Experimental Characterization and Modelization of Ion Exchange Kinetics for a Carboxylic Resin in Infinite Solution Volume Conditions. Application to Monovalent−Trivalent Cations Exchange (original) (raw)
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Fluid Phase Equilibria, 2005
The distribution of solutes and solvent between an aqueous solution of salt and an ion exchange resin has been measured at ambient temperature. The experiments have been performed for aqueous solutions of KNO 3 , KCl, Ca(NO 3 ) 2 and CaCl 2 in the concentration range of 0-3N. The absorption has been measured for three gel-type and three macroreticular resins with a degree of cross-linking varying from 10.5 to 18.5%. The experimental results have been modeled with the Extended UNIQUAC model combined with an elastic term taking the elastic properties of the resin structure into account. The model shows very good predictions with varying degree of cross-linking, and the deviations between model results and experimental data are all within the experimental error.
Chemical Engineering Science, 2005
A generalized theoretical model for the measurement of effective diffusion coefficients of heterovalent ions in macroporous ion-exchange resins by the zero-length column method was developed. The model includes the resistance to mass transfer both in the particle and in the film and described ion fluxes with Nernst-Planck equations. Equilibrium was described using the Langmuir type empirical equation. The values of intraparticle diffusivity of Cu 2+ , Cd 2+ , Zn 2+ , and H + on commercial Lewatit TP-207 were obtained by non-linear regression, these values agree fairly well with data reported previously in literature. The following trend was observed: D Cu > D Zn > D Cd .
Kinetics in a chelate ion exchanger—I. Theoretical analysis
Chemical Engineering Science, 1986
A kinetic model for sorption of metallic ions by a chelate ion exchanger is proposed in which the resistances of intraparticle diffusion and chelate complex formation reaction are both included. The Nernst-Planck equation is applied to the flux of ions in the resin particle. Analytical solutions are given for the limiting cases of diffusion control and reaction control, and numerical solutions are presented for the general case in which both resistances are significant. The analytical solution for diffusion control, which is based on the shrinking core model, gives the fractional exchange as a function of the difiusivities and valencies of the counter-ions. Uptake curves are calculated from the theoretical equations to show how the kinetics are influenced by the equilibrium constant, the diffusivity ratio of the counter-ions, the rate constant for the chelate complex formation reaction and the ionic valencies. The range in which the analytical solutions can be considered as an acceptable approximation is given.
Multicomponent equilibria on ion-exchange resins
Fluid Phase Equilibria, 1996
A model based on the mass action law for the prediction of multicomponent ion exchange equilibria is developed. Ideal behavior for both the solution and the solid phase and the existence of a distribution of functional groups with different adsorption energies (and then equilibrium constant) are assumed. The parametric behavior of the model is analyzed by considering the ion exchange equilibria between both homovaient and heterovalent ions. The reliability of the model, which is characterized by two parameters for each binary system, is tested by comparison with experimental results for inorganic species as well as for several amino acids on strong acid cation exchange resin. It is shown that ion exchange in system involving NC counterions can be predicted from the knowledge of the experimental behavior of only (NC-1) binary systems, thus in agreement with the so called triangle rule.
Chemical Engineering Science, 2004
A generalized theoretical model for the measurement of e ective di usion coe cients of heterovalent ions in ion exchange resins by the zero-length column method was developed. The model included the resistance to mass transfer both in the particle and in the ÿlm and described ion uxes with Nernst-Planck equations. Equilibria were described using a model based on the mass action law. The values of intraparticle di usivity of Cu 2+ , Cd 2+ , Zn 2+ , and H + on commercial Amberlite IR-120 were obtained by non-linear regression, these values agree fairly well with data reported previously in literature. The following trend was observed: DCu ¿ DZn ¿ D Cd .
Kinetics of ion exchange accompanied by neutralization reaction
AIChE Journal, 1988
Ion exchange accompanied by a neutralization reaction has been analyzed for the general cases where the bulk solution contains a neutral salt and an acid or a base, e.g., [R-HI + (NaCI + NaOH). Both intraparticle and liquid film diffusion are considered. The Nernst-Planck equation was applied for the fluxes of the ionic species in the liquid film and the resin phase with a mobile reaction plane in the liquid film. When the solution contains acid or base more than 50%, the exchange rate is approximated by the case for pure acid or base solution: the reaction plane is located at the solid / liquid interface. When the solution contains acid or base less than 50% (this situation is generally encountered in the case where a neutral salt flows through a mixed bed of OH-form and H-form resins), the mobile reaction plane should be considered. When the ratio of intraparticle diffusion resistance to liquid diffusion resistance defined in the text is larger than 2, the exchange rate can be approximated by intraparticle diffusion control. The larger the ratio, the faster the reaction plane moves to the resin particle surface. Experimental uptake curves for the ion exchange systems [R-HI + (NaCI + NaOH) and [R. OH] + (NaCI + HCI) confirm the above conclusions.
