Selectivity in foam separation by control of charge on the extracting solute: metal-chloro complexes

Abstract

The application of selective concentration by foam separation of trace species via control of charge on these species has been investigated. The removal of anionic chloro complexes of iron(III), mercury (II), and cobalt(ll) has been examined. Distribution factors, F/C, as a function of hydrochloric acid concentration have been measured with the cationic surfactant, hexadecyltrimethylammonium bromide; the trends have been found to be similar to those obtained in ion-exchange measurements, with an anionic exchanger. In the case of iron(III), F/C has also been measured as a function of surfactant concentration, initial FeCL 3 concentration, and % ethanol in water. Total reflux foam separation measurements were performed for selective removal. It was found that IO -7 M FeCl 3 could be selectively removed in the presence of a 100-fold excess of HgCl 2. Further, HgCI 2 could be selectively concentrated at I M hydrochloric acid and 10 -7 M in the presence of CoCl 2. A model based on a mobile ion-exchanger surface is presented to explain qualitatively the trends observed.