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Capillary electrokinetic separations: Influence of mobile phase composition on performance

Description: The composition of the mobile phase employed in capillary zone electrophoresis and the related technique, micellar electrokinetic capillary chromatography, is an important factor in determining separation performance. The influences of ionic salt, surfactant, and organic solvent mobile phase additives on separation efficiency, retention, and elution range are discussed and demonstrated. 23 refs., 2 figs., 2 tabs.
Date: January 1, 1990
Creator: Sepaniak, M.J.; Swaile, D.F.; Powell, A.C. & Cole, R.O.
Partner: UNT Libraries Government Documents Department

Carrier facilitated transport through membranes

Description: Facilitated transport is a process whereby the diffusion of a solute across a membrane is chemically enhanced. In this report an analysis is given of a facilitated transport system involving a volatile species A which reacts with a nonvolatile carrier species B to form the nonvolatile product AB. The species A is transported across the membrane by ordinary diffusion, as well as by the diffusion of the product AB. It is assumed that the reaction rates are large, so the reactions are confined mostly to thin boundary layers near the surfaces of the membrane. The method of matched asymptotic expansions is used to derive the asymptotic solution of the nonlinear boundary value problem governing equilibrium. The effect of various parameters on the facilitation factor is analyzed in detail.
Date: June 1, 1980
Creator: Kaper, H.G.; Leaf, G.K. & Matkowsky, B.J.
Partner: UNT Libraries Government Documents Department

Capillary liquid chromatography using laser-based and mass spectrometric detection

Description: The DOE-supported research performed during the past year has mainly focused on investigating and minimizing three problems that limit the practical utility of these capillary electrokinetic separation techniques in chemical analysis. (1) Analyses are hindered by poor reproducibility. This is largely a result of complicated and irreproducible capillary wall-solute interactions that often result in adsorption and mobility changes. (2) While the (micellar electrokinetic capillary chromatography) (MECC) technique permits the separations of neutral solutes, hydrophobic compounds are difficult to separate and manipulation of capacity factors (k's) is critically important. (3) The very small solute band volumes require that on-column detection be performed (usually optical detection) and this seriously limits detectability. In addition to these projects, the electrokinetic equivalent of affinity chromatography and development of remote fiber-optic sensors to measure chemical carcinogens and other compounds have been investigated. 5 refs., 2 figs.
Date: January 1, 1990
Creator: Sepaniak, M.J. & Cook, K.D.
Partner: UNT Libraries Government Documents Department

Adsorption on mixtures of ion exchangers

Description: A theoretical study has been made of adsorption on mixtures of ion exchangers. The effect of variables such as the concentration of the ion being adsorbed, the concentration of the supporting electrolyte, loading, the values of the capacities and equilibrium constants for the various exchange processes, and the fraction of each adsorber in the mixture on the observed distribution coefficient has been investigated. A computer program has been written to facilitate the calculation of distribution coefficients for the adsorption of an ion on a given mixture of ion exchangers under a specified set of conditions.
Date: March 1, 1979
Creator: Triolo, R. & Lietzke, M.H.
Partner: UNT Libraries Government Documents Department

Loading and unloading resin from MPPF rapid ion-exchange columns

Description: A process was developed which permits changing the resin in the Multipurpose Processing Facility Rapid Ion Exchange columns, without replacing the entire column assembly. The columns remain on the rack during the resin removal and replacement. The resin displacement process consists of a resin unloading and a resin loading step. During resin removal, the spent resin is hydraulically displaced from the columns to a resin collection tank, and then transferred to the evaporator for dissolution. Fresh resin is loaded into the empty column by hydraulic displacement or a combination of vacuum loading followed by hydraulic displacement. In the hydraulic displacement loading process, the amount of fresh resin needed to load the columns is transferred to a resin displacement tank where the resin is hydraulically displaced to the appropriate column. In the vacuum loading process, part of the resin feed is loaded directly into the column by applying a negative pressure to the column.
Date: October 1, 1981
Creator: Ng, W.C.
Partner: UNT Libraries Government Documents Department

Future directions for separation science in nuclear and radiochemistry

Description: Solvent extraction and ion exchange have been the most widely used separation techniques in nuclear and radiochemistry since their development in the 1940s. Many successful separations processes based on these techniques have been used for decades in research laboratories, analytical laboratories, and industrial plants. Thus, it is easy to conclude that most of the fundamental and applied research that is needed in these areas has been done, and that further work in these ''mature'' fields is unlikely to be fruitful. A more careful review, however, reveals that significant problems remain to be solved, and that there is a demand for the development of new reagents, methods, and systems to solve the increasingly complex separations problems in the nuclear field. Specifically, new separation techniques based on developments in membrane technology and biotechnology that have occurred over the last 20 years should find extensive applications in radiochemical separations. Considerable research is needed in such areas as interfacial chemistry, the design and control of highly selective separation agents, critically evaluated data bases and mathematical models, and the fundamental chemistry of dilute solutions if these problems are to be solved and new techniques developed in a systematic way. Nonaqueous separation methods, such as pyrochemical and fluoride volatility processes, have traditionally played a more limited role in nuclear and radiochemistry, but recent developments in the chemistry and engineering of these processes promises to open up new areas of research and application in the future.
Date: January 1, 1986
Creator: Pruett, D.J.
Partner: UNT Libraries Government Documents Department

