Selective separation of lanthanides by supported liquid membranes containing Cyanex 925 as a carrier

The work describes in detail the transport of lanthanides between chloride solutions by a facilitated transport through a supported liquid membrane (S LM) containing Cyanex 925 (a mixture of alkylphosphine oxides, Cyanamid). T he chemical nature of this carrier requires a strong difference of chloride content between the two sides of the membrane which leads to a strong rise in the osmotic pressure. The influence of physical and chemical parameters affecting the transport o f neodymium was determined including stirring rate and the chemical composi tion of the feed and stripping solutions. The highest permeability coeffici ents (cm min(-1)) were obtained under the following conditions: 1.0 M Cyane x 925 in kerosene (membrane), stirring rate 1200 rpm, feed solution of 2.5 M NaCl at pH 4.0 and a stripping solution of 0.8 M HCl. Under these conditi ons, the SLM is shown to be effective for the transport and separation of n eodymium. Separation of lanthanide mixtures is possible. The selectivity of the system is such that Yb is the most favourably transported and La the l east favoured, following the correlation Yb>Tb>Nd much greater than La. (C) 1999 Elsevier Science B.V. All rights reserved.