ABSTRACT

Selective chemical leaching technique has been applied to the study on the partitioning of major and minor constituents into individual mineral species in ferro-manganese nodules formed in limestone areas of the Ryukyu Islands. The technique includes the use of 25% CH₃COOH, 1 M NH₂OH·HCl-25% CH₃COOH and 30% H₂O₂ solutions. Treatment with 25% CH₃COOH solution led to the leaching of 51% of Ca, 0.6% of Fe and 1.5% of Mn. Successive leaching with 1 M NH₂OH·HCl-25% CH₃COOH solution led to the leaching of 32% of Fe and almost 100% of Mn. The rate of leaching is largely dependent on the mineral components in the nodules. Minor elements are concentrated in the ferro-manganese fraction which is leached with 1 M NH₂OH·HCl-25% CH₃COOH solution. The rate of leaching is 100% for Co, 93% for Cu, 87% for Pb, 82% for Cd, 76% for Ni and 45% for Zn. Some parts of the elements remained insoluble in the above solutions. The remained fraction may have been associated with either stable clay lattice structure or stable oxide forms of lithogenous origins.