This review covers cyclic separation methods used for adsorption, ion exchange, and chromatographic separation processes where the cyclic parameter is a thermodynamic variable which changes the equilibrium distribution coefficients of the solutes. The cyclic methods reviewed include heatless or pressure-swing adsorption, parametric pumping, and cycling zone adsorption. These cyclic techniques have been studied as a possible preparative chromatographic separation method or for continuous production from adsorption or ion exchange columns.

Cyclic Separation Processes

A package for thermal parametric pumping adsorptive processes

Parametric pumping is the name given to a novel separation device developed by Richard Wilhelm and co-workers(1,2,3). The principle of operation depends on an immobile phase (e.g. adsorbent) to alternately retard and release selected species. This action coupled with a synchronous periodic fluid flow causes the selectively adsorbed species to be literally pumped from one region to another. In the successful experiments(2,3) a single packed column was used with reservoirs attached to each end. A water jacket surrounding the bed was heated or cooled synchronously with periodic fluid motion. Figure 1 outlines the principle of operation. Essentially, the process operates in a “bucket-brigade” fashion. If one follows the travels of a single solute (see Figure 1) in a non-adsorbable solvent we see that during downflow the column is cooled thus retarding (adsorption step) the solute, allowing the solvent to move unimpeded. When the flow direction changes to an upward motion, the column is heated, releas...

Progress in Parametric Pumping

In this work scale-up concerns in adsorptive parametric pumping operation in recuperative mode are studied An experimental study of the purification of wastewater containing 100 ppm of phenol using a polymeric adsorbent (Duolite ES861-Rohm and Haas, France) is reported A completely automated pilot plant (column and ancillary equipment, product receivers, sampling, collector and analytical devices) is described The plant is computer controlled enabling automatic data acquisition for temperature, pressure and flowrate

Adsorptive separation by thermal parametric pumping part II: Experimental study of the purification of aqueous phenolic solutions at pilot scale

The term “parametric pumping” implies the idea of pumping, that is of transport of material (in our case, ionic species) up along some potential scale (in our case, chemical potential), at the cost of degradation of some flux of energy (to be specified later). The term “parametric” refers to the fact that the energy flux just mentionned is obtained by modulating some intensive thermodynamic parameter such as temperature, pressure, ionic strength, pH, electric potential, … Typical examples are temperature-swing ion-exchange and pressure-swing adsorption. The concept of parametric pumping is due to Wilhelm and coworkers (1966, 1968). Their original results deal with adsorption from the liquid phase, modulated by temperature. Let us examine how these phenomena are implemented.

Parametric Ion-Exchange Processes (Parametric Pumping and Allied Techniques)

A continuous pump in which the feed and product streams flow steadily both in upflow and downflow is experimentally investigated in the model system toluene-n-heptane on silica gel adsorbent. The experimental data compare reasonably well with analytical results based on an equilibrium theory. The operating conditions necessary to achieve high separation factors are shown to be dependent on the relative magnitudes of penetration distances and the height of the column.

Separations via continuous parametric pumping

A thermal continuous parametric pump for separating multicomponent mixtures was experimentally investigated using the model system tolueneaniline-n-heptane on silica gel adsorbent. A simple method for predicting separations is presented and is found to be in good agreement with the experimental results. The method, based on an equilibrium theory, invokes the assumption that a multicomponent mixture contains a series of pseudo binary systems. Each binary system consists of one of the solutes as one component and the common inert solvent as the other component.

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J. D. Stokes

Papers

Separations via continuous parametric pumping

Separation of multicomponent mixtures via thermal parametric pumping