Reductive leaching of manganese deep sea nodules containing 27.4% Mn and 7.3% Fe was carried out to achieve a maximum extraction of Ni, Cu, Co, and Mn and to separate Fe-concentrate convenient for the subsequent ferromanganese production. Leaching of nodules in SO2-H2O-H2SO4, SO2-H2O-H2SO4Na2SO4 and H2SO4-FeSO4 solutions was tested. Fe was separated as jarosite in two ways: simultaneously with the nodules leaching in the presence of Na2SO4 and in a subsequent step after nodules leaching. The jarosite was desulfurized via solution conversion to ferric oxides catalysed by FeSO4. After the reductive dissolution followed by jarosite precipitation and transformation to ferric oxides, Fe was recovered as well filterable solid, and quantitative amount of Mn, Co, Cu, and Ni was obtained in a dissolved form.


Manganese" deep-sea nodules mainly contain Mn and Fe oxides with minor amounts of Cu, Ni, Co, AI, Ti, Mg, Ca, and Si. Ni, Co, and Cu are the components, which are worthy extracting from nodules with a high yield. The majority of Cu and Ni can be dissolved without a complete dissolution of the manganese or iron phases on the contrary, Co is very strongly bonded by Mn(IV) oxides and its extraction is impossible without simultaneous solubilization of Mn. Because manganese dioxide is stable in oxidising aqueous environment, the manganese and cobalt extraction can only be carried out under reducing conditions. Several reducing agents were used for reduction of Mn02 in aqueous media, such as S02, FeS04, and charcoal (Fuerstenau and Han, 1977, Das et aI, 1982). The objective of this study was to determine the optimum conditions of reductive sulphuric leaching of polymetallic manganese deep-sea nodules, under which it is possible to achieve a maximum extraction of Ni, Cu, Co and Mn and to separate Fe-concentrate, which is convenient for the subsequent ferromanganese production.

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