Properties Of Cation-exchange Membranes Research Articles

Improvement the physicochemical properties of cation exchange membranes by incorporation SiO2-co-Ag nanoparticles

Improvement the physicochemical properties of cation exchange membranes by incorporation SiO2-co-Ag nanoparticles

Diffusion and Osmotic Permeability of Ion Exchange Membrane MK-40 Using Sodium Chloride Solution

Cation exchange membrane (MK-40) is a commercial membrane with a fixed group that is an important part of the electrodialysis (ED) process. Sodium chloride (NaCl) diffusion and osmotic permeability for MK-40 was studied. A cell containing two compartments was used to analyse the properties of the MK-40 membrane fixed between them. Furthermore, the influence of temperature, NaCl concentration, and operating time on MK-40 properties was investigated. The results showed that the highest diffusion permeability coefficient of NaCl was 7.37×10-9 (m2/s), and the maximum osmotic permeability coefficient of distilled water was 43.8×10-9 (m2/s) at NaCl solution concentration of 0.1 M and 50oC. Generally, the permeability was constant beyond 60 min of operational time. Additionally, the minimum diffusion permeability coefficients of the MK-40 membrane fell by about 22% over time when the concentration of NaCl solution was 1 M at 25oC. To conclude, membrane properties in the ED process depend on the two electrodes (a cathode and an anode), without the diffusion of salts particles. Meanwhile, the most important properties of cation exchange membranes (CEMs) used in electrodialysis are increased membrane efficiency when water and salts transport decrease through CEMs, which leads to a decrease in energy consumption. Thus, the MK-40 membrane showed a good properties due to its low diffusion permeability for concentrated NaCl solution at elevated temperatures and minimum reduction in diffusion permeability of concentrated NaCl solution over time.

The effect of crosslinking polymer layer on the electrochemical properties of cation-exchange membrane

ABSTRACT The paper deals with the surface modification of a heterogeneous cation-exchange membrane with the application for electrodialysis, electrodeionisation, and electrolysis. CM(H)-PP (cation exchange membrane based on polyethylene binder) membrane was covalently attached with poly(divinylbenzene-co-4-vinylbenzylchloride). We have achieved better properties than commercially available heterogeneous ion-exchange membranes in the field of chemical, electrochemical properties by the formation of layer. Ion-exchange capacity was determined with maximum value 2.99 meq g−1 dry matter, area resistance 9.9 Ω cm2 and specific resistance 149 Ω cm, permselectivity 93.4%.

Development of Water Vapor Transport Resistance Protocol and Analysis

W. L. Gore and Associates, Inc. (Gore) supports the lowest $/kW fuel-cell systems through development of thin, reinforced membranes, ca. 10 µm or less. Thin membranes decrease cost by reducing material content and facilitate higher performance through increased proton conductance and faster water transport. However, it has been postulated that an interfacial water transport resistance, significantly different than the bulk resistance, will dominate for thin membranes. For example, in a previous study, the interfacial effect accounted for half of the total transport resistance for a 10 µm membrane at 30% RH1. Understanding water transport through the membrane is necessary for system-level models to design optimal operation strategies. Gore implemented a protocol and analysis method for characterizing water transport properties of cation exchange membranes. Water flux is driven across the membrane by a chemical-potential gradient at different water activity levels. The water balance is tracked by monitoring the dew point at cell inlet and outlet and closes within 10%. Fick’s law is used to normalize flux data by the activity gradient across cell and inverted to calculate a total transport resistance. Cell hardware with 5 cm2 active area and straight-channel flow field configuration was used. Further details will be discussed in this presentation. Using this method, the bulk permeability of extrusion cast Nafion 11x films is 0.16 µmol/cm/s at 30% relative humidity (RH) and 95 °C, which is in agreement with literature at similar conditions1. An Evaluating the Measurement Process (EMP) study was used to quantify the amount of variation arising from measurement device and operator. With a sample size of 4, the protocol is able to detect a difference in total water transport resistance greater than 0.3 m2-s/mol. The protocol was used to study a series of 700 EW cast film thicknesses from 7 – 70 µm to separate individual contributions to the total water transport resistance, RTotal = RGas + RBulk + RInterfacial. The gas-phase transport resistance, RGas, was separated using hydrogen and nitrogen carrier gasses. The bulk water transport resistance, RBulk, is equal to thickness divided by bulk permeability. Figure 1a shows bulk permeability increases with higher water content, as expected due to the percolating network of water conducting channels2. Typically, any residual resistance is attributed to an interfacial effect, which has been rationalized by the orientation of the hydrophobic backbone toward surface2. In this study, the interfacial resistance is indistinguishable from zero. The equivalent thickness of membrane interface is shown in Figure 1b as a function of RH. ACKNOWLEDGMENTS The authors gratefully acknowledge the contribution of the Electrochemical Products team of W. L. Gore and Associates, Inc. REFERENCES Kienitz, B., Yamada, H., Nonoyama, N. & Weber, A. Z. Interfacial Water Transport Effects in Proton-Exchange Membranes. J. Fuel Cell Sci. Technol. 8, 011013-1-011013-7 (2011).Kusoglu, A. & Weber, A. Z. New Insights into Perfluorinated Sulfonic-Acid Ionomers. Chem. Rev. 117, 987–1104 (2017). Figure 1

