EXTRACTION AND SEPARATION OF RARE-EARTH ELEMENTS BY TRI-NORMAL-OCTYLMETHYLAMMONIUM NITRATE

The extraction of rare-earth nitrates was studied, using tri-n-octylmethylammonium nitrate in xylene as an extractant and ammonium nitrate as a salting-out agent. The capability of this extractant decreases continuously with atomic number apart from a slight increase from Gd to Tb. An extraction scheme occurring for all elements is presented. In this it is assumed that extraction occurs via reaction with monomer, R, of the extractant and the successive stage-wise formation of two extracts, Ln(N03)3 • 5R and (Ln(N03)3)2 * 5R. The fraction of 1:5 complex is very close to 1 at low loadings, whilst for all elements the fraction of 2:5 complex increases with increased loading. The formation of 1:5 complex is most favored with La and less favored with elements of higher atomic number. The inherent limitation of this extraction system for separation into individual elements is also discussed. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.