Multicomponent Fixed-Bed Ion Exchange: Verification of Equilibrium Coherence Theory

Abstract

The coherence method, a technique for modeling multicomponent fixed-bed adsorption with time dependent feed conditions, has been applied to a fixed-bed ion-exchange system under a variety of operating conditions. Theoretically, the method can handle multicomponent systems with initial and feed conditions of any degree of complexity. This paper will present the results of an experimental study to verify the practical utility of the coherence method. A ternary ion-exchange system of K⁺, Na⁺, Li⁺ on a fixed bed of AG-50WX8 resin has been studied. Breakthrough curves have been obtained for single abrupt, multiple abrupt, and linear influent composition changes. A non-equilibrium model has also been developed and has been used to describe limiting binary exchange cases. The experimental breakthrough curves have been compared with the predictions of both models.     

EQUILIBRIUM OF METALS WITH IMINODIACETIC RESIN IN BINARY AND TERNARY SYSTEMS

ABSTRACT

Experiments of binary and ternary ion exchange equilibrium of heavy metals and sodium were carried out in a complexing iminodiacetic resin Lewatit TP 207. First, binary equilibrium data were obtained at different temperatures and ionic strength and fixed to models considering two different ion exchange stoichiometrics. For ternary equilibrium data, two distinct simple models were applied. One to be applied to systems showing very different selectivity for the metals (for instance, Cu²⁺/Co²⁺/Na⁺) and the other for systems with similar selectivity for the metals (such as Zn²⁺/Co²⁺/Na⁺). The ternary equilibrium data obtained is presented in this work and fitted using the two above mentioned models. These models allow us to obtain the equilibrium parameters for binary and ternary system to be used in the design of equipment using this iminodiacetic resin.     

The adsorption behavior of cesium on poly(N-isopropylacrylamide/itaconic acid) copolymeric hydrogels

In this study, N-isopropylacrylamide/itaconic acid (NIPAAm/IA) hydrogels prepared by irradiating with γ radiation were used in experiments on cesium ion adsorption. The cesium ion adsorption capacity of the hydrogels was investigated as a function of Cs⁺ concentration, pH and temperature. The adsorption behavior of cesium was evaluated by using the radiotracer method. The adsorption isotherm models were applied to the experimental data, and it was seen that Freundlich isotherm explained the adsorption better than Langmuir isotherm. Two simplified kinetic models including pseudo-first-order and pseudo-second-order equation were selected to follow the adsorption processes. The Cs⁺ adsorption could be best described by the pseudo-first-order equation. The thermodynamic parameters including ΔG°, ΔH° and ΔS° for adsorption processes of Cs⁺ on the hydrogel were also calculated, and the negative ΔH° and ΔG° confirmed that the adsorption process was exothermic and spontaneous.     

Experimental and modeling analysis of the formation of cuprous intermediate species formed during the copper deposition on a rotating disk electrode

Two comprehensive kinetic models reported in the literature for the copper deposition in sulfate media are modeled and compared with experimental data (linear sweep voltammetry) in order to disclose the role and phase of the cuprous species as intermediates. Differences in the phase of these species are considered for each model, i.e. Cu(I)_ads and Cu⁺. Modeling considers the formation of copper in two mono-electronic steps and account for mass transport by diffusion and convection in a RDE. Reasonable fits were obtained for both models at different experimental conditions (e.g. Cu²⁺ bulk concentration, rotation rate). It was found that this behavior is possible due to the low concentrations of cuprous species and their rapid consumption to form metallic copper, i.e. not rate-controlling step. Further insights of the kinetic and mass transport contributions of this system were obtained for both models by computing some variables that cannot be experimentally measured (i.e. surface concentrations). The first reaction in the mechanism was found to be the rate-determining step. A set of optimum kinetic parameters and constants obtained from the analysis of the models are also reported in this study.     

The study of kinetic models for ligand exchange of anions as ligands using ligand-exchange resin

A comparative study of kinetic models for ligand exchange of I⁻ → Cl⁻ and Br⁻ → Cl⁻ as ligands as a function of pH and concentration using diaminoethyl-sporopollenin (DAE-sporopollenin) resin were investigated during the ligand-exchange reaction of the liquid phase. A batch technique was employed for the study of the kinetics of I and Br/Cl exchange as ligands. Five kinetic models were applied to the experimental data. The rate of ligand exchange was increased with decreasing of the hydrated ionic radius and pH. The curve fitting of the mathematical models and the behavior of the kinetic curves are discussed for direct ligand exchange under the conditions employed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1225–1234, 1997     

