Separation of Thorium from Rare Earths, Zirconium, and Other Elements by Cation Exchange Chromatography

Abstract

Thorium has a high affinity for the Dowex 50 cation exchange resin and it is not eluled tom a column of the resin even by relatively concentrated hydriochloric acid. Semiquantitative affinities for AG 50 resins in hydrochloric acid were investigated for 23 cations, and ''single element'' elution curves were prepared for those with high affinities. A method was developed a separate thorium quantitatively, even in small amounts. from zirconium and the rare earths. (auth) l599l An investigation was made of the reproducibility of the platinum bath technique for determining oxygen in titanium and its alloys. Although several variations of the platinum-bath technique were tried, the results were not satisfacarily reproducible. However, a modified technique, platinum aux, was developed. The accuracy of the dry-crucible and the platinum-flux techniques as applied to unalloyed titanium, and one alloy, Ti-6A14V, was determined by using standard samples. Both techniques appeared capable of recovering at lesst 92% of the oxygen in unalloyed titanium standards. In most cases the recovery was much better. Average oxygen recovery from Ti-6Al-4V alloy standards was 93% by both the platinum-flux and the dry-crucible techniques. Studies on the reproducibility of analytical values made on three other alloys, Ti-8Mn, Ti-2Fe- 2Cr-2Mo, and Ti-5Al-2.5Sn,more » indicated that satisfactory results could be obtained by both techniques. (auth) l5992 Tantalum and niobium are separated and determined gravmetrically by precipitation with selenious acid from highly acidic solutions in the absence of complex ing agents. Hydrogen peroxide is used in the preparation of the solution and later catalytically destroyed during digestion of the precipitate. From 0.2 to 30 mg, separately or in mixtures, of niobium or tantalum pentoxide can be separated from mixtures containing 100 mg each of the oxides of scandium, yttrium, cerium, vanadium, molybdenum, iron, aluminum, tin, lead, and bismuth with a single precipitation; and iron 30 mg of titanium dioxide. and 50 mg each of the oxides of antimony and therium, when present separately, with three precipitations. At least 50 mg of uranium(VI) oxide can be separated with a single precipitation when present alone; otherwise, three precipitations may be needed. Zirconium does not interfere when the tantalum and niobium contents of the sampls are small, but in general, zirconium as well as tunssten interfere. The method is applied to the determination of the earth acids in tantaloniobate ores. (auth)« less