Oxidative pressure leach recovery of precious metals using halide ions

Abstract

A method for recovering a precious metal from a host material, comprises the steps of subjecting the host material to an oxidative pressure leach process, in the presence of a halide ion constituent, preferably a chloride ion, which is reactive with the precious metal, and at an elevated temperature of at least 170° C. to cause at least a portion of the precious metal to be extracted by a leach solution in the form of a precious metal-bearing chloride complex, and recovering the precious metal from the leach solution. When the host material is a smelt malte material including a base metal and a precious metal, said malte is subjected to a first oxidative pressure leach process to recover substantially all of said base metal in the form of at least one sulphate complex into a first leach solution, and then said malte material is subjected to a second oxidative pressure leach process in the presence of a halide ion constituent and at a temperature sufficient to cause at least a portion of said precious metal to be recovered into a second leach solution, from which the precious metal is extracted.

1 . A method for recovering a precious metal portion and a base metal portion from a host material, comprising the steps of: 
 subjecting said host material to an oxidative pressure leach process, in the presence of a chloride ion constituent at a temperature of at least 170 degrees Celsius in order to form a leach solution containing at least one precious metal-bearing chloride complex and a base metal complex; and    recovering said precious metal from said chloride complex.    
     
     
         2 . A method as defined in  claim 1  wherein the base metal complex is a base metal-bearing sulfate.  
     
     
         3 . A method as defined in  claim 1  wherein the leach solution is at a pH of less than 0.5.  
     
     
         4 . A method as defined in  claim 1  wherein the temperature ranges from 195 to 275 degrees Celsius.  
     
     
         5 . A method for leaching a precious metal from a host material, comprising the steps of: 
 subjecting said host material to an oxidative pressure leach process, in the presence of a chloride ion constituent at a temperature of at least 170 degrees Celsius in order to form a leach solution in which the leached precious metal is exclusively contained in a chloride complex; and    recovering said precious metal from said chloride complex.    
     
     
         6 . A method as defined in  claim 5  wherein the temperature is at least 180 degrees Celsius.  
     
     
         7 . A method as defined in  claim 6  wherein the temperature ranges from about 180 degrees Celsius to 295 degrees Celsius.  
     
     
         8 . A method as defined in  claim 5  wherein the leach solution is at a pH of less than 0.5.  
     
     
         9 . A method as defined in  claim 5  wherein the temperature is at least 195 degrees Celsius.  
     
     
         10 . A method as defined in  claim 5  wherein the temperature ranges from 195 to 275 degrees Celsius.  
     
     
         11 . A method for leaching a precious metal and a base metal from a host material in a single step by subjecting the host material to an oxidative pressure leach process, in the presence of a chloride ion constituent and at a temperature of at least 170 degrees Celsius in order to form a leach solution containing at least one precious metal-bearing chloride complex and the base metal.  
     
     
         12 . A method for economically leaching a precious metal from a host material, comprising the step of leaching said host material with salt water at a temperature of at least 170 degrees Celsius, in the presence of an oxidant and at sufficient pressure to form, in the leach solution, a chloride complex containing the precious metal.  
     
     
         13 . A method as defined in  claim 12  wherein the salt water is ground water, sea water or otherwise naturally formed.  
     
     
         14 . A method as defined in  claim 12  wherein the precious metal bearing chloride complex is a platinum-, palladium- or a gold-bearing complex.  
     
     
         15 . A method for recovering a precious metal from a host material, comprising the steps of: 
 subjecting said host material to an oxidative pressure leach process, in the presence of a halide ion constituent which is reactive with said precious metal, and at a temperature sufficient to cause at least a portion of said precious metal to be extracted by a leach solution; and    recovering said precious metal from said leach solution.    
     
     
         16 . A method as defined in  claim 15  wherein said precious metal includes a platinum group metal or gold.  
     
     
         17 . A method as defined in  claim 15 , wherein the halide ion is provided by adding a halide salt to said leach solution.  
     
     
         18 . A method as defined in  claim 15  wherein said halide ion is selected from the group chloride, iodide cobromide.  
     
     
         19 . A method as defined in  claim 16  wherein the halide salt is a chloride salt.  
     
     
         20 . A method as defired in  claim 19  wherein the chloride salt includes sodium chloride, calcium chloride or potassium chloride.  
     
     
         21 . A method as defined in  claim 15  wherein said halide ion constituent is a chloride ion which is present at a concentration ranging from about 0.5 g/L to about 100 g/L.  
     
     
         22 . A method as defined in  claim 21  wherein said chloride ion constituent is present at a concentration ranging from 1 to 20 g/L.  
     
