Recovery of copper powder from copper concentrates and from solutions of copper(II) sulfates using sulfur dioxide and aqueous acetonitrile

Abstract

Copper concentrates can be sulfation roasted and leached with water to produce impure solutions of copper(II) sulfate. Copper sulfites are precipitated from aqueous copper(II) sulfate solutions with soluble salts of sulfurous acid like (NH 4) 2SO 3 or Na 2SO 3. The water insoluble copper sulfites dissolve in acetonitrile—water (AN/H 2O) and reduce Cu 2+ to give acidic solutions containing up to 2.4 M Cu + as Cu 2SO 4. Removal of acetonitrile by steam and disproportionation, gives up to 75 g pure particulate copper per litre of such solutions. Conditions for the recovery of Chevreul's salt from solution using different sulfite bases and for its dissolution in CuSO 4/AN/H 2O are determined. It is shown that both temperature and the molar ratios of Chevreul's salt and CuSO 4 are important in the efficiency and stoichiometry of the dissolution reaction. Methods of separating copper and nickel from solutions of copper(II) and nickel sulfates, and of recovering copper from dilute (< 0.1 M) solutions of copper(II) sulfate, are suggested. A flow-sheet which combines these reactions and methods to recover copper from sulfation roasted chalcopyrite concentrates is proposed.