Selectivity Of Ion Exchange Resin Research Articles

ANALYSIS OF EXISTING METHODS FOR IMPROVING THE PHYSICAL AND CHEMICAL CONDITIONS OF THE ION EXCHANGE PROCESS IN WATER TREATMENT

The article deals with the issues of existing processes for improving the physical and chemical conditions of the ion exchange process in water treatment. Patents and publications on the use of the ion exchange method in water treatment have been analysed. The expediency and scientific significance are determined by the possibility of further improving the efficiency of the ion exchange process in water treatment on the basis of the obtained results. Existing methods, such as thermal and cryogenic treatment, membrane plants, distillation and reverse osmosis, have a number of disadvantages, such as high energy consumption of the process and the inability to be used on an industrial scale. A promising method to improve the efficiency of modified ion exchange resins is to use the effect of a magnetic field on the feed water with constant stirring. The article analyses ion exchange resins and their problems, existing research aimed at modernising the ion exchange process, considers ways to optimise the selectivity of ion exchange resins, their modification with dendritic aggregates, and the use of mixed cationic and anionic ion exchange resins. Regeneration of ion-exchange resins using ammonium bicarbonate technology, reagent-free regeneration methods, such as electrodialysis, electrodionization systems, in order to reduce process waste, possible schemes of using ion-exchange plants in combination with other methods of water treatment. The analysis shows the relevance of using the ion exchange process in water treatment and the prospect of further research on ways to intensify the process to reduce energy and economic resources. The obtained results demonstrate the most advanced ways to improve the method of ion exchange for water treatment, such as reagentless regeneration of ionites using electrodialysis, modification of resins by introducing the necessary functional groups.

Thermodynamic study of ion exchange reaction to predict ionic selectivity using ion exchange resin Indion-850

The thermodynamic study was carried out to predict the selectivity behaviour of ion exchange resin Indion-850 towaed various inorganic anions like chloride, iodide, sulfate, and oxalate. The equilibrium constant Kstd values for the ion exchange reactions were calculated at different temperatures from which the enthalpy values where obtained. The Kstd values were observed to increase with the rise in temperature, indicating endothermic ion exchange reactions. The thermodynamic data obtained here reveal that iodide ions were more strongly retained on the resin surface compared to chloride ions. Also the low enthalpy and high equilibrium constant values for oxalate ions indicate the greater selectivity of ion exchange resin for oxalate ions as compared to sulfate ions.

Selectivity study of strongly acidic cation exchange resin Amberlite IR-120

The thermodynamic measurements was carried out to study the selectivity of cation exchange resin Amberlite IR-120 in protonated form with respect to Mg2+, Ca2+, Sr2+ and Ba2+ ions in solution. The equilibrium constant K was calculated using the activity coefficients of ions in solution as well as in the resin. The K values calculated for the reacting systems increase with temperature that suggests the endothermic exchange reactions with estimated enthalpy values of 38.8, 20.6, 8.45, and 7.24 kJ mol−1, respectively. On the basis of calculated parameters, the selectivity of ion exchange resin with respect to various bivalent ions in the solution was predicted. The method used in our experimental work provides a basis for characterization of ion exchange resins, which can be promising materials for efficient separation of ions from industrial waste effluents.

Raman study on the speciation of copper cyanide complexes in highly saline solutions

Previous studies have established that the following three copper(I)-cyanide complexes form in aqueous solution: [Cu(CN) 2] −, [Cu(CN) 3] 2− and [Cu(CN) 4] 3−. The distribution of these complexes in solution at equilibrium is highly dependent upon the CN/Cu molar ratio. The speciation of copper cyanide complexes in highly saline solutions is of interest to Australian mining companies because of the unusually highly saline process water used on the goldfields of Western Australia (ca. 200 g/l total dissolved solids). This study has used the vibrational technique of Raman spectroscopy to determine the effect of highly saline water on the equilibrium distribution of copper cyanide complexes in solution for various CN/Cu molar ratios. For the first time it has been shown that in highly saline solutions the equilibrium distribution of copper cyanide complexes changes significantly. It has been established that [Cu(CN) 3] 2− predominantly forms in highly saline solutions for CN/Cu molar ratios of 2.2 to 2.5, where previously it has been shown that both [Cu(CN) 2] − and [Cu(CN) 3] 2− exist in non-saline solutions. Furthermore, in saline solutions containing an excess of cyanide (ca. 200 mg/l) only [Cu(CN) 4] 3− exists in solution and the formation of [Cu(CN) 3] 2− has not been observed. This phenomenon has been used to explain the increased selectivity of ion exchange resins for gold cyanide in highly saline solutions.

