A Novel Continuous Rotating Annular Liquid Chromatograph with a Multichannel Peristaltic Pump for Variable Eluent Withdrawal

Abstract

A novel continuous rotating annular chromatograph is proposed and used for the separation of amino acids. The system is equipped with a multichannel peristaltic pump to withdraw the eluent and to easily regulate its flow rate. The inlet of the annular chromatographic packed bed is divided into a number of chambers to prevent circumferential dispersion of the sample. The mass transfer characteristics of the apparatus were theoretically analyzed by using a two-dimensional transport model. The experimental results for solute elution are well simulated by the transport model. Solute dispersion in the annular column was found to be negligible. A shallower liquid depth in the inlet chamber gave sharper concentration peaks. An increase in the number of feed nozzles and the installation of inlet chambers were found to be preferable for multicomponent separation.     

INTERIONIC AND INTERMOLECULAR INTERACTIONS IN ION-EXCHANGE AND SORPTION SYSTEMS INVOLVING PHYSIOLOGICALLY ACTIVE SUBSTANCE

ABSTRACT

This paper reviews the results obtained by studying the sorption of physiologically active substances (PAS) of different types such as, amino acids, nucleotides and melanoidins on ion exchangers and non-ionogenic sorbents. The review is mainly focused upon die mechanisms of interaction of PAS molecules in the sorbent phase. The contribution of ion-ionic, ion-molecular and intermolecular interactions to the overall sorption effect is discussed. The results of studying ion-exchange isothermal supersaturation of amino acid solutions on anion exchangers are reported and discussed. The mechanisms of aging of ion-exchange materials in the course of recovery of PAS from fermentation broths and hydrolysates are proposed.     

Modeling of Sorption Dynamics in Transition Metal Ion–Weak-Base Ion Exchanger Systems in Terms of Surface Complexation Theory

A model is constructed for sorption dynamics in multicomponent ion-exchange systems with a weak-base ion exchanger. The model is based on computer-solved nonlinear material balances and internal-diffusion kinetic equations. The multicomponent equilibria involving a weak-base ion exchanger are described in terms of surface complexation theory. According to this theory, the fixed amino groups of the ion exchanger (Lewis bases) and sorbate anions form complexes with metal cations (Lewis acids). These complexes are located in different Stern layers at different distances from the surface. Sorption dynamics models are considered for the frontal ion-exchange chromatographic separation of the H⁺/A/B/X (A, B; = Cu²⁺, Zn²⁺, Ni²⁺, Cd²⁺; X = Cl^–, SO ₄ ^2– ) systems on the amino-containing weak-base ion exchangers Purolite A-109 and Fuji PEI-CS-07. Frontal ion-exchange chromatograms are compared for a number of multicomponent systems.     

Adsorption Isotherms of Amino Acids and Kinetic Analysis of Ion-Exchange Chromatographs by the Moment Method

Abstract

Adsorption isotherms of three amino acids (aspartic acid, glutamic acid, and glycine) were measured in a single solute or multisolutes by the batchwise method. Kinetic parameters were determined in a column packed with ion-exchange resin by the moment method. The equilibrium constants obtained by both methods were in good agreement. Experimental elution curves agreed well with calculated one.     

Modeling of Ion-Exchange Column Operation. I. Equilibrium Model for Univalent-Divalent Exchange

Abstract

A mathematical model is presented for the operation of an ion-exchange column exchanging divalent cations for univalent cations. Local equilibrium is assumed to be maintained between the ion-exchange resin and the aqueous phase. The cubic equations arising from the assumption of local equilibrium are solved by Tartaglia's method. The two partial differential equations describing the advective motion of the ions are approximated by two sets of coupled ordinary differential equations. The advective terms in these are represented by an asymmetrical “upwind” algorithm which greatly reduces spurious numerical dispersion.     

Modified Shrinking Core Model for Reversible Sorption on Ion-Exchange Resins

Abstract

A modified shrinking core model is proposed to correlate dynamics of acid sorption on weak base ion-exchange resins in free base form. The model considers reversibility of the sorption process which is ignored in the conventional shrinking core model. The model is easy to apply and is shown to yield results which are in agreement with a computationally intensive rigorous model. The model is successfully verified using the experimental data on sorption of strong acids (HCl and HNO₃) on weak base resins (Dowex WGR-2 and Amberlite IRA-93).     

SURFACE IMPREGNATED SULFONATE ION EXCHANGERS: PREPARATION,PROPERTIES AND APPLICATION

ABSTRACT

This paper reviews the results obtained by studying Surface Impregnated Sulfonate Ion Exchangers (SISIE) obtained by modification of macroporous or gel polysterene-divinylbenzene polymers with toluene solutions of dinonytnaphihalene sulfonic acids. Capacities of SISIE of the first type are directly proportional to the concentration of the modifying solution and to the specific surface area of the matrix. Capacities of gel SISIE are much less than those of macroporous samples and depend on the crosslinking of the matrix. Stabilization of SISIE capacity and improvement of their kinetic properties can be achieved using “wet drying ” technique. Successive impregnation of the same SISIE sample may be used to increase the capacity of the resin. The ion-exchange properties of SISIE are mainly determined by their micellar structure which also defines the areas of possible applications of these ion-exchange materials such as, e.g. ion chromatography and some others Several models have been successfully applied to describe the features of ion exchange processes on SISIE. Application of SISIE as convenient model systems to study aminecarboxylate interaction of amino acid molecules is illustrated by suspension effects measured in SISIE-zwitterlyte and SISIE-HCI suspensions and by the results obtained by the laser-acoustic study of these systems.     

Ion-Exchange Selectivities of Periderm and Cuticular Membranes toward Alkali Cations

Abstract

The ion-exchange selectivities of lithium, sodium, potassium, and cesium on isolated potato periderm (solanum tuberosum) and pear fruit cuticular membranes were investigated; the general order of preference both for cation selectivities and ion-exchange capacities was lithium > sodium > potassium > cesium. The potato periderm and pear fruit cuticular membranes exhibited a behavior typical of ion-exchange resins of the weak acid type. At constant pH7, the ion-exchange capacities of periderm and cuticular membranes increased with hydrated ionic radius, and also with increasing pH and neutral salt concentration, and decreased with crystal ionic radius. Counterion selectivities also exhibited the same behavior. The ion-exchange properties are discussed in terms of the structure and function of potato periderm and pear fruit cuticular membranes.     

Isotope Effects in Ion-Exchange Equilibria in Aqueous and Mixed Solvent Systems

Abstract

Isotope effects in ion-exchange equilibria in aqueous and mixed solvents are analyzed in terms of the general features of ion-exchange equilibria and of isotope effects in chemical equilibria. The special role of solvent fractionation effects in ion-exchange equilibria in mixed solvents is pointed out. The various situations arising in isotope fractionation in ion exchange in mixed solvents due to solvent fractionation effects are theoretically discussed. The experimental data on lithium isotope effects in ion-exchange equilibria in mixed solvents are shown to conform to the above situations. The limitations of ion-exchange equilibria in mixed solvents for isotope fractionation are pointed out.     

Removal of Chlorophenols from Aqueous Solution by Anion-Exchange Resins

Abstract

The effects of pH value and chloride ion concentration on the removal of chlorophenols from aqueous solutions by Purolite A-510 resin [macroreticular polystyrene-divinylbenzene resin with R(CH₃)₂(C₂H₄OH)N⁺ group] are discussed by the species distributions of chlorophenols. Those chlorophenols include phenol, 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. The investigations showed that the chlorophenols could be removed effectively at alkaline conditions where the ion-exchange reaction was dominant. Also, the removal of chlorophenols increased with the number of chlorine atoms on the chlorophenols. The removal of chlorophenols via the ion-exchange reaction was hindered by the presence of chloride ions. The effect of chloride ions, however, was diminished in acidic solutions where the adsorption reaction was dominant. The proposed equilibrium model, which considers both adsorption and ion-exchange reactions, adequately describes the sorption behavior of chlorophenols. The partition constants of the protonated chlorophenols can be estimated from the octanol/water partition coefficients of the phenolic compounds.     

Ion-Exchange Equilibrium of Ca2+, Mg2+, K+, Na+, and H+ Ions on Amberlite IR-120: Experimental Determination and Theoretical Prediction of the Ternary and Quaternary Equilibrium Data

Abstract

A study of the cation-exchange equilibria between Amberlite IR-120 resin and aqueous solutions of calcium, magnesium, potassium, and sodium chlorides and hydrochloric acid has been made. Experiments were carried out at 283, 303, and 323 K with solutions having total cation concentrations of approximately 0.1, 0.3, and 0.5 N. Experimental data for the ion-exchange equilibria of the ternary and quaternary systems are reported. These systems exhibit nonideal characteristics in both phases. The predictions have been based on the reaction equilibrium constants and correlations for the activity coefficients in both phases. A model which allows the prediction of multicomponent ion-exchange equilibria from binary data has been developed. Predictions of ternary and quaternary systems based solely on the binary data are in good agreement with the experimental results.     

The Separation of Zn and Cu Using Chelating Ion Exchangers and Temperature Variations

Abstract

This paper reports the results of a study on the ion-exchange equilibrium of Cu ²⁺ and Zn ²⁺ at different temperatures on chelating ion-exchange resins: Amberlite IRC-718 (iminodiacetic acid based functional groups), VPC-1 (picolinic acid based) and thiourea-based resins. The separation factors and the conditional equilibrium constants of the ion-exchange reaction were determined in temperature range from 15 to 75 °C. An estimation of thermodynamic functions has also been carried out. Possibility of the separation of Cu and Zn mixture by dual temperature ion-exchange method has been demonstrated.     

