Interactions between large organic cations and cation exchange membranes

Interactions between cation exchange membranes and large organic cations have been studied; namely (1) adsorption and electrodialytic desorption of cationic surface active agents, and (2) change in transport properties of the membranes by adsorption.N-dodecyl pyridyl compounds, such as N-dodecyl pyridinium bromide (C₁₂-Py), N-dodecyl dipyridyl bromide (C₁₂-Dipy) and N-dodecyl tripyridyl bromide (C₁₂-Tripy) were used for the adsorption and electrodialytic desorption; and for the study on the change in transport properties of membranes, N-dodecyl pyridinium chloride, C₁₂-Py, C₁₂-Dipy, C₁₂-Tripy and hexadecyl trimethylammonium chloride were used. It was confirmed that the higher the molecular weight of the cation the longer the time required to reach adsorption equilibrium, and that the amount of adsorption exceeded the ion-exchange capacity of the membrane. After equilibrium was attained, electrodialytic desorption from the membranes was difficult.The adsorption or ion-exchange of large organic cations was effective to the permselectivity of the cation exchange membrane to the sodium ion in electrodialysis of a solution of sodium chloride and calcium chloride. The relationship between the permselectivity and the properties of the cations was examined.     

Adsorption of metal cations from aqueous solutions onto the pH responsive poly(vinylidene fluoride grafted poly(acrylic acid) (PVDF-PAA) membrane

This study investigated the influence of pH of adsorption medium and co-adsorptive metal cations for the adsorption of potassium (K⁺) and magnesium (Mg²⁺) ions onto poly (vinylidene fluoride) grafted poly(acrylic acid) (PAA-PVDF) membrane. At pH 4.8, the adsorption of potassium and magnesium was minimal, because of nearly non-dissociated carboxylic acid groups of PAA-chains, but adsorption increased with increasing ion concentration. The interaction of the studied cations between PVDF-PAA membranes increased considerably at pH 7.0 the dissociation of carboxylic acid groups of PAA. The addition of ionic substances (calcium (Ca²⁺) and sodium (Na⁺) to the adsorption medium reduced the adsorption of potassium and magnesium onto the membrane, because of co-adsorption. Divalent calcium reduced more effectively than univalent sodium the adsorption of potassium and magnesium onto the membrane. In conclusion, co-adsorbing ions reduced the adsorbed amount of potassium and magnesium ions due to binding competition. The percentual adsorbed values suggest that adsorption affinity of studied ions onto the PVDF-PAA membrane followed the order Na⁺ < K⁺ < Mg²⁺ < Ca²⁺. The effect of metal cations on drug adsorption from biological fluids needs research in the future, because e.g. PVDF-PAA membrane has been used in drug separation processes.     

Electrodialytic transport properties of heterogeneous cation‐exchange membranes prepared by gelation and solvent evaporation methods

The heterogeneous cation‐exchange membranes were prepared by employing two different methods: immersing the cation‐exchange resin‐loaded membranes in gelation bath; evaporating the solvent upon casting a uniform solution of cation‐exchange resin on a glass plate. The effect of resin loading on the electrochemical properties of the membranes was evaluated. The permselectivity of these heterogeneous membranes and transport number of calcium ions relative to sodium ions was evaluated with respect to the extent of resin loading and the methods of preparation. It is found that the membrane potential, transport number, permselectivity, and relative transport number are prominently high in the solvent evaporation method compared with the gelation method. The transport number of calcium ions relative to sodium ions in the solvent evaporation method increased monotonously with increasing resin loading. However, the increase of resin loading did not influence much on the relative transport numbers in the gelation method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 198–207, 2006     

Interaction of cation-exchange membrane with polycation. II. Poly(N-alkyl-4-vinylpyridinium halides)

The effect of the hydrophile–lipophile balance (HLB) of poly(N-alkyl-4-vinylpyridinium halides) (PAVP) on the interaction between PAVP and the cation-exchange membrane was elucidated by using various alkyl groups: methyl, ethyl, octyl, and so on. In the electrodialytic concentration of sea water by using the membrane on which PAVP has been adsorbed or ion-exchanged, the ratio of monovalent cations to total cations in the concentrated brine, β (Na+K), is almost same at the initial stage in species of PAVP. However, the deterioration ratio of β(Na+K) is smaller with decreasing HLB. In order to obtain the large value of β(Na+K), poly(N-methyl and dodecyl-4-vinylpyridinium chloride) (PMDVP), was investigated. PMDVP, of which the ratio of pyridinium groups quaternized with 1-bromododecane to total pyridinium groups (Qd) is about 40%, shows high initial value of β(Na+K) and its good durability.     

