Autoclave Leaching of Copper-Nickel Matte Produced from Duluth Gabbro.

摘要

The U.S. Department of the Interior,Bureau of Mines,is conducting laboratory-scale research to determine the leaching conditions required with sulfuric acid for extracting base metal from a matte with a copper-to-nickel ratio of 6to 1. The matte (61.2pct Cu, 9.7pct Fe, 21pct S,and about 5 oz of precious metals per ton) was prepared from Duluth Complex (Minnesota) ore by smelting a bulk sulfide flotation concentrate. The matte was preleached at atmospheric pressure to selectively extract 20pct of the nickel,and the undissolved solids were referred to as the matte residue. Autoclave leaching of the matte residue extracted over 95pct of the nickel,copper,and iron. The remaining leach residue in the autoclave contained over 100 oz of precious metals per ton. The leaching conditions required were matte grind of greater than 98pct minus 325mesh,pulp concentration of 5 g/l,total pressure of 100psig with oxygen at 150C or 400psig with air at 180C, 50 g/l H2SO4, 700rpm agitator speed,and 6hours of leaching time. The leaching time was decreased to 2hours by increasing the agitator speed to 1,300rpm. Sulfuric acid concentration greater than 50 g/l did not appreciably enhance the base metal extraction,but with less acid,residues with higher iron concentrations were obtained. Supersaturation of the liquor as prevented at 150C by using a lixiviant that contained 30 g/l Ni and 20 g/l Cu.