Continuous Annular Chromatograph Research Articles

Separation characteristics of boron isotopes in continuous annular chromatography

A well designed continuous annular chromatograph (CAC) column was set to study the enrichment of Boron isotopes. The column is 820 mm high and consists of a rotational annulus with an outer diameter of 246 mm and a width of 15 mm. The weak basic resin (Diaion WA21J), the boric acid and water were used as the absorbent, the feed and the eluent respectively. The effects of CAC rotating speed, concentration of boric acid and flow ratio of eluent to feed on the enrichment of 10B were investigated. The concentration of boron isotope was determined by a Thermal Elemental X7 ICP-MS (Thermo Electron Co., USA). It is shown from the experimental results that 10B and 11B can be separated effectively by this CAC column. By fitting the experimental elution profiles based on reliable mathematic models and software the mass transfer coefficient k and adsorption equilibrium constant K values of 10B and 11B in CAC column were estimated. It is clear from this study that the CAC has practical continuous operational capabilities in comparison with fixed batch chromatography and is an effective technology for separating boron isotopes.

Influence of Reaction Kinetics on the Performance of a Chromatographic Reactor

In general, the economic use of chromatographic reactors depends on the reaction and separation parameters. In this work, the continuous annular chromatograph as multifunctional reactor (CACR) and the CACR with upstream tube reactor (TUBR + CACR) were investigated.

Two separation modes combined in one column: sequential ion-exchange separation and size-exclusion chromatography of green fluorescent protein

Purification of green fluorescent protein from a crude solution has been investigated using a combined system of ion-exchange chromatography and size-exclusion chromatography packed into one column of a continuous annular chromatograph. Performing the chromatography with two different sorbents packed into a single column reduces transfer losses and the hold steps between the two separation steps can be eliminated. Appropriate running conditions for the continuous separation mode were achieved by searching for optimal ones in conventional batch-wise operation. Green fluorescent protein was expressed in Saccharomyces cerevisiae, enzymatically lysed and the extract was used as the feed stock. Superdex 200 prep grade was packed into an annular chromatograph (outer diameter: 15 cm, inner diameter: 14 cm) and on top a 1.5 cm layer of the anion-exchange sorbent Source 30 Q. Green fluorescent protein was enriched by the anion-exchange resin and further purified by the size-exclusion gel. Purity was analyzed by sodium dodecyl sulfonate–polyacrylamide gel electrophoresis (SDS–PAGE), Western blotting, fluorescence intensity, and analytical size-exclusion chromatography.

Heat Transfer and Hydrodynamics in Preparative Continuous Annular Chromatography (P-CAC)

Radial velocity profiles due to radial temperature gradients inside a preparative continuous annular chromatograph (P-CAC) are calculated and their influence on the separation performance is studied. A commercially available version of a P-CAC, which can be thermostatted from the inner cylinder, is investigated. The coupled equations for heat transfer and fluid flow are solved with a finite difference method. As an example, the movement of a concentrated and an infinitely diluted aqueous sucrose solution through a cation exchange resin is examined. Calculations are performed for a desired operating temperature of 60 °C and different inlet temperatures. The influence of the velocity profiles on the elution profiles is first investigated for the simple case, where only temperature effects occur, and second in combination with mass transfer effects. A comparison with peak broadening in the isothermal case shows that the influence of mass transfer and temperature is of the same magnitude.

Separation of protein mixtures by continuous annular chromatography with step elution

The chromatographic separation of protein mixtures with step elution was studied in a continuous annular chromatograph (CAC) unit. A truly continuous, steady-state separation of mixtures of bovine serum albumin and hemoglobin was obtained with the strong-acid, macroporous resin S-Sepharose. With an appropriate selection of operating conditions, an essentially complete separation was obtained, with a simultaneous concentration of the more strongly retained species, hemoglobin. A model was developed to predict the CAC behaviour step elution conditions. The model predictions, based solely on independently derived values of equilibrium and rate parameters, were found to be in excellent agreement with the experimental results, so long as the resolution of different hemoglobin variants did not occur. Except for these conditions, the model provides a useful tool for design and optimization, and a comparison with the experimental results shows that the continuous step elution fractionation of protein mixtures by CAC can be obtained with essentially the same resolution as that of an equivalent conventional chromatograph.

Displacement separations by continuous annular chromatography

AbstractContinuous displacement chromatography separations are obtained using a continuous annular chromatograph (CAC). The apparatus consists of a rotating annular bed. At fixed positions at the top of the bed, four solutions are continuously supplied: the feed mixture to be separated, a displacer solution, a regenerant, and a rinse. The four solutions flow concurrently through the bed with little mixing. If the bed is sufficiently deep, a fully developed displacement train forms and the separated components are continuously recovered at various angular locations at the bottom of the bed. Mixtures of amino acid were separated by cation exchange displacement chromatography in a laboratory‐scale CAC. Separation and concentration of dilute mixtures was obtained with a continuous separation performance comparable with the performance of a conventional chromatograph. A mathematical model is developed to describe the separation and provide guidance in design and optimization.

