Dielectric properties of ion-exchange beads of sulfonic acid type dispersed in aqueous solutions — effect of fixed charge density

Ion-exchange beads with different densities of fixed charges were prepared by sulfoethylation of dextran gel beads. The relative permittivities and the electrical conductivities of the ion-exchange beads in a sodium form were evaluated by a dielectric technique consisting of the following two procedures proposed in a previous study (2): (a) Dielectric measurements for densely packed sediments of the ion-exchange beads; (b) Analysis of the observed dielectric relaxations by means of a theoretical equation of interfacial polarization for suspensions of spherical particles. The deduced permittivities of the ionexchange beads in equilibrium with water were about 60, which is lower than those of outer aqueous phases. The deduced conductirities were of the order of 1 to 10 mS cm^–1 and were increased reasonably with the fixed charge density. Closer consideration on these deduced values indicates that no specific interaction exists between the counter ions and the fixed charges irrespective of changes in fixed charge density and temperature.     

Carbon and SiC macroscopic beads from ion-exchange resin templates

A method for preparing carbon and SiC macroscopic beads using ion-exchange resins as a macrotemplate that determines the macroshape and the pore structure of the product materials is reported. First, silicates are ion-exchanged into the resins to prevent the resin from collapsing during subsequent carbonization and allow them to be used as precursors for SiC formation. SiC is prepared via carbothermal reduction of carbon/silica composite beads obtained upon carbonization of the resin/silicate in an inert atmosphere. Finally, silica is removed by HF etching. Very high-surface area (1670-2026 m2 g-1) micro- or micro-/mesoporous carbon beads and relatively high-surface area (35-63 m2 g-1) macro- and meso-/macroporous SiC beads were prepared by the described method. The pore structure and the macroshape of the particles were controlled by the type of ion-exchange resins employed, gel or macroreticular.     

Ion Exchange and Protonation Equilibria of an Amphoteric Ion-exchange Resin in the Presence of Simple Salt

The influence of simple salts on the ion exchange and protonation equilibria of an amphoteric ion-exchange resin, which has strong base and weak acid moieties in a single functional group fixed onto the styrene-DVB matrix, has been investigated. Concentrations of ionic species in the amphoteric ion-exchange resin in equilibrium with various sodium salt solutions were estimated by (23)Na NMR spectroscopy. For the NaClO(4) system, the ratio of sodium ion concentration in the resin phase to that in the equilibrium solution was greater than 1 and increased with a decrease in the salt concentration. In contrast to an ordinary cation-exchange resin, the ion exchange behavior of Mg(2+) and Ca(2+) on the amphoteric ion-exchange resin showed a marked dependence on the kinds of salts: the distribution coefficients for the NaCl system were independent of the salt concentration, while the log D vs. log[Na(+)] plots for the NaClO(4) system showed linear relationships with slopes being neither -2 nor 0. Apparent protonation constants of the carboxylate in the functional group of the resin in equilibrium with NaClO(4) solutions were greater than those with NaCl solutions. The ion exchange and protonation properties of the amphoteric ion-exchange resin were elucidated on the basis of the information about the salt concentrations in the resin phase estimated by the NMR method.     

The Rate Problem of a Thermally Regenerable Ion-Exchange System

Earlier equilibrium studies have established the thermal dependence of the equilibrium between salt solution and a mixed bed of weakly basic and weakly acidic ion-exchange resins. High resin utilization can be achieved if the resin properties and equilibrium conditions are optimized; the equilibrium characteristics of polyacrylic acid and polyvinylbenzyldiethylamine resins are quite suited for the practical desalination of brackish waters.

However, the adsorption rates exhibited by normal-sized resin beads of this type are much too slow for satisfactory operation of the process because of the low concentration of protons available for transfer between the resins. It is shown that increasing the porosity of the resins improves amine resin kinetics 10-fold and carboxylic acid resin kinetics 6-fold. Nevertheless such improvements are still inadequate for practical purposes, and it is concluded that for satisfactory rates to be achieved systems having much shorter diffusion paths are necessary.

