General Survey of Adsorptive Bubble Separation Processes

Abstract

In this article we present a general survey of adsorptive bubble separation processes. These separation methods involve the use of selective adsorption at gas-liquid interfaces, the interfaces being generated by gas bubbles in aqueous media. A variety of processes based on this mechanism have been developed, and these methods are described in this review. The underlying concepts in this field are then explored so that the similarities between the methods can be seen. Engineering applications, as well as our own work on analytical applications, are presented. Suggestions are also made as to future potentialities for these adsorptive bubble separation processes. Finally, to place these methods in proper perspective, the techniques are compared to such widely used processes as ion exchange and liquid-liquid extraction.     

Removal of As(V) and Cr(VI) Ions from Aqueous Solution using a Continuous,Hybrid Field‐Gradient Magnetic Separation Device

Abstract

A continuous flow colloidal affinity magnetic separation device is used for the removal of As(V) and Cr(VI) from aqueous solutions. Langmuir isotherms fit the adsorption behavior of the individual ions on Orica MIEX^® ion exchange particles. In a mixture of equal weight percent As(V) and Cr(VI), the adsorption of As(V) begins only above a critical cut‐off concentration, implying preferential adsorption of the higher valence ion at the available sites. Cr(VI) is removed selectively from the mixture in the continuous flow device, consistent with the presence of a higher concentration of the higher valence ion in the proximity of a charged (anion‐exchange) surface.     

Combined Ion Exchange—Solvent Extraction (CIESE): A Novel Separation Technique for Inorganic Ions

Abstract

In the present paper a novel separation technique for inorganic ions is described. This has been termed combined ion exchange—solvent extraction (CIESE), because it is assumed that both ion exchange and solvent extraction are operative simultaneously to effect the separations. This concept is illustrated with two examples: the separation of iron(III), Co(II), and Ni(II) on the ion-exchange resins Dowex 50 and Dowex 1 using acetone or tetrahydrofuran—hydrochloric acid mixtures, and the separation of uranium from numerous metal ions on Dowex 50, employing as eluent a medium consisting of tetrahydrofuran—nitric acid. Because this separation principle is superior to methods employing the conventional separation techniques of ion exchange in pure aqueous solutions and of common liquid-liquid extraction, it is expected that it will also find application for the solution of other problems encountered in inorganic analytical chemistry.     

THE SEPARATION OF Au(III) AND Pd(II) IN HYDROCHLORIC ACID SOLUTIONS BY STRONG ANION TYPE II EXCHANGE RESINS: THE EFFECT OF COUNTER ION CONCENTRATION AND TEMPERATURE

ABSTRACT

The separation of gold and palladium ions in hydrochloric acid solutions by strong anion Type II exchange resins is studied in batch and column operations. Increases in the hydrochloric acid concentration and the temperature of the adsorption process have the effect of decreasing the adsorption capacity and the separation factor of both metals. A faster kinetics of the adsorption process of both ions results from temperature increase and this effect is higher for gold ions as a result of greater changes in its diffusivity. Although the adsorption capacity of palladium ions is lower at equilibrium conditions, the adsorption isotherms obtained suggest that they are more strongly retained by the polymers.

The high capacities of these resins for both metals permits their use in the preconcentration of gold and palladium but their application in quantitative separation is restricted by the co-elution of up to% of the interfering ion during the desorption process. The best method for ion desorption is sequential elution with% ammonia for palladium recovery followed by 0·5M thiourea in HCI 1M for the recovery of gold.     

Alkaline Phosphatase Purification: A Comparison of Prep-PAGE with Cyclic Processes

Abstract

Enzyme purification has been investigated in a preparative-scale polyacrylamide gel electrophoresis system, the Buchler Poly-Prep 200. Experimental results are presented for the optimization of this process using human placental alkaline phosphatase as a typical enzyme. The variables considered are electric field strength, feed concentration, buffer ionic strength, and buffer pH. Enzymes may also be purified by adsorption/desorption onto an ion exchange resin such as DEAE Sepharose in either of two cyclic processes-parametric pumping or cycling zone adsorption. Comparison of the three processes indicates that polyacrylamide gel electrophoresis has the highest purification factor and the greatest enzyme activity recovered, but also the lowest rate of production.     

