Ammoniacal leaching of roast reduced deep-sea manganese nodules

The paper describes the reduction-roast ammonia leach process developed at NML for recovery of copper, nickel and cobalt from polymetallic sea nodules . A brief account of the development of a two stage ammoniacal leaching sch eme with a prior pre-conditioning step is given. The necessity of monitorin g redox potential in the first stage leaching to control cobalt recovery ha s been emphasized. Based on the two stage leaching scheme, recycle leaching has been carried out to generate leach liquor having suitable composition for:thr subsequent solvent extraction-electrowinning operation. The average recovery of metals in 16 cycles of leaching has been found to be 92% Cu, 9 0% Ni and 56% Co. (C) 1999 Elsevier Science B.V. All rights reserved.