Influence of natural sorbents on the immobilization of spent ion exchange resins in cement

Summary Leach characteristics of ¹³⁷Cs and ⁶⁰Co radionuclides from spent mix bead ion exchange resins and both ordinary Portland cement and cement mixed with two kind of natural sorbents (bentonite and clinoptilolite) have been studied using the International Atomic Energy's (IAEA) standard leach method. The waste immobilization performance of low-level wastes in natural sorbent mixtures was determined. The solidification matrix was a standard Portland cement mixed with 290-350 (kg/m³) spent mix bead exchange resins, with or without 1-10% of bentonite or/and clinoptilolite. The leaching rates from the cement-bentonite matrix were measured after 300 days as ⁶⁰Co: (1.20-9.72) ^. 10^-5 cm/d and ¹³⁷Cs: (1.00-9.22) ^. 10^-4 cm/d. From the leaching data, the apparent diffusivity of cobalt and cesium in cement-bentonite or/and clinoptilolite matrix with a waste load of 350 kg/m³ of spent mix bead exchange resin was calculated as ⁶⁰Co: (1.0-5.9) ^. 10^-6 cm²/d and ¹³⁷Cs: (0.48-2.4) ^. 10^-4 cm²/d. The compressive strength of these samples is determined according to the ASTM standards.     

The influence of thermal treatment on the properties of sorbents prepared from water conditioning precipitates

Sorbent samples based on the thermally activated precipitate formed in iron removal from under-ground water (water conditioning wastes) were studied by low-temperature nitrogen adsorption and thermal and X-ray analysis. The precipitate was found to be a material with a developed porous structure (the specific surface area of the initial sample was 229.9 m²/g). Calcining at 300°C decreased the specific surface area of the samples by 1.6–1.7 times and increased the volume of sorbing pores by 1.6 times. The precipitate material largely contained iron phases. An increase in the temperature of calcining contributed to deeper crystallization of the main phase, α-Fe₂O₃.     

The nature of ion exchange selectivity of phenol-formaldehyde sorbents with respect to cesium and rubidium ions

The structure of aqua complexes of alkali metal ions Me⁺(H₂O) _n , n = 1−6, where Me is Li, Na, K, Rb, and Cs, and complexes of 2,6-dimethylphenolate anion (CH₃)₂PhO⁻ selected as a model of the elementary unit of phenol-formaldehyde ion exchanger with hydrated alkali metal cations Me⁺(H₂O) _n , n = 0−5, was studied by the density functional method. The energies of successive hydration of the cations and the energies of binding of alkali metal hydrated cations with (CH₃)₂PhO⁻ depending on the number of water molecules n were calculated. It was shown that the dimethylphenolate ion did not have specific selectivity with respect to cesium and rubidium ions. The energies of hydration and the energies of binding of alkali metal cations with (CH₃)₂PhO⁻ decreased in the series Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺ as n increased. The conclusion was drawn that the reason for selectivity of phenol-formaldehyde and other phenol compounds with respect to cesium and rubidium ions was the predomination of the ion dehydration stage in the transfer from an aqueous solution to the phenol phase compared with the stage of binding with ion exchange groups.     

Modification of properties of ion exchange membranes

Summary Interaction between ion exchange membranes and surface active agents was observed by electrodialyzing the salt solution containing the surface active agent. The behavior of the electric resistance of the membrane during the electrodialysis, the current efficiency and the adsorbed or ion-exchanged amount and the permeated amount of the surface active agent were observed. Generally, the electric resistance of the membrane during the electrodialysis increased remarkably when the ionic surface active agent having the opposite charge to ion-exchange groups of the membrane was contained in the solution. And the correlation of the behavior of the electric resistance of the membrane to the electrodialysis condition, species of surface active agents and species of membranes was mainly observed. Results were as follows. 1) The adsorption' or ion-exchange of ionic surface active agent on the membrane was remarkably emphasized by the electric field. 2) The degree of the increase in the electric resistance of the membrane was remarkable when the surface active agent had the high molecular weight and the bulky molecular structure. 3) The degree of the increase in the electric resistance was remarkably various according to species of the membranes.From these results, a protecting method for the change of these membrane properties was examined. When the ion exchange membrane was treated with the polyelectrolyte solution having the opposite charge to ion exchange groups of the membrane, the increase in the electric resistance by ionic surface active agent was depressed. Generally, though the change of electrodialysic properties of the membrane by the ionic surface active agent was remarkable in the membrane having the tight structure, the change of the properties of the membrane having the tight structure was easy to be protected by the polyelectrolyte treatment. Though the ionic surface active agent having the bulky molecular structure made the properties of the membrane change remarkably, the change of the properties of the membrane by the bulky surface active agent could be easily protected by the polyelectrolyte treatment.

