The leaching kinetics of cobalt and nickel from aluminum-coprecipitated products
- PDF / 446,208 Bytes
- 6 Pages / 584 x 778 pts Page_size
- 103 Downloads / 166 Views
I.
INTRODUCTION
C O B A L T and nickel are strategic commodities vital to a modem industrial society. In the processing of natural ores bearing cobalt and nickel, one of the most industrially difficult problems is the efficient separation of these two metals from each other due to their chemical similarity. The selective recovery of these metals from leach liquors is poor especially when the concentration of these metals is low. Previous studies ~'2'3 showed that cobalt can be separated from nickel in dilute solutions, at concentration less than 50 ppm, preferentially by coprecipitating cobalt with higher valence ions such as AI(III), Fe(III), Cr(III), and Mn(IV). The kinetics of the coprecipitation of cobalt and nickel with AI(III) and Fe(III) in ammoniacal solutions has recently been established. 3 The rate of the coprecipitation of cobalt was found to be more than 10 times that of nickel which suggested that the coprecipitation process could be a powerful technique for the separation of these two metals. When cobalt is precipitated with aluminum, the coprecipitated product exhibits a well-defined crystal structure with a formula 5CoO • A1203 • 6H:O, while nickel is incorporated with the coprecipitated product by chemisorption, t.3,4 The coprecipitation process is incomplete without redissolution of cobalt and nickel. The redissolution behavior of these metals from coprecipitation products has not been established. In this investigation, the redissolution kinetics of cobalt and nickel from coprecipitated products with aluminum has been investigated. The effect of aging on the dissolution behavior of cobalt and nickel has also been investigated.
K.N. HAN is Professor, Department of Metallurgical Engineering, South Dakota School of Mines and Technology, 500 East St. Joseph Street, Rapid City, SD 57701. C. O. NEBO is Lecturer, Department of Metallurgy and Materials Engineering, Anambra State University of Technology, Enugu, Nigeria. W. AHMAD was formerly Research Assistant, Department of Metallurgical Engineering, South Dakota School of Mines and Technology. Manuscript submitted September 11, 1986.
METALLURGICALTRANSACTIONS B
II.
EXPERIMENTAL
In all experiments, reagent grade metal nitrates were used. Stock solutions of 1000 ppm each of aluminum, cobalt, and nickel nitrate solutions were prepared and used in the production of coprecipitated products. Coprecipitation products were prepared by initially adding cobalt and nickel nitrate solutions to an ammonia/ ammonium nitrate solution to make up 150 ppm each of cobalt and nickel and 0.5 M total ammonia solution. This solution and a predetermined aluminum solution were then placed in a water bath which had been set at a desired temperature. The final pH of the solution was maintained at 10. When the temperature of these solutions reached the required value, 25 °C in this study, the two solutions were mixed instantaneously. The final aluminum concentration of the mixture of these solutions was adjusted to be 300 ppm. It was observed in earlier investigations 3'4
Data Loading...