Rate phenomena in uranium extraction by amines

Description: Kinetics studies and other rate measurements are reviewed in the amine extraction of uranium and of some other related and associated metal ions. Equilibration is relatively fast in the uranium sulfate systems most important to uranium hydrometallurgy. Significantly slow equilibration has been encountered in some other systems. Most of the recorded rate information, both qualitative and quantitative, has come from exploratory and process-development work, while some kinetics studies have been directed specifically toward elucidation of extraction mechanisms. 71 references.
Date: January 1, 1979
Creator: Coleman, C.F. & McDowell, W.J.
Partner: UNT Libraries Government Documents Department

Separation and characterization of coal derived components. Quarterly report, 1 October 1983-31 December 1983

Description: No new field-ionization data was obtained this quarter. For preasphaltenes, elemental analysis data was obtained on Kentucky and Wyodak preasphaltene samples. In conjunction with the preasphaltene work, solubility and thin-layer chromatography experiments were performed. The results indicated that basic alumina would not be useful as a general stationary phase for the separation of preasphaltenes. Several experiments were carried out with Chromasorb T, and the results showed it would be an adequate substitute for Fluoropak. The hydrocarbons in a sample from Pittsburgh Energy Technology Center were separated by the number of double bonds. The optimum mobile phases for the separation of monohydroxyl aromatics and dihydroxyl aromatics by reversed-phase liquid chromatography were obtained. In addition, a means of predicting retention in normal-phase chromatography was considered, and a NO/sub 2/ high-performance chromatographic column showed promise for the separation of compound classes. 6 references, 4 figures, 7 tables.
Date: January 16, 1984
Creator: Hurtubise, R.H. & Silver, H.F.
Partner: UNT Libraries Government Documents Department

Synthesis and analysis of novel polymers with high permselectivity and permeability in gas separation applications

Description: Significant progress was made toward developing advanced materials for gas separation membrane applications and rationalizing molecular structure and efficacy: Synthesized and tested polyarylates based on terephthalic or isophthalic acid or a tertiary butyl derivative of the isophthalic acid with different diols to illustrate the effects of: opening'' the matrix by incorporation of bulky packing inhibiting groups such as the tertiary butyl moiety inhibition of backbone motion via meta connected backbone connections and tightening'' of the matrix by incorporation of polar halogens. Completed high temperature characterization of sorption and transport properties for novel materials. Continued studies of the phenyl-substituted polymers aimed at producing super stable high temperature useful polymers for gas separations. Synthesized a polyarylate based on the spirobiindane diol and bibenzoyl acid chloride to incorporate long flat packable bibenzoyl units between packing disruptive spirobiindane units in an attempt to control the segmental level morphology to produce highly selective bottleneck'' regions between highly open regions.
Date: December 31, 1991
Creator: Koros, W.J. & Paul, D.R.
Partner: UNT Libraries Government Documents Department

Mathematical model for multicomponent separations on the continuous annular chromatograph

Description: A model for multicomponent separations on ion exchange columns has been adapted for use in studying the performance of the continuous annular chromatograph. The model accurately predicts solute peak positions in the column effluent and qualitatively predicts trends in solute effluent resolution as a function of increasing bandwidth of the solute feed pulse. The major virtues of the model are its simplicity in terms of the calculations involved and the fact that it incorporates the nonlinear solute-resin binding isotherms common in many ion exchange separations. Because dispersion effects are not accounted for in the model, discrepancies exist between the shapes of the effluent peaks predicted by the model and those determined experimentally.
Date: December 1, 1980
Creator: Bratzler, R.L. & Begovich, J.M.
Partner: UNT Libraries Government Documents Department

Multi-column step-gradient chromatography system for automated ion exchange separations

Description: A multi-column step-gradient chromatography system has been designed to perform automated sequential separations of radionuclides by ion exchange chromatography. The system consists of a digital programmer with automatic stream selection valve, two peristaltic pumps, ten columns, and a fraction collector. The automation allows complicated separations of radionuclides to be made with minimal analyst attention and allows for increased productivity and reduced cost of analyses. Results are reported for test separations on mixtures of radionuclides by the system.
Date: January 1, 1985
Creator: Rucker, T.L.
Partner: UNT Libraries Government Documents Department