Studies of selective adsorption resins. XXVI. Removal of calcium and magnesium ions in a salt solution with chelating resin containing aminomethylphosphonic acid groups

Removal of calcium and magnesium ions in a salt solution with the macroreticular chelating resin containing aminomethylphosphonic acid groups was investigated. The resin (RMT-P) exhibited high affinity for calcium and magnesium ions in a salt solution containing 200 g/dm³ of sodium chloride. In the column method, calcium and magnesium ions in a salt solution were preferentially absorbed on the RMT-P, when the salt solution containing 100 mg/dm³ of calcium or magnesium ion was passed through the RMT-P column at a space velocity of 15 h^?1. The calcium and magnesium ions adsorbed were eluted by allowing 1 mol/dm³ hydrochloric acid to pass through the column. The recycle of adsorption and elution was found to be satisfactory.     

Electrically-switchable, permselective membranes prepared from nano-structured N-doped DLC

In this study, we report a fabrication of a conductive DLC through-hole membrane with highly ordered nanopore arrays by template synthesis using an anodic porous alumina and effects of intrinsic properties of DLC (a wide working potential range and low ion adsorption) on ion permselectivity when the membrane is applied to separate ions.We have successfully fabricated the conductive DLC membranes that have pore diameters ranging from 14 nm to 105 nm and show electrically tunable charge selectivity. With these membranes, fluxes of cations across the membrane can be reduced by applying positive potentials and can be increased by applying negative potentials. In the case of anions, a selectivity pattern opposite to cations was observed. Inside pore surfaces of the conductive DLC membrane could have excess charge by potentiostatically charging. This excess charge regulates ion transport across the membranes. The membranes reject ions of the same sign as excess charge and transport ions of the opposite sign. The permselectivity of the membrane can be reversibly switched from cation-permselective to anion-permselective by changing potentials applied to the membrane (because the signs of excess charge can be controllable by applied potentials).DLC membrane exhibited ion permselectivity even in an electrolyte solution including ions strongly adsorb to electrode surfaces such as Na₂SO₄ and HCl solutions. By using DLC membrane, ion permselectivity can be controlled in real samples commonly including adsorbing ions (that cannot be controlled with Au nanotubule membrane due to a specific adsorption to electrode surfaces).We could also demonstrate the permselectivity of target ions by controlling the potential applied to the membrane even in the mixed solution, which contains both cations and anions and is close to actual samples including ions aimed to be separated.     

Conduction and Mass Transfer in Reinforced Cation Exchange Membranes

Abstract

The transport of sodium chloride and calcium chloride through two types of reinforced perfluorinated cation exchange membranes under an electrical field gradient was studied to determine the effect of calcium ion interferences to sodium ion migration. Electromigration-electroosmosis experiments were performed in a diaphragm cell. The concentration of all ions in each half cell was maintained constant by a feedback mechanism. For single salt experiments, the salt flux of calcium ions was half the salt flux for sodium ions. The water flux was higher for the membrane with the greater reinforcement. The effect of two cations competing for migration to the membrane matrix was studied by experiments utilizing a feedback mechanism for each cation. The flux ratio of sodium ions to calcium ions decreased as the concentration of calcium chloride was increased for experiments where the solutions contained mixtures of sodium chloride and calcium chloride.

The electrical conductivity of the membranes was measured using in a diaphragm cell having one movable electrode, allowing for resistance measurements at different path lengths. The resistivity for the membranes in solutions having only one cation was greater for calcium chloride solutions than for sodium chloride solutions. The resistivity of the more reinforced membrane was greater. For a mixture of sodium and calcium ions, as the calcium ion content decreased and the sodium ion concentration was held constant, an increase in resistivity was observed.     

