RI 3073 Extraction of Soluble Copper from Ores in Leaching by Percolation

"This repot continues the series of papers being prepared at the Southwest Experiment Station of the Bureau of Mines in cooperation with the department of mining and metallurgy, University of Arizona, on factors involved in the leaching of ores. A list of previous publications is given in the bibliography at the end of this paper.Four factors are essential to the leaching of any copper-bearing ore: (1) A solution that will attack the copper minerals must get into the body of the ore particles; (2) the copper minerals must be dissolved by the solution; (3) the solution containing the dissolved copper must find its way out of the voids of the rocks into the main solution; and (4) the copper in solution must be recovered by some means of precipitation.This paper considers the third step -- the extraction of the water-soluble copper. From leached ores. The usual commercial practice in leaching copper ores consists of: (1) Crushing the ore to pass through a screen with approximately one-quarter or one-third inch openings; (2) charging the crushed ore into a fat; (3) adding, usually by upward percolation, a solution that will attack the copper minerals; and (4) washing the copper-laden solutions out of the ore with solutions weaker in copper than the pregnant solution, and finally with water. A countercurrent system of leaching and washing is usually employed. In some plants the solutions are circulated during leaching and washing, and in others they are not. In some plants the wash solutions are added by upward percolation, while at Chuquicamata the so-called ""piston-displacement"" method of washing is employed.The following condensed resume of the leaching cycle of the plant of the Inspiration Consolidated Copper Co. is given to present to the reader a picture of the steps involved in a typical leaching cycle. This plant was recently described in detail.4 The ore, crushed to pass openings 11/2 inches in diameter, passes over a screen with ¼-inch openings. The undersize from the screen goes to a Dorr howl classifier that removes the primary slime from the circuit. The overflow from the classifier is treated in a slime-leaching plant. The oversize of the ¼-inch screen passes through rolls, where it is crushed to pass a 3/8-inchscreen. The undersize from the 3/8-inch screen join with the coarse material from the classifier, and the combined products become the feed to the leaching vats. There are 13 concrete lead-lined leaching vats. The complete leaching cycle is 13 days. Eight tanks are under acid-iron content at all times; three are being washed, one tank is being filled, and the one is being excavated. The electrolyzed solution from the tank house, to which amount of new acid has been added, is put on the oldest tank of ore under need This solution travels from tank to tank and finally emerges from the newest ore"