Effect of the porous structure of polymer on the kinetics of Ni<Superscript>2+</Superscript> exchange on hybrid inorganic-organic ionites

Hybrid organic-inorganic ion exchangers are obtained by incorporating amorphous zirconium hydrophosphate into the gel of strong acidic cation exchange resin. Hybrid organic-inorganic ion exchangers are obtained by modifying strong acidic cation exchange resin with amorphous zirconium hydrophosphate. The synthesized materials are studied by standard porometry contact. It is found that raising the inorganic component content to 34 wt % diminishes the microporosity of the samples and simultaneously enhances the of meso- and macropore volume. Experiments establish that modification of a polymer matrix lowers the self-diffusion coefficient of Ni²⁺ from 8.1 × 10⁻¹² to 2.4 × 10⁻¹²–4.1 × 10⁻¹² m² s⁻¹; nevertheless, an inorganic ion exchanger minimizes the inhibitory effect of co-ions on the Ni²⁺ → H⁺ exchange rate. One possible mechanism for of filling of the matrix by with particles of zirconium hydrophosphate is discussed.     

Preparation of poly(glycidylmethacrylate‐divinylbenzene) weak acid cation exchange stationary phases with succinic anhydride,phthalic anhydride,and maleic anhydride for ion chromatography

In this work, poly(glycidylmethacrylate‐divinylbenzene) microspheres were prepared and applied for the preparation of weak acid cation exchange stationary phases. Succinic anhydride, phthalic anhydride, and maleic anhydride were selected as carboxylation reagents to prepare three weak acid cation exchangers by direct chemical derivatization reaction without solvent or catalyst. The diameters and dispersity of the microspheres were characterized by scanning electron microscopy; the amount of accessible epoxy groups and mechanical stability were also measured. The weak acid cation exchangers were characterized by Fourier transform infrared spectroscopy; the content of carboxyl groups was measured by traditional acid base titration method. The chromatographic properties were characterized and compared by separating alkali, alkaline earth metal ions and ammonium and polar amines. The separation properties enhanced in the order of succinic anhydride, phthalic anhydride, and maleic anhydride modified poly(glycidylmethacrylate‐divinylbenzene) cation exchangers.     

双功能聚合物基质阳离子交换固定相的制备及其在离子色谱中的应用

离子色谱是分离分析阳离子型化合物的重要手段之一。高效阳离子交换固定相的制备研究对离子色谱技术的发展具有重要的意义。该文以丙烯酸和顺丁烯二酸酐为单体,2-巯基乙基磺酸钠为巯基改性剂,提出了聚合物基质微球巯基改性自由基聚合修饰方法,用以制备新型双功能的阳离子交换固定相。该固定相以羧基和磺酸基为功能基,仅用简单的强酸淋洗液便可以实现常规阳离子的基线分离。利用色谱学模型,对金属离子和有机胺的保留行为进行了研究。采用梯度淋洗模式,可在24 min内实现10种阳离子的分离,表明固定相具有优异的色谱性能。“巯基-烯”修饰方法简单、高效。此外,通过调节巯基改性剂的比例能够实现对固定相交换能力的调控。     

Kinetic Regularities of the Kabachnik–Fields Reaction under Catalysis by Sulfonic Cation Exchangers Based on Petroleum Asphaltenes

Kinetics and Catalysis - Strongly acidic cation exchangers were obtained by the sulfonation and successive sulfonation and nitration of petroleum asphaltenes. The cation exchangers were...     

Fluidization of cation exchangers with regenerating sulfuric acid solution

Dependences of the bed expansion of cation exchangers (weakly acidic Lewatit CNP 80 and strongly acidic KU-2×8) on the flow velocity, temperature, and concentration of the regenerating sulfuric acid solution were determined. An equation describing the dependence of the bed expansion of cation exchangers on the flow velocity, temperature, and concentration of sulfuric acid, common to the two ion exchangers, was derived, which allows a priori determination of the extent of bed expansion in regeneration of cation exchangers in the fluidization mode.     

Sorption of Eremomycin on Carboxylic Cation Exchangers

The relationships of sorption of antibacterial antibiotic eremomycin on carboxylic cation exchangers were studied. The difference between gel-like and structurally segregated carboxylic cation exchangers were analyzed by potentiometric titration. The optimal conditions for sorption and desorption of eremomycin were found.     

