Iron(III) extraction by LIX 860 and its influence on copper(II) extraction from sulphuric solutions

Abstract

Solvent extraction of iron(III) by means of the commercial salicylaldoxime LIX 860 and its influence on copper(II) extraction from sulphuric solutions has been studied. Extraction experiments were carried out varying the equilibration time, temperature, extractant concentration, aqueous pH and the ferric and cupric ions concentrations. Iron(III) extraction by LIX 860 can be represented by the reaction:

Fe3aq+3HRorgtwo left arrowsFeR3org+3H+aq in which HR represents the extractant molecule. Iron(III) extraction can be performed at pH values above 1 and the extraction reaction is endothermic. It was determined that, for the above reaction, log Kext(25°C) is −1.196 and the corresponding values of ΔH°, ΔG°(25°C) and ΔS°(25°C) are 8.6 kJ/mol, 6.8 kJ/mol and 0.006 kJ/mol K. It was also concluded that, under the present experimental conditions, copper(II) is extracted preferably to iron(III) and the presence of this ion does not appreciably influence the equilibrium constant of the copper extraction reaction by LIX 860.