Mass Transfer and Kinetics of Ion Exchange
Abstract
These papers were written by leading scientists and technologists working in the field of ion exchange, and they discuss the synthesis, equilibria, transport phenomena, kinetics and design of ion exchange resins and membranes, both systematically and progressively. This volume also reflects recent developments in the field, with sections dealing with novel areas of application for ion exchange, such as, pollution control, energy conservation and the recovery and recycling of non-renewable materials.
Chapters (14)
Ion exchange is a phenomenon which has been around on Earth from very early times, perhaps something of the order of 109 years, and in the Galaxy probably for a trifle longer. Recognition of the phenomenon (in soil) is conventionally attributed to Way, and Thompson, about 130 years ago (1); though it may well have been used by Moses on the bitter waters of Marah several millenia before (2), this was on Divine recommendation (3) and inadequately documented.
The ideal case of an ion-exchange resin is that of a homogeneous isotropically-swelling gel with a regular distribution of charged functional groups throughout the particle. For convenience, the particle geometry should be spherical, since this requires only one parameter for its definition, and of course each particle should have the same radius. The charged groups should each have a single counterion, and the Donnan membrane effect should permit virtually no invasion of external electrolyte. When considering the exchange of ions in such a system, both the original counterion and the ion for which it exchanges should be of the same size, hydration, and valency, and should have identical diffusion coefficients both in the external solution, and inside the homogeneous gel phase. Again for convenience we should wish the resin to show no preference for one ion rather than the other.
The discussion of a topic such as the acrylic-based ion exchange resins before a group such as the NATO/CNR course requires some background indoctrination in order that a proper perspective be developed and maintained.
The development of a model for the prediction of ion-exchange selectivity has been described in detail. Cation-exchange selectivity in aqueous media is shown to be determined by the difference in interaction of various cations with water. The difference in selectivity is resolvable through the analysis of osmotic coefficient data obtained for the pure ionic forms of the linear polyelectrolyte analogue of the cross-linked cation exchange resin. The utility of this approach has been tested and is shown to be applicable to a weakly dissociated cation-exchange resin as well as to the fully dissociated one. The insight gained from this study is believed to be useful to the analysis of mass transport phenomena in cation-exchange materials.
The purpose of this paper is to review the fundamental principles underlying ionic selectivity in “macroscopic” systems such as ion exchangers and ion exchange membranes, whose counterion concentrations are constrained by electroneutrality. I will bring up to date an earlier theory of equilibrium selectivity (1,2) so as to include the considerable progress that has occurred since 1961, particularly for species other than the Group Ia cations. However, I will not deal in detail with kinetic aspects of selectivity since these are more appropriately covered elsewhere in the context of biological membranes (3) which, because of their extreme thinness, can deviate from electroneutrality locally. Indeed, much of the progress in selectivity has occurred in the field of “microscopic” (e.g., biological) membranes, whose thickness (<100 Angstroms) is small relative to the Debye length so that the usual electroneutrality constraint does not apply locally. This has the consequence that, whereas the sites of macroscopic systems are always effectively “saturated” (i.e., completely occupied), those in biological membranes are often empty, so that they are not necessarily constrained to strict ion exchange behavior and are said to obey “independence” (3).
The theory of ion exchange kinetics has come a long way from its origins oven, a century ago but still has muck distance to cover. In the earliest speculations about “base exchange” in soils, forces other, than those of inanimate nature were suspected to have their part. This view was superseded by an almost equally speculative one regarding ton exchange as a chemical reaction of a kinetic order corresponding to its stoichiometric coefficients. Only the concentrated, extensive, theoretical and practical studies in connection with the Manhattan project in World War II revealed ion exchange as essentially a statistical redistribution of ions by diffusion, with a rate limited by mass transfer resistances in either the particle or the external fluid. The next step ahead ms taken in the 1950’s with the realization that ions, as carriers of electric charges, are subject to the electric field their own diffusion generates. In other words, they obey the Nernst-Planck equations more closely than Fick’s simpler laws. Actually, this was a rediscovery since the Nernst-Planck equations had been proposed as early as 1913 for ionic diffusion in glasses and had become stock in trade of membrane science ever since Teorell and K. H. Meyer published their pioneering studies in 1935.
A kinetic investigation on a certain ion exchange process may be aimed at different objectives. For the pure researcher it may be finalized either to ascertain the kinetic mechanism in a new system or, more generally, to confirm experimentally the existing rate theories, still largely relying on hypotheses more than on facts. The applied researcher may desire to know, at a certain stage of development of a new application (usually after the equibrium evaluation), how the kinetic feature of the resin investigated compares with its selectivity performance. Finally, the design engineer may need to determine experimentally mass transfer coefficients and other kinetic parameters necessary to design an ion exchange plant.
A common question pertinent to many of the talks presented at this meeting is the following: What is the range of validity of model theories, of kinetic descriptions, of the NERNST-PLANCK equations, of STEFAN-MAXWELL equations, of the variational principle proposed by DICKEL etc.? The most general formalism we have today is that provided by the so-called non-equilibrium thermodynamics. The fact it uses only general and unexceptionable “first principles” such as the conservation of mass, momentum and energy and the second law of thermodynamics is at once its strength and weakness; i.e., although it is of great generality, it yields only minimal information in a specific problem.
