PATENT

3240.  SCHALLER, P., FROELECKE, E., MEYER, K., ROELEN, O., AND LÜBEN, R.  (Hydrocarbon synthesis Corp.)  Thorium Recovery From Precipitates Also Containing Iron.  United States Patent 2,330,750, Sept. 28, 1943.  Chem. Abs., vol. 38, 1944, p. 1331.

Precipitates such as those from a spent catalyst treatment, which contain Th and a substantial amount of Fe, as obtained by the action of an alkaline precipitating agent on salt solutions containing Th and Fe, are treated by a method that involves a first stage including the steps of dissolving the precipitates in an acid, such as NHO₃ adding to the solution thus obtained more alkali carbonate, such as Na₂CO₃, than required to convert  all the Th in the solution into Th carbonate, thereby precipitating all of the Fe while leaving most of the Th in solution as Th alkali metal double carbonate, and separating the precipitate from the solution; at least one subsequent stage including the steps of dissolving the last-mentioned precipitate containing the Fe and some of the Th in an acid, such as HNO₃ and adding to the solution thus obtained approximately the same quantity of alkali carbonate as used in the first stage, so that all Fe present is again precipitated while substantially all the Th that was associated with the Fe remains in solution, a moderately elevated temperature, suitably about 40°-50°, being employed in the precipitation of the Fe in the first stage and a higher temperature, suitably about 75°-90°, in the precipitation of the Fe in any subsequent stage.