Ion exchanger operations

Cycle A complete course of ion-exchange operation. For instance, a complete cycle of cation exchange would involve regeneration of the resin with acid, rinse to remove excess acid, exhaustion, backwash, and finally regeneration. 

Dynamic system An ion-exchange operation wherein a flow of the solution to be treated is involved. 

Cyclic enone, 12 185 Cyclic ethers, 10 567, 569 12 663 polymerization, 14 271 Cyclic fatigue, in ceramics, 5 633-634 Cyclic gas generators, 6 786-787, 789, 827 Cyclic halides, 19 56 Cyclic hexakis(thio-l,4-phenylene), melt polymerization of, 23 705 Cyclic hydrocarbons, 13 687 Cyclic hydroxyalkyl alkyl peroxide, 18 454 Cyclic ion exchange operation, 14 408-413 Cyclic ketones, 12 176, 177 14 590-592. See also Cyclic 1,2-diketones physical properties of, 14 591t hydroxyalkyl hydroperoxides from, 18 450... 

In general, large industrial fixed beds operate under near-adiabatic conditions, whereas small laboratory-scale fixed beds may approach isothermal operation (Ruthven, 1984). Especially, for most environmental applications, for catalytic, adsorption, and ion-exchange operations, the species to be removed are in such low concentrations that the operarion is nearly isothermal. Thus, the heat transfer to the external fixed-bed wall is often of minimal importance. 

The energy balance (3.301) is applicable for catalysis, adsorption, and ion exchange. More specifically, in catalysis, where the steady-state condition exists, frequently the accumulation term is zero. In contrast, adsorption and ion exchange operate under unsteady-state condition. The analysis of the energy balance equation for catalytic fixed beds is presented in detail in Section 5.3.4. 

Fig. 1. Schematic flowsheet of uranium processing (acid leach and ion exchange) operation. Numbers refer to the numbers that appear in the boxes on the flowsheet. Operations (3), (6), (9), and (11) may be done by thickening or filtration. Most often, thickeners are used, followed by filters. The pH of the leach slurry <4) is elevated to reduce its corrosive effect and to improve the ion-exchange operation on the uranium liquor subsequently separated, In tile ion exchange operation (7), resin contained in closed columns is alternately loaded with uranium and then eluted. The resin adsorbs the complex anions, such as UC fSO 4-. in which the uranium is present in the leach solution. Ammonium nitrate is nsed for elution, obtained by recycling the uranium filtrate liquor after pH adjustment. Iron adsoibed with the uranium is eluted with it. Iron separation operation (8) is needed inasmuch as the iron hydroxide slurry is heavily contaminated with calcium sulfate and coprecipitated uranium salts. Therefore, the slurry is recycled to the watering stage (3). Washed solids from 1,6). the waste barren liquor from (7), and the uranium filtrate from (11) are combined. The pH is elevated to 7.5 by adding lime slurry before the mixture is pumped to the tailings disposal area. (Rio Algom Mines Limited, Toronto)...

As there is practically no difference in the laboratory data with bed depths of 32 inches and 64 inches, and ion exchange operations are reversible, it appears necessary to strip the product from one ion exchange stage of its ammonium bicarbonate before sending it on to the next stage. 

These cations are not definitively linked to the framework but may be replaced by other cations during an ion-exchange operation. Whatever the exchange conditions, and in particular the pH, zeolites are cation exchangers and have a constant number of exchange sites, which is equal to the number of aluminum atoms in their framework. 

Physico-chemical speciation refers to the various physical and chemical forms in which an element may exist in the system. In oceanic waters, it is difficult to determine chemical species directly. Whereas some individual species can be analysed, others can only be inferred from thermodynamic equilibrium models as exemplified by the speciation of carbonic acid in Figure 9. Often an element is fractionated into various forms that behave similarly under a given physical (e.g., filtration) or chemical (e.g., ion exchange) operation. The resulting partition of the element is highly dependent upon the procedure utilised, and so known as operationally defined. In the following discussion, speciation will be exemplified with respect to size distribution, complexation characteristics, redox behaviour and methylation reactions. 

The theory presented in this article will apply directly to adsorption and to ion exchange operations. A number of related operations can also... 

In most ion exchange operations, an ion in solution is replaced with an ion from the resin and the former solution ion remains with the resin. In contrast, ion exchange chromatography uses the ion exchange resin as an adsorption or separation media, which provides an ionic environment, allowing two or more solutes in the feed stream to be separated. The feed solution is added to the chromatographic column filled with the separation beads and is eluted with solvent, often water in the case of fermentation products. The resin beads selectively slow some solutes while others are eluted down the column (Fig. 1). As the solutes move down the column, they separate and their individual purity increases. Eventually, the solutes appear at different times at the column outlet where each can be drawn off separately. 

Figure S.13 Four cycles of fixed-bed ion-exchange operation. F = feed B = barren solution.

Capacity Operating — the fraction of total capacity used in an ion-exchange operation. Total — the ultimate or maximum ion-exchange capacity of a resin. 

Upon completion of the ion exchange operation, the zeolite was separated from the solution via filtration, then washed once using 500 ml of DI water. Ion exchanged zeolite ZSM-5 (in the NH/ form) was forwarded for preparation as particles. A small portion of the zeohte crystals were calcined at 550°C for 3 hours in order to decompose the armnonium complex, then forwarded for characterization. 

Electrochemical methods can be used in the destruction of nitrate [34], which may arise as part of ion exchange operations. Regeneration of the effluent from ion exchange resin beds can be achieved by a combined process of cathodic reduction and anodic oxidation. 

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