Basic concepts, including the role of equilibrium, stoichiometric, and rate relations on the performance of fixed, monovariant sorption beds are reviewed, with emphasis on simple, idealized, linear-driving force rate models. A novel method is presented for combining film- and particle-diffusion mechanisms. The number of variables involved is reduced by combination into dimensionless groups, and the types of column performance are illustrated by generalized time-distance plots with concentration contours. A method for deriving rate constants and mechanism parameters from an ionexchange isotherm and a constant-pattern effluent-concentration history is presented. Calculation methods are classified and outlined for the axis intercepts, the noncoherent, and the coherent portions of constant and proportional-pattern concentration contours. Column design is illustrated by example.
Ion exchange is an old process as we can believe from Aristotle’s statement that water loses part of its salt when flowing through sand. However, only in 1850, Thomson and Way stated the principles governing the interaction of fertilizers with soil (exchange Ca++/NH
4+.)and the first industrial unit for water softening using aluminosilicates was developed by Gans fifty years later. A spectacular development began in 1935 with the synthesis of organic ion exchanger resins by Adams and Holmes. The 1950 were the “Golden Age of Ion Exchange” (1) because this operation was considered as an unit operation as a consequence of the work of Vermeulen et al., at Berkeley.
A comprehensive treatment of mass transfer in ion exchange and adsorption processes, based, among others, on Thomas(l) and De Vault(2) theories, has been given by Hiester, Vermeulen and Klein(3) for continuous fixed bed and batch operations, under both favorable and unfavorable equilibrium conditions. Complete analytical solutions for real systems, however, were provided only when limiting boundary conditions are assumed (e.g., constant separation factor, linear equilibrium, etc.).
The name “ion-exchange membranes” arose because the first such articles were made by preparing in sheet form the conventional organic ion-exchangers available 30 years ago. The purpose of these membranes is not to exchange ions but to transmit them in a controlled way. The name “selectively ion-permeable membranes” would indicate their function more clearly. From these origins the polymer chemistry of ion-exchange membranes has become more sophisticated and this article will consider some of these chemical developments. To understand them in context it is necessary to say something first about the physical chemistry of membranes and to outline some processes in which they are either in use already or under serious consideration.
The first investigations of Boyd (1) concerning the kinetics of ion exchange are based on a solution of the second Fick’s law. Thereby the boundary conditions were taken into account by the well known method developed by Fourier in his famous book “Theorie Analytique De La Chaleur” (1822) (2).
Accurate measurements of the isothermal transport of ions and of water across a synthetic ion-exchange membrane were made. A feedback method was used, in which electrolyte transport is determined by the amounts of electrolyte and water respectively that have to be added to and/or withdrawn from the half-cells separated by the membrane so as to keep the solution concentrations constant. This automatic feedback is actuated by conductivity probes.
Four groups of experiments, leading to the measurement of eight independent transport coefficients, could be readily made in the “concentration-clamp” apparatus developed in our Laboratory, viz. (a) electric conductivity, (b) hydraulic permeability and streaming potential, (c) electromigration and electroosmosis, and (d) osmosis, dialysis, and membrane potential. [The ninth parameter (“degree of hyperfiltration”) cannot be measured with sufficient accuracy in the existing” “concentration-clamp” apparatus.] In systems of membranes separating two dilute sodium-chloride solutions, in which silver-silver chloride electrodes are immersed, two reciprocity relations could be checked.
It was found that these two reciprocities hold for a cationexchange membrane (CL-25T, Tokuyama Soda Co., Tokuyama City, Japan); the highest solution concentration was 0.5N NaCl. Comparison of the conductance coefficients to those of C-103 (American Machine and Foundry Co., Stamford, Conn.), measured previously, indicates higher permeability characteristics for CL-25T.
... Mathematical modeling of kinetics and mass-transfer in electrochemical events, even in their simplest statement, generally consists of dealing with various physico-chemical parameters, as well as complicated mathematical problems. In this study we analyse the matematical and numerical models of mass and charge transport in a controlled potential experiment in electrochemistry, called chronoamperometry [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. In the case of two-species (oxidized and reduced species) migrating under the influence of the electric field, the mathematical model and governing equations are derived in [1]. ...
... Evidently the backward problem (10) is well-defined due to the given finel condition ϕ(x, T ) = 0. Let us calculate the right hand side terms of (10). Due to the boundary condition ϕ(0, t) = 0, t ∈ (0, T ] we have ϕ t (0, t) = 0 Taking into account the initial and boundary condition in (8) and (10) the integral identity (9) becomes to the following identity: ...
The mathematical model related to controlled potential experiments in electrochemistry is studied. Ion transport is regarded
as the superposition of diffusion and migration under the influence of an electric field. Modeling of the experiment leads
to the nonlocal identification problem for nonlinear parabolic equation. It is shown that in some cases the nonlocal identification
problem can be transformed to an initial value problem for nonlinear parabolic equation. The finite diference approximation
of this problem, with the appropriate iteration algorithm, is derived. Based on these algorithms the solution of the identification
problem is presented. The obtained results permits one to derive the behaviour of the current response Ic(t){\mathcal{I}}_c(t) , depending on time, also the relationship between the current response Ic(t){\mathcal{I}}_c(t) and Gottrellian IG{\mathcal{I}}_G is obtained in explicit form. An influence of the valences oxidised and reduced species is also analyzed.
