Selective Leaching of Manganese Nodules Using Sulfur Dioxide as a Reductant

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The selective extraction of nickel, cobalt and copper from manganese nodules was achieved by using ammoniacal solution as a solvent and using sulfur dioxide as a reductant. The selective extractability was a pronounced with raising leaching temperature. When the nodules were leached in the solution using lower concentrations of ammonium ion, manganese and iron were also extracted considerably at lower concentrations of sulfur dioxide. The suitableness of selective extraction was decided by pH of the solution, and the limit value was estimated at pH=6.Manganese ammonium sulfite hydroxide was detected as a leaching residue using ammonia solution as a solvent, and manganese carbonate was detected at the ammonium carbonate solution leaching. When the nodules were leached in the mixed solution of ammonia and ammonium carbonate using sulfur dioxide as as a reductant, the extraction of manganese was lower using higher concentrations of ammonium carbonate, and that of iron was lower using higher concentrations of ammonia water.The extraction percentages of metallic components under optimum conditions were 99% for copper, 98% for nickel, 95% for cobalt, 3% for manganese and 1% for iron, respectively. This method of leaching may be effective for the treatment of manganese nodules because there are high extraction of valuabl emetals and good selective extractability.