1.1 Introduction to Ion Exchange and Ion Exchangers

Dorfner, Konrad

doi:10.1515/9783110862430.7

Cited by 15 publications

(11 citation statements)

References 116 publications

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“…This is problematic, for as Reynolds pointed out, "the best solid phase activity model is still being debated, and may not be the same for all systems" (Reynolds, 2009). To circumvent this difficulty, it is customary in engineering applications to use molar concentrations, assume that all activity coefficients are equal to unity, and then calculate a selectivity coefficient, K, for the system (Dorfner, 1991a). It should be noted that since activity coefficients are being ignored, large errors can be introduced if one were to extrapolate equilibrium values beyond the region tested.…”

Section: Introductionmentioning

confidence: 99%

Development of an engineering model for nickel loading onto an iminodiacetic resin for resin-in-pulp applications: Part I—Method development and discussion of rate limiting factors

McKevitt

Dreisinger

2012

Hydrometallurgy

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Section: Introductionmentioning

confidence: 99%

Development of an engineering model for nickel loading onto an iminodiacetic resin for resin-in-pulp applications: Part I—Method development and discussion of rate limiting factors

McKevitt

Dreisinger

2012

Hydrometallurgy

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“…Resins were conditioned by following a standard procedure [15]. The conversion of the resins to the desired ionic form was carried out in a reactor under batch conditions.…”

Section: Resins Loadingmentioning

confidence: 99%

The effect of resin particle size on the rate of ion release: interactions in mixed bed systems

Torrado

Valiente

2004

Analytical and Bioanalytical Chemistry

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The aim of the present study is to evaluate the influence of resin particle sizes on the rate of ions release from a mixture of ion-exchange resins (named NMTD) which supplies calcium, fluoride, and phosphate ions as the main mineral content, and to elucidate the different phenomena taking place through the related ion-exchange process. The final goal of the study, related to dental application (enamel restoration), is to limit the particle size range, since the rate of ion release is a key parameter in the successful achievement of such objective. Weak-type ion-exchange resins, loaded with the appropriate ions, were ground and sieved into granulometric fractions of bead diameters of 0.1-0.075, 0.075-0.063, and 0.063-0.05 mm. Particle size was controlled by a laser diffraction particle distribution analyzer. The experiments on the kinetics of ions release were carried out under batch conditions in artificial saliva desorption solution thermostatized at 37 degrees C. The release of Ca(2+) and F(-) was determined by corresponding ion-selective electrodes automatically controlled, whereas H(2)PO(4)(-) was measured spectrophotometrically by the inductively coupled plasma-optical emission technique (ICP-OES). The results of this study show that the process of ion-exchange for the different particle size fractions of resins is critical for the study of the kinetics release of the ions immobilized in the corresponding mixed bed polymeric matrices. In fact, despite the apparent narrow range of particle sizes of the mixed bed systems studied, appreciable differences in the rate of ions release are obtained. Since the ion release rate is depending on the contact surface, an increase of factor of 2 in particle size represents an increase of an order of magnitude of the resin contact surface due to the resin porosity. In this concern, it has been observed that the rate of ions release increases when particle size decreases. The interactions occurring during the ion release from the mixed bed resins (containing calcium-, fluoride-, and phosphate-loaded resins) can be interpreted by the following phenomena: H(2)PO(4)(-), which hardly modifies its rate of release in the presence of Ca(2+) and F(-) in the mixture, promotes a considerable increase in the rate of Ca(2+) release due to the formation of a calcium dihydrogen phosphate soluble complex. F(-) also produces an acceleration in the rate of Ca(2+) release due to the formation of solid CaF(2 )on the surface of cationic resin particles, which in contrast leads to a decrease in the rate of F(-) release.

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“…23 The conversion of the resins to the desired ionic form was carried out in columns under dynamic conditions by flowing aqueous solutions of the corresponding concentrations through the resin bed. After complete loading, the resin phase was successively washed with water to remove the excess of electrolyte solution, quantitatively removed from the column and separated from water by filtration, followed by drying in an oven (60-70…”

Section: Resins Loadingmentioning

confidence: 99%

“…24 A weighed portion of each resin was introduced in a 10 cm column (8 mmØ) and the counterion of interest was eluted with HCl in the case of the cationic resin and with NaNO 3 in the anionic one. Eluate was collected periodically in volumetric flasks and analyzed.…”

Section: Resins Capacitymentioning

confidence: 99%

“…25 A small portion of loaded resin was introduced into a column connected to a thermostat and a solution of artificial saliva KCl and 0.5g dm −3 NaCl, pH = 5.5) passed through the resin bed at a high flow rate (∼30 cm 3 min −1 ). All the resulting eluate was collected in volumetric flasks, analyzed and these analytical data transformed to the degree of conversion, , by using the equation:…”

Section: Ion Exchange Kineticsmentioning

confidence: 99%

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Calcium and fluoride release from ion exchange polyphasic systems

Torrado

Valiente

2003

J of Chemical Tech & Biotech

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The present study concerns the kinetics of ion exchange accompanied by CaF 2 precipitation in tri-phasic and quadri-phasic systems involving a weak base anionic exchanger and a carboxylic cationic exchanger in the F − and Ca 2+ forms, respectively, in contact with a solution of artificial saliva. It was shown that in both systems the rate of Ca 2+ release from the cationic exchanger is much lower than that of F − from the anionic one. The rate of release for both ions, controlled by intraparticle diffusion, has been characterized by a Fick's law model. The kinetic parameters of effective rate of release (B) and diffusion coefficient (D) of the respective ion in the resin phase depend on the type of resin and the presence of different numbers of phases. The amount of the precipitate crystallizing on the surface of the resin beads depends on the type of the ion exchange resin, its particle size and on the ratio of resin components. By varying this ratio and the particle size of the ion exchangers it is possible to accomplish the precipitation mostly on the larger surface of the ionic exchanger.

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1.1 Introduction to Ion Exchange and Ion Exchangers

Cited by 15 publications

References 116 publications

Development of an engineering model for nickel loading onto an iminodiacetic resin for resin-in-pulp applications: Part I—Method development and discussion of rate limiting factors

Development of an engineering model for nickel loading onto an iminodiacetic resin for resin-in-pulp applications: Part I—Method development and discussion of rate limiting factors

The effect of resin particle size on the rate of ion release: interactions in mixed bed systems

Calcium and fluoride release from ion exchange polyphasic systems

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