Two further approaches to the rate problem are discussed, both involving the synthesis of novel resin systems. A mixed bed of microbeads (10-20 p) reacts at acceptable rates but presents mechanical problems; the magnetic flocculation of finely divided magnetic resins is reported as one possible solution to this problem. Another avenue is the synthesis of normal-sized beads of the amphoteric and snake-cage variety. Resins of this type that exchange at suitable rates are described.     

Utilization of ion exchangers in analytical chemistry XXVI : Application of the ion-exchange method to solutions containing oxidants

The free acid form of a cation-exchange resin of the sulfonated hydrocarbon type (Dowex 50) can be used for a quantitative liberation of the corresponding acids from salt solutions containing oxidants that are reduced by phenolic resins. Positive results have been obtained with solutions containing bromate, iodate, periodate, molybdate, and chromate. With permanganate a partial reduction occurs which prevents the application of the ion-exchange method for quantitative separation of solutions containing permanganate.     

Anion-exchange initiation of reactions: Detection and spectrophotometric determination of aliphatic amines with 2,4-dinitrophenylhydrazine

The role of anion-exchange resin beads in the initiation of reactions of tertiary amines with 2,4-dinitrophenylhydrazine has been explored. This reagent has been used for the selective detection and determination of aliphatic amines. Radiochemical studies have been performed to show that the coloured species is adsorbed but not exchanged on ion-exchange beads. A model for the interaction is proposed.     

Synthesis and properties of poly(hydroxamic acid) from crosslinked poly(methacrylate)

Poly(hydroxamic acid) chelating ion-exchange resin was prepared from crosslinked poly(methacrylate) beads. The starting polymer was prepared by a suspension polymerization of methacrylate and divinyl benzene. Conversion of the ester groups into the hydroxamic acid was carried out by treatment with hydroxylamine in an alkaline solution. Hydroxamic acid capacity of the product was 2.71 mmol/g. The resin exhibited high affinity towards Fe(III) and Pb ions and its capacities for Fe(III), Pb, Cu, Ni and Co ions were pH dependent. The ability of the resin to carry out the separation of Fe(III)CuCo/Ni and PbNi ions is also reported.     

Preparation of ion-exchange beads based on poly(methacrylic acid) brush grafted chitosan beads: Isolation of lysozyme from egg white in batch system

Poly(methacrylic acid) brush grafted crosslinked-chitosan (chitosan-g-poly(MAA)) beads were prepared in two sequential steps: in the first step, chitosan beads were prepared by phase-inversion technique and then were crosslinked with epichlorohydrin under alkaline condition; in the second step, the graft copolymerization of methacrylic acid onto the chitosan beads was initiated by ammonium persulfate (APS) under nitrogen atmosphere. The chitosan-g-poly(MAA) beads were first used as an ion exchange support for adsorption of lysozyme (LYZ) from aqueous solution. The influence of pH, equilibrium time, ionic strength and initial LYZ concentration on the adsorption capacity of the chitosan-g-poly(MAA) ion-exchange beads has been investigated in a batch system. Maximum LYZ adsorption onto chitosan-g-poly(MAA) beads was found to be 65.7 mg/g at pH 6.0. The experimental equilibrium data obtained LYZ adsorption onto chitosan-g-poly(MAA) ion-exchange beads fitted well to the Langmuir isotherm model. Kinetics parameters of this adsorption system were also analyzed by using the equilibrium experimental data. The result of kinetic analyzed for LYZ adsorption onto ion-exchange beads showed that the second order rate equation was favourable. Finally, the chitosan-g-poly(MAA) ion-exchange beads were used for the purification of LYZ from egg white in batch system and the purity of the eluted LYZ from ion-exchange chitosan-g-poly(MAA) beads was determined as 94% by HPLC from single step purification.     

Polymeric Sorbents for Bile Acids. III. Hydrophilic and Hydrophobic Models 0f Cholestyramine

Abstract

A study is presented of the binding of glycocholate bile salt anions by crosslinked polymeric beads consisting of either an acrylamide or a Merrifield resin. Various amine-containing pendant groups have been synthesized onto the functional sites of the backbones of these resins, thus forming bile acid sorbents. Based on the effects of systematic changes in the structure of the functional groups on the sorption isotherms, it is shown that the extent of binding is favored by changes that increase the basicity, especially quaternization. On the other hand, sorption is inhibited by extensive crosslinking. It is concluded that the sorption of glycocholate by these sorbents involves an ion-exchange mechanism.     

