Processing of Deep-Sea Manganese Nodules at NML for Recovery of Copper, Nickel & Cobalt

: This paper describes the reduction-roast-ammonia leach-solvent extraction-electrowinning process
developed at NML for recovery of copper, nickel and cobalt from polymetallic sea nodules. Behaviour of various
reductants at different temperatures and their role in reduction roasting of sea nodule have been discussed. The
optimum reductant requirement, time and temperature for roasting have been determined. A brief account of the
development of a two-stage ammoniacal leaching scheme with a prior pre-conditioning step is given. The necessity
of monitoring redox potential in the first stage leaching to control cobalt recovery has also been elucidated.
Separation and recovery of metals from the anunoniacal leach liquor has been carried out by solvent extraction-electrowinning technique and the flow-sheet developed for this along with the nickel bleed stream treatment and electrowinning ofNi and Cu have been described.