EXTRACTION METHODS FROM REFRACTORY ORES

Abstract

A method for extracting and separating Gold, Silver, Copper, Zinc and/or Lead from an Arsenic-containing ore, concentrate or tailings characterized in that the extraction is carried by roasting in the presence of a calcium-containing material and at least one of an alkali metal halide and alkaline metal halide. In the method, Arsenic remains immobilized in the extraction residue.

Claims

1. A method for extracting at least one metal from an Arsenic-containing ore, concentrate or tailings, the method comprising: mixing the ore, concentrate or tailings with a calcium-containing material and at least one from an alkali metal halide and alkaline metal halide; heating the mixture in the presence of air or oxygen, and thereby producing metal-containing volatile complexes and a solid residue comprising immobilized arsenic; condensing the volatile complexes in a scrubber containing at least one dry sorbent bed, and thereby producing a metal-loaded sorbent bed; recovering the metal from the metal-loaded sorbent bed; and disposing of the residue containing immobilized Arsenic.

2. The method of claim 1, wherein the metal is Gold, Silver, Copper, Zinc, Lead, or any mixture thereof; and wherein if a mixture of metals is extracted, each of the metals is condensed into a separate sorbent bed.

3. The method of claim 1 or 2, wherein the calcium-containing material is selected from calcium carbonate, calcium chloride, calcium phosphate, calcium sulfate, calcium sulfide, calcium hydroxide, calcium oxide, and any mixture thereof.

4. The method of claim 1, wherein the calcium-containing material is selected from lime, limestone, calcite, dolomite or any mixture thereof.

5. The method of claim 1, wherein the ore, concentrate or tailings is an Arsenic Silver containing ore, concentrate or tailings.

6. The method of claim 1, wherein the ore, concentrate or tailings comprises an Arsenic Gold containing ore, concentrate or tailings.

7. The method of claim 1, wherein the heating step is performed in a fluid bed reactor.

8. The method of claim 1, wherein the heating step is performed at a temperature in the range from 850 C. to 1200 C.

9. The method of claim 1, wherein the heating step is performed under a reduced pressure in the range from a 0.5% to 10% decrease from the standard sea-level atmospheric pressure of 101.325 kilopascals.

10. The method of claim 1, wherein the sorbent is a material selected from alumina, zeolite, silica, aluminum oxide, quartz, or any mixture thereof.

11. The method of claim 1, wherein the ore, concentrate or tailings comprises a mixture of at least two compounds comprising metals selected from Gold, Silver, Copper, Zinc and Lead, and the heating step of claim 1 produces at least two of the Gold, Silver, Copper, Zinc and/or Leadcontaining volatile complexes, and wherein the metals are separated from each other into fractions containing predominantly individual metals by condensation into separate sorbent beds.

12. The method of claim 1, wherein the calcium-containing material is lime.

13. The method of claim 1, wherein the calcium-containing material is calcium chloride and/or calcium hydroxide.

14. The method of claim 1, wherein the sorbent is alumina.

15. The method of claim 1, wherein the at least one from the alkali metal halide and alkaline metal halide is sodium chloride, calcium chloride or any combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 represents a block diagram of the present process for extraction and separation of metals from refractory ores, concentrate or tailings.

DETAILED DESCRIPTION

[0030] The present disclosure provides a method for processing ores, concentrates and/or tailings which comprise Arsenic and at least one of the following metals: Gold, Silver, Copper, Zinc and/or Lead. In an ore, concentrate and/or tailings, Gold, Silver, Copper, Zinc and/or Lead is typically present in a form of a compound, including a siliceous, carbonaceous, sulphide and/or arsenosulphide compound. A feed material comprising the ore, concentrate and/or tailings may be mixed with a calcium-containing material and at least one from an alkali metal halide and alkaline metal halide. The feed material may be optionally crushed to a particle size of 20 to 200 mesh prior to mixing.

[0031] An alkali metal halide has a general formula M.sub.aX, wherein M.sub.a is an alkali metal and X is a halogen. Examples of suitable alkali metal halides include sodium chloride (NaCl), potassium chloride (KCl) and lithium chloride (LiCl).

[0032] An alkaline metal halide has a general formula MX.sub.2, wherein M is a metal of group 2 of the Periodic table and X is a halogen. Examples of suitable alkaline metal halides include calcium chloride (CaCl.sub.2), magnesium chloride (MgCl.sub.2), beryllium chloride (BeCl.sub.2) and barium chloride (BaCl.sub.2).