Catalysts for Hydration of Cyclohexene to Cyclohexanol

The hydration of cyclohexene was determined in a stirred tank of 100 mL in a batch mode in the presence of modified or unmodified resin as catalyst. The ion-exchange sulfonate resin was modified with alkyl secondary amine. At an optimum amination rate of 15%, the conversion of cyclohexene reached to 22% and the selectivity of cyclohexanol was 95.6%. In a temperature range of 90―150 ℃, the activity and selectivity of the modified resin ca-talyst were much higher than those of the unmodified resin catalyst, which was attributed to the inclusion formed between cyclohexene and alkyl chain and also the quasi-lipophilic phase formed around the outer surface of resin beads. The formed quasi-lipophilic phase formed enhanced the conversion of cyclohexene and depressed the formation of by-products.     

Sulfonated and sulfoacylated poly(styrene-divinylbenzene) copolymers as packing materials for cation chromatography

Three different types of cation exchangers were produced from four basic poly(styrene-divinylbenzene) substrates with different properties. Porous PS-DVB resin beads were functionalized by sulfonation and sulfoacylation under various conditions to produce sulfonated resins with exchange capacities of 0.03-1.80 mM g(-1). The matrix with 50% of cross-linking is most suitable for updating by the proposed technique. Sulfuric and chlorosulfonic acids were used as the reagents for sulfonation. The sulfonating conditions, capacities, and the technique of the synthesis are given. The effects of parameters of the sulfonation reaction and the composition of the reactionary mixture on ion-exchange capacity of the sorbents were investigated. Selectivity and efficiency of the separation of some inorganic cations and derivatives of amines and hydrazines on the resins obtained are compared by ion chromatography with conductometric detection. As a result, the sulfoacylated resin was proved more efficient for the separation of these analytes. The resolution of the analytes strongly depends on the degree of functionalization. The best performance about 19,000 plates m(-1) was obtained using the sulfopropionylated beads with an ion-exchange capacity of 0.3 mM g(-1). The prepared sulfoacylated cation exchanger was compared with the commercially available Dionex CS-12 packing material. It was found that the separation of alkaline ions and 1,1-dimethylhydrazine (UDMH) were much better that those for the commercial material.     

Droplet deformation in dc electric fields: the extended leaky dielectric model

The leaky dielectric model (LDM) was extended to large droplet distortions in dc electric fields. The resulting extended LDM (ELDM) reduces to the LDM for small droplet aspect ratios and to the pure dielectric model when the ratio of droplet and matrix conductivities equals the inverse ratio of their permittivities. The ELDM distinguishes between two types of phenomena possible at high electric fields: continuous deformation and hysteresis. For droplets deforming parallel to the electric field, the relationship that distinguishes between the two phenomena is a function of the droplet and matrix conductivities and viscosities but not of their permittivities. For droplets deforming perpendicular to the electric field, the relationship is a function of the droplet permittivities and conductivities but depends only slightly on the ratio of their viscosities. Some of the predictions of the LDM and the ELDM were compared with our own data and with data from the literature. For the systems that deformed parallel to the field direction, the ELDM not only predicted the data qualitatively but also predicted the data quantitatively when the experimental errors in its input parameters were taken into account, whereas the older LDM did not even predict the qualitative trend of the data. For the systems that deformed perpendicular to the field direction, however, the ELDM predicted the observed the aspect ratios in only one out of the four systems examined. In the other three systems, the LDM appeared to give reasonable predictions when either the ratio of the matrix/droplet viscosities was relatively small or the value of total charge relaxation time was relatively large. Thus, the applicability of the ELDM, as presently formulated, appears to be limited in the case of deformations perpendicular to the electric field.     

