Method for the recovery of gold using autoclaving

Claim 1

A pretreatment method for recovering gold comprising: (a) forming an aqueous slurry of refractory sulfidic gold-containing ore; and (b) subjecting said aqueous slurry in the presence of an alkaline material to an oxidation step, said oxidation step includes simultaneously: (i) autoclaving said aqueous slurry and (ii) oxygenating said autoclaved aqueous slurry; wherein said oxidation step is sufficient to oxidize refractory sulfidic compounds in said ore and said autoclaving being at a temperature of between about 400° F. and about 500° F. and an oxygen overpressure of between about 50 psig and about 100 psig for an aqueous slurry residence time in said autoclave sufficient to oxidize said refractory sulfidic compounds of said ore.

Claim 14

A method for recovering gold from refractory sulfidic gold-containing ore comprising: (a) forming an aqueous slurry of said ore with a soluble alkaline material; (b) subjecting said aqueous slurry to oxidation in an autoclave, said oxidation includes simultaneously: (i) autoclaving said aqueous slurry, said autoclaving being at a temperature between about 400° F. and about 500° F.; (ii) oxygenating said autoclaved aqueous slurry; (c) cooling said oxidized aqueous slurry; (d) thickening said aqueous slurry, said thickening includes separating a liquid fraction from said aqueous slurry whereby a solids fraction of said aqueous slurry having a solids concentration of greater than about 40 percent by weight is obtained; (e) adding an alkaline agent in an amount sufficient to adjust said cooled aqueous slurry to about pH 10; (f) simultaneously contracting the oxidized aqueous slurry in a plurality of stages with a cyanide complexing agent and a granular activated carbon, said activated carbon being circulated contercurrent to said cyanide aqueous slurry, a temperature of said cyanide aqueous slurry being maintained between about 40° F. and 100° F. whereby said gold is absorbed on said activated carbon; and (g) separating said gold laden activated carbon from said aqueous slurry.

Claim 15

A method for recovering gold from refractory sulfidic gold-containing ore comprising: (a) forming an aqueous slurry of said ore with a soluble alkaline material; (b) subjecting said aqueous slurry to oxidation in an autoclave, said oxidation includes simultaneously: (i) autoclaving said aqueous slurry, said autoclaving being at a temperature between about 400° F. and about 500° F.; (ii) oxygenating said autoclaved aqueous slurry; (c) cooling said oxidized aqueous slurry; (d) thickening said aqueous slurry, said thickening includes separating a liquid fraction from said aqueous slurry whereby a solids fraction of said aqueous slurry having a solids concentration of greater than about 40 percent by weight is obtained; (e) adding an alkaline agent in an amount sufficient to adjust said cooled aqueous slurry to about pH 10; (f) simultaneously contracting the oxidized aqueous slurry in a plurality of stages with a cyanide complexing agent and a granular activated carbon, said activated carbon being circulated contercurrent to said cyanide aqueous slurry, a temperature of said cyanide aqueous slurry being maintained between about 40° F. and 100° F. whereby said gold is absorbed on said activated carbon; and (g) separating said gold laden activated carbon from said aqueous slurry.

Claim 19

A method for recovering gold from gold containing ores comprising: (a) forming an aqueous slurry of refractory sulfidic gold-containing ore having at least about 8 percent metal carbonates, said aqueous slurry having a solids content between about 20 percent and about 45 percent by weight; (b) adding Na 2 CO 3 to said aqueous slurry at a rate of between about 50 pounds and about 100 pounds of Na 2 CO 3 per ton of dry ore; (c) autoclaving said formed aqueous slurry for an autoclave residence time of at least 2 hours in an autoclave at a temperature between about 400° F. and about 500° F. while simultaneously oxygenating said slurry by feeding an oxygen containing gas into said autoclave at an overpressure between about 50 psig and about 100 psig; (d) cooling the oxidized aqueous slurry; (e) thickening said aqueous slurry, said thickening includes separating a liquid fraction from said aqueous slurry whereby a solids fraction of said aqueous slurry having a solids concentration of greater than about 40 percent by weight is obtained; (f) adding an alkaline agent in an amount sufficient to adjust said cooled aqueous slurry to about pH 10; and (g) recovering gold from said aqueous slurry utilizing a cyanide leach technique.

Claim 20

A method for recovering gold from gold containing ores comprising: (a) forming an aqueous slurry of refractory sulfidic gold-containing ore having at least about 8 percent metal carbonates, said aqueous slurry having a solids content between about 20 percent and about 45 percent by weight; (b) adding Na 2 CO 3 to said aqueous slurry at a rate of between about 50 pounds and about 100 pounds of Na 2 CO 3 per ton of dry ore; (c) autoclaving said formed aqueous slurry for an autoclave residence time of at least 2 hours in an autoclave at a temperature between about 400° F. and about 500° F. while simultaneously oxygenating said slurry by feeding an oxygen containing gas into said autoclave at an overpressure between about 50 psig and about 100 psig; (d) cooling the oxidized aqueous slurry; (e) thickening said aqueous slurry, said thickening includes separating a liquid fraction from said aqueous slurry whereby a solids fraction of said aqueous slurry having a solids concentration of greater than about 40 percent by weight is obtained; (f) adding an alkaline agent in an amount sufficient to adjust said cooled aqueous slurry to about pH 10; and (g) recovering gold from said aqueous slurry utilizing a cyanide leach technique.