ADSORPTION OF HYDROXYOXIME-BASED EXTRACTANTS ON SILICA AND MICA PARTICLES IN COPPER-EXTRACTION PROCESSES

Adsorption of the commercial copper extraction reagent LIX860 was stud ied using silica and phlogopite mica as model adsorbents and isooctane and isooctane/toluene mixture as model diluents to investigate the re asons which may contribute to the accumulation of solid fine particles at the interface between the aqueous and organic phases in metal extr action processes, The adsorption of pure 5-dodecylsalicylaldoxime (the active compound in LTX 860) from isooctane follows Langmuir type adso rption behaviour on silica giving a surface area of 0.61 nm(2)/molecul e for the monolayer which compares favourably with the value estimated from molecular models when the aromatic ring is assumed parallel to t he surface. On phlogopite, the observed adsorption density continuousl y increases with reagent concentration. At highest, the adsorption den sity on mica is about 3-4 times higher than on silica. This is explain ed by a perpendicular orientation of the aromatic ring on mica. Adsorp tion 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 ph ase were observed to decrease adsorption of the reagent on silica. (C) 1998 Elsevier Science B.V. All rights reserved.