Enthalpies of sorption of glycine from aqueous solutions by carboxylic cation exchangers

The influence of glycine acidity on its interactions with carboxylic cation exchangers in the protonated and deprotonated forms was investigated by the calorimetric and sorption methods. The enthalpies of sorption of glycine on KB-2 and KB-4 cation exchangers at various pH were determined.     

Production of <Superscript>88,89</Superscript>Zr by proton induced activation of <Superscript>nat</Superscript>Y and separation by SLX and LLX

^natY foil was irradiated by 20 MeV proton to produce no-carrier-added ^88,89Zr. A comparative evaluation on radioanalytical separation methods of ^88,89Zr was carried out from irradiated target matrix by both liquid–liquid (LLX) and solid–liquid (SLX) extraction methods using di-(2-ethylhexyl) phosphoric acid (HDEHP) dissolved in cyclohexane as liquid cation exchanger and Dowex 50W-X8 H⁺ form (20–50 mesh) as solid cation exchanger. Both the methods offer good separation and high yield of nca ^88,89Zr but SLX offers much higher separation factor and better yield.     

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.     

Effect of gamma radiation on organic ion exchangers

Effects of gamma radiation on indigenous strong cation and anion exchange resins have been studied in HCl medium up to a dosage of 3600 kGy. The ion exchange capacities of cation and anion exchangers decreased by around 20% at 2400 kGy of absorbed dose. Decrease in salt-splitting capacity and total exchange capacity for both cation and anion exchangers were comparable up to 2400 kGy. Above 2400 kGy, a marginal loss in the capacity was observed for cation exchangers whereas a drastic reduction was noticed for the anion exchangers. The distribution coefficients for zirconium, antimony and cobalt, measured in HCl medium, did not change significantly for 2400 kGy of absorbed dose. Crushing strength and moisture retention capacity did not exhibit any specific trend with the absorbed dose.     

Separation of no-carrier-added <Superscript>149</Superscript>Gd from <Superscript>12</Superscript>C activated natural praseodymium matrix

¹⁴⁹Gd was produced from the ¹²C induced reaction on natural praseodymium target. No-carrier-added (nca) ¹⁴⁹Gd was separated from the bulk target matrix by liquid–liquid extraction (LLX) using cation exchanger di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane. High separation factor of 2,450 was achieved at the optimal experimental condition when 1% HDEHP and 0.1 M HCl were used as organic and aqueous phases respectively. The result was also compared with the previous reports.     

Density functional theoretical study on attachment sites of Mg<Superscript>2+</Superscript> and Ca<Superscript>2+</Superscript> and metal ion affinity to Crenulatin molecule

Crenulatin (C₂₅H₂₀O₁₀) is a flavonol derivative and has been isolated from the roots of Rhodiola crenulata (Hook. F. et Thoms.), a widely used medicinal herb. Magnesium and calcium cations play an important physiological role in biological systems. In this work, interactions of magnesium and calcium divalent cations with Crenulatin molecule were studied. Density functional theory (DFT) was used to determine coordination geometries and absolute metal ion affinities (MIA) for all possible stable complexes. The results show that calcium and magnesium cations are able to interact with the Crenulatin molecule through mono-, bi-, and tricoordination. B3LYP/6-31G(d) bond energies for all complexes reveal that magnesium cation has a greater affinity to Crenulatin molecule than calcium cation. The calculated value of Mg²⁺ cation affinity, including the zero-point vibrational energy (ZPE) and basis set superposition error (BSSE), is 231.8 kcal mol⁻¹ for the most stable complex. Entropy (ΔS) and free energy (ΔG) variations for the metalation processes considered here have also been reported. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

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.     

Sorption of Cs<Superscript>+</Superscript> and Sr<Superscript>2+</Superscript> by ion exchanger based on titanium phosphate

Sorption capacity of a composite ion exchanger based on titanium phosphate for Cs⁺ and Sr²⁺ cations was studied. The effect of pH and concentration of salts and, in particular, sodium chloride in solution on the sorption efficiency and distribution coefficient was analyzed. The diffusion coefficients were calculated for the Cs⁺ and Sr²⁺ cations and the time of half-exchange of the Na⁺ cation for the Cs⁺ and Sr²⁺ cations was found.     

Thermochemical kinetics of the formation of supramolecular compounds of amino acids with carboxylic cation exchangers

The kinetics of sorption of glycine and methionine from aqueous solutions with various acidities on the carboxylic cation exchangers KB-2 and KB-4 in protonated, deprotonated, and copper forms at 298 K was studied by microcalorimetry. In the sorption of the amino acids on the copper forms of the cation exchangers, the heat flux changes its sign. The character of the aliphatic amino acid-carboxylic cation exchanger interparticle interaction depends on the ionic form of the cation exchanger. As determined by the sorption method and IR spectroscopy, the nature of the glycine and methionine sorption sites in the ion exchanger phase changes on passing from the protonated to the copper form of the sorbent.     