Assessment of kinetic and isotherm models for competitive sorption of Cs+ and Sr2+ from binary metal solution onto nanosized zeolite

This study examined the sorption performance of synthesized nanosized zeolite for the elimination of Cs⁺ and Sr²⁺ cations in a binary metal system. The influence of pH, sorbent amount, temperature, and contact time was studied. The relationship between each of these parameters and the removal efficiency was investigated. An analysis of the rate data was performed using both pseudo-first- and second-order reaction models. The ranking of three equilibrium sorption isotherm models used (Redlich–Peterson, Langmuir, and Freundlich) with a variety of numbers of parameters was determined using the corrected Akaike’s information criterion. The results demonstrate that a pseudo-second-order model fits the sorption kinetic data better than a pseudo-first-order model. The isotherm model rank order that best described the data statistically was Redlich–Peterson?>?Langmuir?>?Freundlich for the cesium ions and Langmuir?>?Redlich–Peterson?>?Freundlich for the strontium ions. Our results revealed that the existence of Sr²⁺ caused a significant reduction of Cs⁺ sorption in the binary metal mixture according to a lumped parameter model and vice versa. The results show that the synthesized material’s surface had a relatively stronger affinity for Cs⁺ than for Sr^2+.     

Equilibrium and kinetics of heavy metal ion exchange

Ion exchange has a great potential to remove heavy metals from industrial wastewaters or heavy metal-containing sludge. In order to design and operate heavy metal removal processes, the equilibrium relationship between ions and resin must be known a prior. A series of ion-exchange equilibrium tests of Cu²⁺/H⁺, Zn²⁺/H⁺, and Cd²⁺/H⁺ systems using Amberlite IR-120 were performed. The equilibrium data were analyzed by the Langmuir isotherm, Freundlich isotherm, and selectivity coefficient approaches. The thermodynamic parameters such as Gibbs free energy change, enthalpy change, and entropy change were calculated. By comparison of the selectivity coefficients, the affinity sequence to IR-120 is Cu²⁺ > Zn²⁺ > Cd²⁺ > H⁺. Moreover, in order to understand the heavy metal extraction kinetics in the presence of Amberlite IR-120, the ion-exchange kinetics was also studied. The ion-exchange kinetic data were regressed by the pseudo first-order, second-order models, and a reversible reaction model. The activation energies calculated from the rate coefficients at different temperatures are 15.41, 7.04, and 17.01 kJ/mol for copper, zinc, and cadmium, respectively. Although the pseudo first- and second-order models are easier to use for data analysis, the resultant model parameters depend on operating conditions. The reversible reaction model is capable to predict the effects of resin to solution ratio, initial heavy metal concentration, and temperature on the ion-exchange kinetic curves.     

Kinetic Evaluations for the Sorption Process of Lanthanide Ions with Poly-<Emphasis Type="Italic">O</Emphasis>-toluidine Zr(IV) Tungstophosphate

The kinetic models for sorption of La³⁺, Ce³⁺ and Nd³⁺ ions on poly-o-toluidine Zr(IV) tungstophosphate (POTZr(IV)WP) were investigated under effecting of contact time, initial concentration and temperature. A comparison of kinetic models applied to the adsorption rate data of La³⁺, Ce³⁺ and Nd³⁺ ions on POTZr(IV)WP was evaluated for the pseudo-first order, the pseudo-second order, homogeneous particle diffusion and intra-particle diffusion kinetic models. The results showed that both the pseudo second-order and the homogeneous particle diffusion models were found to best correlate the experimental rate data. The particle diffusion coefficients (D_i) and energy of activation (E_a) have been estimated. These investigations revealed that the equilibrium is attained faster at higher temperatures.     

ION EXCHANGE SELECTIVITY OF A RESORCINOL-FQRMALDEHYDE POLYCONDENSATE RESIN FOR CESIUM IN RELATION TO OTHER ALKALI METAL IONS

ABSTRACT

Ion exchange isotherms for the ion-pairs Li⁺ -Cs⁺, Na⁺ -Cs⁺ and K⁺ -Cs⁺ have been measured for a cesium selective resorcinol—formaldehyde polycondensate resin synthesized in the laboratory- The equilibrium data have been used to calculate the thermodynami c equilibrium constants as well as standard free energies of ion ex change and thus arrive at a selectivity series for the above ions- The high selectivity towards cesium as compared to other alkali metal ions has been discussed in the 1ight of existing theories and models of ion ex change phenomena.     

