Acid pressure dissolution of matte produced from the alloy obtained from direct smelting of sea nodules

An alternate processing option for sea nodules by direct reduction smelting—matte formation—pressure leaching route is proposed and a detail study on matte leaching under oxygen pressure is reported in this paper. Friable mattes containing different percentage of sulphur were prepared by adding sulfur to the molten alloy produced from sea nodules smelting. The matte of composition: 24.8% Cu, 26.0% Ni, 0.98% Co, 23.8% Fe and 23.8% S was subjected to pressure leaching in sulphuric acid medium under oxygen pressure. To optimize the dissolution condition, effect of various parameters like leaching temperature, oxygen partial pressure and sulphuric acid concentration were studied and discussed. It was observed that, the recovery of copper, nickel and cobalt increases with increase in reaction temperature, acid concentration as well as with increase in oxygen partial pressure. The requirement of acid is more for dissolution of matte containing less sulphur. More than 97% Cu, 98% Ni and Co recovery from the matte containing 23.8% S is achieved with only 1% (v/v) sulfuric acid at 160°C temperature and 100 psi oxygen pressure. The major advantage of pressure dissolution of typical matte containing high iron is that, it catalyses the dissolution reaction and finally rejected in the form of leached residue. The detail mechanism of the dissolution reaction is proposed