Crude electrorefining electrolyte obtained from ICC (Ghatsila,India) copper dust

Abstract

Copper dust from ICC, Ghatsila (India) was characterised and water leached. Water leaching at room temperature for 1 h dissolves as much as 50% copper present in the sample. The water leach residue, consisting mostly of oxides, was moistened with H₂SO₄ then baked (sulphatising roasted) in static conditions for 30 min at 973 K. The baked mass was found to contain CuSO₄, CuSO₄3H₂O, CuSO₄5H₂O, Cu₂O(SO₄) and Fe₂O₃. Copper in the baked mass can be leached quantitatively in 1 h at room temperature by even 0·1% H₂SO₄ solution. Optimum conditions of baking and leaching for the highest recovery of copper have been determined. The solutions obtained by sulphuric acid leaching of water leached and baked material contain about 2-3 g/l iron in both ferrous and ferric states. This iron can be largely precipitated out by adding lime to adjust the pH to 3·60 followed by passing air through the solution at 353 K for 4 h. The precipitate can easily be separated by filtration and the filtrate is of electrorefining electrolyte grade containing 44·05 g/l copper and 0·9 g/l iron. The iron content may further be reduced to 0·63 g/l by single stage extraction using 0·05 M D2EHPA solution.