The effect of salinity on the capacity and selectivity of ion exchange resins for gold cyanide

Despite the success of several resin-in-pulp pilot plant operations in the Western World and large scale plants in the former Soviet Union the process of extracting gold from slurries using ion exchange resins is yet to gain recognition as a viable alternative to the carbon-in-pulp process. An experimental research program has investigated the potential use of anion exchange resins containing a variety of quaternary ammonium functional groups in highly saline process water such as that found in Western Australia. The effect of univalent and bivalent ions on gold adsorption has been studied. It was shown that the selectivity of the resin for gold cyanide was enhanced with increasing ionic strength. It has been proposed that the degree of hydration, polarisation and size of the adsorbing species are factors that contribute to the observed change in selectivity of the ion exchange resin at different salinity. It was observed that in highly saline solutions copper cyanide did not load significantly on any of the experimental resins studied. Furthermore, it has been shown that an existing commercial non-selective resin loads no significant amount of copper cyanide under saline conditions. It is proposed that the apparent change in selectivity of resins for gold cyanide is caused by anions that have a stronger affinity for the resin in these highly non-ideal solutions as well as a possible change in the distribution of copper cyanide complexes in solution. The results of this study demonstrate that the selectivity of ion exchange resins in highly saline water is significantly improved and as a consequence the resin-in-pulp process may be more efficient than carbon-in-pulp in process streams of high salinity.

Nitrate Selectivity of Ion-Exchange Resins and of Their Model Compounds. II. Viscosity and Density of Benzyltrialkylammonium Salts in Aqueous Solution and 14N N.M.R. Relaxation of the Nitrate Ion

The densities and viscosities of benzyltrialkylammonium chlorides and nitrates were determined in aqueous solution; the alkyl substituents were methyl, ethyl, propyl , butyl and pentyl . The concentration dependence of the 14N nuclear spin relaxation of the nitrate ion was used to find ion pair association constants for comparison with those derived from conductivity measurements (Part I). Density measurements were used to determine partial molar volumes, and viscosity measurements to find hydrodynamic volumes of the solutes. With the assumption of additivity of ionic volumes, cationic volumes calculated from the two series of chloride and nitrate salts agreed well. The increase in the ratio of hydrodynamic to partial ionic volumes with increasing chain length of the alkyl substituent was interpreted as a corresponding increase in hydrophobic hydration.

Nitrate Selectivity of Ion-Exchange Resins and of Their Model Compounds. I. Conductance Measurements on Benzyltrialkylammonium Salts

The concentration dependence of the conductance in aqueous solution of a series of benzyltrialkylammonium chlorides, nitrates and sulfates was measured. The n-alkyl substituents in this series were methyl, ethyl, propyl , butyl and pentyl. The conductances of the chlorides, nitrates and sulfates fit satisfactorily the electrostatic ion pairing models relevant to 1 : 1 and 1 : 2 electrolytes. The extent of ion pairing is small in all the solutions studied but consistently larger for nitrates and sulfates compared with chlorides. The dependence of the association constants on the alkyl substitutents shows different trends for the monovalent anions compared with the sulfate salts.