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Zusammenfassung Die Wechselwirkung von Ionenaustauschermembranen mit grenzflächenaktiven Stoffen wird durch Elektrodialyse untersucht. Der elektrische Widerstand der Membranen steigt während der Elektrodialyse beträchtlich an, wenn die grenzflächenaktiven Ionen entgegengesetzte Ladungen wie die Austauschergruppen der Membranen haben. Es wurde gefunden, daß 1. die Adsorption oder der Ionenaustausch der grenzflächenaktiven Ionen an der Membran beträchtlich durch das elektrische Feld verstärkt wird; 2. die Zunahme des elektrischen Widerstandes groß ist, wenn das grenzflächenaktive Ion ein hohes Molekulargewicht hat und möglichst sperrig ist; 3. die Widerstandsänderung merklich von der Art der Membran beeinflußt wird. Auf Grund dieser Versuche wurde die Möglichkeit geprüft, die Zunahme des Membranwiderstandes bei Gegenwart grenzflächenaktiver Stoffe durch Adsorption von Polyelektrolyten zu reduzieren.

     

The role of temperature in ion exchange processes of separation and purification

The evolution of ion exchange processes for separation and purification of substances by use of the influence of temperature both on the equilibrium and the dynamic properties of some ion exchange resins is discussed. Significant improvement of some ion exchange separations, diminishing of reagents consumption and waste quantities is achieved. In the same way, environmentally non-hazardous reagentless ion exchange methods of divalent and monovalent ionic mixtures separation are developed. This report is based on experimental studies of the equilibrium, dynamic and some other properties of ion exchange resins.     

Study of temperature effect on uni-univalent and uni-bivalent ion exchange reaction

Ion exchange equilibrium constant (K) for Cl⁻/Br⁻ and Cl⁻/C₂O₄²⁻ system was studied at different temperatures from 30 to 45°C. For both uni-univalent and uni-bivalent exchange systems, the value of K increases with rise in temperature i.e., from 1.16 at 30°C to 2.95 at 45°C for Cl⁻/Br⁻ system and 19.5 at 30°C to 30.0 at 45°C for Cl⁻/C₂O₄²⁻ system indicating the endothermic ion exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution. The article is published in the original.     

离子交换纤维的交换动力学研究

本文研究了VS-1型强酸性阳离子交换纤维的交换动力学.在有限浴条件下,用放射性示踪法,研究了温度,搅拌速度,溶液浓度及pH 值对该离子交换纤维的异相同位素交换反应的影响.并推导出离子交换纤维的交换动力学方程,计算出不同条件下的粒内扩散系数D及液膜中的传输系数D/δ.从机理上明确了交换纤维的交换反应速率远比球形树脂快的原因     

Chemical composition and ion exchange properties of zeolites

Series of exchange selectivity for alkali cations in zeolites change in a regular manner in dependence on the ratio (z) between the number of particles capable of solvating cations in the frameworks of zeolites (molecules of zeolite water, one-fourth of the framework oxygen ions) and the number of zeolite cations. For z=5–6 zeolites have maximum selectivity for large cations, for z<3–4 they selectively absorb sodium, while if z<2 they selectively absorb lithium. An analysis is given of the reasons of this dependence of the ion exchange selectivity of zeolites on the chemical composition of their frameworks. It is shown that the free energy of solvation of cations in zeolites is less than the free energy of their hydration. The effect of transformation of the selectivity series of zeolites can be connected with the contribution, on the part of the effect of redistribution of water between the solid and liquid phases of the ion exchange system, to the free energy of ion exchange reactions, which differs in dependence on the composition and structure of the crystals.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 3, pp. 378–382, May–June, 1990.     

On the influence of ion exchange on the local structure of the titanosilicate ETS-10

The effect of ion exchange with different monovalent cations (NH(4)(+), K(+), Na(+) and Cs(+)) on the local structure of the titanosilicate ETS-10 has been studied by (29)Si MAS NMR and Raman spectroscopy. Although X-ray diffraction shows no significant influence of ion exchange on the long range order, ammonium exchange is found to result in substantial damage to the local structure. Ion exchange experiments with alkali cations under significantly more acidic conditions clearly show that the structural damage brought about by ammonium exchange is not caused by the low pH of the exchange solution. The exchange with potassium and caesium ions also leads to significant changes in the (29)Si NMR and Raman spectra. However, these changes can largely be reversed by sodium back-exchange.     

Polyelectrolyte sorbents based on aliphatic ionenes for ion chromatography

2-4, 3-4, 2-8, 3-8, 3-6, 4-6, 6-8, 6-10-ionenes (polymers with quaternary nitrogen atoms in the main chain) served as modifiers in synthesizing polyelectrolyte sorbents for ion chromatography. The approaches to the synthesis and their stability are discussed. Cluster analysis was applied to separate aliphatic ionenes to three groups as chromatographic modifiers, namely hydrophilic, hydrophobic, and intermediate. Each group is characterized by a certain selectivity to sulfate, perchlorate, iodide and thiocyanate. The sorbents show high selectivity and efficiency up to 15 000 theoretical plates per meter.     