A novel method for the determination of iodide in table salt by X-ray fluorescence

A novel HI generation technique was developed and evaluated for the determination of iodide in table salt. HI was generated from the samples by the addition of concentrated sulfuric acid and adsorbed onto an ion-exchange resin loaded paper disk. The disk was then measured by X-ray fluorescence. The method compared favorably to the cellulose pellet technique, being more sensitive and reproducible and requiring less time per analysis. The method was applied to six samples of table salt and one of sea salt.     

Sorption and exclusion of polar solutes on cross-linked polymers

Summary The interstitial volume in ion-exchange columns packed with beads of gel-type is a well defined quantity. The retention volumes of dextran and high relative molecular mass polyethylene glycols are identical. For macroreticular resins and cross linked polyvinylpyrrolidone the retention volume depends on the structure and relative molecular mass of the polymer indicating that no strict borderline exists between the resin phase and the mobile phase.     

An investigation on the high-frequency dielectric dispersion of concentrated ion-exchange resin beads suspensions

In this paper, dielectric measurements were carried out on concentrated suspensions of D₃₅₄ ion-exchange resin (IER) beads dispersed in electrolyte solutions. The distinct high-frequency dielectric behavior occurring in the megahertz frequency range was interpreted based on the understanding of the interparticle interaction and the properties of the constitute phases. The results indicated that the dominant parameter of continuous phase influencing HFDD is the solution concentration after full Donnan equilibrium, while the dominant parameter of dispersed phase influencing HFDD is the fixed charge density. In addition, properties of the dispersed IER beads including electric conductivity and permittivity were obtained in terms of the Hanai’s method.     

Preparation of strong anion-exchange chromatographic packings based on monodisperse polymeric beads and their application in the separation of biopolymers

A new hydrophilic strong anion-exchange (SAX) stationary phase for HPLC has been synthesized by chemical modification of macroporous 8.0-m monodisperse poly(glycidylmethacrylate-co-ethylenedimethacrylate) beads (P_GMA/EDMA). The stationary phase was evaluated in detail to determine its ion-exchange properties, separability, reproducibility, hydrophilicity, and the effect of column loading and pH on the separation and retention of proteins. It was found to have an ion-exchange chromatographic (IEC) retention mechanism. The highest dynamic protein loading capacity of the synthesized SAX packing for BSA was 22.6 mg g^–1. Five proteins were separated within 6.0 min using the synthesized SAX resin. The SAX resin was also used for rapid separation and purification of recombinant human stem cell factor (rhSCF) from a crude extract solution in only one step. The purity of the purified of rhSCF was >92.4%.     

A novel primary amine-based anion exchange membrane adsorber

A novel anion exchange membrane adsorber is presented which shows excellent impurity removal under different buffer conductivities ranging from 2 to 2 7mS/cm. The membrane utilizes a primary amine ligand (polyallylamine) and was designed specifically to bind impurities at high salt concentrations. Studies with DNA, endotoxin, and virus spiked into buffer at varying salt conditions were done, resulting in clearance of >3, 4, and 4 LRV, respectively, with negligible change on increasing salt up to 27 mS/cm conductivities. Verification of virus removal in mAb feedstocks is also shown. The data are compared with other membrane adsorbers and a conventional resin which utilize traditional chemistries to demonstrate improved purification performance with the primary amine ligand. Additional data on scale-up of the membrane adsorber device is discussed. A stacked flat-sheet design was implemented to ensure linear scale-up of performance using bovine serum albumin (BSA) as a model. The linearly scalable device, coupled with the highly effective membrane for virus, DNA, and endotoxin removal, represents a step forward in polishing technology for the purification of monoclonal antibodies and recombinant proteins.     

Kinetics of Adsorption of Thymopentin on a Gel-Type Strong Cation-Exchange Resin

The ion-exchange kinetics have been determined for adsorption of thymopentin on a gel-type sulfonated styrene–divinylbenzene resin converted to the ammonium form. Batch equilibrium and kinetic experiments were performed in chloride ion solutions of different concentration. Equilibrium data revealed isotherms were a good fit to the constant separation factor isotherm. Because of the high capacity and low cost of the resin its use for uptake of thymopentin was economically feasible. Kinetic data were compared with the predictions from the Nernst–Planck and Fick models. The intraparticle and effective diffusivity of thymopentin were obtained from these models.