Ion exchange column operation

Figure 7 Schematic diagram of two-sectional countercurrent ion-exchange column operating at different temperatures to provide recovery of waste-free bromine from seawater.

Down flow - Conventional direction of solutions to be processed in ion-exchange column operation, that is, in at the top, out at the bottom of the column. 

If the ion exchange column is loaded with several ions of similar charge, B, C, etc., elution curves may be obtained for each ion by the use of appropriate eluants. If the elution curves are sufficiently far apart, as in Fig. 7.2, a quantitative separation is possible only an incomplete separation is obtained if the elution curves overlap. Ideally the curves should approach a Gaussian (normal) distribution (Section 4.9) and excessive departure from this distribution may indicate faulty technique and/or column operating conditions. 

Such processes can be conducted continuously (whereas an ion-exchange column is always operated discontinuously). 

Figure 5.17. Dual-column ion exchange preconcentration valve. Sa, Sb samples A and B Ca, Cb ion exchange columns A and B Ea, Eb eluant (2 M nitric acid) for columns A and B Wa, Wb waste lines for samples and eluants A and B W waste lines AAS atomic absorption spectrometer. The dimensions of the base plate of the valve are 70 x 45 x 10 mm. See text for details of operation. Source [661]...

Semibatch Operations, The ion exchange column of Fig. 26.1(c) is an example of the batch treatment of solids in which the flow of fluid closely approximates... 

Thermal-ionization mass spectrometers (TIMS) combine a hot-filament source with a magnetic-sector mass spectrometer. The mass spectrometers are operated at low to moderate mass-resolving power. A large number of elements can be measured with thermal ionization mass spectrometry. Special care is taken to purify the samples using ion exchange columns. Samples are loaded onto the filaments along with an emitter, and a typical run may take several hours. Modem systems have multiple collectors so that several isotopes can be measured simultaneously. High-precision measurements are done with Faraday cup detectors, but low-abundance isotopes can be measured on electron multipliers. Modem machines are capable of precisions of 0.1 to 0.01 permit. 

In summary we underline the fact that as far as urine analysis is concerned, and this is also true for blood, the most satisfactory results published so far are those obtained with Moore and Stein s 1954 procedure (see (b) Dowex 50-X4 columns) whereas the two latest improvements in technique open the way to much wider investigation in this field of biochemical and medical research. The technique is also applicable for the determination of a single amino acid, adequate shortcuts and simplifications in the procedure being introduced accordingly. As examples, we shall mention that appropriate rapid operations have been described for the separation on ion exchange columns and subsequent determination of (3-alanine (C20), (3-aminoisobutyric acid (E5) or y-aminobutyric acid (W1). Similar adjustments may also be made for other amino acids, such as the basic amino acids, for instance, with Moore and Stein s 1954 procedure (M15). 

The experimental measurement of some of the parameters that describe the operation of a real PFIEBR consisting of natural sodium clinoptilolite ion-exchange columns for removing Pb2+, Ni2+, Co2+ and Cu2+ from water solutions (see Figure 7.13a through d) was carried out. 

Satisfactory column operation is dependent on temperature, particle size, density, and compressibihty. A minimum of pressure drop, of the order of 1 lb/in.Vft resin depth is obtained with clean resin beds. The presence of slimes and precipitates, which causes channeling, increases the pressure drop. A backwashing step, involving the upward flow of fluid to expand the resin particles so that the fine, extraneous material in the ion-exchange columns can be removed is used to prevent channeling. 

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