Chromatographic Separation by Foam

Abstract

The development of a unique chromatographic separation method based on liquid foams is described. The sorption bed is liquid foam moving in a tall vertical column in plug flow manner. The foam is eluted from the top counter-currently to its motion. The mechanism of separation of mixtures is based on adsorption to bubble surface and/or utilizing the foam producing surfactant as a selective carrier. It is shown how this technique can be used for pulse as well as for continuous chromatographic separations. Results of some systematic studies on the effect of two independent variables, foam velocity and elution rate, on separation of mixtures of organic dyes is presented and discussed.     

Energy Consumption of Chemical Uranium Enrichment

Abstract

A quantitative study of chemical separation energy for enriching uranium-235 by the redox chromatography was conducted. Isotope exchange reactions between U⁴⁺-UO₂ ²⁺ ions in the enrichment column are maintained by the redox reactions. The chemical separation energy is ultimately supplied by hydrogen and oxygen gas for regenerating redox agents. The redox energy for the isotope separation is theoretically predicted as a function of the dynamic enrichment factor observed in the chromatographic development of uranium adsorption band. Thermodynamic treatments of the equilibrium reactions implies an “inverse redox reaction” which can be enhanced by the chemical potential of the ion-exchange reaction of oxidant. Experimental results showed 30 to 90% recovery of the redox energy by the inverse reaction. These results will devise a simplified redox chromatography process where a number of columns in one module is reduced.     

Mechanism of the Adsorption of Ammonium Ions from Aqueous Solution by a Chinese Natural Zeolite

Abstract

The adsorption of ammonium ions onto a Chinese natural zeolite in an agitated batch adsorber was studied. A trial‐and‐error non‐linear method was developed to examine two widely used isotherms, the Langmuir and Freundlich. The data gained from the adsorption system fitted the Freundlich isotherm better. An ion exchange model, describing the relationship among the total metal ions in the solution, NH₄ ⁺ removed from the solution, and ions initially released from the zeolite, was developed for the adsorption system. In addition, a parameter of the ion exchange potential was defined to describe the adsorption mechanism. Ion exchange was the main mechanism that accounted for the adsorption of ammonium ions onto the Chinese natural zeolite.     

Separation of Aromatic Carboxylic Acids Using Quaternary Ammonium Salts on Reversed‐Phase HPLC. 1. Separation Behavior of Aromatic Carboxylic Acids

Abstract

In order to develop separation processes and analytical methods for aromatic carboxylic acids for the coal oxidation products, the separation behavior of aromatic carboxylic acids on a reversed‐phase HPLC using eluent containing quaternary ammonium salt has been investigated. The retention mechanism of aromatic carboxylic acids was discussed on the basis of both ion‐pair partition model and ion–exchange model. The retention behavior of aromatic carboxylic acids possessing one (or two) carboxylic acid group(s) followed the ion‐pair partition model, where linear free energy relationship was observed between the capacity factor and the extraction equilibrium constants of benzoic acid and naphthalene carboxylic acid. Besides, the retention behavior followed ion‐exchange model with increasing the number of carboxylic acids, where the capacity factor of benzene polycarboxylic acids is proportional to the association constants between aromatic acids and quaternary ammonium ions calculated on the basis of an electrostatic interaction model.     

Solvent Extraction,Membranes, and Ion Exchange in Hydrometallurgical Dilute Metals Separation

Abstract

The separation methods which are used in the hydro-metallurgical field are reviewed and compared. Some processes in solvent extraction in use for recovery of crucial metals which are important to the U.S. defense and economy are presented. Various commercial extractants are reviewed and categorized. Other methods such as liquid membranes and ion exchange resins used for dilute metal ions separation are summarized. These methods are compared with solvent extraction. Problems to overcome in the further development of these separation methods are also identified and discussed in this paper.     

