Recovery of cobalt from Taylor Gem ore by aqueous oxidation

The problem of recovering cobalt from a cobalt arsenide ore in caustic, ammonia, and water solutions, all under oxygen pressure, has been examined. A wide range of temperatures and pressures were used to produce either a soluble or an insoluble oxidized form of cobalt. Subsequent treatment of certain oxidized residues included sulphuric acid and caustic leaching, and ammonium hydroxide leaching under hydrogen pressure. A general outline of the ore treatment in all the above solutions is presented to indicate the course of the research and to show why certain procedures were used. Consideration is then given separately to the experimental work in each of the solutions with regards to equipment, procedure arid results. In each case a discussion of the results is given together with free energy calculations which justify some of the conclusions. Caustic treatment of the ore proved difficult but both ammonia and water treatment showed good possibilities for commercial development. In caustic solution, oxidation of the ore followed by a hot, 25% sulphuric acid leach' extracted only 70% cobalt. In ammoniacal solution the cobalt was oxidized completely to the residue and 95% of it was then leached in hot, dilute sulphuric acid but solution contamination by arsenic was serious. In water solutions between 85% and 90% of the cobalt was recovered directly in a fairly pure solution provided enough iron was present as pyrite to precipitate the arsenic.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat