Method and process for the enhanced leaching of copper sulfide minerals containing chalcopyrite

Abstract

A method of leaching a copper bearing sulfide mineral slurry containing chalcopyrite is described. The method comprises the steps of providing a slurry having chalcopyrite particles therein, exposing the slurry to an acidic leach solution, and chemically leaching copper from the slurry into the acidic leach solution in the presence of microwave irradiation. The microwave irradiation of the slurry takes place under process conditions whereby crystalline pyrite may be formed in-situ on surfaces of the chalcopyrite particles. Crystalline pyrite may be formed on surfaces of the chalcopyrite particles from amorphous phase pyrite. Leached copper is recovered from said acidic leach solution. A device for more efficiently leaching a copper bearing sulfide mineral slurry containing chalcopyrite is also described herein.

What is claimed is: 
     
         1 . A method of leaching a copper-bearing sulfide mineral slurry, comprising the steps of:
 (a) providing a slurry having copper sulfide particles therein;   (b) exposing the slurry to an acidic leach solution;   (c) chemically leaching copper from the slurry into the acidic leach solution in the presence of microwave irradiation, under conditions whereby crystalline pyrite can be formed in-situ, on surfaces of the copper sulfide particles;   (d) generating microwaves at a predetermined frequency or intensity that is configured for forming crystalline pyrite on surfaces of the copper sulfide particles in-situ; and   (d) recovering leached copper from said acidic leach solution.   
     
     
         2 . The method of  claim 1 , wherein step (c) is further performed under conditions whereby elemental sulfur (which may form surface passivation layer(s) on the copper sulfide particles as a result of exposure to the acidic leach solution), is prevented from entering a plasma phase. 
     
     
         3 . The method of  claim 2 , further comprising forming crystalline pyrite on surfaces of the copper sulfide particles in-situ and/or converting amorphous pyrite to crystalline pyrite. 
     
     
         4 . The method of  claim 1 , wherein step (b) comprises mixing the acidic leach solution with the slurry in a tank. 
     
     
         5 . A method according to  claim 4 , wherein the tank comprises an agitation mechanism, a fluidization mechanism, or a mechanism for changing a residence time of the slurry in the tank. 
     
     
         6 . The method of  claim 4 , wherein the tank comprises at least one microwave generating device which provides said microwave irradiation. 
     
     
         7 . The method of  claim 6 , wherein the tank comprises multiple microwave generating devices. 
     
     
         8 . The method of  claim 1 , wherein the microwave irradiation is provided intermittently. 
     
     
         9 . The method of  claim 1 , wherein the microwave irradiation changes in intensity as a function of time. 
     
     
         9 . The method of  claim 1 , wherein the microwave irradiation changes in frequency as a function of time. 
     
     
         10 . The method of  claim 1 , wherein step (b) and/or step (c) is performed above atmospheric pressure. 
     
     
         11 . The method of  claim 1 , further comprising adding catalytic pyrite to the slurry and acidic leach solution to instigate galvanic reactions. 
     
     
         12 . The method of  claim 1 , wherein said copper sulfide particles comprises at least one of chalcopyrite (CuFeS 2 ), chalcocite (Cu 2 S), bomite (Cu 5 FeS 4 ), covellite (CuS), digenite (Cu 2 S), enargite (Cu 3 AsS 4 ), tennantite (Cu 12 As 4 S 13 ), or tetrahedrite (Cu 12 Sb 4 S 13 ). 
     
     
         13 . The method of  claim 1 , wherein the crystalline pyrite formed on the surfaces of the copper sulfide particles comprises micro- or nano-scale particles. 
     
     
         14 . The method of  claim 1 , wherein the crystalline pyrite formed on the surfaces of the copper sulfide particles in-situ, is capable of catalyzing a reduction of Fe3 +  (Ferrous iron) to Fe2 +  (Ferric iron). 
     
     
         15 . The method of  claim 1 , further comprising providing microwaves which have been optimized through the process of measuring microwave absorption for FeS 2(Amorphous)  to maximize the conversion efficiency to FeS 2(Crystalline) . 
     
     
         16 . The method of  claim 1 , further comprising tuning one of a frequency or an intensity of said generated microwaves during leaching to maintain optimized formation of crystalline pyrite on surfaces of the copper sulfide particles in-situ and/or to maintain optimized copper leaching kinetics. 
     
     
         17 . A device for leaching a copper bearing sulfide mineral slurry, comprising:
 (a) a tank for providing a slurry having copper sulfide particles therein; and,   (b) at least one microwave generating device configured to irradiate the slurry during leaching: wherein the at least one microwave generating device is capable of producing microwaves at a predetermined frequency and intensity which are configured to facilitate in-situ crystalline pyrite formation on surfaces of the copper sulfide particles in the slurry.   
     
     
         18 . The device of  claim 17 , wherein the at least one microwave generating device is further configured to produce microwaves which are configured to prevent elemental sulfur (which may form surface passivation layer(s) on the copper sulfide particles), from entering a plasma phase. 
     
     
         19 . The device of  claim 17 , wherein the tank is configured to withstand a mixture of acidic leach solution with the slurry in a tank. 
     
     
         20 . The device of  claim 17 , wherein the tank comprises a window comprising a microwave-permeable material. 
     
     
         21 . The device of  claim 17 , wherein the tank comprises an agitation mechanism, a fluidization mechanism, or a mechanism for changing residence time of the slurry in the tank. 
     
     
         22 . The device of  claim 21 , wherein the agitation mechanism comprises an impeller, the fluidization mechanism comprises a fluidized bed, and the mechanism for changing residence time comprises a false bottom, interior chamber, dividing wall, baffle, lamella, screen, slip stream area, or tortuous path. 
     
     
         23 . The device of  claim 17 , wherein the at least one microwave generating device is configured to irradiate slurry in the tank intermittently. 
     
     
         24 . The device of  claim 17 , wherein at least one microwave generating device is configured to irradiate slurry in the tank with different frequencies. 
     
     
         25 . The device of  claim 17 , wherein the at least one microwave generating device is configured to irradiate slurry in the tank at various intensities. 
     
     
         26 . The device of  claim 17 , wherein the at least one microwave generating device comprises a plurality of microwave generating devices. 
     
     
         27 . The device of  claim 26 , wherein a plurality of microwave generating devices are configured to emit different microwave signals in any one of intensity, frequency, or continuity. 
     
     
         28 . The device of  claim 17 , wherein the tank comprises a cooling system to cool the slurry prior to or during leaching, particularly during microwave irradiation. 
     
     
         29 . The device of  claim 28  wherein said cooling system comprises a heat exchanger, a cooling fin, a cooling pipe, or a cooling rod protruding into the tank. 
     
     
         30 . The device of  claim 17 , wherein the device comprises at least one reflector within the tank, which may be provided on a wall, a baffle, or an impellor. 
     
     
         31 . The device of  claim 17 , wherein said at least one microwave generating device further comprises means for adjusting a frequency or intensity of said generated microwaves during leaching to maintain optimized formation of crystalline pyrite on surfaces of the copper sulfide particles in-situ and/or optimized copper leaching.