hydrometallurgical recovery of copper and nickel powders from the copper bleed solution of indian sea nodules

Abstract : The copper bleed solution containing -40 g/L Cu, 20 g/L Ni and 180 g/L sulphuric acid is generated during the separation and recovery of metals by solvent extraction-electrowinning (SX-EW) in a close-loop operation for the ammoniacal leach liquor of Indian Ocean nodules. This paper describes the development of a process to produce high value copper and nickel powders following partial decopperisation, crystallization of mixed sulphate salt and aqueous hydrogen reduction. The copper powder was produced in an autoclave from the sulphate solution at initial hydrogen pressure of 26 bar in 90 minutes at 413 K. Subsequently, nickel powder was recovered (99%) in two stages from the solution of pH 4.5 at 40 bar pressure and 463 K after removal of residual copper as sulphide. Nickel recovery in one stage was however observed to be 98% when hydrogen reduction was carried out from an ammoniacal solution in the pH range 9-11. P/M grade copper and nickel powders of acceptable purity were produced from the bleed solution.