... This technique has been used to determine free Cd and Pb ions in natural samples such as freshwater rivers, and, due to the small volumes of the donor and acceptor solutions, equilibrium was reached in 6 h, much faster than the usual 36 h deployment. Although the transport of ions through ion exchange membranes has been extensively studied [4,[28][29][30][31], no work has exploited this process in analytical applications. In this work, the dynamic information contained in the transient metal flux was considered and compared with the equilibrium situation. ...
The Donnan membrane technique (DMT), in which a synthetic or natural solution (the “donor”) is separated from a ligand-free solution (the “acceptor”) by a cation-exchange membrane, is a recognized technique for measuring the concentration of a free metal ion in situ, with coupling to electrochemical detection allowing for the quantification of the free metal ion directly on site. However, the use of the DMT requires waiting for the free metal ion equilibrium between the donor and the acceptor solution. In this paper, we investigated the possibility of using the kinetic information and showed that non-equilibrium experimental calibrations of Cd and Pb with the ISIDORE probe could be used to measure free metal concentrations under conditions of membrane-controlled diffusion transport. The application of this dynamic approach made it possible to successfully determine the concentration of free Cd in synthetic and natural river samples. Furthermore, it was found that the determination of free Cd from the slope was not affected by the Ca concentration ratio between the acceptor and donor solution, as opposed to the traditional approach based on Donnan equilibrium. This ISIDORE probe appears to be a promising tool for determining free metal ions in natural samples.
... 56 Using a fundamental approach for fixed bed separation processes, breakthrough profiles were normalized using the throughput ratio. 57,58 A throughput ratio of 1 corresponds to the stoichiometric throughput if there was no mass transfer zone (MTZ), calculated by dividing the total mass of chromium removed at complete breakthrough by the raw water concentration. When normalized to stoichiometric throughput, breakthrough profiles collapsed on each other (Fig. 1B). ...
Ion exchange is effective for hexavalent chromium removal from drinking water sources, but non-target anions (i.e., arsenic, vanadium, and uranium) that co-occur in water sources must be assessed to inform,...
... Consequently, the most commonly used resins in uranium recovery processes were strong base anion exchange resins containing quaternary ammonium groups (Streat et al., 1987). Based on this fact, many researches have reported the application of several anion exchange resins upon the sulfate leach liquors such as Amberlite IRA-400 (Guettaf et al., 2009, andKhawassek 2014), Amberlite IRA-402 (Abdel Aal 2014), AMn resin (Mirjial 2007), Amberlite IRA-425 (Abd El-Ghany et al., 1994), Dowex-IX8 (Barnes et al., 1974), Ambersep 920U Cl, and Amberlite IR-118H (Cheira 2014, Liberti et al., 1983, and Kilislioglu et al., 2003 for uranium recovery from its solutions. On the contrary, Sadeek et al. was used amine functionalized glycidyl methacrylate to extract uranium species in the nitrate media (Sadeek 214 EBRAHIM A. GAWA D et al., 2014). ...
The present work aims to study the adsorption behavior of uranium ions from nitrate solutions using the strong acid cation exchange Amberlite IR120 resin. Batch shaking sorption experiments are carried out to evaluate the performance of the studied resin in the uranium adsorption. The adsorption parameters including contact time, pH, initial uranium concentration and temperature have been optimized. The physical parameters including the adsorption kinetics, the isotherm models and the thermodynamic data have also been determined to describe the nature of the uranium adsorption by the investigated resin. The modellated data has been found to agree with both the exothermic pseudo first order reaction and the Langmuir isotherm. The applied procedure was used for uranium ions removal from scrub and raffinate liquors.
... Kinetic investigation on a certain ion exchange process may be undertaken either to ascertain the kinetic mechanism in a new system or, more generally, to confirm experimentally the existing rate theories or one may desire to know, at a certain stage of development of a new application, moreover to determine experimentally mass transfer coefficients and other kinetic parameters necessary to design an ion exchange plant (21) . ...
The present work deals with the adsorption of uranium from sulfuric acid solution using the strong
base anion exchange Lewatit Mono Plus M500 (LMP) resin. Batch shaking sorption experiments are
carried out to evaluate the performance of (LMP) anion exchange resin in the uranium adsorption.
The adsorption parameters including contact time, pH, initial uranium concentration and temperature
have actually been optimized. The physical parameters including the adsorption kinetics, the isotherm
models and the thermodynamic data have also been determined to describe the nature of the uranium
adsorption by the LMP resin. The working resin has been found to agree with both the pseudo second
order reaction and the Langmuir isotherm.
