tested in batch and continuous operation modes, this solution showed that the initial sulfide concentration needed to achieve results of practical value was within 200 to 300 mg dm−3. The predominating final products of the energy production process were sulfite and sulfate ions. Very low overpotentials and mass transfer resistances were observed. The mass balance and the electrochemical parameters showed about 30% efficiency in sulfate ions as the final product. Efforts should be made to enhance sulfide to sulfate conversion. The observed current and power density were comparable and even better than some of the results so far reported for similar systems. Three types of ion exchange membranes were tested. Comparison of their ion conductivity to literature data shows good performance. At higher initial sulfide concentrations polysulfides and thio-compounds were formed with considerably low current yield.

Effect of operational conditions on post-treatment of RO permeate of geothermal water by using electrodeionization (EDI) method

With the growing of electronics, semiconductors, food and pharmaceutical manufactures, the need of water quantity with high purity is increasing. The water quality needed should be with high electrical resistance and free of weakly ionized dissolved species. Integration of separation processes such as reverse osmosis (RO) and electrodeionization (EDI) was proven to be successful to produce water with high quality. This paper is about the applicability of EDI method for post-treatment of RO permeate of geothermal water. For this purpose, the effects of process parameters such as feed flow rate, electrical potential applied, type of ion exchange membranes, and cell number on reduction of electrical conductivity and the contents of boron, silicon and arsenic in EDI product water were investigated. In addition, pseudo first order and pseudo second order kinetics models, infinitive solution volume (ISV) and unreacted core (UCM) models were applied to determine the rate controlling steps of the removal of electrical conductivity and boron by EDI process. Obtained results revealed that a EDI product water containing ˂0.20mg B/L, ˂0.05mg Si/L and ˂0.10μg As/L was produced using a multi-cell EDI in which ion exchange resins in mixed bed configuration is placed between Neosepta CMX-AMX ion exchange membrane pair. These results were obtained when the optimum flow rate of 1.08L/h and electrical potential of 20V were applied to multi-cell EDI. At the optimal operational conditions, boron removal was found to be governed by second order kinetic model and the determining steps were film diffusion and liquid film according to ISV and UCM models, respectively. It was observed that thick ion exchange membranes were better than thin ion exchange membranes for polishing RO permeate of geothermal water by using EDI process.

Dependency of migration and reduction of mixed Cr2O72−, Cu2+ and Cd2+ on electric field, ion exchange membrane and metal concentration in microbial fuel cells

Abstract Metallurgical microbial fuel cells (MFCs) are holding great promise for metal waste and wastewater treatment with simultaneous metal recovery and separation, where ion exchange membranes (IEMs) are used as separators between the CH 3 COO − and PO 4 3− filled anodes, and metal ions filled cathodes. How these ions migrate across the IEMs with simultaneous metal reduction on the cathodes, however, is not yet fully understood. Therefore, two proton exchange (N117 and N212), a cation exchange (CEM) and an anion exchange (AEM) membranes were studied to evaluate the suitability of IEMs as separators of MFCs for reduction of mixed Cr 2 O 7 2− , Cu 2+ and Cd 2+ at each metals of either 10 mM or 1.0 mM, as a model for a wide variety of metals in practical electroplating and mining industries. It was found that circuit current directed reduction of more metals on the cathodes with less migration across the IEMs, compared to the more metal transport in the absence of circuit current. CEM was the most beneficial for less cross-over of Cr 2 O 7 2− from one side, and CH 3 COO − and PO 4 3− from the other side, despite slight more migration of Cu 2+ and Cd 2+ than that of AEM. A higher metal concentration with each of 10 mM led to more metal transport through the IEMs than that of 1.0 mM. This study demonstrates the dependency of migration and reduction of Cr 2 O 7 2− , Cu 2+ and Cd 2+ on electric field, type of IEM and metal concentration, and thus provides a new insight into metallurgical MFCs for remediating Cr 2 O 7 2− , Cu 2+ and Cd 2+ co-contamination with simultaneous metal recovery.

Reinforcing fabrics as the mechanical support of ion exchange membranes

Mechanical, physical and electrochemical characteristics are one of the important properties of ion exchange membranes. These parameters are required for a next operation and for an application in an electrodialysis (as tightness of a stack, energy consumption, capacity of electrodialysis). The goal of this article is comparison of the influence of the different reinforcing fabric on the properties of ion exchange membranes. Six types of ion exchange membranes with the nonwoven fabric, the monofilament knit, the multifilament knit, the monofilament woven fabric, the multifilament woven fabric, and for comparison non-reinforcing ion exchange membranes were chosen. The most important properties of a fabric in this application are thickness, free area related to the warp and the weft, mechanical strength, the material (shrinkage), type of fabric (plain or twill weave, a knit, monofilament, multifilament) and of course price. Electrochemical, physical and mechanical properties of ion exchange membranes were studied. Non-reinforcing ion exchange membranes have lower mechanical strength, but the best elongation. These ion exchange membranes report big relative dimension changes after swelling in demineralized water and the lowest value of the areal resistance. The most appropriate ion exchange membrane is with woven fabric from monofilaments after comparison with other ion exchange membranes in terms of the quality of the lamination and other electrochemical, physical and mechanical parameters.

Comparative Efficacy Study of Different Types of Ion Exchange Membranes for Production of Ultrapure Water via Electrodeionization

High purity ultrapure water is required in the electronics and pharmaceutical industries. Herein, we report production of high purity ultrapure water (18.5 L/h) by electrodeionization (EDI) technique in a laboratory scale EDI unit (effective membrane area 24 cm × 6 cm) using polyethylene interpolymer based ion-exchange membranes. The ultrapure water also prepared by EDI process in the same EDI unit using two different types of commercial membranes (Ionsep and Fujifilm type II). The resistance of ultrapure water was 18.2 MΩ cm with the interpolymer based membranes at 25 V/cell pair applied potential, whereas with commercial Ionsep and Fujifilm type II membranes the final resistance of ultrapure water was 15 MΩ cm and 17.1 MΩ cm respectively at 30 V/cell pair applied potential. The power consumption (W) and current efficiency (CE) values were 0.324 KWhkg–1 and 58.86% respectively for interpolymer based ion-exchange membranes, whereas for Ionsep and Fujifilm type II membranes, W and CE values were 0.658 and ...