The Chemical Engineering Journal, 1988
Intraparticle ion-exchange mass transfer in ternary systems has been analysed according to the Nernst-Planck equation. T?&W&'LC& WLR@Z?%%~~ CUMXML~~~'~Y~ pT+Ofiles and electric potential profiles for the (H'-Na+-Zn") system have been derived and discussed in relation to changes with time in the experimental mean concentrations in the resin phase. In the [R-H] + &V~.0~ f ZX&VD~}~> ~'&?m A?& &G&9 IA!-Na] + (HNO, + Zn(N03)2} system (adsorption process), She concentration profiles of Na+ and H+ each respectively showed a peak: ihe faster ion in the Liquid phase was transported against its concentration gradient ibecause of the eIe&icpotentialgradient. In the [R-Zn] + {HNO, + NaNOJ and [R l NQ + R l Zn ] + HiV03 systems, no peak ap-Ipeare& in the concentration propies. TRese results agree wittr the trend in the ex_oerimentul mean concentrations of the ions mtth time. Since it appeared that the use of the Nernst-Planck equation, with the assumptions of constant self-diffusivities and of constant particle diameter, caused very little error, this simple theory should be useful for estimating ion-exchange rates in ternary systems.
Reactive Polymers, 1993
The surface complexation theory considers the sorption of ions as a local equilibrium reaction, which is caused by the amphoteric behaviour of the surface. Application of this theory to exchange equilibria with ordinary and chelating weak-acid ion exchange resins which can release protons has opened the way for a comprehensive description. Binary equilibria are described by a logarithmic equilibrium parameter, which is a linear function of the composition of the resin phase. Multicomponent equilibria are considered as a superposition of several binary equilibria. The approach considers the pH-dependent dissociation of functional groups. Furthermore, chemical reactions in the liquid phase in which exchangeable species are involved, can readily be taken into account.
A New Model for the Simulation of Ion Exchange Equilibria
Industrial & Engineering Chemistry Research, 1995
A model based on the mass action law for the prediction of multicomponent ion exchange equilibria is developed by assuming ideal behavior for both the solution and the solid phase, and the existence of a distribution of functional groups with different adsorption energies (and then equilibrium constants). The reliability of the model, which is characterized by two parameters for each binary system, is tested by comparison with a remarkably large set of literature experimental data. It is shown that ion exchange equilibria in systems involving a total number of N , counterions can be predicted from the knowledge of the experimental behavior of only (N,-1) binary systems, thus in agreement with the so-called triangle rule. This greatly reduces the experimental and modeling effort needed to develop a multicomponent model with respect to other approaches which require the investigation of all possible pairs of counterions present in the system, i.e., N&N,-1)/2 binary systems.
Absorption of water/methanol binary system on ion-exchange resins
The Canadian Journal of Chemical Engineering, 2010
Polymeric ion-exchange resins are widely used in important industrial processes for both separation and reaction applications. Due to their particular cross-linked structure, these materials are subjected to a remarkable swelling phenomena when are contacted with polar solvents like methanol or water. The high liquid volume retained and the selectivity towards the absorption of particular substances can results in a significant alteration of the liquid reactive mixture composition when polymeric resins are used as catalysts. In this situation the bulk liquid phase and the absorbed phase are different in composition and the kinetics could be strongly affected as the chemical reaction occurs mainly on the internal surface of the resin particles. The correct description of the kinetics for such systems requires additional information regarding the phase partitioning of the various components between the liquid and the absorbed phase. In this work, experimental absorption data, concerning the binary system methanol-water partitioned in the presence of Amberlyst 15 and Relite CFS, two sulphonic ion-exchange resins, typically used as esterification catalysts, are presented. This mixture is of great interest in the esterification reaction of free fatty acids (FFAs) that is nowadays considered a suitable pre-treatment of cheap feedstock for biodiesel production. The data collected on binary systems water-methanol, at different temperatures, have then been successfully correlated by a multicomponent competitive absorption model that could be useful, in the future, in a wider kinetic study. The same model has also been tested on data taken from the literature. Les résineséchangeuses d'ions polymériques sont largement utilisées lors de processus industriels importantsà la fois pour les applications de séparation et de réaction. En raison de leur structure réticulée particulière, ces matériaux sont soumisà un remarquable phénomène de gonflement lorsqu'ils sont en contact avec des solvants polaires comme le méthanol ou l'eau. Le volume liquideélevé retenu et la sélectivité vers l'absorption de substances particulières peuvent menerà une modification considérable de la composition du mélange réagissant liquide lorsque des résines polymériques sont utilisées comme catalyseurs. Dans cette situation, la phase liquide volumique et la phase absorbée sont différentes sur le plan de la composition et la cinétique pourraitêtre fortement touchée alors que la réaction chimique se produit principalement sur la surface interne des particules de résine. La bonne description de la cinétique pour de tels systèmes exige des renseignements supplémentaires sur la séparation des phases des divers composants entre la phase liquide et la phase absorbée. Dans ce travail, les données d'absorption expérimentales sont présentéesà propos du système méthanol-eau séparé, en présence d'Amberlyst 15 et de Relite CFS, deux résineséchangeuses d'ions sulphoniques typiquement utilisées comme catalyseurs d'estérification. Ce mélange est d'un grand intérêt pour la réaction d'estérification des acides gras libres (AGL) qui est maintenant considérée comme un prétraitement approprié de la matière biologique bon marché pour la production de biodiésel. Les données recueillies sur les systèmes binaires eau-méthanol,à différentes températures, ontété corrélées avec succès par un modèle d'absorption compétitiveà composants multiples qui pourraitêtre utile,à l'avenir, dans uneétude cinétique plus approfondie. Le même modèle aégalement eté misà l'essai avec des données prises dans la littérature.