Patent ID: 7918919

Claim:
A method, comprising: (a) slurrying a feed material to provide a slurried feed, the feed material comprising a refractory sulfide-containing material, the material comprising at least about 0.05 oz/tonne of a precious metal, at least about 0.75 wt % sulfides, and at least about 0.5 ppm mercury and the slurried feed comprising at least one halogen; (b) oxidizing the refractory sulfide-containing material at elevated temperature and super-atmospheric pressure to convert at least most of the sulfide sulfur to sulfate sulfur and form an oxidized precious metal-containing material, wherein, during step (b), dissolution of mercury from the sulfide-containing material is inhibited by performing at least one of the following: (B1) maintaining a dissolved ferrous iron concentration in a liquid phase of the slurried feed of at least about 0.5 g/L; (B2) maintaining at least about 10 mole % of soluble iron in the liquid phase in the ferrous state; (B3) maintaining an oxidation/reduction potential (ORP) of no more than about 530 millivolts, relative to a standard silver chloride electrode; (B4) contacting the halogen with a component that causes formation of a halogen-containing reaction product, the halogen-containing reaction product not comprising the precious metal or mercury and being substantially insoluble in the liquid phase; and (B5) contacting the halogen with a component that causes formation of a halogen-containing reaction product, the halogen-containing reaction product not comprising the precious metal or mercury, being more stable under the operating conditions of step (b) than a halogen complex comprising the mercury, and is substantially soluble in the liquid phase; and (c) thereafter recovering the precious metal from the oxidized precious metal-containing material to form a precious metal product, wherein no more than about 25% of the mercury in the feed material is dissolved in the liquid phase during step (b).