Recovery of copper from copper ores

Claim 1

A method of recovering copper from copper ores by caustic leaching, the ores having been crushed and ground and then leached in a strong sodium hydroxide solution, wherein the improvement comprises; subjecting the ores to three separate leachings with a different leach solution, removing the ore solids from the solution, washing the solids with a hot aqueous solution containing a minimum of approximately 160 grams of sodium hydroxide per liter at a temperature in the neighborhood of 180* to 200* F., which results in removal of copper from the voids between the solid particles but does not dilute the sodium hydroxide solution sufficiently to allow reprecipitation of copper previously extracted by leaching of the copper ores, and recovering the copper from the solution by electrolysis.

Claim 2

A method of recovering copper from finely divided oxidized copper ores by leaching with a sodium hydroxide solution wherein the improvement comprises: in a first step, treating previously untreated ore with a low copper pregnant aqueous solution having a sodium hydroxide concentration of not less than 160 grams per liter to remove and put into the solution a percentage of the copper from the ore to produce a high copper pregnant sodium hydroxide solution, removing the high copper solution resulting from said first stage, separating the copper therefrom; in a second stage, treating the solids from the first stage with another supply of said aqueous sodium hydroxide solution to remove a further percentage of the copper from the ore and produce a lower copper pregnant sodium hydroxide solution than that produced in the first stage, withdrawing the lower copper solution from the second stage; and in a third stage, treating the solids from the second stage with another supply of sodium hydroxide solution and separating the copper therefrom, and recovering the copper from said solutions by electrolysis.

Claim 6

A method of recovering copper from the finely divided oxidized ores from a grinding mill wherein the ores are leached with a sodium hydroxide solution to remove the copper, wherein the improvement comprises: in a first stage, treating the ore with an aqueous sodium hydroxide solution having a sodium hydroxide concentration of a minimum of 160 grams per liter to dissolve at least part of the copper in the solution; in a second stage, treating the solids from the first stage with another supply of sodium hydroxide solution to remove additional copper from said solids, separating the pregnant sodium hydroxide solution from the solids, and, after the final treatment of the solids with the sodium hydroxide solution, introducing said solution into said grinding mill with a fresh supply of ore, and introducing the ground ore and sodium hydroxide solution from the grinding mill to said first stage, the sodium hydroxide solution having first been subjected to electrolysis to recover the copper therefrom.

Claim 8

The method of recovering copper from copper carbonate ores which are crushed, ground and leached in a solvent and the copper recovered from the solvent, wherein the improvement comprises: in a first stage, agitating the finely divided copper carbonate ores in a concentrated aqueous solution having a 160 grams per liter minimum concentration of sodium hydroxide for a period of 10 to 30 minutes, the sodium hydroxide solution being heated to a temperature of between approximately 180* to 200* F., removing the pregnant solution therefrom; in a second stage, agitating the slurry from the first stage in a similar sodium hydroxide solution for a period of 10 to 30 minutes; in a third stage, agitating the slurry from the second stage in a sodium hydroxide solution other than that used in the second stage, separating the pregnant solution therefrom, and recovering the copper from the pregnant sodium hydroxide solutions of said stages by electrolysis.