GB1219305A - Separating thorium from rare earth metals - Google Patents

Abstract

1,219,305. Separating thorium from rare earths. DOW CHEMICAL CO. 21 March, 1968, No. 13741/68. Heading C1A. Thorium values are separated from rare earth metals when both are contained in an aqueous acidic solution by (1) contacting the aqueous solution with a water-immiscible extractant comprising a mixture of (a) a dialkyl orthophosphoric acid, and (b) one or more of a trialkyl phosphate, a dialkyl alkylphosphonate, an alkyl dialkylphosphinate and a trialkyl phosphine oxide; each alkyl group having 4-18 carbon atoms; the molar proportions of (a) and (b) being 3 : 1 to 1 : 3; (2) separating the phases; (3) contacting the organic extract with either 6-12 molar HCl or 0À5-12 molar HNO 3 and (4) separating to produce an organic phase containing the thorium and an aqueous phase containing the rare earth metals. Ferric ion may also be present in the aqueous solution. The extractant may be used directly or in a solvent, for example hydrocarbons, halogenated hydrocarbons or ethers. The organic phase may be contacted with 10% HF to precipitate ThF 4 and the rare earth metals may be obtained from the acid medium by partial distillation and adding oxalic acid or NaOH to precipitate the R.E.M. values. The source liquor may be uranium depleted leach liquor, and may contain ferric iron, and the process may be continuous or batchwise, using for example, simple mixing tanks, mixing settlers, direct or counter current flow columns. The examples use di-(2-ethyl hexyl) orthophosphate + tributyl phosphate in kerosene as extractant.