Ion and water transport properties of cation exchange membranes prepared by heavy-ion-track grafting technique

ABSTRACT For high-performance electrodialysis of saline water, cation exchange membranes (CEMs) that actively transport Na+ and restrict water permeation are required. In this study, we prepared novel CEMs by a heavy-ion-track grafting technique and measured their membrane resistance and water permeation flux as transport properties. The prepared nanostructured CEMs exhibited lower resistance and lower water flux than the commercial CEM. Na+ ions were efficiently transported through their unique one-dimensional ion channels (low resistance), while water transport was suppressed due to the very low water uptake of the CEMs. These results demonstrated the high potential of these nanostructured CEMs for use in practical saline water electrodialysis.

Improving electrochemical properties of cation exchange membranes by using activated carbon-co-chitosan composite nanoparticles in water deionization

In this study, the influence of various weight ratios of activated carbon (AC)-co-chitosan (CS) composite nanoparticles in the matrix of ion exchange membranes was examined to adapt their electrochemical characteristics based on the combination of high surface area and adsorptive property of activated carbon nanoparticles and the hydrophilicity and functionality of chitosan. Scanning electron microscopy (SEM), scanning optical microscopy (SOM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), water content, ion exchange capacity (IEC), water contact angle, membrane potential, transport number and permselectivity, sodium flux, and membrane electrical resistance were used in membrane characterization. The fabricated membranes were also utilized in copper removal from water. The SEM and SOM images exhibited a uniform distribution of nanoparticles (NPs) on the surface of membranes. The membrane surface hydrophilicity was decreased; surface roughness and water content increased by utilizing AC-co-CS composite NPs. Membrane IEC was initially enhanced by utilizing composite NPs up to 0.5% wt and then decreased by more increase in additive ratios from 0.5 to 2%. Increasing trend was observed again at higher NPs concentration. Similar trend was also found for sodium flux. Membrane potential, t-number, permselectivity, and membrane electrical resistance initially represented an enhancing trend by use of AC-co-CS composite NPs up to 0.5% wt in membrane body and then decreased by more increase of NPs concentration from 0.5 to 8% wt. The fabricated membranes containing AC-co-CS nanoparticles showed good capacity in Cu removal from water. Membrane mechanical strength was improved initially by utilizing AC-co-CS composite NPs and then decreased at high additive concentration.

Structural properties of cation exchange membranes: Characterization, electrolyte effect and solute transfer

