Sulphuric acid leaching of cobalt-bearing manganese wad

Abstract

Manganese wad from the Mt. Tabor region of Queensland, Australia, contains in excess of 1% cobalt with lesser amounts of nickel and copper. As such, it presents a significant cobalt resource, particularly in terms of Australia's cobalt requirements. Because of the remote location and the lack of infrastructural facilities, potential processing routes need to be kept as simple as possible. There are many similarities between terrestrial manganese wads and deep-sea manganese nodules, and so routes developed for the processing of the latter should be applicable to the wad. Of these routes, sulphuric acid leaching at atmospheric pressure and ambient temperature appears to have considerable potential. This paper describes the results obtained with sulphuric acid leaching using the pug, agitated tank and column techniques. Even with excess acid, dissolution of the cobalt, copper and nickel from the wad was found to be extremely slow, with reaction times of weeks and months required for more than 50% dissolution. No conditions could be found where selective dissolution of cobalt, copper and nickel over manganese occurred. Comparative tests were carried out with Pacific Ocean deep-sea manganese nodules. Because of the low leaching rate found with sulphuric acid at atmospheric pressure and ambient temperature, commercial exploitation of the Mt. Tabor wad with this leachant under these conditions seems unlikely. Previously reported work indicates that a better approach will be to use sulphur dioxide as the leachant, even though this is a considerably more expensive leachant.