Preparation of a water-permselective composite membrane by the concentrated emulsion method: Its swelling and permselectivity characteristics

A water-permselective composite membrane was prepared by the concentrated emulsion polymerization method. A large volume fraction of an aqueous sodium acrylate solution was dispersed in a small amount of divinyl benzene. Each of the two phases contained a suitable initiator and the continuous phase contained an appropriate surfactant. The concentrated emulsion thus obtained has the appearance and behavior of a gel. The gel was sandwiched between tow glass plates and subjected to polymerization via heating at 45°C for 24 h. The resulting membrane was dried and further employed in several kinds of experiments. The swelling of the membrane in water depends on the pH of water and can be as large as 86. At low pH values, the swelling was very small. The permeation rate of a water-ethanol mixture was in the range of 96–560 g/m² h and decreased with increasing alcohol concentration and increasing poly(sodium acrylate) fraction in the membrane. The permselectivity varied between 32 and 235, increasing with increasing poly(sodium acrylate) fraction in the membrane and with increasing or decreasing ethanol concentration (depending upon the composition of the membrane). The activation energy for pervaporation varied between 6.58 and 8.14 kcal/mol, depending upon the composition of the feed. The permselectivity decreased slightly with increasing temperature.     

Blends of polyurethane carboxylates with styrene vinylpyridinium copolymers

This is a continuation of an ongoing investigation of miscibility enhancement via ionic interactions in urethane-styrene blends. The present study deals with a polyurethane which contains in the hard segments pendant carboxylate groups neutralized by ammonium ions while the polystyrene contains pendant vinyl pyridinium methyl iodide groups. Miscibility of the styrene is seen with the hard segments of the urethane because of ion pair/ion pair interactions. Methanol extraction raises the T_g because it eliminates low molecular weight components, without removing the microions.     

Water–ethanol permseparation by pervaporation through photocrosslinked poly(vinyl alcohol) composite membranes

Water–ethanol permselectivity was investigated by pervaporation through composite membranes which were prepared by coating photocrosslinkable poly(vinyl alcohol) containing pendant styrylpyridinium group (0.86–3.93 mol %) on porous films. These membranes were water-permselective, and the selectivity was dependent on the state of membranes; namely, incorporation ratio of styrylpyridinium group on poly(vinyl alcohol), molecular weight of the base polymer, coating thickness of a photopolymer, etc. Photocrosslinkable styrylpyridinium group showed, of course, the ionic character by a pyridinium moiety to work on permseparation of water effectively as well as preventing the dissolution of membranes by crosslinking. Membranes based on the higher molecular weight poly(vinyl alcohol) (P = 1700) gave the higher permselectivity of water in general than those of lower molecular weight (P = 500) one. Swelling of the polymers reached 160%, and permeation rate through the membranes increased with the increase of swelling. Selective diffusion of water was found to take place in swelling, and to play a part in the water-permseparation through the membranes.     

Effects of metal ions on the thermal decomposition of brown coal

Pyrolysis experiments of Loy Yang brown coal from Victoria, Australia, were performed to examine the influence of coexisting metal species. Sodium, magnesium, calcium, barium and nickel were loaded either by ion exchange or by impregnation. The metal-loaded samples were heated under helium at the rate of 5°C/min up to 900°C. Exchanged metal ions affected the course of decomposition in various ways. The temperature of maximum rate of weight reduction was lower for sodium, barium and nickel exchanged brown coal than that for acid-washed coal by 50°C, while the presence of magnesium and calcium did not influence the decomposition temperature compared to that for acid-washed coal. The volatile matter yield decreased and the yield of C₁ gases increased with the amount of nickel or calcium loading. The char yields were almost the same regardless of the cations present, but the surface area of chars varied with metal species and metal loading. In particular, the surface area of char obtained from sodium exchanged coal decreased dramatically with increasing sodium content. The influence of impregnated metal species was found to be different somewhat from those of ion exchanged species, suggesting different interaction with coal surfaces.     

Permeability of mono-carboxylate ions across an anion exchange membrane

Transport numbers of several aliphatic and aromatic carboxylate ions across an anion exchange membrane were determined on the basis of the transport number of the co-ions across the membrane in electrodialysis. Also, the specific conductivity and water content of each carboxylate ionic-form membrane were measured.The transport number of lower aliphatic carboxylate ions decreases slowly with increasing molecular weight, but it decreases markedly where the carbon number is over five. In particular, the transport number of caprylate or of caprate ions is below 0.5, and these ionic-form membranes apparently lose the characteristics of an anion exchange membrane. For aromatic carboxylate ions, the benzoate ion a higher transport number, but p- or O-hydroxybenzoate ions only about 0.6. The specific conductivity and water content of each carboxylate ion having a lower transport number are very small compared with other carboxylate ions of higher transport number. This suggests that the hydration number and the activity of ions with a lower transport number are small in anion exchange membranes.     