Experimental investigations have shown that the presence of electrolytes has a strong influence on the transfer of neutral organic solutes through ion exchange membranes used in electrodialysis. It was further demonstrated that this influence is due to the impact of the membrane counter-ions on the noncovalent interactions existing between the hydrated and charged polymer chains in the membrane.The aim of this work is to investigate the structural properties of hydrated CMX membranes equilibrated with different counter-ions. Different methods, such as Infrared spectra (IR), contact angle and Differential Scanning Calorimetry (DSC) measurements, were used to characterize the membrane samples soaked in different electrolytes. In addition, IR spectra were calculated using a quantum mechanics approach and compared with the experimental ones. Shifts of characteristic IR peaks as function of membrane ionic form were observed in both experimental and computed spectra. Both spectra present shifts to lower wavenumber in presence of cations with higher hydration number. The contact angle of CMX membranes also increases in presence of more hydrated ions revealing a decrease of the hydrophilicity of the membrane. Concerning DSC, the freezing temperature of the water entrapped in the membrane polymeric network soaked with different electrolytes was measured. A shift at lower temperature was found for more hydrated trapped ions. The computational and experimental membrane structural properties were correlated with the corresponding transfer properties (sugar fluxes) and a good agreement was obtained.

Change of surface and structure properties of cation exchange membrane in a microbial fuel cell

In this study, the two-chambered microbial fuel cell (MFC) was continuously long-term operated a young landfill leachate in order to evaluate the impact of cation exchange membrane (CEM) fouling on MFC performance. During the operation, the voltage output decreased sharply to almost zero and the voltage output was recovered completely after replacement of CEM, which implied that the voltage decrease was totally due to fouling of the CEM with the observations of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, the scanning electron microscopy (SEM) and long-term operation. The fouled membrane was washed with H2SO4 in order to recover the CEM via removing salts on membrane surface and the replacement of cations on the negatively charged sufonate sulfonate groups with the H+. After acid treatment, the current and power recoveries were only around 38% and 15%, respectively. The membrane was completely fouled again after one week of operation. Moreover, an alkali treatment with NaOH was applied in order to recover the CEM by removing organics on membrane surface. However, the alkali treatment had almost no effect on the fouled membrane depending on current output.

Effects of biofouling on ion transport through cation exchange membranes and microbial fuel cell performance

This study examines the effects of biofouling on the electrochemical properties of cation exchange membranes (CEMs), such as membrane electrical resistance (MER), specific proton conductivity (SC), and ion transport number (t(+)), in addition to on microbial fuel cell (MFC) performance. CEM biofouling using a 15.5 ± 4.6 μm biofilm was found to slightly increase the MER from 15.65 Ω cm(2) (fresh Nafion) to 19.1 Ω cm(2), whereas an increase of almost two times was achieved when the electrolyte was changed from deionized water to an anolyte containing a high cation concentration supporting bacterial growth. The simple physical cleaning of CEMs had little effect on the Coulombic efficiency (CE), whereas replacing a biofouled CEM with new one resulted in considerable increase of up to 59.3%, compared to 45.1% for a biofouled membrane. These results clearly suggest the internal resistance increase of MFC was mainly caused by the sulfonate functional groups of CEM being occupied with cations contained in the anolyte, rather than biofouling itself.

Electrodialytic transport properties of cation exchange membranes prepared from poly(vinyl alcohol) and poly(vinyl alcohol-co-2-acrylamido-2-methylpropane sulfonic acid)

In this study, cation exchange membranes with an interpenetrating network structure were prepared by blending poly(vinyl alcohol) (PVA) and a polyanion, poly(vinyl alcohol-co-2-acrylamido-2-methylpropane sulfonic acid). The membranes obtained were physically cross-linked by annealing them and chemically cross-linked by reaction with various concentrations of glutaraldehyde (GA) aqueous solutions. The effect of the cross-linking conditions and polyanion content on the ionic transport properties through the membranes was investigated. The water content of the membranes increases with increasing polyanion content and with decreasing GA concentration. The charge density of the membranes increases with increasing polyanion content and have a maximum value. The maximum value increases with increasing GA concentration. The dynamic transport number of the membranes increases with increasing polyanion content and with increasing GA concentration while the membrane resistance increases with increasing GA concentrat...

Structure and Electrochemical Properties of Cation-Exchange Membranes Based on Partially Imidized Polyamidoacid

The transport of water molecules and the distribution of functional groups in polyamidoacid carboxyl-containing cation-exchange membranes based on pyromellitic acid are studied by NMR and ESR techniques. It is shown that the self-diffusion coefficients of water differ in the gel and intergel regions. Structural parameters of conducting channels in the gel regions are determined. In electrodialysis of one-component and binary solutions, polyamidoacid membranes possess higher transport numbers and separation coefficients of counterions that are less hydrated in solution.

