Warren G. Sisson

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...

High-capacity pressurized continuous chromatograph

Abstract Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. The feed material is continuously introduced at a stationary point at the top of the bed, and eluent is allowed to flow everywhere else around the annulus. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effects of annulus width and diameter have been studied using the same device with annulus widths up to 114.3 mm. With this largest width, approximately 96% of the area available within the outer cylinder is devoted to the rotating sorbent bed. Further annulus-width studies have been pursued on units with 89- and 445-mm diameters. These geometric extensions to the basic concept allow extremely large capacity i...

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.

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 ...

Droplet size characteristics and energy input requirements of emulsions formed using high-intensity-pulsed electric fields

Experimental methods have been developed to measure droplet size characteristics and energy inputs associated with the rupture of aqueous droplets by high-intensity-pulsed electric fields. The combination of in situ microscope optics and high-speed video cameras allows reliable observation of liquid droplets down to 0.5 ..mu..m in size. Videotapes of electric-field-created emulsions reveal that average droplet sizes of less than 5 ..mu..m are easily obtained in such systems. Analysis of the energy inputs into the fluids indicates that the electric field method requires less than 1% of the energy required from mechanical agitation to create comparable droplet sizes.

A rotating annular chromatograph for continuous metal separations and recovery

Abstract Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. By continuously introducing the feed material to be separated at a stationary point at the top of the bed and eluent everywhere else around the annulus, elution chromatography occurs. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence, the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effect of annulus width and diameter has recently been studied using the same device with a 50.8-mm-wide annulus and another 0.6-m-long chromatograph with an 89-mm diameter and annulus widths of 6.4, 12.7, and 22.2 mm. These columns have been constructed of Plexiglas and typically operate at a gauge pressure of 175 kPa. To further study the effect of size and pressure, a new 445-mm-diam by 1-m-long column with a 31.8-mm-wide annulus has been fabricated. Its metal construction allows preparative-scale operation with a wide variety of liquids at pressures to 1.3 MPa. Three metal recovery systems have been explored: (i) separation of iron and aluminum in ammonium sulfate-sulfuric acid solutions; (ii) separation of hafnium from zirconium in sulfuric acid solutions; and (iii) the separation of copper, nickel, and cobalt in ammonium carbonate solutions. This last system simulates the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. It has been studied, using similar conditions, on each of the chromatographs, and the results demonstrate the effect of column dimensions on the quality and quantity of the separation.

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.The separation of sucrose, glucose, and fructose, using the calcium form of cationic ion exchange resin, uses water as the isocratic eluent. A synthetic mixture of the sugar was explored in fixed columns, then on a bench scale unit. The results almost perfectly scaled to the pilot unit when loading was low and feed mixtures were of low viscosity. Factors such as column loading, feed-to-eluent ratio, and feed concentration were explored. An industrial sugar mixture containing the three sugars and a number of higher molecular sugars was successfully separated. Based on these results, recommendations are made concerning an optimized scaling of the process.

Removal of submicron silica particles from tert-amyl alcohol by dielectric/electric packed bed filtration

Abstract A packed bed with an applied electric field is used to remove submicron and nanometer particles from a nonconducting or slightly conducting solution. Several studies have shown that the application of an electric field to a packed bed significantly increases the performance of the filtration. To enhance the electric-field filtration efficiency, it is desired that the packing materials have a higher dielectric constant than the solution so that the electric-field lines will be diverted into the packing materials. In the present studies, a dc voltage of 0 to 8 kV/cm is applied to a packed bed (2.5-cm diameter and 3.0-cm length) filled with 1-mm-diameter glass beads. The filtration medium contains submicrometer or nanometer SiO2 particles dispersed in tert-amyl alcohol. Two particle sizes are investigated: the average particle sizes are about 300 nm and 50 nm, respectively. Visible light spectrophotometry is used to estimate the amount of SiO2 particles in the effluent. The experimental results are ...

Multiphase electrodispersion precipitation of zirconia powders

The multiphase electrodispersion precipitation of zirconia powders has been done The multiphase in the electric dispersion reactor (EDR). This paper presents the first results obtained where the bench-scale EDR unit was operated in the continuous mode to synthesize 130 {+-} 2 g of ZrO{sub 2} powder in approximately 12 h. An aqueous solution of zirconyl nitrate was dispersed and precipitated in a 2-ethyl-l-hexanol continuous phase containing 0.012 {und M} to 0.12 {und M} ammonia. A gravity settler was used to remove soft agglomerates of the ZrO{sub 2} particles from the organic solvent. Electric bed filtration was employed to remove the fines from the solvent, which was then recycled. The particle-size distribution was varied by changing the electric field strength. At high field strengths (approximately 20 kV/cm), the particle sizes ranged from approximately 0.1 to 5 {mu}m. The dried powder had a consistency of talcum powder. Microwave and conventional heating experiments showed that the powders were sinterable. The BET surface area of the powders ranged from approximately 20 to 90 m{sup 2}/g.

Use of the electrically driven emulsion-phase contactor for a biphasic liquid-liquid enzyme system

An alternative approach to the operation of bioprocessing systems within non-aqueous environments would require the development of reaction systems that would provide effective interfacial contact between the biocatalyst, contained within an aqueous phase, and the organic phase containing the substrate. A biphasic liquid-liquid (BLL) reactor that provides for intimate liquid-liquid contact would be the most probable approach for this application. For the BLL reactions considered in this work, the overall effectiveness of the system will depend on both compatibility of the biocatalyst with the chemical species present and intrinsic reaction and interfacial transport phenomena typically involved with liquid-liquid operations. The focus of this article is to investigate the removal and oxidation of p-cresol dissolved in toluene by aqueous-phase horseradish peroxidase. Contacting of the liquid-liquid biphasic enzyme system is carried out in an advanced solvent extraction contacting device, the electrically driven emulsion-phase contactor (EPC).