Chiral separation with polyurea membrane consisting of L‐lysinyl residue: Proposal of facile method for prediction of permselectivity

Novel chiral polyureas were prepared from L ‐lysine‐4‐nitroanilide and 2,4‐toluene diisocyanate. The polyurea thus prepared gave a durable self‐standing membrane that can be directly converted into molecular recognition membranes by applying an alternative molecular imprinting. The Z‐D ‐glutamic acid (D ‐Glu) molecularly imprinted membrane adsorbed D ‐Glu in preference to L ‐glutamic acid (L ‐Glu) from racemic mixture of Glu and vice versa. Those two types of molecularly imprinted membrane showed optical resolution ability, adopting a concentration gradient as a driving force for membrane transport. A facile method to predict permselectivity of racemic mixture of charged permeant was proposed. From the observed membrane resistance, the permselectivity was predicted. The predicted permselectivity coincided with the observed one. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Removal and recovery of gallium and indium lons in acidic solution with chelating resin containing aminomethylphosphonic acid groups

Removal and recovery of gallium and indium ions in acidic solution with the macroreticular chelating resin containing aminomethylphosphonic acid groups was investigated. The resin (RMT-P) exhibited high affinity for gallium and indium ions in sulfuric acid solution. In the column method, gallium and indium ions in sulfuric acid solution (0.05 or 0.5 mol/dm³) were favorably adsorbed on the RMT-P when the solution containing 27.6 mg/dm³ of gallium ion or 51.4 mg/dm³ of indium ion was passed through the RMT-P column at a space velocity of 15 h^?1. The gallium and indium ions adsorbed were eluted by allowing 1 mol/dm³ sodium hydroxide or 4 mol/dm³ hydrochloric acid to pass through the column. The proposed resin appears to be useful for the recovery of gallium and indium ions in sulfuric acid solution.     

Properties of a cation-exchange membrane adsorbed or ion-exchanged with hexadecylpyridinium chloride

Some electrochemical properties of a cation-exchange membrane that had been adsorbed or ion-exchanged with hexadecylpyridinium chloride were observed. Two observations were made: (1) current/voltage curves (2) electric resistance of the membrane during the electrodialysis, and current efficiency of cations.Adsorption of or ion-exchange with hexadecylpyridinium chloride was carried out by immersion of the membrane in an aqueous solution of hexadecylpyridinium chloride for a given period.As the period of immersion of the membrane in the solution of hexadecylpyridinium chloride increased, the voltage of current/voltage curves remarkably increased at low cd. The current/voltage curve of the membrane immersed more than 16 h was different from that immersed less than 16 h. When the membrane which had been adsorbed or ion-exchanged with hexadecylpyridinium chloride was used in electrodialysis, the electric resistance of the membrane increased remarkably, and showed a maximum value during the electrodialysis as the immersion period increased. These phenomena are attributable to the transformation of the cation-exchange membrane to the bipolar type ion-exchange membrane and then the transformation of the bipolar type to the amphoteric type because hexadecylpyridinium ion, in the membrane's structure, functions as fixed ion-exchange group.     

The molecular mechanism for destabilization of foams by organic ions

The effect of tetraalkylammonium ions on the destabilization of foam has been studied by measuring the half-life of foam (τ_1/2), area/molecule at the air/water interface, surface viscosity and critical micelle concentration (CMC) of sodium dodecyl sulfate (SDS). The area/molecule of SDS in organic salt solutions, calculated from the Gibbs isotherm, increases as the size of organic ion increases, and surface viscosity of the film decreases with the size of organic ions. The interaction of tetraalkylammonium ions with SDS decreases the CMC of the solution, and hence the concentration of SDS monomers decreases. The CMC of SDS decreases with the increase in the size and concentration of organic ions. The decrease in the CMC, increase in the area/molecule of SDS at the air/water interface and the decrease in surface viscosity by tetraalkylammonium ions all work to decrease the foam stability. The results indicate that the change in intermolecular distance between surfactant molecules in the adsorbed film by organic ions can significantly influence the surface viscosity and foam stability. The foam destabilizing efficiency of tetra-alkylammonium ions was superior or equivalent to that of tributyl phosphate and 2-ethyl hexanol, which are used in many antifoaming formulations.     

