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PALLADIUM
Natural Abundance, Stable Isobars Pd102, 0.96%, Ru102 Pd104, 10.97%, Ru106 Pd105, 22.2%, Cd106 Pd106, 27.3%, Cd108 Pd108, 26.7%, Cd110 Pd110, 11.8% Powdered palladium metal is the only charge material which has been used in the separation of palladium isotopes. The metal is used in a special graphite source block which is heated by electron bombardment. Because of the high cost of Pd, unresolved charge material is recycled and recovered. The source, receiver, and liner are washed in nitric acid and the solution is filtered and evaporated to a small volume. Concentrated hydrochloric acid is added in sufficient quantity to combine with the nitric acid present to form aqua regia, and the solution is evaporated to dryness forming palladium dichloride. Solids removed in the filtration are combined with the graphite salvage and ignited in oxygen. The ash produced is leached with aqua regia until all the Pd is dissolved. Combined leach solutions are evaporated to dryness yielding palladium dichloride. The palladium dichloride solids are combined and treated with concentrated ammonium hydroxide until they are completely dissolved. This forms a solution of tetramminepolladous chloride which, when acidified with hydrochloric acid, precipitates the yellow dichlorodiammine palladium. The precipitate is removed by filtering, and the filtrate is treated with an alcoholic solution of dimethylglyoxime to recover traces of palladium not precipitated as the dichlorodiammine. The dimethylglyoxime precipitate is filtered, washed with alcohol, and transferred to a beaker where it is digested with nitric acid. When the precipitate is dissolved, ammonium hydroxide is added until the solution is basic. The solution is then acidified with formic acid and digested to precipitate elemental Pd. The yellow dichlorodiammine palladium from the first precipitation is transferred to a crucible and thermally decomposed to the element, which will contain a small amount of blue palladium oxide. This mixture is combined with the metal from the formic acid reduction and digested with formic acid to insure that all the palladium is in the elemental form. The product is dried at 110° C and stored for future use. Palladium and its compounds are not considered toxic. |
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