     
         23 . A method as defined in  claim 22  wherein said chloride ion constituent is present at a concentration ranging from 1.5 to 10 g/L.  
     
     
         24 . A method as defined in  claim 23  wherein said chloride ion constituent is present at a concentration ranging from about 3 to about 6 g/L.  
     
     
         25 . A method as defined in  claim 15  wherein said temperature ranges from about 170 degrees Celsius to about 300 degrees Celsius.  
     
     
         26 . A method as defined in  claim 25  wherein said temperature ranges from about 195 degrees Celsius to about 275 degrees Celsius.  
     
     
         27 . A method as defined in  claim 26  wherein said temperature ranges from 200 degrees Celsius to 250 degrees Celsius.  
     
     
         28 . A method as defined in  claim 27  wherein said temperature ranges from 210 degrees Celsius to about 230 degrees Celsius.  
     
     
         29 . A method as defined in  claim 15  wherein said leach solution is acidic.  
     
     
         30 . A method as defined in  claim 29  wherein said acid is sulphuric acid.  
     
     
         31 . A method as defined in  claim 30  wherein said sulphuric acid is at a concentration ranging from 1 to 500 g/L.  
     
     
         32 . A method as defined in  claim 31  wherein said sulphuric acid is at a concentration ranging from about 5 to about 250 g/L.  
     
     
         33 . A method as defined in  claim 32  wherein said sulphuric acid is at a concentration ranging from about 10 to about 100 g/L.  
     
     
         34 . A method as defined in  claim 15  further comprising, before the recovering step, the step of separating barren solid residue from said leach solution.  
     
     
         35 . A method for recovering a precious metal from a host material, comprising the steps of: 
 placing said host material in a pressure leaching vessel;    subjecting said host material to an oxidative pressure leach process, in the presence of a halide ion constituent which is reactive with said precious metal, and at a temperature sufficient to cause at least a portion of said precious metal to be extracted by a leach solution; and    recovering said precious metal from said leach solution.    
     
     
         36 . A method as defined in  claim 35  wherein said oxidative pressure leach process takes place in the presence of a gaseous oxidant.  
     
     
         37 . A method as defined in  claim 36  wherein said gaseous oxidant is oxygen gas.  
     
     
         38 . A method as defined in  claim 37  wherein said oxygen gas is injected into said vessel at an oxygen partial pressure of between 1 and 500 psig.  
     
     
         39 . A method as defined in  claim 38  wherein said oxygen partial pressure is between 10 and 200 psig.  
     
     
         40 . A method as defined in  claim 39  wherein said oxygen partial pressure is between 50 and 100 psig.  
     
     
         41 . A method as defined in  claim 15  wherein said host material is a processed ore body.  
     
     
         42 . A method as defined in  claim 15  wherein said host material is an ore concentrate.  
     
     
         43 . A method as defined in  claim 15  wherein said host material is a matte material from a smelting process.  
     
     
         44 . A method for recovering a precious metal from a smelt matte material, wherein said matte material includes a precious metal constituent and a base metal constituent, comprising the steps of: 
 subjecting said matte material to a first oxidative pressure leach process, with sufficient oxidant and at a selected temperature to recover substantially all of said base metal constituent in the form of at least one sulphate complex into a first leach solution; and then    subjecting said host material to a second oxidative pressure leach process, in the presence of a halide ion constituent which is reactive with said precious metal, and at a temperature sufficient to cause at least a portion of said precious metal to be recovered into a second leach solution; and then    recovering said precious metal from said leach solution.    
     
     
         45 . A method as defined in  claim 44  wherein the first oxidative pressure leach process occurs at a temperature ranging from 100 to 190 degrees Celsius.  
     
     
         46 . A method as defined in  claim 45  wherein the first oxidative pressure leach process occurs at a temperature ranging from 120 to 170 degrees Celsius.  
     
     
         47 . A method as defined in  claim 44  wherein the first oxidative pressure leach process occurs at a temperature ranging from 130 to 150 degrees Celsius.  
     
     
         48 . A method for recovering a precious metal from a smelt matte material, wherein said matte material includes a precious metal constituent and a base metal constituent, comprising the steps of: 
 subjecting said matte material to a single oxidative pressure leach process, in the presence of a halide ion constituent which is reactive with said precious metal constituent, and at a temperature sufficient to cause substantially all of said base and precious metal constituents to be recovered into a first leach solution; and    recovering said precious metal from said leach solution.    
     
     
         49 . A method as defined in  claim 48  wherein the halide is chloride.  
     
     
         50 . A method as defined in  claim 15  wherein the host material includes a laterite.