Sugar Separations on a Pilot Scale by Continuous Annular Chromatography

AbstractA pilot‐scale continuous annular chromatograph has been developed for scale‐up and optimization studies. The chromatographic apparatus consists of a slowly rotating annular bed of sorbent material. The feed mixture which is to be separated is continuously introduced at a stationary point at the top of the bed, while eluent flows over the remainder of the annulus. The rotation of the sorbent bed coupled with the elution development induced by the downflow of eluent causes the feed components to appear as individual helical bands, each of which has a characteristic, stationary exit point. The separation of sucrose, glucose, and fructose, using the calcium form of a cation‐exchange resin, was investigated using water as the eluent. Experiments were carried out both with a synthetic mixture of the sugars as well as with an industrial feedstock. The separation was explored first in a bench‐scale conventional fixed‐bed column and then in the pilot‐scale continuous chromatograph. Factors such as column loading, feed‐to‐eluent ratio, and feed concentration were investigated both experimentally and theoretically. The results of bench‐scale experiments were carried out in the limit of infinite dilution, almost perfectly scaled to the pilot unit when loading was low and feed mixtures were of low viscosity. Very significant deviations from ideality were, however, observed at high feed loadings, when the feed viscosity exceeded that of the eluent by more than a factor of 2.

SEPARATION OF METALS BY CONTINUOUS ANNULAR CHROMATOGRAPHY WITH STEP ELUTION

Abstract A continuous annular chromatograph (CAC) was used to separate dilute aqueous mixtures of iron and chromium salts using Dowex 50W-X8 as the sorbent. While an isocratic separation of the two species could be easily obtained, this mode of operation resulted in excessive dilution of the products. Introduction of a step in eluent concentration, however, permitted a much more efficient separation of the two metals. Separation of Fe3+ and Cr3+remained nearly complete but elution of the more strongly retained species (Cr3+) occurred over a much narrower angle and dilution of the product streams was significantly reduced or even eliminated in some cases. A theoretical model was developed to describe the operation of the continuous annular chromatograph with step elution. With the inclusion of significant dispersive factors (axial dispersion and film mass transfer resistance), the solution of the model equations provided an excellent prediction of the experimental CAC data. Similar improvements to the CAC ...

Pilot-scale studies of sugar separations by continuous chromatography

A pilot-scale continuous Chromatograph has been developed for optimization studies and scaling factor evaluations. The continuous annular Chromatograph consists of a slowly rotating annular bed of ion exchange resin to which feed is continuously introduced at a stationary point at the top of the bed while eluent flows over the remainder of the annulus. The rotation of the sorbent bed coupled with the simultaneous elution chromatography causes the separated components of the feed stream to appear as helical bands, each of which has a characteristic, stationary exit point.

Separation of sugars by continuous annular chromatography

Continuous chromatographic separations of aqueous fructose-glucose-sucrose solutions have been investigated in a laboratory-scale continuous annular chromatograph (CAC) using calcium-exchanged Dowex 50W-X8 resin. Comparative studies have also been conducted using a conventional fixed-bed column packed with the same resin. Complete resolution of fructose-glucose mixtures could be obtained both in a 60-cm-long CAC and in a conventional column of the same length with a sugar feed concentration of up to 200 g/L. Partial resolution of sucrose in three component mixtures was also obtained, and the three sugars were completely separated from added higher-molecular-weight saccharides. Results have been analyzed in terms of approximate linear chromatographic theories and orthogonal collocation of exact mass transfer model equations for fixed and rotating beds. A systematic, comparative evaluation of factors affecting process performance and design procedures is presented.

Continuous ion exchange separation of zirconium and hafnium using an annular chromatograph

A pressurized continuous annular chromatograph (CAC) has been developed for truly continuous ion exchange preparative separations. This device utilizes a slowly rotating annular bed of sorbent material, fixed multiple feed points, and fixed withdrawal locations. Most of our investigations have been performed with a CAC of 280 mm diameter and 600 mm in length, but a larger model has recently been designed and constructed. A detailed study has been made of the separation of copper, nickel, and cobalt components from a simulated carbonate leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Recent studies have investigated the ion exchange separation of zirconium and hafnium from a sulfate feed solution. Nuclear reactor-grade zirconium, containing < 0.01% hafnium by weight, and hafnium, containing <1% zirconium, have been continuously prepared using cation exchange resin in the pressurized CAC. This device, because of its continuous feed and product withdrawal, its adaptability to largescale operations, and its ability to separate many components, is expected to make chromatography a more competitive process in the industrial sector.

Pressurized Continuous Chromatography

Abstract A pressurized continuous annular chromatograph has been developed for preparative separations. This device utilizes a slowly rotating annular bed of sorbent material, fixed multiple feed points, and fixed withdrawal locations. Most of our investigations have been performed with a 28-cm-diam column, but a larger model is being designed and constructed. The separation of copper, nickel, and cobalt components from a carbonate solution has been studied in detail. This solution simulates the leach liquor from the Caron process for recovering nickel and cobalt from laterite ores. Use of continuous gradient elution has been demonstrated. Recent studies have investigated several separations, including that of zirconium and hafnium (necessary for the production of zirconium for use in nuclear reactors), on a preparative scale. This system, because of its continuous feed and product withdrawal, its adaptability to large-scale operations, and its ability to separate many components, is expected to make chro...

Operation of an Improved, Continuous Annular Chromatograph

Abstract A rotating annular chromatograph has been demonstrated to have utility in the continuous separation of solutes in a feed stream. Recent modifications to the system have resulted in a more efficient separation. Design of the inlet and the exit has been significantly changed to improve chromatograph performance. Refinements have also been made to the method of gradient elution. The effects of changing superficial velocity and initial resin loading on the height equivalent to a theoretical plate are shown for the ternary nickel-cobalt carbonate amine system. A continuous separation of this ternary mixture utilizing pH gradient elution is presented.