Cation Exchange Chromatographic Elution and Separation of Rubidium

Abstract

The systematic cation exchange chromatographic separation of rubidium on Dowex 50W-X8 was carried out with mineral acids and their salts as eluants. A selectivity scale for various eluants in terms of the elution constant was devised. Rubidium was separated from a large number of elements in binary mixtures by the process of gradient or selective elutions or selective sorption. The noteworthy feature of the method is the sequential separation of rubidium from alkali as well as alkaline earth elements.     

Multidimensional mass spectrometry methods for the structural characterization of cyclic polymers

Several synthetic methods have been developed for the tailored preparation of cyclic macromolecules due to their unique physical and chemical properties. Unequivocal characterization of the macrocyclic architectures has remained challenging, however, because isomeric linear structures often exist, or the spectral features of linear vs. cyclic chains are similar. To address this problem, multidimensional mass spectrometry (MS) techniques have been evaluated for the separation and identification of polymeric macrocycles. Tandem mass spectrometry (MS²) is found to be ideally suitable for the differentiation of linear and cyclic architectures whose molecular ions exhibit distinct fragmentation characteristics. Conversely, differences in macromolecular sizes and shapes can be exploited to identify the correct architecture by ion mobility mass spectrometry (IM-MS). A third option, chromatographic separation (LC) before MS analysis, is available for the detection of cyclics in complex mixtures. The capabilities of these techniques and combinations thereof are demonstrated with specific covalent or supramolecular (co)polymers.     

Simplified Predictions of Breakthrough Fronts for Constant-Pattern Adsorption and Ion Exchange

Abstract

The loading cycle of many (perhaps most) commercial adsorption and ion exchange operations involves a favorable isotherm. Concentration fronts for favorable isotherms approach a constant pattern for long bed lengths, and most industrial adsorption and ion exchange operations use sufficiently deep beds that the constant-pattern conditions are approached. Once a constant pattern is established, the region around the front can be analyzed using conventional methods developed for continuous absorption/stripping operations, but the location of the feed and withdrawal points must be assumed to move down the bed at the same rate at which the front moves. Using this approach, the constant-pattern front can be calculated for any shape of constant-pattern isotherm. The dimensionless distance in the bed is expressed in terms of transfer units, and the shape of the front can be evaluated graphically even when the relations can not be integrated analytically. This procedure is illustrated for binary ion exchange isotherms. In the simplest cases, exchange of ions with like charge, the integration can be performed analytically. For other cases, numerical and graphical solutions are illustrated.     

Performance of C18 Derivatized Silica Gels: A Structure-Performance Study

Abstract

Significant performance differences in the separation of desamido-insulin from insulin and of amitriptyline from imipramine have been found for five, macroscopically similar, preparative C18 silica materials. Structure-performance relations have been used to understand this difference. Physical measurements on the unpacked silica gels as well as chromatographic measurements have been carried out. The latter measurements comprise: hydrophobicity, metal impurity, steric selectivity and silanol activity. The performance difference could not be explained by the difference in hydrophobicity, steric selectivity or metal impurity between the materials. Instead a correlation between the silanol ion exchange activity and the selectivity could be found. The highest performance was found under conditions where the silanol groups have a moderate activity. For the separations considered in this work, the silanol groups have a beneficial effect.     

Isolation of Trypsin from Bovine Pancreas Using Immobilized Benzamidine and Peptide CTPR Ligands in Expanded Beds

Abstract

Peptide CTPR and p‐amino benzamidine (PAB) immobilized on Streamline? were utilized as the chromatographic matrices for trypsin purification from bovine pancreas. By using a clarified pancreas extract, maximum capacity for CTPR‐Streamline was 47.4 mg/mL and for PAB‐Streamline 78.9 mg/mL while Kd values were 0.39 and 0.38 respectively. Dynamic capacity was 23.0 and 46.0 mg/mL for CTPR‐ and PAB‐Streamline respectively. When the purification process was applied to unclarified pancreas extract in the expanded‐bed adsorption mode, 80% trypsin recovery with a purification factor of 18.7 was achieved. Cationic and anionic trypsin obtained from the affinity column were separated by ion‐exchange chromatography.     