Non-trivial temperature effects on the cation exchange chromatography and chelation ion chromatography of metal ions

The effect of column temperature upon the retention of metal ions on sulfonated and mono-, di-, and amino-carboxylated cation exchange columns has been investigated. The retention of alkali, alkaline earth and transition metal ions on each of the above types of cation exchanger was studied over the temperature range 19-65 degrees C. A major difference between the behaviour of mono- and divalent metal ions was shown on each of the above stationary phases, with the monovalent alkali metals exhibiting clearly exothermic behaviour (a decrease in retention with increased temperature) under acidic eluent conditions and an apparent relationship between retention factor and the magnitude of the temperature effect. The effect of temperature upon alkaline earth metal ions was less defined, although strongly endothermic behaviour (increase in retention with temperature) could be seen on all stationary phases through correct choice of eluent. The transition metal ions studied showed endothermic behaviour on all four stationary phases, with the sulfonated column unexpectedly showing the largest increases in retention. The above behaviour can be partially explained through the dominance of the type of solute-stationary phase interaction governing retention. In several of the above columns, both ion-exchange and surface complexation interactions can occur, with the effects of temperature indicating which process dominates under specific eluent conditions.     

制备温度对Fe-B纳米金属玻璃组成及性质的影响

通过调变反应温度,制得了B含量变化范围较大的Fe100-xBx(x=23～40)系列纳米金属玻璃。用Mossbauer,ICP,XRD,TEM,DSC等实验手段,研究了制备条件对B含量的影响及其原因,样品的结构、晶化温度/微粒的聚集状态和表观粒度等物性与反应温度(B含量)的关系,揭示了Fe-B纳米金属玻璃的化学制备研究中反应温度的重要作用。     

Study of the influence of water matrix components on admicellar sorbents

Hemimicelle-based and/or admicelle-based solid-phase extraction (SPE) has recently been proved to be a fruitful strategy for the extraction and concentration of a wide variety of organic pollutants. This research focus on the effect of river and wastewater matrix components on the adsorption of sodium dodecyl sulfate (SDS) onto alumina, which is the most-used sorbent in hemimicelle-based and/or admicelle-based SPE, and we discuss the analytical consequences of the modifications observed. The effect of electrolytes (0.1 M NaCl), precipitating agents (127 and 333 mg L⁻¹ CaCl₂) and major organic components in wastewater (19.8 mg L⁻¹ carbohydrates, proteins and fats and 10 mg L⁻¹ linear alkylbenzene sulfonates (LAS) and rivers (8 mg L⁻¹ humic acid) on the SDS adsorption isotherm was investigated. Also, the global effect of matrix components was assessed using a river sample. Three types of sorbents were considered (hemimicelles, mixed hemimicelles/admicelles and admicelles). Electrolytes were found to compete with surfactant molecules for charge surface sites in the early part of the hemimicellar region; precipitating agents yield insoluble salts with the aqueous surfactant in equilibrium with admicelle-based sorbents; and organic matter did not have any influence at all. The matrix component concentrations investigated were above the usual range present in rivers and wastewater, which makes this study applicable to a wide number of environmental water samples. From the results obtained, simple rules were established to prevent and detect matrix-induced surfactant adsorption modifications, which permits us to know, a priori, the suitability of these sorbents for a specific application and allows the development of more straightforward and robust methods.     

Observations on the effect of temperature on performance and stability of anion exchange columns in ion chromatography

Summary The influence of column temperature on elution behaviour of several ions on anion-exchange resin beds of the Dionex Ion Pac type was investigated. Iodate, bromate, bromide and iodide ions were separated on Ion Pac AS9SC column in the temperature range of 10°C–55°C, using NaHCO₃/Na₂CO₃ and NaHCO₃ eluents. Free energy, enthalpy and entropy changes for respective ion exchange reactions were calculated and compared with literature data for classical gel type exchangers. In most cases the enthalpy change was a function of temperature. The work at elevated temperatures caused progressing resin degradation i.e. loss of strongly basic groups, accompanied by formation of weakly basic groups and also some weakly acidic groups. Similar resin degradation was observed for Ion Pac AS5 column. Observations on the changes of the plate height with the retention factor and temperature lead to conclusion that in some circumstances longitudinal diffusion in the resin phase also contributes to the total plate height.     

