Ion exchanger selectivity

The flow along the membranes also improves the mass transport there, and the separators between the membranes are constmcted to provide good flow distribution and mixing on the membrane surfaces. Membrane sizes are often about 0.5 x 1 m, spaced about 1 mm apart. Many types of polymers are used to manufacture these ion-exchange-selective membranes, which are often reiaforced by strong fabrics made of other polymers or glass fibers. 

Barter, R.M. and Klinowski,). (1974) Ion-exchange selectivity and electrolyte concentration. J. Chem. Soc. Faraday, 2080-2091. 

Another study involving cation—sulfonate interactions in Nafion (1200 EW) is that of Yeager, who investigated the property of equilibrium ion exchange selectivity at 25 The results of this study are... 

Yeager suggests that the major factor involved in the ion exchange selectivity of Nafion is the positive entropy change associated with the replacement of H+ with the metal ion, which is accompanied by water release and polymer contraction. 

Hawkins (19) showed that synthetic Sr mordenite gave Sr2+/Ca2+ ion exchange separation factors ranging from 8.4 to 3.5 as compared with 0.5 to 1.6 obtained with his synthetic Ca mordenite. X-ray data for the synthetic Sr mordenite agree with the Oman pattern, but no data were presented for the synthetic Ca mordenite. Perhaps the Sr mordenite and Ca mordenite samples differed in their framework structures, and this was the reason for their different ion exchange selectivity. 

Sr mordenite synthesized by Barrer and Marshall (16) gave the Cmcm x-ray pattern and was C-centered orthorhombic by electron diffraction. However, other electron diffraction studies, also by Kerr (12), revealed some synthetic Sr mordenite crystals of the Immm structure prepared at similar synthesis conditions. Future work should examine synthetic Sr and Ca mordenite specimens further for the possible presence of other framework structures, and correlation of structures with Sr2+/Ca2+ ion exchange selectivity. 

ION EXCHANGE SELECTIVITY AS A SURROGATE INDICATOR OF RELATIVE PERMEABILITY OF HOMOVALENT IONS IN REVERSE OSMOSIS PROCESSES Parna Mukherjee and Arup K. SenGupta... 

Samanta, S. K. and Misra, B. M. Ion Exchange Selectivity of a Resorcinol-Formaldehyde Polycondensate Resin for Cesium in Relation to Other Alkali Metal Ions, Solvent Extr. Ion Exch, 13(3) (1995), 575-589. 

Structure Ca10(PO4)e(OH)2 crystalline, nonstoichiometric mineral rich in surface ions (primarily carbonate) Analytical Properties Separation of proteins overcomes some difficulties associated with ion exchange selectivity and efficiency depend to some extent on particle geometry (i.e., sphere, plate, etc.)... 

The permselectivity is the product of ion-exchange selectivity and mobility selectivity. The mobility of different ions is determined mainly by steric effects, that is, the size of the ions and the cross-linking density of the membrane [4],... 

Termination in a large resistance, i.e. a blocked interface such as a metal totally covered with oxide or a highly resistive membrane used in ion exchange selective electrodes (Section 13.6) (Fig. 11.18c). This is sometimes referred to as the finite Warburg impedance. 

A thin film of a membrane-forming material is deposited on a metal wire (silver, platinum, nickel, etc.) or on carbon, the membrane being, for example, a liquid exchanger immobilized in PVC (Fig. 13.12). This electrode is thus similar to an ion-exchange selective electrode, but without solution and without internal reference. The detailed mechanism of its operation is not clear but it is certain, and logical, that the interface... 

The relatively high Si/Al content of mordenite confers on it a certain acid stabihty that enables it to be used to remove water from acid gas streams such as reformer recycle hydrogen, reformer catalyst regeneration gas, HCl, CI2, and chlorinated hydrocarbons. It can also be used to treat off-gas for removal of oxides of sulfur and nitrogen (SO and NO ). Mordenite s ion-exchange selectivity for Cs has been used to remove Cs radioisotopes from nuclear waste (Zeolon 900) and it is used in Japan on a plant scale to separate gases from the air. 

Presented in Fig. 12 is a separation scheme in which use is made of the change in ion-exchanger selectivity affected by altering the solution concentration [31,32]. Selectivity changes such as these are particularly large for exchanging ions of different charge. 

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