Selective separation of some heavy metals by poly(vinyl alcohol)‐grafted membranes

A poly(vinyl alcohol) membrane (PVA) was modified by radiation graft copolymerization of acrylic acid/styrene (AAc/Sty) comonomers. The Cu and Fe ion‐transport properties of these membranes were investigated using a diaphragm dialysis cell. In the feed solution containing CuCl₂ or a mixture of CuCl₂ and FeCl₃, the PVA‐g‐P(AAc/Sty) membranes showed high degrees of permselectivity toward Cu²⁺ rather than toward Fe³⁺. The permeation of Cu²⁺ ions through the membranes was found to increase with decrease in the grafting yield. However, as the content of Cu²⁺ ions in the Cu/Fe binary mixture feed solutions decreased, the rate and the amount of transported Cu²⁺ through the grafted membrane decreased, with no appreciable permselectivity toward Fe³⁺. When Fe²⁺ ions were used instead of Fe³⁺ ions in the feed solution containing Cu²⁺, the transport of both Cu²⁺ and Fe²⁺ through the membrane was observed. The rate of transport of Fe²⁺ was higher than that of Cu²⁺. In addition, it was found that the selective transport of ions was significantly influenced by the pH difference between both sides of the membranes. As the pH of the feed or the received solution decreased, both Cu²⁺ and Fe³⁺ passed through the membrane and were transported to the received solution. The role of carboxylic acid and the hydroxyl groups of the grafted membranes in the transportation process of ions is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 125–132, 2000     

Inferences on the mechanism of emulsion polymerisation of styrene from characterisation of the polymer end-groups

Solute electrolyte and adsorbed emulsifier can be removed by ion exchange from polystyrene latices prepared with persulphate initiator. Rigorous purification of the ion-exchange resins is necessary to avoid contamination by leached polyelectrolytes. These ion-exchanged latices are stabilised by strong acid surface groups - sulphate end-groups of the polymer molecules. The number of surface groups as determined by conductometric titration of the latex, plus the number buried within the particle as determined by conductometric titration of the polymer in solution (or by X-ray fluorescence), is less than the expected value of two per polymer molecule. The other end-groups are shown to be hydroxyl groups by oxidation to the carboxyl form followed by ion exchange and titration. The total number of end-groups thus determined is close to two per molecule. As the pH of the polymerisation medium is decreased, the proportion of hydroxyl end-groups increases and that of the sulphate end-groups decreases. No carboxyl groups are detected in ion-exchanged latices prepared in a nitrogen atmosphere, independent of the nature of the emulsifier. The dye partition method gives end-group concentrations that are far lower than those determined by titration or X-ray fluorescence, probably because the formation of the dye end-group ion-pair is not complete. Finally, for latices prepared at relatively low emulsifier concentrations, the contribution of the sulphate end-groups to the surface charge density is significant and cannot be overlooked, as has been done in the past.     

盐交换凹凸棒黏土的理化性质及其对双氯芬酸钠吸附性能的影响

将凹凸棒黏土采用不同价态的硫酸盐和相同价态不同用量硫酸盐交换后,通过红外光谱、扫描电镜、比表面积和ζ电位的测定,考察了盐交换处理对凹凸棒黏土微结构和理化性能的影响。在此基础上,考察了处理凹凸棒黏土对双氯芬酸钠的吸附影响。结果表明,金属盐交换凹凸棒黏土对双氯芬酸钠的吸附量不仅与所交换金属离子的价态有关,更与凹凸棒黏土的微孔比表面积和微孔体积有关。当硫酸铝用量为凹凸棒黏土量的0.5%时,其交换凹凸棒黏土对双氯芬酸钠的吸附量最大,达到了126 mg/g,与凹凸棒黏土原矿相比,吸附量提高了近4倍。     

Toluene vapor removal using an inorganic/organic double-network ion gel membrane

ABSTRACT

Tough gel membrane composed of a large amount of an ionic liquid and an inorganic/organic composite double-network (inorganic/organic DN ion gel membrane) was examined to remove toluene vapor from toluene vapor/N₂ mixed gas. The DN ion gel membrane with 80 wt% of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide showed higher toluene vapor permeability (more than 30,000 barrer) and toluene vapor/N₂ permselectivity (690) than the supported ionic liquid membrane. The toluene vapor permeability and toluene vapor/N₂ permselectivity were maintained under pressurized condition. It was confirmed that the toluene vapor permeation was limited by intramembrane diffusion of the dissolved toluene vapor.