Strong acidic ion exchangers structure by inverse steric exclusion chromatography

A number of strongly acidic ion exchangers, both of the standard gel and of the macroreticular type, were investigated by inverse steric exclusion chromatography in an aqueous medium, using D₂O, sugars, and dextrans as standard solutes. Their structure was characterized as an assembly of isoporous fractions by using Ogston's model of the porous medium. The data thus obtained were correlated with those on the catalytic activity of ion exchangers for the hydrolysis of saccharose.     

New High-Performance Techniques for Ion-Exchange Separation

Results of the use of water-soluble cationic polymers for the synthesis of new anion exchangers for ion chromatography, capillary electrophoresis, and electrokinetic chromatography were summarized. The influence of functional groups in polymer molecules on the selectivity of the ion-chromatographic determination of ions and their mobility in capillary electrophoresis was considered.     

Catalytic activity of iron-containing polymers in hydroxylation of benzene with hydrogen peroxide

Hydroxylation of benzene with hydrogen peroxide in aqueous acetonitrile at 50°C was studied. The KU-2-8 and KU-1 cation exchangers, and also specially synthesized cation exchangers and phenolformaldehyde resins derived from pyrocatechol and resorcinol, all modified with Fe(III) cations, were used as catalysts. The macrocomplex KU-2-8/Fe³⁺ showed the highest catalytic activity and ensured 32% yield of phenol in 15 min. The formation of phenol depends in a complex fashion on the initial concentration of hydrogen peroxide, content of Fe(III) ions in the polymer, and reaction time.     

Chelating ion-exchangers containing N-substituted hydroxylamine functional groups: Part I. N-aroylphenylhydroxylamines

Chelating ion exchangers containing N-carbonylphenylhydroxylamine functional groups have been synthesized and their exchange behaviour with copper, cobalt, iron, vanadium and uranium investigated. Of the two polymers described, a linear oxime-carbonyl polymer exhibited chelating capacity as a function of pH analogous to the chelates formed by BPHA. An oxime-carbonyl polymer based on polyethyleneimine had high capacities for the metal ions studied, but the principal mode of reaction was by electron donation from nitrogen atoms. The absence of co-ion in metal ion capacity studies indicates the possibility of formation of 1:2 and 1:3 metal complexes with the resin. Separations of iron(II)-iron(III) and vanadium-iron appear possible.     

The Effects of Polymer Properties and Solution Composition on the Distribution,Properties, and Amount of Water in Swollen Ion Exchangers

The effects of the composition and concentration of an external solution on the swelling degree of polystyrene-based ion exchangers crosslinked with different amounts of divinylbenzene have been analyzed within the heterophase model of polymer gel structure. It has been confirmed experimentally that, upon variations in the composition of the external solution, the swelling degree of polymers is determined by the content of “sorbed” water alone. Therewith, the volume of the external solution incorporated into the swollen polymer remains constant; i.e., it depends neither on an ionic form of an ion exchanger nor the concentration and composition of the external solution, but rather depends linearly on the polymer crosslinking degree. An algorithm has been proposed for calculating the volume of water in a polymer gel and some quantitative estimates have been presented.     

Polyelectrolyte Sorbents for Ion Chromatography

A method for the synthesis of new anion exchangers for ion chromatography has been proposed. The method is based on the fact that interaction of water-soluble anionic polymers with materials containing negatively charged sulfo groups on the surface gives rise to polyelectrolyte complexes. It is demonstrated that replacement of functional groups in molecules of the polymer affects the selectivity of the ion-chromatographic determination of ions. Recommendations are given for selecting a polymer for the determination of mixtures of inorganic anions and anionic complexes of transition metals in ethylenediaminetetraacetic acid.     

Sorption of binary liquid mixtures on polymer networks Part I. Determination of surface excess isotherms and free energy functions

Two groups of polymer networks (polymer resins) are investigated by selective liquid sorption fromn-propanol-water mixtures. Group 1 consists of gel polymerized polar (hydrophilic) ion exchangers which swell in the binary liquid mixture. Group 2 consists of non-polar, non-swelling, macroporous resins. The free energy isotherms accompanying the sorption processes are calculated from the excess isotherms and the bulk activities. The adsorption excess free energies reveal the differences in polarity of the polymer network.     