Structure and ion exchange properties of tunnel type titanium silicates

A large number of titanium silicates are known to exist in the mineral realm and recently a considerable literature has developed concerned with the synthesis and properties of these and related compounds. This paper describes two such families that have tunnel structures filled with cations that may easily be exchanged. A sodium titanosilicate of ideal formula, Na₂Ti₂O₃(SiO₄)₂·2H₂O, is tetragonal and built up of Ti₄O₄ cubane-like structures linked together by silicate groups in the a and b directions in the form of a square. In the c-axis direction, the cubane groups are linked by oxo-groups to form a framework enclosing tunnels parallel to the c-axis direction. The several ion exchange sites were identified based upon X-ray diffraction studies and the reason for the great affinity of this compound for Cs⁺ elucidated. The second family of compounds have the general composition M₃H(TiO)₄(SiO₄)₃·4H₂O (M=alkali metal cation) and have the pharmacosiderite structure. The sodium or potassium phases are selective for Sr²⁺ and Cs⁺. These compounds are cubic and have similar Ti₄O₄ cubane-like groups. In this case, the connectivity via silicate groups extends along all three crystallographic axes equally. This change in crystal system has a profound effect upon the ion exchange behavior. This effect, as well as the effect of germanate substitutions for silicate, will be described.     

The differential enthalpy of ion exchange on selective ionites

The problem of the experimental determination of the differential enthalpy of ion exchange is considered. The high errors in the enthalpies of ion exchange based on experimental corrected equilibrium coefficients substantially decrease the value of the parameters obtained this way. A method is suggested for finding the differential enthalpies of ion exchange on selective ionites on the basis of an analysis of only the composition of solutions in equilibrium systems at two temperatures. This allows the enthalpies to be determined with substantially lower errors than when traditional techniques are used.     

Modification of properties of ion exchange membranes V. Structure of cationic polyelectrolyte on the surface of cation exchange membranes

Summary Electrodialytic transport properties of cation exchange membrane are changed by adhesion of polyethylene imine on the membrane surface. The effect of conformation of polyethylene imine molecules on the transport properties of the membrane, thickness of adherent layer and mechanism of adhesion were discussed. Observed were relative transport numbers of calcium ions to sodium ions,P _Na ^Ca , current efficiency, electric resistance of the membrane during electrodialysis and pH-shift of anolyte after electrodialysis. P _Na ^Ca decreased remarkably, when the conformation of polyethylene imine was compact by adding salt to the solution, adjusting pH of the solution to a high value where polyethylene imine was scarcely protonated and adding water-soluble neutral polymers and multivalent anions. It was confirmed that the conformation of polyethylene imine on the membrane surface controlled the degree of the change of the transport properties of the membrane. The adherent amount of polyethylene imine on the cation exchange membrane was calculated assuming that a monolayer of polyethylene imine molecules with hydrodynamic radii was formed. This differed markedly from the amount observed. The reason for the difference was discussed. There was no observation of salting out by sodium chloride and calcium chloride. It was concluded that the polyethylene imine molecules on the cation exchange membrane are mainly bound by ion-exchange.

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Zusammenfassung Die elektrodialytischen Transporteigenschaften von Kationenaustauschmembranen werden mit Polyäthylenimin (PEI) als kationischer Polyelektrolyt verändert. Sie werden durch die Konformation des PEI in der Lösung beeinflußt.Als Transporteigenschaften werden die relativen Transportzahlen der Ca-Ionen im Vergleich zu Na-Ionen, der elektrische Widerstand der Membran während der Elektrodialyse and die pH-Änderung nach der Elektrodialyse im Anodenraum untersucht.

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With 13 figures and 3 tables     

Study of the effect of oxidative-bisulfite modification of the cotton cellulose on its ion exchange properties

The effect of chemical modification on the sorption properties of cotton cellulose toward Cu(II) and Ni(II) ions was studied. The modification was carried out in two stages: oxidation of cellulose with the formation of dialdehydocellulose, followed by its sulfonation. The optimal conditions for modifying the cellulose to produce a sorbent capable to remove effectively the heavy metal ions from aqueous solutions of corresponding salts were elucidated. The modified sorbent exceeds the native cellulose in the sorption capacity (in terms of sorption maximum) about 3 times, therewith the time of extraction of heavy metal ions is reduced from 45 to 8 min. The high sorption properties are defined by the formation of new sorption sites -SO₃Na along with initially formed -COOH groups on the sorbent surface.     

Study on the influence of humic acid of different molecular weight on basic ion exchange resin's adsorption capacity

In this paper, humic acid (HA) was ultra-filtered into different molecular weight sections and was characterized by multi-element analysis, UV₂₅₄/TOC, FT-IR and three-dimensional fluorescence spectrometric. Since humic acids of different molecular weights have different hydrophilic and molecular size, the maximum adsorption capacity of basic ion exchange resins appears on the humic acid whose molecular weight ranges from 6000 to 10,000 Da.