Capacity of ion exchange resins

Table VI. Effect of Time on Sulfonation of Styrene-Polyprogylene Copol3nners as Measured by Capacities of Ion Exchange Resins...

See above— Iron. When primary treatment is absent, oxidized form can penetrate membrane, then precipitate Reduces capacity of ion-exchange resin for hardness deactivates cathode coating and so increases voltage... 

The most direct method for determining charge content of a gel is by titration of the sample. These methods are extensively used to determine the capacity of ion exchange resins and are discussed in detail in that literature [24]. The method of the titration briefly described here is for anionic gels characterization of cationic gels would require the analogous titration be performed using acid solution as a titrant. 

Variances in resin performance and capacities can be expected from normal annual attrition rates of ion-exchange resins. Typical attrition losses that can be expected include (1) Strong cation resin 3 percent per year for three years or 1,000,000 gals/ cu.ft (2) Strong anion resin 25 percent per year for two years or 1,000,000 gals/ cu.ft (3) Weak cation/anion 10 percent per year for two years or 750,000 gals/ cu. ft. A steady falloff of resin-exchange capacity is a matter of concern to the operator and is due to several conditions ... 

Most types of ion-exchange resin suffer some breakdown and volume loss over time because of attrition, excessive heat, or other factors. Water softeners should be inspected annually, and a double backwash procedure should be provided. This generally lifts the broken resin ( fines ) to the top of the bed, where it can be removed and replaced to restore capacity. Allow for 5 to 10% resin operating capacity loss per year because of physical breakdown. At many sites the resin is unfortunately not inspected regularly but merely replaced when a serious decline in operating capacity is noticed. Here a resin life expectancy of, say, 6 to 8 years probably is the norm. 

A full bed-depth, core sample should be taken of ion-exchange resin and checked for cracked and broken beads, iron fouling, and loss of capacity. The bed should be checked for loss of volume. 

A form of erosion especially relating to the frictional wear of ion exchange resins, such as that of water softener resin, causing loss of capacity. 

Fouling of pores of ion-exchange resins by the presence of organic contaminants in the water being processed. The resin gradually loses its capacity and requires cleaning. 

The use of ion exchange resins and natural or synthetic inorganic exchange materials in the nuclear industry is well documented ( ). In the waste solidification application, the titanates or niobates offer no unique sorption properties. They do, however, provide a relatively high overall sorption capacity for a variety of nuclides in materials which can be converted into a stable ceramic host for the sorbed ions. After the sorption process, the column bed must be consolidated to reduce surface area. The project emphasis was directed toward a stable waste form and a considerable effort was devoted to producing and characterizing a highly dense form with favorable physical, chemical and thermal properties (l ). 

Chromatography of polysaccharides on silica gel and on carbon columns has been used to a limited extent. The use of ion-exchange resins has been investigated by Deuel and coworkers. The colunms had low capacities, and part of the material appeared to be irreversibly adsorbed. Deuel and coworkers, however, have reported better results when columns of cationic derivatives of cellulose, for instance (diethylaminoethyl)-cellulose, are used. Electrophoresis both by the Tiselius method on columns and on filter paper or glass-fiber sheets can give good separa-... 

The research effort in perfecting a resin system capable of efficient performance in a thermally regenerate ion-exchange process can be divided into two distinct phases 2U 229>- (i) selection of mixtures of weakly basic and weakly acidic resins as suitable systems and extensive study of the relationship between the chemical structure, basicity, acidity, and thermal stability of ion-exchange resins of the weak electrolyte type, and (ii) efforts put forth to increase the rate of salt uptake and capacity of thermally regenerable systems. 

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