Selective Separation of Metals from Deep-Sea Ferromanganese Nodules by Sulfur Dioxide Reduction

Abstract

An investigation of the reaction of deep-sea ferromanganese nodules with SO₂ has been carried out in the temperature range 300 and 600 ddot]C. Maximum sulfation occurs with dehydrated nodules after treatment with a SO₂-O₂ gas mixture at 400 ddot]C. X-ray photoelectron spectroscopy and x-ray diffraction techniques indicate that the oxides of manganese, which are major components in the nodules, are sulfated. The oxides of Cu, Ni, and Co are also converted into their sulfates when reacted with SO₂ and O₂, and Mn, Cu, Ni, and Co can be nearly quantitatively extracted by leaching the sulfated nodules. Iron, which is also a major component and present as goethite, a-FeO(OH), is not sulfated but transformed into hematite, α-Fe₂O₃. Thus it can be separated from other metals which form water-soluble sulfates during the high-temperature sulfation process.