Showing papers in "Separation Science and Technology in 1968"

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.

The Extent of Separation: A Universal Separation Index

Abstract: A universal separation index, the extent of separation, is proposed and mathematically described. This index is easily calculated, normalized, invariant to a permutation in indices, and conceptually similar to the De Donder extent of reaction. It applies to any type of separation system, any initial or final level of component purity, any concentration profile (if one exists), any initial amount of components, multicomponent systems, and both separation and mixing processes. The index is employed to characterize one of the simplest of all separation systems—the single equilibrium stage.

Study of Soluble Tungstate Species by Solvent Extraction

Abstract: Tungsten is extracted from acidic tungstate solutions by the long-chain tertiary alkyl amine, tri-n-caprylamine, in benzene. Distribution data derived from solvent extraction are interpreted in terms of the predominating tungsten species present in the aqueous phase. The results show that the nature of the tungstate species extracted by tri-n-caprylamine changes markedly with the pH of the system. Further, the order of extraction is consistent with the order in which tungstate species should form as a function of the ratio of acid equivalents to moles of tungstate ions in solution.

Gel Chromatographic Behavior of Aqueous Ferric Nitrate

Abstract: Ferric nitrate solutions with different degrees of hydrolysis were investigated on polydextran gels having various exclusion limits. Typically chromatograms exhibited two well-resolved peaks, one at the void volume and the other at the total liquid volume of the gel. The respective peaks corresponded to higher and lower molecular weight fractions of the iron in the injected sample. Similar behavior was observed in “negative-peak” investigations where the positions of sample and eluent were reversed. Frontal analysis of the iron solution showed two breakthroughs corresponding to excluded iron moving in the void volume and admitted iron moving near the total liquid volume of the gel. The molecular size distribution of the ferric nitrate samples was studied as a function of OH-Fe ratio by noting changes in the percentage of iron in the respective fractions for gels having known exclusion limits.

Application of Gel Chromatography to Small Molecules. II

Abstract: This presentation is an extension of earlier work (1) in which liquid chromatographic separations of hydrocarbons, alcohols, triglycerides, and surfactants with molecular weights ranging from 100–1000 were made, using columns packed with porous polymeric beads. The fractionation capability of the porous gels was extended to smaller molecules through the development of small porosity gels. The gels separate according to molecular size and are therefore useful for both separation and identification purposes. Since porous gels require no stationary liquid phase, long column life is achieved without a saturated carrier. In this work a high-resolution gel column system yielding greater than 180,000 theoretical plates was investigated, and the high-resolution capability of small-molecule gel permeation chromatography (GPC) was explored.

Cation-exchange separation of scandium from the rare-earth elements.

Abstract: From certain organic solvents containing organic phosphorus compounds such as trioctylphosphine oxide (TOPO), bis(2-ethylhexyl)orthophosphoric acid (HDEHP), or tri-n-butylphosphate (TBP) and hydrochloric acid, scandium is much less retained on the strongly acidic cation-exchange resin Dowex 50 than are all other members of the rare-earth group. Thus on this resin in a medium which is 95% tetrahydrofuran, 5% 6 M hydrochloric acid, and 0.1 M TOPO, the separation factor for scandium-rare earths is greater than 4 × 103 (corresponding to distribution coefficients of 4 × 103 for all the other rare-earth elements). By the use of this system a complete and highly effective separation of tracer and macro quantities of scandium from the rare earths can be achieved on a column of this exchanger. Among the organic solvents investigated, tetrahydrofuran gives the best results. The effectiveness of the organic extractants increases in the order TBP < HDEHP < TOPO

On the Mechanism of Gel Chromatography of Inorganic Salts

Abstract: Sorption isotherms, spectroscopic studies, and chromatographic retention data were used to elucidate the mechanisms involved in the separation of strong electrolytes on polyacrylamide gels. For the most part Bio-Gel P-2 was investigated but some results on the dextran gel Sephadex G-10 are also discussed. On P-2 the primary mechanism is not sieving or exclusion on the basis of size but rather a weak physical sorption of the cations to the gel and probably a hydrogen-bond interaction between the anions and the amide hydrogens. Molecules and ions which are not sorbed on the gel are partly excluded from a fraction of the internal solvent volume which is involved in hydration of the gel matrix and is firmly bound to it. When chromatographing solutions at low sample concentrations on some polyacrylamide gels, Kn falls off drastically. This effect is more pronounced in Sephadex than in Bio-Gel and it has been interpreted as resulting from a Donnan exclusion of anions which arises from a small number of...

