Actinides groups

Thorium, uranium, and plutonium are well known for their role as the basic fuels (or sources of fuel) for the release of nuclear energy (5). The importance of the remainder of the actinide group Hes at present, for the most part, in the realm of pure research, but a number of practical appHcations are also known (6). The actinides present a storage-life problem in nuclear waste disposal and consideration is being given to separation methods for their recovery prior to disposal (see Waste treati nt, hazardous waste Nuclear reactors, waste managet nt). 

Transuranic elements Elements of atomic number >92. All are radioactive and produced artificially all are members of the actinide group. 

The chemistry of the lighter actinides from thorium to americium, all being available in substantial quantities, is now well understood. In the - -4, or higher oxidation states, these elements are best considered as an inner transition series. Their chemistry shows both horizontal similarities within the actinide group and to a lesser degree, some vertical similarities with the group 4, 5, and 6 d-transition elements. All of the actinides in their +3 oxidation states behave in much the same way as the lanthanides. The chemistry of the actinides is reviewed within this context and compared with the corresponding lanthanides. 

Nuclear weapons testing was deliberate however many other releases of radionuclides are accidental. These have included fires and spillages at nuclear reprocessing plants resulting in releases of an assortment of nuclides to the atmosphere and the oceans, including super-heavy elements from the actinide group of the Periodic Table (Fig. 2.2) such as plutonium (Pu). Similarly, accidental sinking of nuclear submarines has released radionuclides to the bottom waters of the... 

Then we would jump to element 104, which should come after the actinide group and be a member of the family of elements including hafnium, zirconium, and titanium. Similarly, element 105 should be chemically related to tantalum, niobium, and vanadium. Heavier elements, through 118, should then fill in the rest of the same horizontal row on the Periodic Table. 

Interest in the criticality of the 14 elements making up the actinide group has, in the past, been limited essentially to u and the isotopes of uranium having mass numbers of 233 and 235. However, some of the lesser known actinides are beginning to find applications for which they are peculiarly adapted and, consequently, are, or will be, produced in si lficant quantities with respect to criticality. To permit the production, recovery, and... 

In these extractants, HNO3 interaction with the extractant occurs with the carbamoyl portion of the molecule (Horwitz etal. 1981), leaving the solvating phosphorus portion of the molecule to interact with the metal ion. These compounds are indeed more efficient extractants of the trivalent metal ions from acidic solutions, able to extract trivalent actinide and lanthanide ions from relatively dilute nitric-acid solutions. Horwitz et al. (1981) have studied the separation of the lanthanides and trivalent actinides from Am to Fm (table 2) using dihexyl-N, N-diethylcarbamoyl-methylphosphonate (DHDECMP) and aqueous nitrate solutions. Steadily decreasing distribution ratios are observed for the lanthanides, but nearly constant D s are found for the trivalent actinides. Group separation does not appear feasible while interlanthanide (but probably not interactinide) separations are possible. However, substitu-... 

Quaternary ammonium compounds are analogous to tetramethylammonium-based anion-exchange resins. They offer additional possibilities over anion-exchange resins for trivalent lanthanide/actinide separation (over resins) in the ability to use solvation effects to enhance separation factors. The first application of quaternary amines to lanthanide/actinide group separation was made by Moore (1964), who examined the system Aliquat 336/xylene/H2S04-NH4SCN. A principal advantage of this method is the relatively low concentration of salts required to attain a usable separation (as compared with tertiary amine/nitrate systems). Several other applications of the method have been summarized by Weaver (1974). 

Fig. 6. Histogram representation of americium/europium separation factors (as representative of lanthan-ide/actinide group separation factors) for a representative collection of separation methods ...

In the lanthanide series, the missing element number 61 was discovered in 1945, which made the lanthanide subgroup complete. The corresponding actinide group was almost empty, as shown in Figure 52.8. The squares 93-103 attracted great interest, typical for science, which in all times has endeavored to fill empty spaces. 

Two specific metal-ligand systems merit mention because of the comprehensive research being carried out currently in the area of transition metal complexes metalloporphyrin derivatives of the lanthanide and actinide groups (Wong et al., 1974 Wong and Horrocks, 1975 Horrocks and Wong, 1976) and phthalocyanine derivatives of most of the rare earths prepared and characterized over the last 20 years (Kirin et al., 1965). 

E transition metal (16e), lanthanide, actinide, group 13 element... 

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