Recovery of copper powders from leach solutions containing copper by means of ammonia, sulphur dioxide and acetonitrile

In this study, copper was precipitated as sulphites to produce copper powders from its impure solutions. Copper (I) sulphate solutions were prepared by utilizing these sulphites, and copper powders were produced by thermal disproportionation. The research was carried out in four steps: In the first step, the ore was dissolved with sulphuric acid. In the second step, the copper in the solution was precipitated as Chevreulʹs salt (Cu2SO3·CuSO3·2H2O) by using ammonia and sulphur dioxide. The appropriate precipitation conditions of Chevreulʹs salt were obtained at pH value of 4, the stirring speed at 600 rpm, the temperature at 60 °C, passing time of SO2 at 1 min and reaction time after passing SO2 at 6 min. In the third step, after filtration, Chevreulʹs salt was dissolved in acetonitrile–water (AN/H2O) system in a nitrogen atmosphere. The appropriate dissolution conditions of Chevreulʹs salt were determined at temperature of 65 °C, pH value at 2.5, stirring speed at 700 rpm and AN/H2O ratio at 41% (v/v). In the last step, the copper powders were produced by thermal disproportionation of copper (I) sulphate at 60 °C and 175 mm Hg pressure in a nitrogen atmosphere. The copper powders produced were pure at 99.85%.