Extraction of Sulfuric Acid in the Tri-n-caprylamine-Benzene System

Abstract: Solvent extraction, molecular weight determination, and infrared analysis have been used to study the nature of the amine salt present in the organic phase in the extraction of sulfuric acid by tri-n-caprylamine. Tri-n-capryl-amine in the concentration range of 0.05–0.25 M extracts sulfuric acid to form either the normal sulfate or the bisulfate salt, depending on the concentration of acid in the aqueous phase. The normal sulfate is monomeric, while the bisulfate is dimeric. Characteristic infrared absorption bands, attributable to the normal sulfate and the bisulfate salt form, were observed.

A Theory of Chemical Separations: The Fundamental Equation for Ideal Partitioning Separation Systems

Abstract: The fundamental conservation-of-mass equation is derived for linear one-dimensional chemical systems in which no lateral diffusion or rate control exists. The theoretical results are applied to (a) a comparison of the fields of chemical separations, thermodynamics, and kinetics; (b) the derivation of a general equation for gradient elution and programmed temperature chromatography; and (c) the description of three new carrier chromato-graphic techniques, carrier magnetochromatography, solid phase carrier electrochromatography, and inverse carrier electrochromatography. The role of chemical equilibria in chromatographic systems is briefly discussed.

Performance Characteristics of a New Continuous-Flow Electrophoresis Instrument

Abstract: An instrument is described for the continuous separation of particles by means of electrophoresis. The effect of field strength, electrolyte flow rate, and sample flow rate on migration distance and particle band width were investigated. The interrelationships between the various operational parameters and particle band resolution are discussed.

The Extent of Separation: Applications to Elution Chromatography

Abstract: The fundamental equations for calculating the extent of separation in binary elution chromatographic systems are derived. At a specific instant of time, the elution curve in such systems is characterized by two quantities: the optimum cut-point location and the optimum extent of separation. Equations relating the optimum extent of separation to the resolution and to the extent of separation for a single equilibrium stage are given. A number of figures obtained from computer examples illustrate the use of the theoretical results, A new type of component detector—a mobile detector—is proposed.

A General Plate-Height Expression for Open Tubular Column Chromatography

Abstract: The plate-height behavior of open tubular columns, for both gases and liquids, has been studied fundamentally in the turbulent flow region. Appriate analytical expressions have been established on the basis of a purely phenomenological description of turbulent flow dynamics. It has been shown that under these flow conditions, the plate height decreases with increasing Reynolds number and that, most significantly, this decrease is strongly dependent on the mass distribution coefficient.

Determination of Water Associated with Some Iron Acetylacetonates and Nickel Glyoximes Extracted into CHCI3

Abstract: Utilizing the Karl Fischer titration technique for the quantitative determination of water, the number of water molecules associated with a molecule of chelate when extracted from water into chloroform was determined for five chelates in the acetylacetone and dimethylglyoxime types. In this investigation no increase in the number of associated water molecules was observed as the bulkiness of the ligand was increased by the substitution of electron-withdrawing groups for methyl groups on the ligand, nor was any increase noted when the metal ion in the chelate was less sterically hindered to the approach of water molecules than in the phenanthroline chelates. The fact that the chelate contains hydrogen-bonded sites does not appear to affect the number of water molecules associated with the chelates investigated here.

Products of the Reaction between Alcohols and Phosphorus Pentoxide: II. Chromatographic Separation of the Products

Abstract: Various solvents and operating conditions were investigated for paperchromatographic separation of the various esters in the mixture obtained by the reaction P4O10 + 4ROH. Optimum separation was obtained with a propanol-isobutanol-water-ammonia solvent at 10° during 16 hr and perchloric acid-ammonium molybdate developer. These conditions were found to produce complete separation in all investigated mixtures, independently of the nature of the organic chain in the esters. Preparative separation of the various products was obtained by column chromatography, using the same solvent as in paper chromatography on a cellulose-packed column.

An Experimental Study of Gas Chromatography in the Turbulent Flow Region in Open Tubular Columns

Abstract: The decrease in the plate height with increasing Reynolds number, predicted by theory, has been verified for gas chromatography in open tubular columns. It has been shown that this decrease is most pronounced when the mass distribution coefficient k = 0 and considerably lessened for k > 0. The Golay equation has been found to break down at relatively low flow velocities, viz., Re ∼ 200.

Chelate Extractions Involving Three Liquid Phases: Role of Water

Abstract: An experimental technique has been developed to determine the effect of solvent polarity on the removal of associated water molecules from metal chelates during extraction. It was found that tris(4,7-diphenyl-1,10-phenanthroline)iron(II) perchlorate had two spheres of water associated with it—one that could be displaced by organic solvent and one that could not.