... İyon değişim proseslerinde kullanılan reçinelerin belirli özelliklere sahip olması gerekmektedir. İyon değiştiricilerde aranan önemli özellikler; kimyasal, fiziksel ve ısıl kararlılık, kontrollü ve etkin değişim kapasitesi, homojenlik, hidrofilik yapı, hızlı iyon değişim ve rejenere imkânı olarak sıralanabilir [3]. ...
In water and wastewater treatment, ion exchange process is especially used to remove heavy metals and
elements leading to hardness. In general, polymeric resins produced synthetically are used in ion exchange
process. In that way, inorganic contaminants in water and wastewater can be removed by binding to functional
groups present in the resin structure. However, the cost of the synthetic ion exchangers, limits the wide range of
application of the method. On the other hand, even if natural zeolites, seen as an alternative to the synthetic
resins, are fall behind the synthetic resins in terms of the performance in the wastewater treatment applications,
they compensate the disadvantage with their low cost. Proliferation of the ion exchange applications in Turkey,
rich in resources of the natural ion exchanger zeolite minerals, will provide significant advantages in terms of
economy and accessibility. In the scope of the study, the most common zeolite types, used in ion exchange
applications, are investigated and some examples are given related to its applications in water and wastewater
applications.
Keywords: Ion exchange, wastewater treatment, zeolite
... 9−28 Most of the early developments in this area are based on the studies of absorption kinetics in ion-exchange resins. 10,22−26 The theory was subsequently extended to ionexchange membranes 1,6,[10][11][12]29 to elucidate the mechanism of ion transport through the membranes. ...
Ion exchange kinetics of a tracer ion (Cs+&Ba2+) in presence of a bulk ion (Na+/H+) has been measured in Nafion-117 membrane for a range of concentration of NaCl/HNO3 using non-stationary radiotracer method. A systematic increase in the ion exchange rate and decrease in the partition coefficients of the tracer ions between membrane and solution have been observed with the increase in bulk ion concentration. The sigmoidal nature of experimental profiles indicates film diffusion controlled kinetics even for well stirred solutions. In absence of an existing analytical or numerical solution, a simple empirical approach has been proposed to find the variable membrane surface concentration; and has been used to solve the membrane diffusion equation by finite difference method. The fitting of the experimental curves with a single diffusion coefficient for Cs+/Ba2+ has been achieved. The exchange rate has been found to be independent of the stirring speed beyond a limiting speed.
... The advantage of IX over other methods such as solvent extraction or even precipitation is that ion exchange can still be viable when feed concentrations have dipped below the economic threshold of the other technologies. It is interesting to note that in some cases the lower the total concentrations of metals in an aqueous stream, the more efficiently an IX resin can perform (Liberti, L. 1983). ...
This paper provides an overview of the potential for recovery of value from contaminated mine waters and waste streams. It discusses various metal ions commonly found in acid mine drainage and other mine waters (mainly Co, Ni, Zn, and U) and evaluates at what concentration they become attractive to investigate for recovery using ion-exchange technology. Waste streams are often treated to achieve compliance with environmental legislation before discharge, but recovery of valuable materials from acid discharge waters can result in economic benefits as well; in certain cases, the recovery of such metals can actually cover the cost of capital and operation and provide an additional revenue stream to the mine. The economics depend on the nature of the valuable metals, their concentrations, and volumes required for treatment. Ion exchange is well established in mining and metallurgical processing as a primary purification technology, treating process streams in which the levels of valuable metals are relatively high. To recover these same metals from surface runoff, tailings, contaminated ground water or mine decant waters; they must be present at a certain level before it becomes worthwhile to fully investigate options for their recovery. We reviewed a number of valuable metals that are likely to be found in mine waters and, based on the capital and running costs, determined the capital payback period for varying contamination levels. Technical issues were discussed and their effect on the economics explored. Using the model developed, it is possible to show early on in a feasibility assessment whether there is economic benefit to the processing of waste water of a given composition from a mining operation. The specific case studies that informed the model are discussed.
... Apparently (Do, 1998), this hypothesis was put forward for the first time nearly one century ago by McBain on the basis of experiments with carbon (McBain, 1919). It was also first recognized by Boyd (Boyd et al., 1947) in the case of ion exchange (Liberti and Helfferich, 1983). In an article published in 1965, Helfferich started by stating: "It has long been known that ion-exchange rates are controlled by diffusion" (Helfferich, 1965). ...
The most popular formula used in the literature about liquid/solid adsorption kinetics to describe diffusion-controlled processes is the intraparticle diffusion (IPD) equation. However, this formula was introduced originally for pure diffusion. It does not account explicitly for the effect of adsorption (except in the limit of very low adsorbate concentration). In this work, the problem of diffusion-controlled kinetics is studied by using a diffusion-adsorption model which should hold when the solute concentration in the external solution is sufficiently high. The case of a finite amount of solute initially in the stirred batch adsorber is solved analytically. For short times, the formula for the uptake turns out to have the same form vs. time as the IPD equation. However, it also predicts a decrease of the fractional uptake with the initial bulk concentration, as observed in the literature, and it shows that the IPD diffusion coefficient is a lumped parameter depending on the experimental conditions. These theoretical results are used for a discussion of the IPD equation and for descriptions of experimental results taken from the literature. © 2016, Universidad Autonoma Metropolitana Iztapalapa. All rights reserved.
