Exchange resins redox

Np through Lr are all prepared artificially by bombardment with neutrons and/or light element ions (He-4, B-10, B-11, C-12,0-16,0-18, Ca-48, Fe-56). Some routes are presented in Table 18.1. The elements have been separated from the targets and other product species by redox reactions, ion exchange, and solvent extraction. In a typical separation, a sulfonic acid ion exchange resin is placed in a column, the tripositive ions of Am through Lr are poured into the column where they are taken up, then the column is eluted with a solution of ammonium a-hydroxybutyrate. As elution proceeds, the An+ ions come off in this order Lr-Md-Fm-Es-Cf-Bk-Cm-Am. They are detected by the distinctive energies of their radioactive emissions. 

Heterogeneous catalysts for liquid phase oxidations can be divided into three different categories (a) supported metals (e.g. Pd/C), (b) supported metal ions (e.g. ion exchange resins, metal ion exchanged zeolites) and (c) supported oxometal (oxidic) catalysts (e.g. Ti1v/SiOg, redox zeolites, redox pillared clays). This division of the various catalyst types will be used as a framework for the ensuing discussion. 

Resins with good hydrodynamic properties and sorption capadties for proteins and enzymes have been prepared by the polymerization of acrylic acid or methacrylic acid and a crosslinking monomer such as 1,3,5-triacryloylhexahydrotriazine (TAT) in aqueous acetic acid using a radical initiator. Methacrylic add-TAT copolymer prqjared by using a redox catalyst is useful as a cation-exchange resin for selective and reversible sorption of proteolytic enzymes such as terrilytin. 

The developments on chelating, amphoteric and redox ion-exchange resins, and applications of ion-exchange resins which are not covered in this review will be discussed in a later publication. 

The simultaneous pre-concentration of manganese, chromium and vanadium is possible by combination of ion-exchange with redox reactions on a Fe(II)-treated resin Beside ion-exchange chromatography reversed-phase methods are very important for trace enrichments On inert materials (e. g. PTFA, Tef-... 

Redox zeolites such as TS-1, and supported metal ion catalysts such as those that use ion-exchange resins as supports are among the other major oxidation catalysts. These were considered earlier in this chapter. 

In addition to ion exchange resins, polymer reagents also include what are called redox or oxidation-reduction polymers which also represent electron transfer agents. Polymer reagents are also used in the Merrifield synthesis of peptides and proteins (see Chapter 30). Other polymer reagents, together with their applications, are... 

The phenomenon of ion exchange ie of great utility in the radiochemical separation of Pu. Cationic Pu in dilute, non-complexing, acid solution will readily adsorb on cation resin in the hydrogen or alkali metal form. On the other hand Pu(IV) and Pu(Vl) form anionic complexes in moderately concentrated nitric or hydrochloric acids and BO will adsorb on anion exchange resins. Anion and cation exchange methods are thus both usable to separate Pu. The anion exchange separation is especially valuable in the laboratory because of the simple equipment required, the ease of manipulation, and the excellent decontamination from fission products by the use of redox cycles. 

Another type of anomalous mass effect resulting from the uneven charge distributions in the isotopic nucld was discussed by Bigeleisen (1996a, b) in order to explain the anomalies revealed by the predse measurements of equihbrium separation factors for uranium isotopes during the U(IV)/U(VI) redox equilibrium carried out on an anion exchange resin (Fujii et al. 1989) (1) separation factors for all the uranium isotopes appeared to be unexpectedly high ... 

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