Liquid-liquid extraction of aluminium and gallium with 5-substituted 8-hydroxyquinolines

Abstract

Various 5-substituted 8-hydroxyquinolines have been synthesized and their extractive properties studied for the separation of Ga and Al in strongly basic medium (3.5 M NaOH). Among the synthesized molecules, only YEN 10 and YAN 5 (with side chains C10H21CHC ∠ C10H21 and C5H11C ∠ C11H respectively) extract the gallium ion. The extracted complexes are Ga (YAN 5)3 and Ga (YEN 10)2(OH)2-Na+ and the conditional extraction constants are 107.5 and 104, respectively. The constants for aluminium extraction are 107.7 and 103.5, respectively. YAN 5 is not selective for Ga versus Al. The rate of phase transfer is first order with respect to Ga and extractant concentrations. The phase transfer constants are 1.2×10-5 for YAN 5 and 1.05×10-5 for YEN 10, if the rate is expressed in mol m-2 s-1 and the concentrations in mol L-1. These values are lower than for Kelex 100. The interfacial measurements show that the 5-substituted molecules are less concentrated at the interface than Kelex 100 molecules. © 1987.