... Various methods exist for the removal of toxic metal ions from aqueous solutions (Bohdana et al., 2008;Delvaux et al., 2000;Crini et al., 2014;Helfferich et al., 1995;Pollution Databse, 2004;Weber et al., 2008). Ion exchange is widely used and with good performance in the removal and recovery of metals from natural water and industrial wastewater (Fu et al., 2014;Samarghandi et al., 2013). ...
The capacity of ion exchange resins, MN 500 and C100 H, for the removal of copper ions from aqueous solution has been investigated under different conditions, namely: initial solution pH, initial metal-ion concentration and contact time.
The adsorption of Cu(II) on these resins follows the first-order reversible kinetic. The film diffusion of Cu (II) in these ion
exchange resins was shown to be the main rate limiting step. The studies showed that these cation exchange resins can be used as efficient adsorbent material for the removal of Cu (II) from aqueous solutions. The adsorption process, which is pH dependent, shows maximum removal of copper in the pH range 2-7 for an initial copper concentration of 10 mg/L.
The adsorption rate constants for all these kinetic models have been calculated. Results showed that the intraparticle diffusion
and initial Cu(II) sorption into resins was the main rate limiting step. The uptake of copper by the ion exchange resins is reversible and thus has good potential for the removal/recovery of copper from aqueous solutions. After the experiments we concluded that such ion exchange resins can be used for the efficient removal of copper from water and wastewater.
... Thus, the total flux consists of a diffusion and a migration component. For more details about chronoamperometry, see, for example, [1,2]. The experiment was modelled in [3], where the authors derive a nonlinear non-self-adjoint parabolic equation and prove the existence of a similarity solution. ...
A numerical method for the solution of a parameter identification problem in a nonlinear non-self-adjoint two-point boundary value problem with an additional nonlocal condition defining the parameter is presented. The equation arises in the modelling of an experiment known as chronoamperometry for the study of kinetics and mass-transfer in electrochemical events. The algorithm is based on the reformulation of the identification problem as a. nonlinear fixed-point problem involving the concentration flux of the reduced species. The linearized boundary value problem is shown to have a unique solution with the unknown parameter uniquely determined by the flux. The linearized BVP is solved using finite differences and the fixed-point is found using the alpha-bisection method. The results of computational experiments are presented and their physical significance is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.
... Mathematical modeling of kinetics and mass-transfer in electrochemical events, even in their simplest statement, generally consists of dealing with various physico-chemical parameters , as well as complicated mathematical problems. In this study we analyse the matematical and numerical models of mass and charge transport in a controlled potential experiment in electrochemistry, called chronoamperometry1234567891011121314. In the case of two-species (oxidized and reduced species) migrating under the influence of the electric field, the mathematical model and governing equations are derived in [1]. ...
The mathematical models of the ion transport problem in a potential field are anayzed. Ion transport is regarded as the superposition
of diffusion and convection. In the case of pure diffusion model the classical Gottrell’s result is studied for a constant
as well as for the time dependent Dirichlet data at the electrode. Comparative analysis of the current response
ID=ID(t){\mathcal I}_{\rm D}={\mathcal I}_{\rm D}(t) and the classical Gottrellian
IG=IG(t){\mathcal I}_{\rm G}={\mathcal I}_{\rm G}(t) is given on the obtained explicit formulas. The approach is extended to find out the current response
Ic=Ic(t){\mathcal I}_c={\mathcal I}_c(t) corresponding to the diffusion-convection model. The relationship between the current response
Ic=Ic(t){\mathcal I}_c={\mathcal I}_c(t) and Gottrellian
IG=IG(t){\mathcal I}_{\rm G}={\mathcal I}_{\rm G}(t) is obtained in explicit form. This relationship permits one to compare pure diffusion and diffusion-convection models, including
asymptotic behaviour of current response and an influence of the convection coefficient. The theoretical result are illustrated
by numerical examples.
... The observed behavior is likely an example for a well known effect described as reaction-retarded diffusion [13]. ...
Most important properties of an ion chromatographic resin are influenced by the resin matrix, the type of functional group and the ion-exchange capacity. Highly crosslinked PS-DVB resins of 5 microm diameter have been functionalized by sulfoacylation, by sulfonation and by dynamic coating over a wide range of exchange capacities. These materials allow a study of the influence of different ion-exchange sites and capacities. The influence of the degree of functionalization on resin performance is completely reverse for sulfoacylated and sulfonated resins. The HETP values for all observed analytes (Cu, Pb, Zn, Ni, Co, Cd, Mn, Ca, Mg) in a tartaric acid elution system decrease for sulfoacylated resins with increasing capacity, for sulfonated resins with decreasing capacity. The performance of sulfoacylated exchangers is better than for dynamically coated ones and far better than for sulfonated resins. The performance of silica gel based cation-exchangers such as BioSil CAT is in most cases better than observed for sulfoacylated resins.
