Studies of the metal-ammonia-carbon dioxide-water system in extraction metallurgy of polymetallic sea nodules

Abstract

The reductive roast-ammonia leach process has been applied to the extraction of nickel, cobalt and copper from ocean-floor manganese nodules. The presence of iron and manganese and their effect in ammoniacal leaching of copper, nickel and cobalt have been studied. Experiments were conducted in leaching of nickel, copper, cobalt, iron and manganese using metal powders in the same ammonia-ammonium carbonate solutions which were used for the leaching of roasted product. It was found that the combined leaching behaviour of copper, nickel and cobalt in the absence of iron and manganese was the same as their individual leaching behaviour. However, when manganese was added, the leachability decreased for each of the metals. The leaching behaviour of the metals was not affected much in the presence of iron in this study. Leaching of the sea nodules showed that the recoveries of cobalt and nickel were lower than obtained in combined leaching of the five metals mentioned above, probably because of the formation of iron-nickel and iron-cobalt alloys during roasting. It was also observed that preconditioning of roasted product without air increased the recovery of nickel and cobalt.