Some physico-chemical characteristics of central Indian Ocean nodules and their effects on extractive metallurgical schemes

Abstract

Some physicochemical properties of sea nodules obtained from the Central Indian Ocean basin have been studied. The bulk density, apparent porosity and specific surface area of the sea nodules have been studied. The bulj density, apparent porosity and specific surface area of the sea nodules have been determined to be 1.4g/cm3, 48% and 198m2/g respectively. The nodules have been found to be extremely friable having the hardness between 2-3 in the Mohs scale. The high free moisture content of about 14% of the sea nodules has been determined by oven heating and TG methods. The heat energy requirement to drive out the free moisture has been estimated from DSC curve. Some mineralogical characterisation studies of the sea nodules have been carried out by polarised microscope, SEM and XRD. These studies reveal the concentric growth structure of nodules, which consist of white, grey and dark bands. The presence of 10Å manganese minerals, -MnO2 and quartz have been identified by XRD method. The chemical analysis of the nodules shows that they contain minor amounts of valuable metals like copper, nickel and cobalt. Due to the complexity and lean grade, high moisture content and high energy requirement to drive out the moisture, it has been suggested that hydrometallurgical processing of the sea nodules would be preferable to their pyrometallurgical processing.