Simulation of continuous packed bed reactive distillation column for the esterification process using activity based kinetic model

A mathematical model for the continuous packed bed reactive distillation process of esterification of acetic acid with methanol is developed. The kinetic rate equation, which plays a major role for the performance of reactive distillation and it is the part of model, is required for the liquid phase reversible esterification reaction. The mineral sulphuric acid is used as the catalyst. The kinetic experiments are carried out under different temperatures in the range of 305.15 to 333.15 K and catalyst concentrations in the range of 0.1267 mole H⁺/lit to 0.6537 mole H⁺/lit. From that experimental data the kinetic model is developed and the same is used for the simulation of reactive distillation process. Equilibrium stage model, in which the vapour and the liquid leaving a stage are assumed to be in equilibrium with each other, has been used for the simulation of reactive distillation process by incorporating our kinetic model. Conversion of acetic acid as function of reflux ratio and reboiler ratio has been predicted. The liquid composition and temperature profiles versus stage number have been also predicted. Finally, the optimum operating conditions obtained from the simulation results for high pure methyl acetate by reactive distillation process.     

Modeling of Drying Curves for Some Foodstuffs Using a Kinetic Equation of High Order

ABSTRACT

Non-linear regression was used to fit a high order kinetic model to drying curves for mango and cassava. For comparison purposes, the same experimental data were also adjusted by non-lines regression to a model based on exponential series, and to another exponential model by simple linear regression. The high order model fit the experimental data with higher precision (r2 Al.98) than the other exponential series models. The proposed higher order model is mathematically simple as compared to the exponential series, and could be used for simulation of drying processes.     

COMPARISON OF ION EXCHANGE AND DONNAN EQUILIBRIUM MODELS FOR THE PH-DEPENDENT ADSORPTION OF SODIUM AND CALCIUM IONS ONTO KRAFT WOOD PULP FIBERS

ABSTRACT

Management of nonprocess element (NPE) accumulation in pulp washing operations requires equilibrium models that predict the distribution of metals between the wash liquor and the pulp fibers. The overall goal of this study was to assess models for predicting the multi-component adsorption of hydrogen ions (H⁺), sodium ions (Na⁺), and calcium ions (Ca⁺²) onto bleached and unbleached kraft pulp fibers over a pH range of 2.7–11. As part of this study, binary equilibrium constants for hydrogen and metal ion exchange on carboxylate sites in bleached pulp (0.041 meq/g dry pulp) were measured at 25°C, with log K ^Na/Ca = ?1.604 ± 0.119, log K ^H/Ca = 0.633 ± 0.087, and intrinsic dissociation constant pK _io of 3.64 ± 0.46. Ion exchange and Donnan equilibrium models adequately predicted the multi-component equilibrium data for competitive adsorption of H⁺, Na⁺, and Ca⁺² onto bleached kraft wood pulp fibers. The ion exchange model was fully predictive, whereas the Donnan model required that the solution pH be known. At pH 2.7–6, the Donnan model predicted the adsorption of Na⁺ and Ca⁺² onto both bleached and unbleached wood pulp fibers better than the ion exchange model. The ion exchange model assumed that residual carboxylate in the pulp served as the only site for the competitive binding of hydrogen and metal ions. In contrast, the Donnan model assumed a non site-specific distribution of metal ions between charged fiber and external solution phases and a carboxylate site specific adsorption of hydrogen ions. Above pH 6, both models failed to predict that the calcium adsorption on unbleached brownstock pulp increased beyond the carboxylate site capacity, suggesting that other functional groups within the brownstock pulp with intrinsic dissociation constant values higher than carboxylate were providing additional binding sites for calcium.     

Effect of Ionic Strength of Solution on Boron Mass Transfer by Ion Exchange Separation

Abstract

In the present study, batch kinetic tests have been performed for boron removal from model solutions using boron selective ion exchange resins Diaion CRB 02, Dowex (XUS 43594.00) and Purolite S 108. Several kinetic models have been used to evaluate the sorption kinetics of boron by means of a well mixed stirred system, diffusional models, pseudo‐first‐order, and pseudo‐second‐order kinetic models. The mass transfer model, based on a well stirred system including maximum capacity (Q_m, mg/g) and Langmuir constant (b, L/mg) values obtained from Langmuir isotherms, has been used to obtain predictive concentration changes against time. The experimental results have been used to compare with the modelling data for different ionic strength media.     

