Leached sea nodules residue was used for the present study for exploring its utilization. The residue generated in ammoniacal- SO2 pressure leaching was water washed to reduce the sulphur content. To improve the Mn/Fe ratio in the residue, it was blended with Fe-Mn slag or Mn ore in the calculated amount and smelting was carried out in 50 kVA submerged arc furnace. Various parameters such as holding time, amount of reductant, power input etc. were investigated. The maximum recovery of Mn from residue blended with Fe-Mn slag and Mn ore was 58% and 65% respectively in the form of silicomanganese.


The most extensive deposit of manganese oxides are found in the world's oceans, which is known as polymetallic sea nodules or deep-sea manganese nodules or ferromanganese nodules that are 0.5–25 cm in diameter, with an average diameter of ∼4 cm. Polymetallic sea nodules are also important resource of strategic metals like copper, nickel and cobalt. Several processes have been developed in various parts of the world to recover these metals (Xueyi et al, 1997; Agarwal and Goodrich, 2003), although none of them is in the stage of commercially exploitable, may be due to some mining and environmental hurdles (Manickam et al, 1996). In India, a pilot plant for the treatment of polymetallic nodules to recover copper, nickel and cobalt was set up at Hindustan Zinc Limited, Udaipur by Ministry of Earth Sciences, Govt. of India (Mittal and Sen, 2003). This is based on the Ammoniacal pressure leaching in presence of sulphur dioxide (Das et al, 1998; Das et al, 1999; Das, 2001). This process generates huge amount of residue (70- 75% of treated nodules) after leaching of Cu, Ni & Co from the nodules.

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