Effect of the porosity of PS–DVB-copolymers on ion chromatographic behavior in inverse size-exclusion and ion chromatography

Small and highly pressure-stable PS-DVB copolymers of different porosity had been prepared by a two-step swelling procedure which enabled variation of diluent composition, an important characteristic affecting the porosity. The polymers were characterized by inverse size-exclusion chromatography and scanning electron microscopy. Subsequent chloromethylation and amination resulted in anion exchangers suitable for ion chromatography.The pore volume and the pore-size distribution is substantially affected by the fraction of the solvens component in the diluent. It was apparent from scanning electron microscopy that surface structure and the size of the polymer particles was not affected by diluent composition. The functionalization process led to a decrease in pore volume. The pore-size distribution remained unchanged during functionalization, which can be explained in terms of partial closing of all pore sizes. The chromatographic efficiency of the functionalized polymers in ion chromatography was highly dependent on diluent composition and the extent of functionalization was determined by the total pore volume.The composition of the diluent is an excellent tool for optimization of polymers used for the synthesis of surface-functionalized anion exchangers.     

A review of the radiation stability of ion exchange materials

A comprehensive literature survey on the radiation stability of ion exchangers resulted in the publication of an extensive data compilation on the effects of ionizing radiation on synthetic organic ion exchangers in this journal (Vol. 97, No. 1). This paper is a brief review of the majorfindings of this literature survey along with similar information on synthetic inorganic ion exchangers. The primary goal of this literature survey is to review present knowledge on the effects of ionizing radiations on synthetic ion exchange materials used in radiochemical processing. Although there are gaps in our knowledge of the mechanisms of radiolytic changes in ion exchangers, the information available in the literature shows some general trends and similarities in observed qualitative effects by different types of organic and inorganic ion exchange materials. These trends and observations have been formulated into a set of qualitative and semi-quantitative statements that can be useful to potential users of ion exchange materials in nuclear material processing and radioactive waste management. Present knowledge, of the behavior of ion exchangers under the influence of ionizing radiations is too limited to justify quantitative predictive modeling.     

Selectivity of ion exchangers in extracting cesium and rubidium from alkaline solutions

We compare the ion exchange selectivity of phenol-type sorbents based on phenol formaldehyde resins, products of condensation of diatomic phenols with formaldehyde, and crosslinked polymer based on C-phenyl[4]resorcinarene resin, for cesium and rubidium ions. It is shown that phenol formaldehyde sorbents are the ones most selective. The interaction of alkali metal cations with the anion of calix[4]arene is investigated via quantum-chemical modeling. It is shown that the selectivity toward cesium and rubidium ions in ion exchangers of the phenolic type is not due to specific interactions of ions with phenolic groups.     

Ion-exchange high-performance liquid chromatography of nucleotides and polypeptides on new types of ion-exchange sorbents, based on polystyrene-coated silicas.

A novel type of ion exchanger was prepared by multipoint covalent binding of polystyrene chains onto the surface of porous silica followed by polymer-analogous modification of the bonded layer. Both anion and cation exchangers were synthesized and examined in the separation of nucleotides and proteins. Rapid and efficient separation of basic polypeptides on strong anion exchangers and that of acidic polypeptides on strong cation exchangers could be achieved. For the separation of complete mixtures of polypeptides the application of zwitter-ionic ion exchangers can be recommended.     

含磺酸,羧酸双功能基树脂对混合氨基酸的分离性能研究

对苯乙烯-丙烯腈-二乙烯基苯(S/AN/DVB)交联共聚机理研究曾发现,丙烯腈作为第三单体,可使DVB竞聚率比在S/DVB共聚体系中降低,相互分离显著,从而有利于合成性能较好的离子交换树脂;本文在此基础上,将S/AN/DVB共聚体中的氰基水解成羧基来合成含磺酸、羧酸双功能基树脂,解决了前人研究中仅有50％的氰基水解成羧基的问题,并首次将这种树脂应用于混合氨基酸的分离。     

Methods for Preparing High Performance Stationary Phases for Anion-Exchange Chromatography

The development of new high-performance anion-exchange stationary phases is one of the priority tasks of modern ion chromatography (IC). Most of the research in this field is aimed at improving the selectivity of anion exchangers and increasing the sensitivity, efficiency, and rapidity of the analysis. The selectivity of the stationary phases is largely determined by the chemistry of the adsorbent surface; therefore, it is particularly important to understand the relationship between the structure of the functional layer of the anion exchanger and its chromatographic properties. This review is devoted to methods for modifying polymer matrices in order to obtain highly efficient anion exchangers for the separation of inorganic and organic anions.     

