Cerium complexes solvent extraction

Separation Processes. The product of ore digestion contains the rare earths in the same ratio as that in which they were originally present in the ore, with few exceptions, because of the similarity in chemical properties. The various processes for separating individual rare earth from naturally occurring rare-earth mixtures essentially utilize small differences in acidity resulting from the decrease in ionic radius from lanthanum to lutetium. The acidity differences influence the solubiUties of salts, the hydrolysis of cations, and the formation of complex species so as to allow separation by fractional crystallization, fractional precipitation, ion exchange, and solvent extraction. In addition, the existence of tetravalent and divalent species for cerium and europium, respectively, is useful because the chemical behavior of these ions is markedly different from that of the trivalent species. 

Tri-n-butyl phosphate, ( -C4H9)3P04. This solvent is useful for the extraction of metal thiocyanate complexes, of nitrates from nitric acid solution (e.g. cerium, thallium, and uranium), of chloride complexes, and of acetic acid from aqueous solution. In the analysis of steel, iron(III) may be removed as the soluble iron(III) thiocyanate . The solvent is non-volatile, non-flammable, and rapid in its action. 

Pu, Zr(+Nb), and Ce and iTithenlum complexes. Neptunium, plutonium, and cerium are made less extractable by reduction to lower oxidation states. Favorable separation of tiranlum from the other elements may be achieved by control.of the nitric acid and saltlng-out agent concentrations. Free halogens are extracted. These elements may be eliminated from solution prior to uranliim extraction. The halogens also combine chemically with a number of solvents eg,. 

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