Electrodialytic transport properties of cation exchange membranes in the presence of cyclodextrins

After commercial cation exchange membranes (NEOSEPTA) had been immersed in an aqueous cyclodextrin solutions, electrodialysis of a 1:1 mixed solutions of alkaline earth metal ions and sodium chloride was carried out in the presence of cyclodextrins in the desalting side solution. Adsorption of the cyclodextrins in the membrane matrix was confirmed by IR spectrum, X-ray photoelectron spectroscopy (XPS) and the weight increase of each corresponding component of the membranes. As a result of adsorption of the cyclodextrins in the membranes, transport numbers of alkaline earth metal ions relative to sodium ions decreased compared with those of the membranes without cyclodextrins. Water content in the membrane increased and a ratio of calcium ions (alkaline earth metal ions) to sodium ions in the membrane phase decreased after adsorption of the cyclodextrins. This is due to existence of the compounds having hydrophilic outer surface, cyclodextrins, in the membrane matrix. The decrease in the transport number of calcium ions relative to sodium ions was due to both decrease in a ratio of mobility of calcium ions to that of sodium ions and decrease in an ionic ratio of calcium ions to sodium ions in the membrane phase.

Transport Properties of Cation Exchange Membranes in the Presence of Ether Compounds in Electrodialysis

Ether compounds such as ethylene glycols with different molecular weights and crown ethers have good affinity to the cation exchange membranes, sulfonated styrene-divinylbenzene membrane (sodium ion form) and perfluorocarbon sodium sulfonate membrane. The impregnated amount of ethylene glycols in the membranes was higher than the water content of the membranes. After the ether compounds had been impregnated in the cation exchange membranes, electrodialysis of mixed salt solutions (1:1 mixture of alkaline earth metal ions or potassium ions and sodium ions) was carried out in the presence of the compounds to observe the change in permselectivity between two cations. Though current efficiency did not change in the presence of the compounds, transport numbers of alkaline earth metal ions relative to sodium ions decreased. Namely, sodium ions permeated through the membrane more selectively than alkaline earth metal ions. This is due mainly to a decrease in the mobility of alkaline earth metal ions in the membrane phase and partially to a decrease in the ion exchange equilibrium constant of alkaline earth metal ions to sodium ions with the membrane. This originates from the difference in ion–dipole interaction between cations and ether groups. The transport number of potassium ions relative to sodium ions also decreased in the presence of the compounds. In particular, the permeation of potassium ions relative to sodium ions remarkably decreased in the presence of 18-crown-6 in the membrane and in the solution due to the formation of a strong complex between potassium ions and 18-crown-6.

Modification of Transport Properties of Ion Exchange Membranes.XV. Preparation and Properties of Cation Exchange Membranes Having a Single Cationic Charged Layer on the Membrane Surface by Sulfonyl–Amide Bonding

Abstract In order to prepare an excellent monovalent cation permselective cation exchange membrane, a polyethyleneimine (PEI) layer was formed with sulfonyl–amide bonding between PEI and sulfonyl chloride groups on one surface of the membrane. Two methods were tried: 1) one surface of the membrane reacted with PEI and the remaining sulfonyl chloride groups were hydrolyzed, and 2) after one surface of the sulfonyl chloride groups had been hydrolyzed, the other surface of the membrane was reacted with PEI and the remaining sulfonyl chloride groups were hydrolyzed. The cation exchange membranes, which had been prepared using both methods, had excellent monovalent cation permselectivity, low electrical membrane resistance and high current efficiency for the long-term electrodialytic concentration of seawater. The reacted amount of PEI on the membrane was about 10% of the cation exchange capacity.

Evaluation of transport properties of cation exchange membranes for application in alkali concentrators

Conductivity and transport properties of commercially available cation exchange membranes were investigated for their application in an electrochemical alkali concentrator. Among the three membranes studied, Nafion1 961 was found to have high conductivity, high sodium ion transport and lower water transport characteristics which are the desired characteristics for fabrication of an alkali concentrator. The effect of concentration gradient between anolyte and catholyte on the overall transport properties is also reported.

