Homogeneous ion exchange

The membrane systems to be considered include what are normally termed homogeneous ion exchangers. Nevertheless, according to the definitions of the introductory section, they should be placed in class (b) because microregions differing in electrical properties can be distinguished, even though this is often done on a purely theoretical basis, as will be seen below. 

A large quantity of homogeneous ion-exchange membranes are made annually for separators in alkaline batteries. See also Batteries. 

In homogeneous ion-exchange membranes the fixed-charged groups are evenly distributed over the entire membrane polymer matrix. Homogeneous membranes can be produced, for example, by polymerization or polycondensation of functional monomers such as phenolsulfonic acid, or by functionalizing a polymer such as polysulfone dissolved in an appropriate solvent by sulfonation. 

Homogeneous ion-exchange membranes can be prepared by polymerization of monomers that contain a moiety that either is or can be made anionic or cationic, or by polymerization of a monomer that contains an anionic or a cationic moiety, or by introduction of anionic or cationic moieties into a polymer dissolved in a solvent by a chemical reaction, or grafting functional groups into a preformed polymer film [10]. 

The kinetic behavior of a well-defined heterogeneous mixture of ion exchangers in a stirred-flow cell has obviously not yet been investigated, neither theoretically nor experimentally. To remedy this situation an attempt is made to extend the theory for homogeneous ion exchangers to... 

Besides, we have to keep in mind that the rate equations derived are for homogeneous ion-exchanger particles. This implies that the particles are monodisperse (same ratio of surface to volume, see Eq. [la]), and that each particle has the same sorption properties, as characterized by its ion-exchange capacity and separation factor (or K. For a given particle, however, it is... 

Homogeneous ion-exchange membranes have significantly better properties in this respect, since the fixed ion charges are distributed homogeneously over the entire matrix. 

Preparation Procedure of Homogeneous Ion-Exchange Membranes. The methods of making homogeneous ion-exchange membranes can be summarized by three different basic procedures ... 

Homogeneous ion-exchange membranes can also be prepared by the introduction of anionic or cationic moieties into a performed film. Starting with a film makes the membrane preparation rather easy. A typical example for this mode of preparing ion-exchange membranes is the sulfochlorination and amination of polyethylene sheets according to the following reaction scheme [24] ... 

Membranes In this technique, different membrane types such as microporous, homogenous, ion exchange, and asymmetric have been employed for sample preparation for GC, HPLC, and CE. The extraction in this technique can be further automated. 

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