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4813200 
Journal Article 
Thermochemistry of the Fe, Ni and Co-NH3-H2O systems as they relate to the Caron process: a review 
Asselin, E 
2011 
1 
Minerals and Metallurgical Processing
ISSN: 0747-9182 
28 
4 
169-175 
WOS:000297714200001 
Passivation of Fe-Ni-Co alloys during the Caron leach process is thought to result in low cobalt recoveries in ammoniacal ammonium carbonate solutions. A brief review of the available thermochemical data for the (Fe, Ni, Co)-NH3-H2O systems has been undertaken. The stability of the Co(II) and Co (III), Ni(II) and Fe(II) ammines was examined through the use of speciation and Pourbaix diagrams at 298 and 333 K and at 6 M total ammonia. Increasing the temperature reduces the stability fields of the ammines and generally constrains the thermodynamic window for the leach. The Fe(II) ammines are only thermodynamically stable under reducing conditions. Polarization experiments show that these ammines are unlikely to form if oxygen is present. Fe-Ni-Co alloy passivation may be alleviated by careful management of potential 
Hydrometallurgy; Thermodynamics; Laterites