Preparation of redox cell properties of cation exchange membrane combined anisotropically with polypyrrole

Trials to produce a cation exchange membrane with anisotropic structure were carried out with cation exchange membranes, pyrrole or aniline, and ferric ions. When one side of a cation exchange membrane of ferric ion form contacted an aqueous pyrrole solution, pyrrole polymerized on only the surface portion of the membrane to produce an anisotropic structure. Evidently a thin, tight polypyrrole layer, through which pyrrole molecules could not permeate easily, was formed on the membrane surface. When this composite membrane was held tightly between two platinum plates, it produced an e.m.f. that was dependent on relative humidity. The e.m.f. was reproducible in wet-dry cycles in air. The e.m.f. seems to have been generated from Fe 2+-Fe 3+ redox reactions, because ferric ions in the membrane were reduced to ferrous ions during the polymerization of pyrrole.

Properties of cation exchange membranes obtained in the presence of diluents

AbstractThe effect of inert diluents on the properties of cation exchange membranes had been studied. The membranes were prepared by modification of high‐molecular polyethylene (M̄n = 1.19 × 106) with styrene and divinylbenzene in the presence of toluence or heptane and following sulphonation. In the monomer mixture the diluent content was in the range of 5–30 wt. % and divinylbenzene was 3 or 7 wt %. The results obtained indicate that the properties of thus obtained membranes depend on the kind and amount of the diluent. It was found that the membranes, obtained in the presence of toluene, have much better transport properties than the membranes obtained in the presence of heptane at the same concentration in the monomer mixture. The best diffusion coefficient for sodium chloride was found for the membranes, obtained in the presence of 5 or 10 wt % toluene.

Effect of intramembrane structure on transport properties of cation exchange membrane prepared by paste method.

Cation exchange membranes were prepared using styrene and divinylbenzene as respective components and polyvinyl chloride cloth and microporous polyethylene film as respective backing materials. The intramembrane structures of synthetic and commercial membranes were analyzed using Tye’s treatment by considering the non-homogeneous charge distribution within the membrane. Volume fractions of the pore, polyelectrolyte and inert polymer phases within the membrane were determined by using the water content of the membrane and the Donnan sorption concentration. The diffusion coefficients of the cupric ion within the pore and resin (i.e., polyelectrolyte and inert polymer) phases were correlated with the respective volume fractions of the membrane. A simplified model of the intramembrane structure was found to be useful for evaluating the sorbed concentration and the membrane conductivity.

Modification of transport properties of ion exchange membrane. XI. Electrodialytic properties of cation exchange membranes having polyethyleneimine layer fixed by acid–amide bonding

AbstractFor the purpose of preparing the monovalent cation permselective membrane for electrodialysis, the membrane having—SO2Cl groups reacted with the polyethyleneimine to form a cationic polyelectrolyte layer on the membrane surface by using the acid–amide bonding. Reaction conditions, i.e., reaction temperature, concentration of the polyethyleneimine solution and the addition of tertiary amines to the polyethyleneimine solution, were all examined in detail. As a result, all the different kinds of polyethyleneimines were effective in obtaining the monovalent cation permselective membrane if the correct reaction conditions were selected. The durability of the monovalent cation permselectivity was evaluated in a continuous electrodialytic concentration of sea water. The monovalent cation permselectivity decreased gradually during the electrodialysis in the cation exchange membrane with the polyethyleneimine layer. Therefore, the cation exchange membrane with the cationic polyelectrolyte layer was further treated with crosslinking reagents, i.e., form aldehyde–hydrochloric acid, epichlorohydrin, etc. or other alkylating reagents. The monovalent cation permselectivity of the treated membranes was almost constant for two months. The crosslinking reaction of polyethyleneimine was more effective than alkylation in maintaining the high permselectivity constantly.

Material properties of cation exchange membranes for chloralkali electrolysis, water electrolysis and fuel cells

Owing to the development of perfluorinated ion-exchange membranes, the application of the membranes in electrochemical cells has advanced greatly, especially in chloralkali electrolysis. Material properties of perfluorinated carboxylate membranes used for chloralkali electrolysis are described in relation to the conditions of their use. Some new membranes for water electrolysis and fuel cells are briefly described.