A theoretical model for adsorption capacities of charcoal beds: I, Relative humidity effects

Description: Water vapor is the major interferent in the adsorption of other vapors from air when that air is passed through an activated charcoal bed. A limited amount of data (published and unpublished) is available on the magnitudes of capacity (or service life) reduction as a function of relative humidity (water vapor concentration) and preadsorbed water. A simple equilibrium model has been developed which quantitatively explains observed humidity effects and allows extrapolation of data to untested conditions. 9 refs., 4 figs., 2 tabs.
Date: January 1, 1987
Creator: Wood, G.O.
Partner: UNT Libraries Government Documents Department

Design and synthesis of reactive separation systems

Description: During the last decade there has been a rapid upturn in interest in reactive distillation. The chemical process industry recognizes the favorable economics of carrying out reaction simultaneously with distillation for certain classes of reacting systems, and many new processes have been built based on this technology. Interest is also increasing by academics and software vendors. Systematic design methods for reactive distillation systems have only recently begun to emerge. In this report we survey the available design techniques and point out the contributions made by our group at the University of Massachusetts.
Date: January 1, 1992
Creator: Doherty, M.F.
Partner: UNT Libraries Government Documents Department

Chelating extractants of improved selectivity. Progress report for period November 1, 1977--July 31 1978

Description: During the current contract period, the high susceptibility of lanthanide chelate stability to steric hindrance was confirmed. The increase in coordination number of lanthanides from lanthanum to ytterbium as evidenced from extraction equilibria serves to increase their separability. 8-Quinolinol immobilized on silica can separate lanthanide ions.
Date: August 1, 1978
Creator: Freiser, H.
Partner: UNT Libraries Government Documents Department

Fundamental studies of separation processes. Technical progress report

Description: Three technical reports have been prepared which deal with the subjects of optimization in supercritical fluid chromatography, the gas chromatographic fractionations of the isotopes of carbon and oxygen in carbon monoxide, and a method for measuring the information content of a complex chromatogram. A fourth report, in preparation, compares different liquid chromatographic column packings with respect to the fractionation of a mixture of oligomers of polystyrene. Two other studies are relatively far along. One is a study of the recycle mode of operation as applied to gas chromatography. The second one deals with the fractionation of vanadium compounds in Boscan petroleum crudes. Finally, there are three other studies that are just getting started. The first involves an examination of pattern recognition as applied to coal tars and petroleum pitches. The second is exploring the possibility of using high-pressure gas chromatography to characterize carbon blacks and charcoals. The third is the long-delayed study of column-switching techniques that do not involve recycle.
Date: August 1, 1979
Creator: Rogers, L.B.
Partner: UNT Libraries Government Documents Department

Cation exchange at pressures up to 400 M Pascals

Description: The effects of pressures up to 400 MPa (approximately 60,000 psi) on the capacity factors of sodium, potassium, rubidium, lithium and magnesium ions were studied using nitrate eluents. The capacity factors, corrected for compression, were changed by almost 25% for rubidium and potassium ions by going from atmospheric pressure to 350 MPa. The corrected capacity factor for magnesium ion changed 15%, whereas those for lithium and sodium were essentially unchanged. The effect was attributed to changes in sizes of the hydrated cations.
Date: January 1, 1977
Creator: Prukop, G. & Rogers, L. B.
Partner: UNT Libraries Government Documents Department

Distribution of naphthalene between commercial resins and water--methanol solutions

Description: Several XAD resins, two of their chemically modified derivatives, and two carbon absorbents were evaluated by measurement of distribution coefficients using the batch method. Numerical comparison of distribution data and graphical interpretation of these resins were also presented. The distribution differences were explained in terms of resin structure and solvent compositions. Naphthalene was the solute for the study, and methanol the solvent. It was found that Spherocarb, a newly developed carbon adsorbent, had very large distribution coefficient. However, in the application for separation, desorption can conceivably be a problem. Distribution data collected can be a valuable aid in the choice of adsorbent, solvent composition and other operating conditions in separation work.
Date: December 1, 1977
Creator: Chu, F.K.C.
Partner: UNT Libraries Government Documents Department

Anion exchange of 58 elements in hydrobromic acid and in hydriodic acid

Description: Anion exchange distributions of 58 elements have been measured from 0.1-8.7M HBr and from 0.1-7.4M HI onto three strong-base resins, 8 and 4% cross-linked and macroporous. Data were obtained by 16- to 18-h dynamic batch contacts. Anion exchange in these media is compared to that in HCl. The effect of resin cross-linkage is considerably greater in HI media than in HBr and HCl media. Examples are presented of potentially useful separations using HBr and HI media alone and in combination with HCl.
Date: February 1, 1978
Creator: Marsh, S.F.; Alarid, J.E.; Hammond, C.F.; McLeod, M.J.; Roensch, F.R. & Rein, J.E.
Partner: UNT Libraries Government Documents Department

