Adsorption of hydroxyoxime-based extractants on silica and mica particles in copper extraction processes

Abstract

Adsorption of the commercial copper extraction reagent LIX860 was studied using silica and phlogopite mica as model adsorbents and isooctane and isooctane/toluene mixture as model diluents to investigate the reasons which may contribute to the accumulation of solid fine particles at the interface between the aqueous and organic phases in metal extraction processes. The adsorption of pure 5-dodecylsalicylaldoxime (the active compound in LIX 860) from isooctane follows Langmuir type adsorption behaviour on silica giving a surface area of 0.61 nm 2/molecule for the monolayer which compares favourably with the value estimated from molecular models when the aromatic ring is assumed parallel to the surface. On phlogopite, the observed adsorption density continuously increases with reagent concentration. At highest, the adsorption density on mica is about 3–4 times higher than on silica. This is explained by a perpendicular orientation of the aromatic ring on mica. Adsorption of the oxime as a copper complex is weaker than that of the free oxime. Increase in diluent aromacity and the addition of an aqueous phase were observed to decrease adsorption of the reagent on silica.