Ion-exchange membranes structure

Pourcelly, G. (2002) Conductivity and selectivity of ion exchange membranes structure-correlations. Desalination, 147, 359. 

An ion-exchange membrane structure which has charged functionalities mixed into the membrane support structure. This structure gives the membrane an ionic character throughout the membrane backbone as opposed to being on the surface of the membrane only. 

Structural and Transport Properties of Perfluorinated Ion-Exchange Membranes Structural Properties of Membrane lonomers... 

Structural and Transport Properties of Perfhorinated Ion-Exchange Membranes Yeo,R.S. Yeager, H. L. 16... 

Typical chemical stractures of ion-exchange membranes for technical applications are shown in Fig. 26.3. Judging superficially, they may look somehow similar, but structural details do lead to important differences in behavior and performance. Membrane fuel cells are discussed in detail in Chapter 20. 

Two comprehensive reviews including functional PFAVE synthesis, copolymerization of functional PFAVE with fluorooleks (mainly TFE), investigations of the structure of the copolymers as well as their ion-exchange membrane properties were prepared by leading specialists from Asahi Glass Co.10 and by Russian specialists from the Membrane Processes Laboratory in the Karpov Research Institute of Physical Chemistry.11... 

The use of suppressors in ion chromatography of quaternary ammonium compounds can be of advantage. These are ion exchange membranes that introduce hydroxide ions instead of the counterion present in the analyte. This simplifies the mixture and enhances the electrolytic conductivity of the sample. The effluent of the suppressor may be nebulized and subjected to field-assisted evaporation, yielding a cloud of ions suspended in the gas phase, which can be introduced into an MS analyzer designed for work at atmospheric pressure. Both the molecular weight and the structure of the quaternary cations can be determined by this method419. 

The same base material has been used by Rhone-Poulenc Industries to develop Ion-exchange membranes for desalination (21-25). Their research has concentrated on polymers of moderate D.S. and low molecular weight (a restriction imposed by their technique of sulfonatlon which may cause polymer degradation). While their method of membrane preparation Is not entirely clear, it Is evident that the Rhone-Poulenc membranes possess the desired structural asymmetry. In this form the SPSF membranes have proven to be equal to, and In some ways superior to, CA membranes. 

In this chapter, we reviewed the structure-controlled syntheses of CNFs in an attempt to offer better catalyst supports for fuel cell applications. Also, selected carbon nanofibers are used as supports for anode metal catalysts in DMFCs. The catalytic activity and the efficiency of transferring protons to ion-exchange membranes have been examined in half cells and single cells. The effects of the fiber diameter, graphene alignment and porosity on the activity of the CNF-supported catalysts have been examined in detail. 

A synthetic ion-selective (ion-exchange) membrane is a dense, nonporous, mechanically stable polymer film about 0.01 —0.04 cm thick. By nonporosity we mean the absence of pores (possibly very tortuous transmembrane channels) with a typical radius above 5 — KM (10-8 cm). Structurally the membrane material is a cross-linked polyelectrolyte. This latter is a polymer containing chemical groups that while in contact with an aqueous solvent are capable of dissociation into charges which remain fixed to the polymer core and counterions which are free to move in the solution. 

Ion-exchange membranes can also be divided, according to their structure and preparation procedure, into homogeneous and heterogeneous membranes [4]. 

Ion-exchange membrane is designed to allow the transport of primarily sodium ions and water from the anolyte to the catholyte compartment, whereas the diaphragm allows the percolation of all the anolyte through the separator. The cation-conducting, ion-exchange membrane is structured to reject anions, as indicated in Fig. 26.9. The chlor-alkali membranes in use today consist of one or more perfluorinated ion-exchange polymeric mate-... 

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