Seawater was investigated as an alternative regenerant source to conventional salt-imported brine solutions in an anion exchange process treating surficial Florida coastal groundwater for the removal of sulfate and organics. Bench-scale column testing revealed that filtered Sarasota Bay seawater efficiently regenerated the anion resin media; however, sulfate exchange capacity decreased by 8.42% compared with conventional 10% salt regeneration methods. Addition of 3% sodium chloride increased regeneration efficiency, reduced exchange capacity losses to 2.4% as compared to conventional 10% salt regeneration methods. Regeneration resulted in 2.13 mg/L of bromide leakage; however, addition of 3% sodium chloride to seawater reduced bromide leakage to 1.25 mg/L. A correlation between bromide exchange and the regenerant chloride-to-bromide molar ratio (CBMR) was observed, yielding less bromide exchange at higher CBMRs. Bromide adsorption followed pseudo 2nd order kinetics and chemisorption was the rate controlling step. Increasing the CBMR of the regenerant was found to shift adsorption behavior, allowing intra-particle diffusion to occur sooner. Bromide equilibrium appeared to follow a logarithmic decay as the CBMR of the regenerant increased. Intra-particle and film diffusion mechanisms were evaluated that indicated the presence of diffusion-based processes and more than one rate controlling step. An empirical function was derived to approximate bromide equilibrium adsorption in relation to a regenerant's CBMR. Seawater as a regenerant when enhanced with sodium chloride shows promise as an anion exchange regenerant; additionally, classification of a seawater regenerant's CBMR can provide insight into the kinetic and equilibrium relationships of bromide exchange.
Adsorption of the gadolinium from H2O and HCl solutions on the ion-exchange resin C100 is investigated. The experiments were carried out by varying the acidity of the liquid phase, the amount of sorbent, and the temperature. The maximal sorption of the ions Gd³⁺ is observed from the solution 0–0.2 M HCl under optimal conditions, the sorption reaches more than 99.5%. Sorption of Gd³⁺ on C100 from H2O solution occurs most intensively during the first 3 min then for 30 min the system smoothly comes to equilibrium. The maximal sorption capacity of the resin C100 amounted to 1.2 ± 0.1 mmol g⁻¹. The thermodynamic parameters of sorption: ΔG = − 24.20 kJ mol⁻¹, ΔS = − 90.27 J mol⁻¹ K⁻¹, ∆H = − 50.93 kJ mol⁻¹ were evaluated. It is shown that the sorption of gadolinium on the ion-exchange resin C100 is described by models of kinetically pseudo-first and pseudo-second order. It is established that the Gd³⁺ sorption on the C100 resin is reversible second order chemical reaction.
Methods for improving the efficiency of large-scale chromatographic ion exchange fractionation will be discussed. For both ”migration” chromatography (the band moves at a finite speed) and ”on-off” chromatography (the material is eluted only when conditions are changed) operation with smaller diameter particles and faster cycles will increase resin productivity. Other methods for on-off chromatography include using layers of different resins, using beds in series, and using moving bed techniques for preliminary fractionation. The efficiency of migration chromatography can be improved by using recycle of segmented recycle, column switching, moving port methods, simulated moving beds, and two-way chromatography methods.
This paper reports the effect of pH on the adsorption characteristics of fungal polygalacturonase in CM-Sephadex ion exchangers, in dilute solutions and in batch operations. The partition coefficient increases sharply at pH below 4.3, reaching a peak at about pH 3.2. Equilibrium isotherms follow the Langmuir law and are strongly affected by pH; the maximum adsorption capacity of adsorbent increases with decreasing pH. These findings reflect the effect of pH on the relative degrees of ionisation of adsorbate and adsorbent, and highlight the need to determine the optimum pH for every specific enzyme system.
This paper reviews five kinetic models potentially applicable to ion exchange with resins of high selectivity: liquid‐phase mass transfer control with linear driving force; solid‐phase diffusion control; chemical reaction control with SN2 mechanism; chemical reaction control with shrinking core mechanism; and solid‐phase diffusion with irreversible equilibrium reaction. The parameters affecting the rate are analyzed.
Ion-exchange resins represent one of the most important waste streams in low-level waste management due to the unstabilized nature of the waste form and the large amount of radioactivity contained. To describe the release of radionuclides from ion-exchange resins stored in a disposal facility, a mechanistic release model was developed. The model is based on description of radionuclide migration both in the resin bead phase and the bulk pore water phase within waste containers. This modeling setup provides the capability to describe all the major physical processes taking place for the release of radionuclides. Because of the difficulty in obtaining analytical solutions, the numerical solution approach was employed in this model. The new resin release model was used to examine key processes and parameters in describing radionuclide release. These were found to be diffusion within the bulk pore water phase, flow rate of infiltrating leachant water, concentration of counterions of the leachant water, and sorption during the transport in the bulk pore water phase. Some parameters were found to have little impact in describing the release. These include the interdiffusion coefficient within resin beads and the density and radius of resin beads. Existing simplified modeling approaches were also compared with the new resin release model, and validities of using these simplified models are discussed.
A generalization of the kinetic equation for the isotope exchange at solid—liquid interface is presented. The generalized equation may be used to describe kinetics of the isotope exchange process limited by surface reactions and diffusion without assumption of spherical symmetry of solid particles.
