Cell separators

7 Solid Polymer Electrolyte Technology Ion-exchange membranes, often used as cell separators (see Sect. 2.4.3.2), 

As discussed in Sect. 2.3.3, the in principle desirable application of an undivided cell will be impossible if a reaction at the counter electrode results in unacceptable consequences, for example, impurities of the product and/or considerable losses in yield and current efficiency. There is a large variety of cell separators available, but none of them can work ideally. 

The task of a cell separator is to impede a direct mixing of anolyte and catholyte and to decrease diffusion, but at the same time the migration of ions has to be possible without a too high voltage drop. Naturally, a compromise of these requirements has to be found. 

The functioning of a separator will be the more difficult, the more different both electrolytes are. With increasing concentration gradients diffusion will be enhanced. It can be reduced using a less porous and/or thicker separator, but then the voltage drop increases. A special problem, that has to be avoided, is a precipitation at the surface or within the separator if the solubility of a compound is smaller in one solution compared with the other. 

If for laboratory experiments an optimal separation of anolyte and catholyte is needed, and a high voltage is acceptable, two separators can be used. The volume between these can additionally be rinsed with a solution for removing compounds that have been transferred through the separators but are not allowed to arrive in the opposite cell chamber. 

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Separation applications Separation cell Separation, liquid-liquid Separation, low energy Separation, magnetic Separation nozzle Separation of fatty acids Separations... 

A method for the fractionation of plasma, allowing albumin, y-globulin, and fibrinogen to become available for clinical use, was developed during World War II (see also Fractionation, blood-plasma fractionation). A stainless steel blood cell separation bowl, developed in the early 1950s, was the earhest blood cell separator. A disposable polycarbonate version of the separation device, now known as the Haemonetics Latham bowl for its inventor, was first used to collect platelets from a blood donor in 1971. Another cell separation rotor was developed to faciUtate white cell collections. This donut-shaped rotor has evolved to the advanced separation chamber of the COBE Spectra apheresis machine. 

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