Technology for Removing Potassium Ion from Concentrated Seawater by Electrodialysis and Solar Salt Dissolved in Brine

Abstract

Cryptomelane-type hydrous manganese dioxide (CRYMO) has a high adsorption selectivity toward potassium ions (K⁺). The distribution coefficients of the highly selective adsorption are evaluated by the theoretically proven calculation method, that adsorption isotherm data and Kielland plot data are taken for granted. The calculated results and the experimental results of the adsorption isotherm show fairly good agreement for a whole range of conditions. CRYMO has been successfully applied to the caustic soda manufacturing process. The concentration of K⁺ in brine for the process was lowered to less than 1 ppb. This purity is sufficient for the high quality caustic soda manufacturing process. Another advantage of CRYMO is its acidification ability for solutions. The brine is acidified with hydrochloric acid before being introduced to the electrolytic bath in the present process.     

Non-isothermal kinetics of metallurgical coke gasification by carbon dioxide

Under non-isothermal conditions, thermogravimetric analysis was applied to study carbon dioxide gasification of three metallurgical cokes. The cokes selected for the study were named Coke A, Coke B and Coke C. The experimental data are fitted using four common gas-solid kinetic models: the homogeneous model, the sharp interface model, the traditional model and the random pore model. It is found that the random pore model most closely reflects the kinetic behavior of coke gasification characteristics. Using the random pore model, the apparent activation energies for gasification of Coke A, Coke B, and Coke C were calculated to be 139.08, 127.78, and 116.32 kJ mol^–1, respectively.     

Effect of particle size on cesium exchange kinetics by K-depleted phlogopite

Cation exchange mechanism and rate of Cs⁺ exchange were investigated in < 2 μm and 20–2 μm particle size fractions of K-depleted phlogopite (Na-phlogopite). The K-depleted phlogopite was prepared from a natural phlogopite by a potassium removal method using sodium tetraphenylborate (NaTPB) at room temperature. X-ray diffraction (XRD) patterns revealed that interlayer K⁺ ions were completely replaced with sodium ions after the potassium removal treatment. Ion exchange isotherms and kinetics were determined for Na⁺ → Cs⁺ exchange with two particle size fractions. The isotherms indicated that both particle size fractions showed high selectivity for Cs⁺. Based on the isotherm tests, ΔG^o values of < 2 μm and 20–2 μm particle fractions were − 6.83 kJ/mol and − 7.08 kJ/mol, respectively. Kinetics of Cs exchange revealed that the 20–2 μm particle size fraction of the K-depleted phlogopite took up more Cs⁺ ions than the < 2 μm particle size fraction. Various kinetic models were applied to describe Na⁺ → Cs⁺ exchange process. Elovich model described the kinetic data of the < 2 μm particle size fraction well, while the modified first-order model or parabolic diffusion model described the data of the 20–2 μm particle size fraction well.     

In-Situ UV-Visible Spectroscopic Study on the Adsorption of some Dyes onto Activated Carbon Cloth

Abstract

Adsorptive removal of the dyes C.I. Basic Blue 9, C.I. Basic Red 2, and C.I. Acid Blue 74 from aqueous solution onto the activated carbon cloth (ACC) has been investigated. The removal of each dye has been followed by in-situ UV-visible spectroscopic method using the so-called scanning kinetics technique. Kinetic data obtained in this way were tested according to pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion models. Pseudo-second order model was found to be the best in representing the experimental kinetic data. Adsorption isotherms at 30°C were derived for each dye. Isotherm data were found to fit best to Freundlich isotherm model among the three isotherm models tested; Langmuir, Freundlich, and Redlich-Peterson. High specific surface area of the ACC allowed almost complete removal of each dye under the experimental conditions applied. Adsorption capacity of the ACC for the three dyes was correlated with the dimensions of dye molecules and pore sizes of the ACC.     

Adsorption behavior of cesium and strontium onto chitosan impregnated with ionic liquid

We briefly studied the adsorption behavior of chitosan impregnated with an ionic liquid (1-ethyl-3-methyl imidazolium chloride) in solutions with Cs⁺ and Sr²⁺ ions. The impregnation of chitosan was realized by ultrasonication method. The impregnated chitosan was analyzed by FTIR, SEM, and EDX in order to show that the chitosan was impregnated with the studied IL. The adsorptive properties of ionic liquid-impregnated chitosan for the removal of Cs⁺ and Sr²⁺ ions from aqueous solutions were studied in a batch adsorption system. The adsorption kinetic was found to follow a pseudo-second-order kinetic model. The experimental data showed good fit to the Langmuir isotherm. The adsorption properties of the chitosan impregnated with the studied ionic liquid were determined in binary, tertiary, and quaternary systems. The adsorption capacity of the IL impregnated chitosan is not significant influenced in the binary systems. The adsorption capacity of the IL impregnated chitosan decreases with the increase of the number of the cation present in solutions. It was observed that the studied adsorbent has a higher affinity for Cs⁺ ions than for Sr²⁺ ions.