Equilibrium anion exchange

Hirsch, R. F. and Portock, J. D. Anion-Exchange Equilibria in Alkaline Media. Anal. Chim. Acta 473 (1970). 24 19057... 

Z. Yan and A. Reiser, Effect of hydrogen acceptors on pKa of phenolic resins Link to dissociation inhibitor, Macromolecules, 1998, 31, 7723-7727 G.O. Roberts and J.R. Millar. Effect of chemical and physical structure on anion-exchange equilibrium in quaternary ammonium ion exchangers, Ion Exchange in the Process Industries, Society of Chemical Industry, London, 1970, p. 42. 

A comprehensive paper by Li, Ding and Fritz [16] used PDDAC as the soluble polymer in a BGE containing a relatively high concentration of sodium chloride or lithium sulfate for the separation of inorganic and organic anions. Anion-exchange equilibrium was proposed, rather than a mechanism that involved only ion-pair formation. 

Ion-Exchange Equilibrium. Retention differences among cations with an anion exchanger, or among anions with a cation exchanger, are governed by the physical properties of the solvated ions. The stationary phase will show these preferences ... 

TABLE 16-7 Equilibrium Constants for Polystyrene DVB Cation and Anion Exchangers... 

We assume that between the membrane phase (n) and the solutions (S and S0) no diffusion potentials occur, i.e., the potential differences (n/S) and 0(n/So) are merely caused by ion-exchange activity. Further, all phases are considered to be homogeneous so that is constant within the membrane and also pi = plQ within the solutions. Let us at first consider the simple system of selective indication of an univalent anion A in the presence of an interfering univalent anion B. Here we obtain the following exchange equilibrium ... 

Strong base anion exchangers, 74 395, 411 Strong inversion, in silicon-based semiconductors, 22 239 Strong nitric acid process, materials of construction for, 77 187-188 Strong phosphoric acids, equilibrium composition of, 78 827t Strontianite, 23 317, 321 Strontium (Sr) 23 316-325 chemical properties of, 23 318 economic aspects of, 23 320-321 effect of micro additions on silicon particles in Al-Si alloys, 2 311-312 in ferrites, 77 59... 

This expression is consistent with theory in the limiting case where the equilibrium constant for anion exchange at the interface is large. 

The presence of color in many industrial effluent streams is highly undesirable. LDHs have been found to be particiflarly effective at removing various synthetic dyes (Table 1) [158]. For example. Acid Blue 29 could be adsorbed on the surface or enter the interlayer region of the LDH by anion exchange an equilibrium time of 1 h with 99 % dye removal was obtained. Furthermore,... 

Since protein adsorption to an anion exchange resin is reversible and does not constitute a classical immobilization, the ability of the resins to retain activity under various conditions must be determined. Macrosorb KAX DEAE bound -D-glucosidase was tested with solutions of primary interest for their final application. Several batch washes of a 1% w/v slurry were required to ensure complete equilibrium elution for a given concentration, as determined from the absence of pNPG units in subsequent washes. Several salt solutions of typical fermentation media components were tested. These included 3 mM to 50 mM solutions of MgSO, KHgPO, NaQ, and sodium acetate. Also, incubations with cellulase solutions were tested to determine if the proteins present in a cellulose hydrolysis would displace the -D-glucosidase. Both of these displacement studies were carried out at 22°C and 40 C. 

Selective ion electrodes (SIE). Selective ion electrodes are essentially variants of the well-known pH meter. They are membrane indicator types of electrodes in which a potential is developed across a membrane in the presence of the ion the size of the potential is related to the concentration and hence can be used to quantitatively detect and measure the species. However, instead of a glass membrane, as in the pH meter, the membranes consist of organics that are immersible in water. For example, anion-sensitive electrodes use a solution of an anion exchange resin in an organic solvent the liquid can be held in the form of a gel, for example, in polyvinyl chloride. The ion reacts with the organic membrane, setting up an equilibrium between the free ion in solution and the ion bound to the membrane, generating a potential difference, which is measured. 

Donnan equilibrium Ions of the same charge as those fixed on an exchange resin are repelled from the resin. Thus, anions do not readily penetrate a cation-exchange resin, and cations are repelled from an anion-exchange resin. 

The leaching reactions and the distribution of the various anionic uranyl species are very dependent on the pH value of the leach liquor and on the sulfate or carbonate concentration. Nominally, only the anionic di- and tri-sulfate or carbonate species will exchange with the functional groups of an anion-exchange resin, but the resin itself can facilitate the formation of complex anions in the resin phase because of the high concentration (approximately 0.5 M) of the co-ion on the functional group. Therefore, a complex equilibrium is established in which the resin is a participant the following reactions describe these equilibria for sulfuric acid leach liquors ... 

The authors first mentioned investigated an anion-exchange membrane consisting of polyethylene imine crosslinked with epichlorohydrin in equilibrium with KC1 solutions. The concentration of Cl- ions and K+ ions in the membrane were determined analytically. The mobility of the Cl- ions in the membrane was determined according to the principle of the moving boundary. Thus in a membrane strip a sharp boundary is formed between the OH- and Cl- ions. This boundary will move under the influence of an electric field. This may be made visible with the aid of an indicator. The speed of the boundary is determined by the slowest ion, by consequence the Cl- ion in this instance. 

By comparison, the catalyzed transesterification reaction between ethylene carbonate and methanol (Equation 7.3) offers an alternative for greening DMC production. In this Asahi Kasei process [27], the preferred catalyst is based on an anion-exchange resin operating under catalytic distillation conditions between 333-353 K. This reactor design shifts the thermodynamic equilibrium towards complete conversion of ethylene carbonate, such that both the yield and selectivity for DMC and monoethylene glycol are 99.5%. The process is capable of supplying monoethylene glycol to the market, and DMC for captive use to produce DPC. 

Kinetic and spectroscopic studies of reactions of several ( )-/J-alkyl-vinyl(phenyl)iodonium tetrafluorob orates with tetrabutylammonium chloride indicate that the vinyliodonium chlorides, generated by anion exchange, are present in equilibrium with the corresponding vinyl(chloro)iodanes (Scheme 48) [140]. Both species undergo vinylic Sn2 reactions with chloride ion, and although the chloroiodanes are less reactive, they are by far the dominant species at equilibrium and account for most of the (Z)-l-chloroalkene production. 

Charges of anionic species of phosphorus oxoacids were determined by an ion-exchange equilibrium method. For this purpose distribution ratios, D, of phosphorus oxoacid between an anion-exchange resin Dowex 1x4 phase and an aqueous solution phase containing tetramethylammonium chloride as a supporting electrolyte were obtained from the absorbancies of phosphorus oxoacid in the aqueous solution phase before and after equilibration. D was defined as the ratio of the concentration of phosphorus in the resin phase to the concentration of phosphorus in the solution phase. 

N-Aminophenanthridinium salts can be obtained by the action of hydroxylamine-O-sulfonic acid on phenanthridine, followed, where required, by anion exchange. The salts readily give rise to the 1,3-dipolar system (202) which exists in equilibrium with its dimer at temperatures below 100°.290... 

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