[0033] Suitable calcium-containing materials include, but are not limited to, calcium carbonate, calcium chloride, calcium phosphate, calcium sulfate, calcium sulfide, calcium hydroxide, calcium oxide, and any mixture thereof. A calcium-containing material may be at least one from lime, limestone, calcite and/or dolomite. Lime is a calcium-containing inorganic mineral in which calcium is mostly in a form of carbonate, oxide, and hydroxide. Limestone is a sedimentary rock which predominantly comprises calcium-bearing carbonate mineralscalcite and dolomite. Calcite is chemically calcium carbonate. Dolomite is chemically calcium-magnesium carbonate.

[0034] The ore, concentrate and/or tailings is mixed with a calcium-containing material and at least one from an alkali metal halide and alkaline metal halide. The mixture is then roasted in the presence of air or oxygen. The term roasting is used interchangeably with the term heating.

[0035] The roasting is performed in a reactor where the air or oxygen is passed through the mixture. A reactor may have a fluid bed. The reactor may be a kiln. The roasting temperature is in the range from 850 C. to 1200 C. The roasting can be performed under a slightly decreased pressure. The pressure can be decreased by 2% from standard atmospheric pressure, and preferably from 0.5% to 10% from the standard-sea level pressure equal to one standard atmosphere (atm) or 101.325 kilopascals.

[0036] Volatile metal chloride complexes of Gold, Silver, Copper, Zinc and/or Lead produced in the heating reaction are absorbed in a scrubber containing at least one or more dry sorbent beds which become predominantly loaded with one of the following metals: Gold, Silver, Copper, Zinc and Lead. Suitable sorbent materials include, but are not limited to, aluminum oxide, alumina, zeolite, silica and quartz. Alumina is an oxide of aluminum occurring in nature as a mineral including such as bauxite or corundum. Zeolites are microporous aluminosilicate minerals. Silica is a silicon dioxide. Quartz is a mineral composed of silicon and oxygen atoms.

[0037] In the present method, metals, such as Gold, Silver, Copper, Zinc and Lead, are removed from the loaded sorbent beds by washing. The sorbent material is dried and recycled. The present method may be used to separate each of Gold, Silver, Copper, Zinc and Lead from a mixture.

[0038] After extraction of metals, the residual material is removed from the extraction reactor. The residual material contains most of the Arsenic in immobilized form and can be disposed of.

[0039] As shown in FIG. 1, which is a block diagram of the present process for extraction and separation of metals, a feed material and reagents are mixed in a mixer and continuously fed to an extraction reactor which may comprise a roasting device, selected from the group of rotary kilns, drum kilns, fluidized bed reactors and entrained flow reactors. The feed material may be an ore, concentrate or tailings. The feed material may comprise at least one of Gold, Silver, Copper, Zinc and Lead. The feed material may comprise a mixture of any two or more from Gold, Silver, Copper, Zinc and Lead. One of the technical advantages of the present method is it can be used for recovery and simultaneously separation of Gold, Silver, Copper, Zinc and Lead from a mixture comprising two or more of these metals.

[0040] As shown in FIG. 1, the resulting mixture of the feed material is heated in an extraction reactor to a reaction temperature in the range from 850 C. to 1200 C. in a stream of air provided by an air blower. This reaction produces a volatile mixture of metal chloride complexes which are collected in a number of scrubbers where the metals are selectively absorbed on sorbents. Chloride-depleted spent gas mixture is washed by water in an air washer. Arsenic containing solid residue is continuously removed from the extraction reactor and is disposed of.

[0041] The present method provides a recovery of the metals with a high yield recovery of Gold, Silver, Copper, Zinc and/or Lead. Importantly, nearly all Arsenic (at least 80% or higher) remains in the solid residue in an extraction reactor and is not converted into a volatile compound.

Example 1

[0042] A concentrate contained 8.0 ppm of Gold, 118.5 ppm of Silver, 0.82% of Arsenic, 0.11% of Copper, 0.14% of Zinc, 0.11% of Lead, 31.1% of Iron Oxide (Fe.sub.2O.sub.3) and 35.5% of Silica (SiO.sub.2) was mixed with 6.5% of Sodium Chloride and 13% of Calcium Hydroxide. The resulting mixture was heated up to 1050 C. in a stream of air under a slightly reduced pressure. The released metal chloride fumes were adsorbed onto several aluminosilicate sorbent beds. After 30 min, the residue was cooled down. The residual material composition was 0.4 ppm Gold (94% yield), 2.5 ppm Silver (98% yield), 58 ppm Copper (95% yield), 57 ppm Lead (95% yield) and 0.059% of Zinc (56% yield). The residue contained 30.1% of Iron Oxide (Fe.sub.2O.sub.3) and 0.77% of Arsenic. Near total Iron and Arsenic remained in the residue. The total weight loss of material during metal extraction was 15% of mostly water. No chlorine was found in the residue. The first sorbent bed contained mostly Zinc, the next sorbent bed contained Lead and Copper, and the followed by Gold and Silver.