Sorption of gaseous ammonia on sulfonated macroreticular ion exchangers

The amount of gaseous ammonia sorbed on dry sulfonated macroreticular ion exchangers with different contents of divinylbenzene was found to be greater than the number of sulfonic acid groups. The excess ammonia could be removed by washing with water. With ion exchangers containing more than 20% of divinylbenzene a certain amount of chemically bonded ammonia could not be removed, even by elution with strong acid. Sorption of ammonia occurred also on dry ion exchangers fully neutralized with sodium ion, and in that case also, ammonia could only partially be removed by water from higher crosslinked samples. On desorption into a gaseous phase the amount of desorbed ammonia was proportional to the surface area of the ion exchanger, since desorption occurred only from surface layers. The results obtained indicate that ammonia migrates among acid groups located within the mass of the ion exchanger.     

Polymer-coated cation exchangers in high-performance ion chromatography: preparation and application

Low-capacity cation-exchange stationary phases for ion chromatography were prepared by coating a vinyl-modified silica gel with polystyrene or poly(glycidyl methacrylate). Strong acid ion-exchange groups were formed by sulphonation with concentrated sulphuric acid or by ring opening of the polymer-coated silica gels with sulphite solution. Carbon-sulphur elemental analyses of the polymer-coated cation exchangers (PCCEs) were applied to determine the average polymer film thickness. The pH stability depended on the polymer film thickness. The PCCEs were stable in the pH range 0.5–9. The low-capacity PCCEs (capacities 18–91 μmol/g) were applied to determine alkali and alkaline earth metal ions in tap and mineral waters.     

Comparative Study of Water Softening with Granular and Fibrous Ion Exchangers

Comparative study of softening of model hard water with both strongly acidic fibrous FIBAN K-1 and granular KU-2 ion exchangers was carried out. The influence of the filter-bed height, packing density of fibrous ion exchangers, volume sorption capacity, and filtering rate on the efficiency of calcium removal from model hard water was analyzed.     

New phosphorus-containing sorbents based on wheat straw and glycidyl methacrylate for Hg<Superscript>2+</Superscript> removal

The possibility of preparing new phosphoric acid cation exchangers based on wheat straw and glycidyl methacrylate was explored. The mercury(II) ion sorption properties of the prepared cation exchangers were studied.     

Removal of185W,99Mo and125Sb radioisotopes from aqueous solutions using polyamine incorporated polysaccharides

Polyamino group-containing resins act both as chelating ion exchangers and weakly basic anion exchangers depending upon the species in contact in the solution. In the present work, ion exchangers based on polyamine incorporated polysaccharides (cellulose and galactomannan or guaran) have been used for removal of radioisotopes of¹⁸⁵W as WO ₄ ^2– ,⁹⁹Mo as MoO ₄ ^2– and¹²⁵Sb as Sb³⁺ from their separate aqueous solutions. These chelating anion exchangers have been synthesized by reaction of polysaccharides with epichlorohydrin followed by the respective polyamines as nucleophiles in a strongly alkaline medium. WO ₄ ^2– and MoO ₄ ^2– are adsorbed from their aqueous solutions through anion exchange process by chloride form of cellulose-triethylenetetraamine (cellulose-trien), cellulose-tetraethylenepentaamine (cellulose-tetren), guaran-triethylenetetraamine (guar-trien) and guar-tetraethylenepentaamine (guar-tetren) weakly basic anion exchangers. Guar-tetren chelating polymer has been found to be highly selective for¹²⁵Sb isotopes presumably due to the presence of chelating cis-hydroxy and tetren groups in the galactomannan matrix.     

Ion-exchange recovery of nickel(II) and cobalt(II) from sulfuric acid solutions

Sorption recovery of nickel(II) and cobalt(II) in their joint presence in sulfuric acid solutions was studied on new samples of domestic ion exchangers of CYBBER brand. It was shown that the ion exchangers under study have a high sorption capacity for ions of both nonferrous metals, depending on the structure of a sorbent and on the acidity of a contacting solution. It was found that, after Co(II) and Ni(II) ions are extracted from weak or strong sulfuric acid solutions, they can be effectively eluted from the ion exchangers under study with a 2 M hydrochloric acid solution to an extent of 85–95% (nickel) and 87–95% (cobalt).     

Characteristics of Novel Types of Substituted Cerium Phosphates

The disodium, dilithium, dipotassium and distrontium forms of cerium phosphate were prepared from their corresponding mono-forms. The chemical content of these inorganic ion exchangers have been characterized by inductively coupled plasma (ICP) spectroscopy. The ion exchange properties of these cation exchangers, their chemical stability and selectivity for certain ions were investigated. It was found that, by introducing different salts into the reaction mixture used to prepare cerium phosphate, robust cation exchange materials of reproducible composition with a good cation capacity, and suitable for column use, are produced. All the ion exchangers with the exception of CeP (dipotassium) show excellent selectivity towards certain cations, thereby increasing the potential practical applications of these inorganic exchangers.