The solvent-gradient operation mode exploited within simulated moving bed (SMB) chromatographic separation processes can be used to improve the efficiency of separations. A detailed model that takes into account non-linear isotherms, solvent gradient, mass transfer resistance, and the discrete event of port periodic switching, was developed in order to simulate the complex dynamics. All design parameters (number, configuration, length and diameter of columns, particle size) and operating parameters (switching period, flow rates of feed, raffinate, desorbent, extract and recycling flow, feed concentrations, different volume fraction of the weak solvent in desorbent and feed) can be chosen correctly by numerical simulation. This model can facilitate the design, operation, optimization, control and scale-up of the non-linear solvent-gradient SMB (SG-SMB) units.
Most important properties of an ion chromatographic resin are influenced by the resin matrix, the type of functional group and the ion-exchange capacity. Highly crosslinked PS–DVB resins of 5 μm diameter have been functionalized by sulfoacylation, by sulfonation and by dynamic coating over a wide range of exchange capacities. These materials allow a study of the influence of different ion-exchange sites and capacities. The influence of the degree of functionalization on resin performance is completely reverse for sulfoacylated and sulfonated resins. The HETP values for all observed analytes (Cu, Pb, Zn, Ni, Co, Cd, Mn, Ca, Mg) in a tartaric acid elution system decrease for sulfoacylated resins with increasing capacity, for sulfonated resins with decreasing capacity. The performance of sulfoacylated exchangers is better than for dynamically coated ones and far better than for sulfonated resins. The performance of silica gel based cation-exchangers such as BioSil CAT is in most cases better than observed for sulfoacylated resins.
Technical feasibility of an ion exchange based process for removal and recovery of the coagulating principle (Al, Fe chemicals) from water clarifier sludges is illustrated. The innovation is a typical example of `conservative technology' applied to the solution of environmental problems, thus allowing for the minimization of the environmental impact related to the disposal of the solid wastes, through conditioning and detoxification of the sludges for land application, and simultaneous recovery of valuable products from non-conventional sources. The paper illustrates laboratory scale comparative experiments between weak (carboxylate) and strong (sulphonic) cation resins performances in reference to a typical acidic leachate from water clarifier sludges (pH 3.5). Together with mechanistic interpretation of the multicomponent-polyvalent Al/Fe/Na ionic system involved, in this paper indications for process optimization are also given.
Sporopollenin, a natural polymer, has been modified for application as a ligand-exchange material. The ligand-exchange Chromatography with the functionalized Lycopodium clavatum is a useful method for the rapid separation of nucleosides and nucleic acid bases. The synthesis of tris(carboxymethyl) ethylene diamine Lycopodium clavatum has been described. The resin contained functional diaminoethane and carboxyl groups. Nickel(II) and cobalt(II) metal ions can easily be immobilized on this carboxylated-diamino-ethyl (CDAE)-sporopollenin. Physico-chemical and chelating properties of Lycopodium clavatum have been studied extensively. Ligand-exchange chromatography of CDAE-sporopollenin has also been compared to the conventional synthetic chelex-100 resin. The kinetics of cytidine in CDAE-sporopollenin resin has been investigated. The rate measurements have been made by a potentiometric technique. The relative rates at which nucleosides bind to the resin are determined by the actual chemical-exchange reaction between ligands and resin.
The diffusional model for the intraparticle ion exchange (IE) kinetics in selective ion exchangers is presented. The model develops the phenomenological formulation based on the irreversible thermodynamics and includes mass balance equations with description of ion fluxes by the Nernst-Plank relations. The model is based on the supposition that during the exchange RA+B = RB + A involving a chemical reaction of counter-ions (B and A) with the resin site R, diey can exist in the exchanger in two states, namely “free” and as the species formed by their combination with fixed groups R. Counter-ions B and A are considered to be immobile while “bound” and to move unimpeded while “free”. The mathematical formulation of the IE kinetic process in this case is described by a system of two nonlinear diffusion equations in partial derivatives where the effective self diffusion coefficients Dii and the cross interdiffusion coefficients Dij depend on the concentration of the diffusing counter-ions (B and A) and coions Y, and also on the values of equilibrium constants KRB and KRA describing the stability of RB and RA complexes in the ion exchanger phase. As the result, the ion fluxes are described within the generalized Fick formulation. Fickian diffusivities Dij compose 2×2 diffusional matrix with determining each of them through the individual diffusivity Di of the ions B, A and F. The set of diffusional equations along with the appropriate initial and boundary conditions solved by using a computer gives transient concentration profiles which compose concentration waves in the ion exchanger bead. For various combination of diffusional and selectivity factors the concentration waves in the bead have been presented in the pseudo 3dimensional space {concentration - radius - time}. This presentation simplifies the interpretation of the process and makes it visual. It is shown that the difference both in concentration waves profiles and rate between forward and reverse exchange of two counter-ions may arise not only from unequal diffusion coefficients but also from unequal dissociation constants of the complexes formed with the fixed groups.
