Precipitation studies of the binary solutions containing Fe (III) and either divalent ion of Mn, Cu, Ni or Co have beend emonstrated with sodium hydroxide, sodium carbonate or calcium hydroxide as a precipitant to provide fundamental information for the recovery of valuable metals from the leach solution of manganese nodules. The Fe ion among five metal-ions precipi tated at the lowest pH range as a ferric hydroxide. Precipitation curve for each of Mn, Cu, Ni and Co ions was found in a range of lower pH than that estimated from the solubility product of the respective hydroxide. The marked coprecipitation of Mn ion with ferric hydroxide was observed in the presence of sodium hydroxide or calcium hydroxide as a precipitant. Sodium carbon ate precipitant provides the best results for Fe separation from either of Mn, Cu, Ni or Co ion with little effect of coprecipitation between these ions. The common ion effect is considered essential for an interpretation of the different behavior among three kinds of precipitants used in each of the binary solutions. The separation tests have been applied to the soluti ons leached from manganese nodule with sulfuric acid. The successful removal of Fe component using sodium carbonate was experimentally performed at a pH of 4.5 from the leach solutions containing Mn, Cu, Ni and Co ions as well as the successive separation of Cu component at pH6.7 from the Mn, Ni and Co ions.