Example 2

[0043] An ore (3.9 ppm Gold, 42.9 ppm Silver, 398 ppm Copper, 494 ppm of Arsenic, 4.47% of Iron Oxide (Fe.sub.2O.sub.3)) was mixed with 13% of Sodium Chloride and 6.5% of Calcium Hydroxide and heated to 1050 C. in a stream of air under slightly reduced pressure. The released metal chloride fumes were absorbed onto several alumina sorbent beds. After 30 min, the residue was cooled down. The residual material contained 0.28 ppm of Gold (95% yield), 26 ppm of Copper (93% yield). The Silver concentration in the residue was below the detection limit of the analytical method used. The concentration of Arsenic was 354 ppm with 81% of Arsenic remaining in the residue. The removed Arsenic was collected in the first sorbent bed together with about 10% of the Copper. Gold and Silver were absorbed in the third sorbent bed with only a small amount in the fourth one. The total weight loss of material during metal extraction was 11% of mostly water. No chlorine was found in the solid residue.

Example 3

[0044] A concentrate (153 ppm Gold, 889 ppm Silver, 223 ppm Copper, 321 ppm of Arsenic, 3.0% of Iron Oxide (Fe.sub.2O.sub.3), 0.60% of Lead and 0.45% Zinc) was mixed with 10% of Calcium Chloride (CaCl.sub.2) and heated to 1050 C. in a stream of air under slightly reduced pressure. The released metal chloride fumes were absorbed onto several alumina sorbent beds. The residual material contained 1.37 ppm of Gold (99% yield), 37 ppm of Silver (96% yield), 32 ppm of Copper (89% yield), 14 ppm of Lead (99% yield) and 73 ppm of Zinc (99% yield).

[0045] The concentration of Arsenic was 318 ppm with 99% of Arsenic remaining in the residue. Most of the Gold and Silver were absorbed on the second sorbent bed, but with significant amounts on the first and the third absorbent beds with only a small amount in the fourth one. The distribution of Zinc and Lead was the same as Gold and Silver with no separation between extracted metals. The total weight loss of material during metal extraction was 19% of mostly water. No chlorine was found in the residue.

Example 4

[0046] A concentrate (103 ppm Gold, 398 ppm Silver, 0.35% Copper, 241 ppm of Arsenic, 3.0% of Iron Oxide (Fe.sub.2O.sub.3), 0.50% Lead, 0.46% Zinc, 0.11% of Uranium was mixed with 6.5% of Sodium Chloride (NaCl) and 6.5% of Calcium Chloride (CaCl.sub.2) and heated to 1050 C. in a stream of air under slightly reduced pressure. The realised metal chloride fumes were absorbed onto several alumina sorbent beds. After 30 min, the residue was cooled down. The residual material contained 2.4 ppm of Gold (98% yield), 18.9 ppm of Silver (95% yield), 111 ppm of Copper (97% yield), undetected amount of Lead (99% yield) and 46 ppm of Zinc (99% yield). The concentration of Arsenic and Uranium in the sorbent beds was below the detection limit of the analytical method employed, with near total retention of Arsenic and Uranium in the residue. The distribution of Zinc, Lead, Copper was the same as Gold and Silver with no separation between the extracted metals. The total weight loss of material during metal extraction was 12% of mostly water. No chlorine was found in the residue.

Example 5

[0047] A Tailing (1.57 ppm Gold, 1150 ppm Copper, 1980 ppm of Arsenic, 49% Iron Oxide (Fe.sub.2O.sub.3), 266 ppm of Lead, 413 ppm Zinc, 92 ppm of Uranium) was mixed with 10% of Sodium Chloride (NaCl) and heated to 1050 C. in a stream of air under slightly reduced pressure. The released metal chloride fumes were absorbed onto several alumina sorbent beds. After 30 min, the residue was cooled down. The residual material contained 0.16 ppm of Gold (90% yield), 8 ppm of Copper (99% yield), 3 ppm of Lead (99% yield) and 27 ppm of Zinc (93% yield). The concentration of Arsenic and Uranium in the sorbent beds was below the analytical detection limit with 100% of Arsenic and Uranium remaining in the residue. The first sorbent bed contained mostly Zinc followed by Lead and Copper, with Gold concentrated in the second sorbent bed. The total weight loss of material during metal extraction was 11% of mostly water. No chlorine was found in the residue.