CPC C22B 3/08 (2013.01) [C22B 3/44 (2013.01); C22B 15/0071 (2013.01); C22B 23/043 (2013.01); C22B 23/0469 (2013.01); C22B 47/0018 (2013.01); C22B 47/0063 (2013.01)] | 6 Claims |
1. Process for the recovery of the metals Mn, Ni, Co, and Cu from polymetallic nodules, comprising the steps of leaching said metals using an SO2-bearing gas as leaching agent in acidic aqueous conditions, wherein the leaching is performed according to a two-stage process comprising the steps of:
a first leaching (L1), wherein a major part of the Mn, Ni, and Co is dissolved by contacting the nodules with a first quantity of SO2-bearing gas in a first acidic aqueous solution of sulfuric acid at a pH of 2 to 4, thereby producing a first leach solution and a first leach residue, which are separated; and,
a second leaching (L2), wherein a major part of the Cu is dissolved by contacting the first leach residue with a second quantity of SO2-bearing gas in a second acidic aqueous solution of sulfuric acid at a pH of less than 1.5, thereby producing a second leach solution and a second residue, which are separated,
wherein the process further comprises:
crystallization of the Mn from the Mn-bearing phase by heating and/or by evaporation of water, thereby obtaining a Mn-bearing solid, which is separated;
pyrolysis of the Mn-bearing solid by heating at a temperature of more than 850° C. thereby forming Mn oxide and an SO2-bearing gas, which is separated; and
recirculation of the SO2-bearing gas to either one or both leaching steps (L1, L2) for use as leaching agent,
wherein an excess of SO2-bearing gas is fed as leaching agent to the second leaching step (L2), thereby obtaining a stream of unreacted SO2, for use as leaching agent in the first leaching (L1) step.
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