Perfectionnements apportés aux procédés et dispositifs pour l'extraction par solvant de métaux.

摘要

In a process for the solvent extraction of metals wherein metals present in a pregnant liquid are extracted into a receptive liquid immiscible with the pregnant liquid, the two liquids are contacted to produce a mixture of extract and raffinate phases which are caused to separate out by subjecting the mixture to one or more high-voltage unidirectional electric fields established with a metallic treating vessel. As shown in Fig. 1, ore is treated at 7 with a leaching agent entering at 8 and the resultant liquor counterflows a stream of receptive liquid from a line 11 in a number of mixer-settlers 12. The resulting mixture is then pumped through a mixer 18, a by-passable de-entrainment tank 19, a mixer 22 and a heat-exchanger 23 to an electric treater 25, wherein the mixture is separated into extract and raffinate phases. The extract phase leaves the top of the treater and flows through a wash column 28, an extraction column 30 and a recovery system 34 which discharges the metal in pure or chemically combined form at 35. To reduce the conductivity of the mixture for the electrical treatment, some of the extract phase may be recycled from the top of the treater 25 to the heat exchanger 23, and some or all of the more conductive liquid at the bottom of the treater 25 may be recycled to the mixer 18. Additionally the tank 19, and a preliminary treating zone 54, Fig. 2, of the treater 25 may be used for gravitational separation of the more conductive phase liquid. The receptive liquid may comprise kerosene or hexane containing a chemical such as alkyl carbitols, alkyl esters or alkyl ketones having a selective affinity for the metal to be extracted. Alternatively the solvent may comprise bis (disubstituted-phosphinyl) methanes of the general type R2 P (O) CH2 (O) PR2, for example bis (di-n-hexylphosphinyl) methane. The Specification describes a specific example of the process as used for the extraction of Uranium U3O8 from an ore concentrate containing 20-30% impurities wherein the ore concentrate is digested with a 1 M nitric acid solution and counterflowed in the mixer-settlers 12 with 30/70% solution of tributyl phosphate in hexane.