Patent ID: 6238566
Filing Date: 2001-05-29
Classification: B01D,C01F,C22B,Y02P

Abstract:
In a multi-stage solvent extraction process comprising at least two successive stages of unit extraction treatments, in each of which an aqueous feed solution containing a rare earth value in the form of rare earth ions in the presence of an acid is contacted with a water-immiscible organic solution of an extractant agent capable of combining the rare earth ions with release of an acid to effect extraction of a part of the rare earth value from the aqueous solution into the organic solution and the aqueous solution separated from the organic solution is, as an aqueous feed solution to the succeeding stage, further contacted with a water-immiscible organic solution of an extractant agent for the rare earth ions to effect extraction of a part of the remaining portion of the rare earth ions from the aqueous solution into the organic solution, the improvement which comprises contacting the aqueous solution separated from the organic extractant solution after the extraction treatment of the first stage with an absorbent of an organic material, and subsequently removing at least a part of the acid contained in the aqueous feed solution by ion exchange dialysis through an ion exchange membrane prior to contacting the aqueous feed solution with the organic solution in a second stage.