EXTRACTION RATE OF PRASEODYMIUM AND NEODYMIUM WITH PHOSPHONIC ACID MONO ESTER

Recently, interest has increased in the practical application of solvent extraction technology for the mutual separation and purification of rare earth metals. 2-Ethylhexyl phosphonic acid mono-2-ethylhexyl ester (henceforth EHPNA) has recently been developed, and was found to have high capability of lanthanoid extraction. This paper reports the extraction rate of praseodymium and neodymium with EHPNA in toluene from hydrochloric acid solution by use of a stirred transfer cell of Lewis type at 298 K. The experimental results suggested the existence of chemical reaction resistance at the interface at low extractant concentration and high pH value in the forward extraction, in addition to the film mass transfer resistances in the aqueous and the organic phases. The time course change of the extraction from mixed lanthanoid aqueous solution was satisfactorily predicted by the extraction model presented. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.