| abstract |
Metal values are extracted from manganiferous ocean floor nodule ore by treating the ore with hydrochloric acid, thereby producing chlorine and a starting pulp containing a solution of the metal chlorides and a solid residue. The starting pulp is subjected to at least two subsequent acidifications with HCl, each acidification being followed by addition of fresh ore, thereby producing chlorine and a final pulp containing a concentrated solution of metal chlorides and a solid residue. The solid residue is separated from the concentrated solution and substantially all the metal values, except manganese and alkali and alkaline earth metals, are separated from the solution. The manganese is separated from the solution by treatment with chlorine, at least the major portion of which was produced in the preceding leaching steps, while maintaining the solution at a pH of between about 3 and 7 by addition of a neutralizing agent such as MgO or Mg(OH)2 whereby the manganese is precipitated in the form of MnO(1+x) in which x is between 0.5 and 0.7. The manganiferous precipitate is separated from the resulting solution of magnesium chloride and the latter is pyrohydrolysed in the atomized state to regenerate the neutralizing agent and HCl, which can be recycled. |