A method of oxidatively treating a gold-bearing mineral material feed to facilitate recovery of gold, the mineral material feed having sulfide material from which gold is difficult to separate and having organic carbonaceous material that has an affinity for at least one member of the group consisting of gold and a gold complex, the mineral material feed being pressure oxidized in the presence of a solubilized form of a halogen which, when in the presence of the organic carbonaceous material, is capable of interfering with gold recovery, the method comprising the steps of:
- pressure oxidizing, in an oxidizing environment at elevated temperature and elevated pressure, a feed, having said mineral material feed slurried with aqueous feed liquid, to free gold from said association with said sulfide material to facilitate recovery of said gold;
- said feed comprising halogen-containing material having halogen, wherein during said step of pressure oxidizing said halogen is in a solubilized form that is capable of complexing with gold that is freed from said association with said sulfide material;
- said organic carbonaceous material, during said step of pressure oxidizing, being capable of capturing and holding gold when said organic carbonaceous material is in the presence of said solubilized form of said halogen;
- effluent from said step of pressure oxidizing comprising solid residue and aqueous effluent liquid;
- wherein, said step of pressure oxidizing is conducted under conditions to suppress the susceptibility of said gold to be captured and held by said organic carbonaceous material, such that following said step of pressure oxidation, greater than about 75 percent of said gold from said mineral material feed is removable from said solid residue by carbon-in-leach cyanidation;
- said conditions including at least one condition selected from the group consisting of:
- (i) a temperature of lower than about 215.degree. C.;
- (ii) a ratio, on a weight basis, of sulfide sulfur to carbonate in said mineral material feed of smaller than about 4 to 1;
- (iii) said aqueous effluent liquid has an oxidation/reduction potential of smaller than about 700 millivolts, relative to a standard hydrogen electrode;
- (iv) said aqueous effluent liquid comprises sulfuric acid in an amount of less than about 28 grams of free sulfuric acid per liter;
- (v) said step of pressure oxidizing is conducted in the presence of carbon dioxide at a partial pressure that is larger than a partial pressure that would be exerted by carbon dioxide generated during said step of pressure oxidizing from carbon released by decomposition of said mineral material feed;
- (vi) said step of pressure oxidizing is conducted in the presence of a component that causes formation of a halogen-containing reaction product that is insoluble in aqueous liquid present during said step of pressure oxidizing;
- (vii) said step of pressure oxidizing is conducted in the presence of a component capable of forming a complex, that does not comprise gold, with said solubilized form of said halogen to bind at least a portion of said halogen and thereby inhibit formation of a gold complex with said solubilized form of said halogen, said complex being soluble during said step of pressure oxidizing;
- (viii) said step of pressure oxidizing is conducted in a reactor with the addition of oxygen gas to the reactor in an amount that is small enough, under reaction conditions present in said reactor, to prevent substantially complete oxidation of ferrous iron to ferric iron during said step of pressure oxidizing;
- (ix) said step of pressure oxidizing is conducted in a batch operation;
- (x) said step of pressure oxidizing is for a time of shorter than about 45 min;
- and
- (xi) said mineral material feed comprises a blend of a first mineral material and a second mineral material, wherein said second mineral material has a higher carbonate content than said first mineral material.