Status of /sup 241/Am recovery and purification at Los Alamos Scientific Laboratory

Description: Americium recovery was initiated at Los Alamos Scientific Laboratory (LASL) in the late 1940's. The early procedures separated gram quantities of americium from large amounts of impurities including plutonium and the rare earths. Ion exchange procedures were developed for further purification. Until recently, no routine processing of americium has been done at LASL for several years. The increasing demand for americium in oil-well logging instruments and other uses led LASL to develop and install a process to recover larger quantities of americium. The LASL process was developed around the chemistry of americium that had been elucidated both at LASL and at other facilities. Presently, the americium feed is obtained as a by-product from a plutonium purification process at the new plutonium facility at LASL. This feed filtrate from a peroxide precipitation process is precipitated as a slurry of hydroxides, filtered, dissolved in nitric acid, and passed through an anion exchange column to remove any residual plutonium. The americium, contained in the effluent, is precipitated as the oxalate and calcined to the oxide. Americium is also available in other highly salted acidic process streams. These should lend themselves to solvent extraction. Developmental work has been promising, and a dibutyl butyl phosphate-kerosene extraction process is being brought on-line.
Date: January 1, 1980
Creator: Ramsey, H.D.; Clifton, D.G.; Hayter, S.W.; Penneman, R.A. & Christensen, E.L.
Partner: UNT Libraries Government Documents Department

Design requirements for uranium ion exchange from acidic solutions in a fluidized system

Description: A fluidized, countercurrent ion-exchange system was developed, operated, and evaluated by the Bureau of Mines in support of its objective to help assure an adequate uranium supply for future national needs. The system consisted of integrated multiple-compartment absorption and elution columns in which the solution flows are continuous, except for short periods when resin increments are withdrawn. The exchange of uranyl sulfate between a simulated acid-leach-uranium solution and a strong-base, ion-exchange resin was studied, together with subsequent elution using an acidified sodium chloride solution. The effects of the number of compartments, compartment height, amount of resin withdrawal, solution flow rate, and column diameter were investigated. Also examined were the kinetic and equilibrium relationships for the absorption and elution steps. The experimental data indicate a strong interdependence between variables. Solution retention time appears to be a major limiting variable in the absorption process, while resin residence time is the determining factor in the elution process. The columns system was efficient over a range of conditions, but close control was needed for optimum operation.
Date: January 1, 1974
Creator: Traut, D.E.; Nichols, I.L. & Seidel, D.C.
Partner: UNT Libraries Government Documents Department

Application of pressurized ion exchange to separations of transplutonium elements

Description: High-pressure ion exchange chromatography, used first for nucleic acid separations, was applied to the production of the heavier actinides, particularly the transcurium elements. Its use at the TRU plant is described. Future developments are considered briefly. (DLC)
Date: January 1, 1980
Creator: Campbell, D.O.
Partner: UNT Libraries Government Documents Department

Synthesis and characterization of an N-(2-hydroxyethyl)-ethylenediaminetriacetic acid resin

Description: A chelating ion-exchange resin with N-(2-hydroxyethyl)ethylene-diaminetriacetic acid (HEDTA) used as the ligand chemically bonded to XAD-4 by an ester linkage, HEDTA-4, was synthesized. It is stable under normal experimental conditions with the liquid chromatograph. The structure of the resin was confirmed by an infrared spectrum, and by potentiometric titrations. The capacity of the resin was also obtained by potentiometric titration and by a nitrogen analysis. The resin was used to pack a column of 5 mm internal diameter and 5 cm long. The effect of pH on the retention of different metal ions on the resin was studied. It was found that the resin was most selective for chromium(III), copper(II), lead(II), mercury(II), uranium(VI), zirconium(IV) and zinc(II) at a pH of less than 3. Furthermore, the resin proves to be functioning with a chelating mechanism rather than ion-exchange, and it can concentrate trace metal ions in the presence of a large excess of calcium and magnesium. This makes the resin potentially useful for purifying and analyzing drinking water.
Date: October 1, 1977
Creator: Lai, Y. F.
Partner: UNT Libraries Government Documents Department

Multi-temperature gas chromatography using isothermal columns in series. Technical report

Description: A computer-controlled three-oven gas chromatograph having a multi-position stream-switching valve has been used first to divide a wide-boiling mixture of n-alkanes into three cuts and then to fractionate each cut using a packed column at a different temperature. After initial injection of the sample into the highest temperature column, the low boilers were switched to a low temperature oven. Then, the mid-boilers were switched to a column at an intermediate temperature. For routine repetitive analyses, the multi-oven approach offers an attractive alternative.
Date: August 11, 1980
Creator: Spencer, W.A. & Rogers, L.B.
Partner: UNT Libraries Government Documents Department