PROCESS FOR THE REMOVAL OF ALUMINIUM AND/OR CHROMIUM FROM NICKELAND?OR COBALT SULPHATE SOLUTIONS AT ATMOSPHERIC PRESSURE

摘要

The present invention relates to the removal of aluminium and/or chronium from nickel and/or cobalt sulphate solutions, by chemical precipitation, at atmospheric pressure. The invention comprises a process for aluminium and/or chromium precipitation, as basic sulphate salts of alunite type, at atmospheric pressure and temperatures not exceeding 100 oC. It achieves equilibrium aluminum and/or chromium concentrations lower than 200 and 50 ppm, respectively as well as excellent filtering properties of the produced precipitate. The pH of the solution is slowly raised, by addition of a neutralizing agent, to a final value in the range 2.5 to 4.5. Addition of seed material is highly advantageous for minimizing the reaction time and enhancing crystal growth of the precipitate. The nickel and/or cobalt losses in the precipitates are kept low. The produced precipitate, after washing with water, is environmentally acceptable for disposal, according to standard tests. The disclosed method for the removal of aluminium and/or chromium enables the treatment of nickel and/or cobalt sulphate solutions, produced by sulphuric acid leaching of nickel ores, for nickel/cobalt separation and recovery by various techniques.