Sorption of Metals by an Amidoxime Chelating Resin. Part I: Equilibrium

ABSTRACT

The complexation equilibrium of metals (copper, lead, and zinc) by using a chelating ion-exchange resin (Duolite ES-346) is analyzed. Two potentiometric titrations of the resin which allow evaluation of the exchange capacity and the pKvalues are carried out. Two equilibrium models (mass action type model and surface complex formation model) are proposed, and their parameters are estimated by fitting model equations to data from batch experiments. The degradation of the amidoxime groups in acidic media and a possible way to minimize that problem is discussed.     

Purification of Nucleoside-5′-diphosphates: A New Ion-Exchange Method

Abstract

Inosine- and uridine-5′-diphosphates can be purified by ion-exchange chromatography utilizing a new ion-exchange method where Type 1 ion-exchange resins and the absorbed nucleoside polyphosphates are changed to the basic form by rinsing the column with dilute sodium hydroxide and subsequently eluting with dilute hydrochloric acid and sodium chloride.     

Kinetic Study of the Extraction of Glutamic Acid by Naphthenic Acid in a Modified Lewis-Type Cell

Abstract

Due to the zwitterionic character, we may extract amino acids with ion-exchange carriers by controlling the pH of aqueous amino acid solutions. A modified Lewis-type cell experiment was conducted to study the extraction kinetics of glutamic acid by naphthenic acid, a cation-exchange carrier. The effects of agitation, interfacial area, carrier concentration, pH, and initial concentration of amino acid on the extraction rate were discussed. By comparison of the experimental results with the proposed interfacial extraction mechanism, it was found that the extraction equilibrium constant, K _cx, is 1.62 × 10^?2, the apparent forward extraction rate constant, k ₁, is 0.63 cm⁴/mol·s, and the reverse rate constant, k _?1, is 38.9 cm⁴/mol·s. The intrinsic chemical reaction is controlled by the formation of an amino acid/carrier complex at the interface. The extraction mechanism proposed was successfully correlated with the experimental results.     

Continuous Separation of Carbohydrates by Ion-Exchange Chromatography

Abstract

A synthetic mixture of fructose, mannitol and sorbitol was continuously separated by a chromatographic method using a cation-exchange resin (Dowex 50W-X8) in its Ca²⁺-form as the stationary phase. An annular chromatograph (AC) was used to achieve a continuous mode of operation. Distribution and mass transfer coefficients of the three substances as well as bed properties were obtained by batch chromatography. The separation was simulated mathematically in terms of an approximate linear chromatographic theory was applied to the modeling of the behavior of the continuous separations. The influence of rotation rate, column loading, eluent flow rate and feed concentration on the resolution of the individual peaks were investigated.     

ION EXCHANGE OF SEVERAL RADIONUCLIDES ON THE HYDROUS CRYSTALLINE SILICOTITANATE,UOP IONSIV IE-911

ABSTRACT

The crystalline silicotitanate, UOP IONSIV IE-911, is a proven material for removing radionuclides from a wide variety of waste streams. It is superior for removing several radionuclides from the highly alkaline solutions typical of DOE wastes. Our laboratory previously developed an equilibrium model applicable to complex solutions for IE-910 (the powder form of the granular IE-911), and more recently, we have developed several single component ion-exchange kinetic models for predicting column breakthrough curves and batch reactor concentration histories. In this paper, we model ion-exchange column performance using effective diffusivities determined from batch kinetic experiments. This technique is preferable because the batch experiments are easier, faster, and cheaper to perform than column experiments. We also extend these ideas to multicomponent systems. Finally, we evaluate the ability of our equilibrium model to predict data for IE-911.     

Competitive Adsorption of Gold Cyanide and Organic Compounds onto Porous Adsorbents

Abstract

Activated carbon has had a tremendous impact on the technology of gold recovery from leached liquors. Ion-exchange resins have been proposed as possible alternatives to carbon, while ion-exchange fibers and membranes were investigated recently as adsorbents for metal recovery in view of their fast rate of uptake. This paper deals with the competitive adsorption of organic compounds and gold cyanide onto activated carbon, ion-exchange resin, ion-exchange fiber, and membrane. Loadings of organic compounds were measured on gold equilibrated adsorbents and compared to loadings on virgin adsorbents. Both the kinetic and equilibrium parameters in a film/surface diffusion model were affected, which indicated a competitive type of mechanism between gold cyanide and organic compounds. A two-component Freundlich-type isotherm fitted the equilibrium for adsorption on carbon, membrane, and fiber. Furthermore, low molecular mass organic substances revealed a smaller inhibiting effect on gold adsorption than long-chain or high molecular mass organic compounds.     

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.     

Centrifugal Contactors: Separation of an Aqueous and an Organic Stream in the Rotor Zone (LA‐UR‐05‐7800)

Abstract

A multi‐phase flow code is used to simulate the separation of an aqueous and an organic stream in the rotor zone of an annular centrifugal contactor. Different values for the mixture viscosity and for the initial volume fractions of the components are considered. A simple model for mass transfer of a species between phases is used. Geometrical effects are found to have significant influence on the separation of the two‐phase mixture.