A look at contemporary ion chromatography

The principles and historical development of ion-exchange chromatography are discussed briefly. Modern ion chromatography includes ion-exchange, ion-pair, ion-exclusion and the chromatography of ion—organic complexes. Each is explained briefly. The major detection systems for ion chromatography are outlined: conductivity (suppressed and non-suppressed), direct and indirect spectrophotometry, spectrophotometry with a post-column reactor, electrochemical, and differential refractometry. The question of isocratic vs. gradient elution is examined briefly. Recent studies on the selectivity of ion-exchange resins are presented. Several examples are given of recent separation methods from the author's laboratory. These include the separation of weak acids by ion-exclusion chromatography, the use of additional ion-exchange columns to enhance the detection of carbonic acid by conductivity, and the determination of metal cations by complexation and subsequent chromatographic separation.

Tissue and regional distribution of cysteic acid decarboxylase. A new assay method.

A sensitive and rapid assay method method for cysteic acid decarboxylase was develped which combined the selectivity of ion exchange resin (a complete retention of the substrate, cysteic acid, and exclusion of the product, taurine) with the speed of a vacuum filtration. The synthesis and purification of 35S-labeled cysteic acid were described. The validity of the assay was established by the identification of the reaction product as taurine. With this new method, the decarboxylase activity was measured in discrete regions of bovine brain. Putamen had the highest activity, 172 pmol taurine formed/min/mg protein (100%), followed by caudate nucleus, 90%; cerebral cortex, 82%; hypothalamus, 81%; cerebellar cortex, 79%; cerebellar peduncle, 59%; thalamus, 42%; brain stem, 25%; pons, 10%; and corpus callosum, 3%. The decarboxylase activity in various mouse tissues was also determined as follows: liver, 403; brain, 145; kidney, 143; spinal cord, 59; lung, 21; and spleen, 10 pmol taurine formed/min/mg. No activity could be detected in skeleton muscle and heart, suggesting a different biosynthetic pathway for taurine synthesis in these tissues. The advantages and disadvantages of the new assay method are also discussed.

Distribution and tissue specificity of 4-aminobutyrate-2-oxoglutarate aminotransferase.

A rapid and specific method for assaying 4-aminobutyrate-2-oxoglutarate aminotransferase was developed. The method was based on the selectivity of ion exchange resin and the speed of vacuum filtration. With this new method, the aminotransferase activity in various tissues has been determined as follows: brain, 10.2; spinal cord, 11.8; liver, 5.7; kidney, 4.6; heart, 0.5; lung, 0.4 nmol glutamate formed/min/mg. No activity could be detected in muscle preparations. When the aminotransferases were tested with the antibody against the purified 4-aminobutyrate aminotransferase from brain, no difference could be detected among brain, spinal cord, and kidney preparations as judged from the results of immunodiffusion, inhibition of enzyme activity by antibody, and microcomplement fixation. It is concluded that 4-aminobutyrate aminotransferases from various tissues of the mouse are probably identical or closely related.

Interrelation of Swelling and Selectivity of Ion-Exchange Resins. II. Relation between Swelling and Exchange Isotherms of a Sulfonic Resin: Alkaline and Alkaline-Earth Counterions

Abstract The swelling of a sulfonic ion exchange resin (ES 28; 8 % divinylbenzene) was measured for hydrogen, alkaline, and alkaline-earth counterions in water, or in equilibrium with solutions of the corresponding chloride, and also for mixed forms. Compared with the (1 M) isotherms, the monomonovalent biionic mixed forms show linear variations of swelling with composition and verify the Rice and Harris model. For monobivalent biionic forms, the equal swelling-equal affinity relationship is only verified at high solution concentrations.

Interrelation of Swelling and Selectivity of Ion-Exchange Resins. I. Determination of Swelling of Sulfonic Resins in Water

Abstract The volume of wet ES 28 and C 25 sulfonic ion exchange resin beads was determined by pycnometry for the H+, Na+, and K+ foms in water, and the relative volume variations were determined by precisely measuring the variations of the bed height in columns when the resins were converted from one ionic form to another. A straightforward correlation was found for the ES 28 resin for which the packing factor β remains sufficiently constant with double-sieved, sufficiently homogeneously dispersed beads. The variations of β have to be taken into account for C 25.