The Effect of Water on the Distribution of Uranyl 8-Quinolinol Chelate between Nitromethane and 1-Decanol

Abstract: An equation of the form y = ABecxn describes the effect of associated water on the distribution ratio of this nonaqueous extraction. It was also determined that there are 9.6 ± 1.5 molecules of water associated per molecule of the chelate when extracted from water into nitromethane or 1-decanol.

Studies of the Formation and Stability of Urea Inclusion Compounds

Abstract: A study was undertaken to determine the relative ease of formation and stability of straight-chain primary and secondary alkanols capable of forming urea inclusion compounds. The compounds studied were 1-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 1-octanol, 3-octanol, 4-octanol, 1-nonanol, 4-nonanol, 5-nonanol, 1-decanol, 1-undecanol, and 1-dodecanol. 1-Heptanol was the shortest alcohol that formed an inclusion compound by the procedure employed. The ease of formation of a straight-chain alcohol was proportional to the number of uninterrupted methylene groups (—CH2—) present. The ease of urea inclusion compound formation generally decreases as the functional group approaches the center of the chain. These conclusions were based on X-ray powder diffraction measurements and the weight of recovered products under equilibrium conditions.

Theoretical Considerations Regarding Tandem Column Arrangements with Application to Gas-Liquid and Gel Permeation Chromatography

Abstract: It is proven that, given a constant flow rate throughout the system, the (2n) possible arrangements (including 180° rotation of any column along the long axis) of n chromatography columns arranged in tandem yield identical elution curves (and therefore identical values of mean residence time and variance). The columns must be of the same cross-sectional area but each can be of arbitrary length. The proof is independent of the nature of the packing material in each column and holds for any given input distribution in time and/or constitution. Also discussed are earlier results for a much more restrictive model, proving the equivalence of n columns in tandem with one long column containing a homogeneous mixture of the n types of packing material in the proper proportion.

The Influence of Axial Dispersion on the Fixed-Bed Adsorption of the Hydrogen Chloride-Chromium Oxinate System

Abstract: The results from a study of the removal of gaseous hydrogen chloride by the solid, metal organic complex, chromium oxinate, in a fixed-bed adsorption column is presented in the form of adsorption curves or exit gas concentration histories. These experimental curves are subsequently compared to the solutions of a theoretical mathematical model representing the adsorption process. The model incorporates axial diffusion, as described by G. I. Taylor. A gas phase mass-transfer resistance and a solid-phase adsorption-desorption rate were considered as the mechanisms for the adsorption model. The solutions to the mathematical model were generated by an analog computer.

Extraction of Bis(2,9-Dimethyl-4,7-Diphenyl-1,10-phenanthroline)Cu(1) Perchlorate and Bis(1, 10-phenanthroline)Cu(1) Perchlorates into Nitrobenzene and Chloroform: Role of Water

Abstract: The number of molecules of water associated with the bis(l,10-phenan-throline)Cu(I) perchlorate extracted into nitrobenzene was found to be 12 ± 3 and for the bis(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline)Cu(I) perchlorate in chloroform, 0 ± 3.

A New Method of Purification of Raw Mixtures of Alkaloids

Abstract: In this paper a new method of purification of raw mixtures of alkaloids by dialysis of aqueous solutions of their salts through a semipermeable membrane is described. The results obtained by using this method of purification of raw mixtures of alkaloids from plant extracts and mother liquors after crystallization of the major alkaloid have been given. In all cases under investigation this method of purification gave crystalline substances.

Computer Calculation of Counter-Double-Current-Distribution Curves

Abstract: A practical method is reported for the calculation by digital computer of counter-double-current-distribution curves of ideal solutes. The method is applicable for the calculation of batchwise operations of the distribution train when the solute is loaded in any number of tubes at any position in the train. Application of the method permits the calculation of the distribution of solutes in the train and in the effluent fractions. The results of calculations of the effects of several modes of operation of the counter-double-current-distribution train are presented. The distribution of a mixture of isoleucine and valine center-loaded into 38 tubes of a 58-tube train is presented as an example.

Preparation of Highly Purified 1,3-Dimethyl-5-t-butylbenzene by Normal Freezing

Abstract: A combination of fractional distillation and normal freezing was used to purify 1,3-dimethyl-5-t-butylbenzene. Analysis by gas chromatography indicates that the final product was > 99.999% pure. A number of physical constants are given of the pure material.