Distribution Coefficients of 60 Elements on Cation and Anion-Exchange Resin in Ammonium Chloride Solutions

ABSTRACT

Ammonium chloride is a widely available non-corrosive and non-toxic chemical. When in contact with protein NH₄Cl is non-destructive and allows softer conditions for labeling of organic substances. These properties make NH₄Cl appropriate for use in multiple areas such as pharmaceutical production, low-background research, etc. For such purposes, a multitude of pure elements could be applied. In order to obtain pure elements their separation (purification) is necessary. One of the most successful methods of elements separation is ion exchange. In this work, we study the distribution coefficient of 60 elements on anion exchange (Dowex 1-x8) and cation exchange (Dowex 50w-x8) resins with NH₄Cl solutions with varying concentrations via ICP-MS.     

Volatile fatty acid adsorption on anion exchange resins: kinetics and selective recovery of acetic acid

ABSTRACT

The removal of volatile fatty acids was examined through adsorption on anion exchange resins in batch systems. During the initial screening step, granular activated carbon and 11 anion exchange resins were tested and the resins Amberlite IRA-67 and Dowex optipore L-493 were chosen for further investigation. The adsorption kinetics and diffusion mechanism and adsorption isotherms of the two resins for VFA were evaluated. Based on the selective adsorption capacity of the resins, a sequential batch process was tested to achieve separation of acetic acid from the VFA mixture and selective recoveries > 85% acetic acid and ~ 75% propionic acid was achieved.     

KINETIC CHARACTERISTICS OF A BATCH ADSORBER OR AN ION EXCHANGE DEVICE OPERATED UNDER NONISOTHERMAL CONDITIONS

Abstract

A model was formulated for a batch adsorber or ion exchange device with heat generation inside the bulk liquid due to mixing or electrical heating and due to heat of adsorption. Internal and external particle mass and heat transfer gradients and heat transfer through the vessel wall were included. The effective diffusion coefficient was taken to be temperature dependent. Numerical calculations (by orthogonal collocation) give conditions for the existence of intra particle nonisothermity and show the effect of mixing and process temperature on adsorption kinetics.     

Lysine Adsorption on Cation Exchange Resin. IV. Temperature Effects on Equilibrium and Kinetics in Batch and Column Systems

Abstract

Ion exchange equilibria and kinetics are determined for lysine adsorption on the strong acid cation exchanger DIAION SK‐1B at temperatures of 25, 40, and 60°C. The ion exchange equilibrium is found to be independent of temperature. Conversely, the kinetics of ion exchange increases dramatically as the temperature is increased. Average ion exchange selectivity coefficients of 6.0 g/cm³ and 0.52 are obtained for the ion exchange of divalent and monovalent cationic lysine with hydrogen ion, respectively. Resin phase diffusivities are determined by fitting batch binary ion‐exchange data with a mass transfer model based on the Nernst‐Planck equations. As the temperature is increased from 25 to 60°C, the resin phase diffusivity increases from 0.04×10^?6 to 0.14×10^?6 cm²/s for divalent lysine and from 0.16×10^?6 to 0.55×10^?6 cm²/s for monovalent lysine. The combination of temperature‐independent ion exchange equilibria and faster mass transfer at higher temperatures results in higher dynamic binding capacity and more efficient desorption of lysine when ion exchange is operated at an elevated temperature. This behavior is confirmed by means of column adsorption/desorption experiments whose results are found to be in agreement with a model incorporating the equilibrium and mass transfer data obtained in this work.     

The Comparison of Operating Time between Batchwise and Columnwise Adsorption

Abstract

The performance of separation processes for batchwise and columnwise adsorption with rectangular isotherms was compared. Experiments were carried out for the ion-exchange system of sodium hydroxide aqueous solution and MR-type cation exchange resin. The operating time was compared based on adsorption efficiencies with respect to the recovery of the solute and the utilization of adsorbent. Batchwise adsorption often required a shorter time than columnwise adsorption. The batchwise operation was more advantageous for greater mass transfer rate, larger adsorbent particles, and a shorter column.