Commercial ion exchangers

Nature of the most abundant comonomer. Nature of the groups devoted to metal uptake. Commercial ion-exchanger. 

The PVA/PSSNa membranes evidence a high permselectivity, comparable with the one of commercial ion exchange membrane as it can see in table 14, where were presented the permeability coefficient (P) and the ratio P to D (diffusion coefficient) that express the effect of porosity and of the electrolyte exclusion. 

The percent ring substitution (% RS) of the polymer with active sites affects catalytic activity. Polystyrenes with < 25 % RS with lipophilic quarternary onium ions are swollen in triphase mixtures almost entirely by the organic phase. Water reduces the activity of anions by hydrogen bonding. In most triphase nucleophilic displacement reactions onium ion catalysts with <25% RS are highly active, and those with >40% RS, such as most commercial ion exchange resins, are much less active. However, low % RS is not critical for the reactions of hydroxide ion with active methylene compounds, as commericial ion exchange resins work well in alkylation of active nitriles. 

The data in Table 7 obtained with equimolar amounts of the polymeric catalysts and the 2-naphthoxide ion should be more reliable because all of the reactive anion is contained within the polymer. These conditions (expts 7-9) gave 100 % O-alkylation, indicating that the active site environment of the polystyrene-bound tri-n-butylphos-phonium ion/naphthoxide ion pair or aggregate is aprotic even with the 60%RS polymer. However, the common benzyltrimethylammonium ion found in commercial ion exchange resins is more hydrophilic, giving both C- and O-alkylation (expts 10 and 11 of Table 7). 

Cicero, C.M., Herman, C.A., Workman, P., Poole, K., Erich, D., Harden, J., Commercial Ion Exchange Resin Vitrification in Borosilicate Glass, Rep. WSRC-MS- 98-00392, Westinghouse Savannah River Co., Aiken, SC (1998)... 

Ion-exchange pigments were developed as nontoxic alternatives to the chromate pigments. They consist of a silicate carrier (zeolite [5.141] or amorphous silica gel [5.142]) to which calcium ions are bound. Commercial ion-exchange pigments have the following properties [5.143]—[5.145] ... 

The first selective membranes based on commercial ion-exchangers were produced around 1950 (61, 68). Since that time about a hundred publications and patents concerning the preparation of ion-exchange... 

In ion exchange, the aqueous phase ions are replaced with H and OH ions. If the aqueous phase ions are in equilibrium with the adsorbed ions, their removal from the aqueous phase causes desorption of the adsorbed ions to maintain the equilibrium until all of the adsorbed ions have been removed. In practice, this removal is quantitative (2-5). Ion exchange is rapid and easily carried out however, commercial ion exchange resins contain leachable polyelectrolytes which adsorb on latex particle surfaces these polyelectrolytes can be removed only by an arduous purification process (2-5). 

The empirical formula of a commercial ion-exchange resin is C8H7S03Na. The resin can be used to soften water according to the reaction provided. Expressed in moles Ca2+ taken up per gram resin used, what would be the maximum uptake of Ca2+ ... 

The water-transport number refers to the number of water molecules transferred by one ion through a given membrane. It depends on the membrane and on the electrolyte, that is, on the size of the ions, their valence, and their concentration in the solution. In aqueous salt solutions and commercial ion-exchange membranes the water transport number is of the order of 4—8, that is, one mole of ions transports about 4—8 moles of water through a typical commercial ion-exchange membrane. 

Defluoridation processes can be classified into four main groups Adsorption methods, in these methods sorbents such as bone charcoal, activated alumina and clay are used in column or batch systems. Ion-exchange methods, these methods require expensive commercial ion-exchange resins. Coprecipitation and... 

The first successful separations of rare earths by this technique was achieved fifty years ago. Two techniques used in the separation of rare earths are (i) displacement chromatography and (ii) elution chromatography. Commercial ion exchangers involving both cation exchangers and anion exchangers are listed in Table 1.18. 

Ion exchange processes function by replacing undesirable ions of a liquid with ions such as H+ or OH from a solid material in which the ions are sufficiently mobile, usually some synthetic resin. Eventually the resin becomes exhausted and may be regenerated by contact with a small amount of solution with a high content of the desired ion. Resins can be tailored to have selective affinities for particular kinds of ions, for instance, mercury, boron, ferrous iron, or copper in the presence of iron. Physical properties of some commercial ion exchange resins are listed in Table 15.4 together with their ion exchange capacities. The most commonly used sizes are -20 + 50 mesh (0.8-0.3 mm) and -40 -h 80 mesh (0.4-0.18 mm). 

Maquart FX, Gillery P, Bernard JF, Mante JP, Borel JP. A method for specifically measuring haemoglobin AIC with a disposable commercial ion-exchange column. Clin Chim Acta 1980 108 329-32. 

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