Biooxidation process for recovery of gold from heaps of low-grade sulfidic and carbonaceous sulfidic ore materials

In a method for biooxidation of a sulfide in an ore body comprising precious metals, wherein said precious metals are dispersed or occluded within said sulfide, the improvement comprising:

• forming particulates from crushed ore particles with an inoculate comprising bacteria capable of attacking, by biooxidation, said sulfide and/or elemental sulfur, and ferrous iron;
• constructing a heap from said particulates for biooxidizing said sulfide and/or elemental sulfur, and ferrous iron;
• biooxidizing said sulfide and/or sulfur and ferrous iron in said heap constructed of said particulates wherein said biooxidation is aided by a formation of at least feric ions in a bioleachate solution dispersed and circulated within said ore body, said solution comprised of nutrients in an acidic medium of a pH less than 2.5;
• recovering soluble excess, non-precious metal values from said solution;
• and thereafter
• recovering said precious metal values from said ore body.

In a method for biooxidation of a pyritic sulfide or an arsenopyritic sulfide in mineral values in a heap forming on ore body wherein said mineral values include precious metal values dispersed or occluded within said sulfides, and wherein the precious metal values are from 0.02 oz./ton to 0.07 oz./ton, the improvement comprising:

• crushing said mineral values to form ore particles of a preselected particle size;
• forming particulates of said particles by admixing thoroughly said particles with an inoculate solution comprising bacteria capable of attacking, by biooxidation, said sulfides and/or elemental sulfur and ferrous iron;
• constructing a heap of said particulates;
• maintaining said heap so as to favor bacterial growth within and on said particulates;
• biooxidizing said sulfides and/or sulfur and iron in said ore particles in said heap constructed of said particulates;
• aiding further said biooxidation by introduction of inoculate solution in said heap;
• circulating continuously said inoculate solution within said heap;
• separating recoverable soluble excess non-precious metal values from said solution of at least ferric ion or arsenate ion species;
• reconstructing said heap of said particulates conjointly with lime, Portland cement, cement dust, or sodium hydroxide addition for neutralization of acidic materials in said particulates;
• and
• recovering said precious metal values from said heap by cyanidation or a thiosulfate treatment of said neutralized, reconstituted particulates.

A process for biooxidation of sulfide values in a precious metal containing ore comprising the steps of:

• constructing particulates from a crushed form of said ore, ore slimes and particles of said ore of a predetermined size, surface area, and an aqueous bacterial inoculant wherein said aqueous content of said ore is from 4% to 12% by weight admixture with said aqueous bacterial inoculant;
• forming a heap of said particulates;
• biooxidizing said particulates for a time sufficient to biooxidize sulfide values in said particulates to make amenable said precious metal in said ore to cyanide, thiourea or thiosulfate leaching;
• and
• recovering precious metal values from said biooxidized particulates.

A method for heap leaching of precious metal-containing crushed sulfide ore of residual precious metal values of less than about 0.1 oz/ton in said ore which comprises:

• a) inoculating said crushed sulfide ore with at least one bacterium suspension, said bacterium being capable of promoting the oxidation of said sulfide ore;
• b) forming agglomerates from said inoculated ore;
• c) constructing a heap of said agglomerates;
• d) biooxidizing for a time at least sufficient to effect oxidation of said sulfides with concomitant substantial liberation of said precious metal for subsequent leaching;
• e) then subjecting said biooxidized heap of ore to heap leaching with a leachant solution selective to the dissolution of said liberated precious metal;
• and, thereafter,
• f) recovering said precious metal values from said leachant treated biooxidized ore, thereby providing an ore residue substantially impoverished in said precious metal.

A method for the biooxidation treatment of a particulate form of a precious metal-containing crushed sulfide ore formed into a static heap which comprises:

• a) providing said sulfide ore in a particle state;
• b) mixing said ore in said particle state with an amount of inoculant suspension sufficient to coat said particles with an inoculant bacterial coating;
• said inoculant suspension comprising a nutrient acid, said inoculant suspension containing a bacterial culture of at least one bacterium contained in said suspension which bacterium has propensity of promoting oxidation of sulfide in said ore;
• c) forming particulates from said particles and said inoculant suspension;
• d) forming a heap of said particulates;
• e) aging said heap of particulates for a preselected time;
• f) biooxidizing said particulates for a time at least sufficient to effect oxidation of sulfide in said ore and liberate said precious metal contained in said ore;
• and
• g) subjecting said heap of biooxidized particulates to leaching with an aqueous leachant solution selective to the dissolution of said liberated precious metal thereby providing a residue impoverished in said precious metal.

In a process for biooxidizing sulfide values in an ore material which is refractory to cyanide leaching in a static heap and to make occluded precious metal values in said ore material accessible for subsequent recovery by a cyanide leachant solution the improvement comprising:

• inoculating particles of an ore material with a bacterial suspension sufficient to initiate a sulfide oxidation reaction throughout a heap;
• forming particulates from said inoculated ore material particles;
• forming a heap of said particulates;
• maintaining a bacterial activity in said heap;
• and
• recovering precious metal values with a leachant for said precious metal values in said ore, wherein said precious metal values are made leachant accessible for recovery due to said bacterial activity.