In recent times, resins with chelating ligands (hydroxamic acids, in particular) have received considerable attention owing to their selective adsorption of gallium from sodium aluminate liquor, commonly known as Bayer liquor. This paper deals with the synthesis of a chelating ion-exchange resin as well as the studies carried out on the resin to ascertain its loading capacity for gallium, kinetics, stability toward acid and alkali besides its recyclability. The paper also gives a description of the ion-exchange cycle besides the design of a laboratory-scale column which shall yield data applicable to the designing of commercial units.
The internal porosity and swelling/shrinking of a chelating iminodiacetic type ion exchange resin have been experimentally studied during the uptake of copper onto it. The swelling of the particle could be analyzed with a modified model on th basis of the unreacted core model (UCM), including the influence of chemical equilibrium. The ion exchange kinetic results in batch experiments are used with the UCM to calculate the effect of pH on the internal diffusion coefficients. Results from shallow bed experiments with mixed internal and external diffusion controls have shown the applicability of the above model to analyze ion exchange with low external velocities.
La porosité interne et le gonflement/retrait d'une résine échangeuse d'ions de type iminodiacétique chélatante ont été étudiés expérimentalement durant la consommation du cuivre. Le gonflement de la particule pourrait être analysé au moyen d'un modèle modifié sur la base du modèle de noyau non réagi (UCM), incluant l'influence de l'équilibre chimique. On utilise avec le modèle UCM les résultats des cinétiques des échanges ioniques dans les expériences discontinues afin de calculer l'effet du pH sur les coefficients de diffusion interne. Les résultats d'expériences en lit peu profond prévoyant des contrôles de diffusion mixtes internes et externes montrent l'applicabilité du modèle ci-dessus pour l'analyse de l'échange ionique dans le cas de faibles vitesses externes.
A kinetic investigation was performed with an ion exchange resin for chromium. A chelating cation exchange resin (Amberlite IRC 718) was used for removal and recovery of chromium. The effect of concentration, resin amount, particle size and stirring speed on kinetics were investigated. The metal concentration range studied was between 5 to 160 mg L−1, the resin amount range was between 5 to 20 mg, the particle size range was between 0.35 to 1.8 mm and the stirring speed range was between 1000 to 3500 rpm.
Kinetic studies were done using a Kressman-Kitchener stirrer reactor system and the results were compared with existing kinetic models. Two models; Nernst-Plank film diffusion control model (fdc) and solid phase diffusion control model (pdc) were identified and the dependence of the rate on parameters, such as solution concentration, particle size, resin amount, stirring speed, etc., was examined for each of them. As a result, interpretation of these data showed that the system is probably controlled both film and particle diffusion.
A kinetic investigation was performed with an ion exchange resin for chromium. A strong cation exchange resin (Amberlite IR
120) was used for removal of chromium. The effects of concentration, resin amount, and stirring speed on kinetics were investigated.
The metal concentration range studied was between 5 to 160 mg/dm3 (the amount of solution was 4 dm3), the resin amount range was between 5 to 20 mg, and the stirring speed range was between 1000 to 3500 rpm. Equilibrium experiments
were performed for calculation of separation factor. Kinetic studies were done using a Kressman-Kitchener stirrer reactor system and the results were compared with existing kinetic models. Two models, Nernst-Plank film diffusion control model (fdc) and solid phase diffusion control model (pdc), respectively were identified, and the dependence
of the rate on parameters such as solution concentration, resin amount, stirring speed, etc. was examined for each of them. The interpretation of these data shows that the system is probably controlled by both film
and particle diffusion.
Ion transport problem related to controlled potential experiments in electrochemistry is studied. The problem is assumed to
be superposition of diffusion and migration under the influence of an electric field. The comparative analysis are presented
for three well-known models—pure diffusive (Cottrell’s), linear diffusion-migration, and nonlinear diffusion-migration (Cohn’s)
models. The nonlinear model is derived by the identification problem for a nonlinear parabolic equation with nonlocal additional
condition. This problem reduced to an initial-boundary value problem for nonlinear parabolic equation. The nonlinear finite
difference approximation of this problem, with an appropriate iteration algorithm is derived. The comparative numerical analysis
for all three models shows an influence of the nonlinear migration term, the valences of oxidized and reduced oxidized species,
also diffusivity to the value of the total charge. The obtained results permits one to estimate bounds of linear and nonlinear
ion transport models.
Adsorption mechanisms of toxic non-ionic organic contaminants (NOCs), aniline and nitrobenzene, with natural-zeolite and organo-zeolite (OZ) were investigated in both batch and continuous systems. In batch tests, the adsorption capacity of aniline and nitrobenzene onto natural zeolite surface is very low or almost nil but becomes significant upon modifying the zeolite surface by hexadecyltrimethylammonium (HDTMA). A partitioning mechanism is proposed to be responsible for the adsorption of NOCs onto OZ. The effectiveness of the partitioning mechanism is directly connected with hydrophobic properties of the NOCs. The column tests were carried out as an indicator for continuous system. The breakthrough curves were constructed for OZ/NOC system and the adsorption capacity of NOCs onto OZ under the present conditions were determined as 2.36 and 3.25 mg per gram of OZ, for aniline and nitrobenzene, respectively. A schematic model is proposed to account for the adsorption of NOCs onto OZ.
ResearchGate has not been able to resolve any references for this publication.