Ionenaustausch Bei Hohen Konzentrationen der Lösung VI. Einfluss des Vernetzungsgrades Auf die Sorpton Anionischer Komplexe von Thallium(III) und Eisen(III) Durch Sulfonsaure Kationaustrauscher

Ion exchange at high concentrations of the mobile phase. VI. The influence of the degree of crosslinking on the sorption of anionic complexes of Tl(III) and Fe(III) by sulphonic cation exchangers The sorption of TI(III) and Fe(III) on sulphonic cation exchangers with 2-16% divinylbenzene has been investigated. In the range of concentration 4-8 mol/1 HBr and 4-10 mol/l HC1 the distribution coefficients decrease with the degree of crosslinking of the matrix. The same dependence has been observed for the selectivity of sorption, i.e. the quotient of the volume distribution coefficient of the trace component and the Donnan coefficient of the electrolyte.     

Interaction energies of histidine with cations (H<Superscript>+</Superscript>, Li<Superscript>+</Superscript>, Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>, Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>)

The imidazol side group of histidine has two nitrogen atoms capable of being protonated or participating in metal binding. Hence, histidine can take on various metal-bound and protonated forms in proteins. Because of its variable structural state, histidine often functions as a key amino acid residue in enzymatic reactions. Ab initio (HF and MP2) calculations were done in modeling the cation (H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) interaction with side chain of histidine. The region selectivity of metal ion complexation is controlled by the affinity of the side of attack. In the imidazol unite of histidine the ring nitrogen has much higher metal ion (as well as proton) affinity. The complexation energies with the model systems decrease in the following order: Mg²⁺ > Ca²⁺ > Li⁺ > Na⁺ > K⁺. The variation of the bond lengths and the extent of charge transfer upon complexation correlate well with the computed interaction energies.     

H+-Ca2+ Equilibrium Exchange on Polyacrylic Cationites

Potentiometric titration curves of carboxyl-containing polyacrylic cation exchangers (Amberlite IRC 86, Dowex MAC 3, Lewatit CNP 80, Purolite C 104, and Relite CNS) in the H form with calcium ions were measured. It was found that the apparent equilibrium constant strongly depended on the composition of resinate solutions, which was indicative of significant deviations of solutions in the cation exchanger gel phase from the ideal behavior. The largest deviations were observed for Dowex MAC 3 ion exchanger, and the smallest, for Amberlite IRC 86. For the other sorbents, the dependences coincided to within measurement errors. The experimental data were treated in terms of six models of the theory of exchange equilibria. The best approximation to titration curves was obtained in terms of the model that suggested the presence of two types of exchange centers in ion exchangers and took into account the influence of the state of three neighboring fixed groups on each spatially separated center. The amounts of centers of all types in the ion exchangers were determined. Differences in the selectivity of the cation exchangers with respect to calcium ions were explained.     

Reaction of sulphate radical anion (SO<Superscript>.</Superscript><Subscript>4</Subscript><Superscript>-</Superscript>) with hydroxy-and methyl-substituted pyrimidines: a pulse radiolysis study

Reactions of sulphate radical anion (SO·₄ ^-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·₄ ^- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH^- leading to the formation of OH adducts.     

Magnetism study of C<Superscript>I</Superscript><Subscript>x</Subscript>Co<Subscript>y</Subscript>[Fe(CN)<Subscript>6</Subscript>]·zH<Subscript>2</Subscript>O (C<Superscript>I</Superscript>=Rb,Cs) Prussian blue nanoparticles

We synthesized a series of cobalt-iron Prussian blue analogues in the form of nanocubes with which we tuned the amount of Cesium cation in the tetrahedral sites of the structure and varied nature of the alkali cation in the compound adopting a single microemulsion technique. Structure and morphology of the compound had been investigated by combining energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP), thermo-gravimetry analysis (TGA), infrared spectroscopy (IR), powder X-ray diffraction (XRD) and Transmission electron microscopy experiments (TEM). To directly determine the coercivity, remanence and Curie temperature, superconducting quantum interference device magnetometer (SQUID) was performed. Our investigation suggests that the amount and nature of the alkali cation are critical parameters for understanding the magnetic properties of the nanoparticles.