The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 29, 2001
Filed:
Feb. 17, 1998
Norifumi Yoshida, Fukui-ken, JP;
Jun-ichi Nakayama, Fukui-ken, JP;
Shin-Etsu Chemical Co., Ltd., Tokyo, JP;
Abstract
Proposed is an improvement in a multi-stage solvent extraction process of a metal value such as rare earth elements from an acidic feed solution containing the metal value in the form of a water-soluble salt by bringing the aqueous solution into contact with a water-immiscible organic extractant solution containing an extractant compound which releases an acid when combined with the metal ions. While the concentration of the acid in the aqueous feed solution is increased when contacted with the organic extractant solution containing an extractant agent of the above mentioned type so as to cause a shift of the extraction equilibrium unfavorably against further extraction of the metal ions, the acid in the aqueous feed solution prior to contacting with the organic extractant solution in a succeeding stage of extraction is at least partly decreased, instead of the conventional expensive way of neutralization by the addition of an alkaline neutralizing agent to the aqueous solution, by ion exchange dialysis with dialyzing water through an anion exchange membrane.