CN111254288A

CN111254288A - Method and system for recovering gold from halogen extraction treatment substance

Info

Publication number: CN111254288A
Application number: CN201811584283.3A
Authority: CN
Inventors: 伯特兰·迪布勒伊; 让·马克·拉兰塞特; 大卫·勒米厄
Original assignee: Dundee Sustainable Technologies Inc
Current assignee: Dundee Sustainable Technologies Inc
Priority date: 2018-12-03
Filing date: 2018-12-24
Publication date: 2020-06-09

Abstract

A method and system for recovering gold and silver from a pregnant solution used for extracting gold from ores using halogens, the method comprising lowering the redox potential of the pregnant solution by mixing the pregnant solution and a reducing agent on the surface of a silicon bed, and flowing the mixture through the silicon bed. The system includes a silicon bed, a feeder for controlling a rich liquid and a reductant feed to direct a mixture having an ORP of less than 550mV to a surface of the silicon bed, and a collector for receiving a lean liquid from the silicon bed after the mixture flows through the silicon bed.

Description

Method and system for recovering gold from halogen extraction treatment substance

Technical Field

The present invention relates to the recovery of gold. More particularly, the present invention relates to a method and system for recovering gold from a pregnant solution derived from the extraction of gold from halogens in ores.

Background

The extraction of gold and silver with halogen chlorides in the presence of bromine is described, for example, in us patents 7,537,741B2, 9,051,626B2 and 9,206,492B 2. According to this method, the extracted noble metal is dissolved in the form of a complex chloride in a salt solution of NaCl and NaBr having an Oxidation Reduction Potential (ORP) in the range of about 1100mV to about 900 mV. Activated carbon cannot be used to recover precious metals from this solution because the halogen (in particular bromine) reacts irreversibly with the carbon, preventing the recovery of the reagent and leaving brominated carbon with indeterminate properties.

Another method for precious metal recovery is based on precipitation of precious metals on particles. For example, in U.S. Pat. No. 9,206,491, a BET specific surface area of 1m is used²Silicon particles in the/g range act as collectors. Substantially all of the gold and silver can be recovered from the pregnant solution using sodium sulfite as the reducing agent. The duration of operation may vary between 1 and 10 hours, depending on the duration of the process, and the consumption of the reducing agent is variable. When silicon is used as the slurry, it results in loss of gold supporting material during filtration.

There remains a need in the art for a method and system for recovering gold from pregnant solutions resulting from halogen extraction.

This specification is directed to a number of documents, the contents of which are fully incorporated herein by reference.

Disclosure of Invention

More specifically, according to the present invention, there is provided a method of recovering gold and silver from a pregnant solution in which gold is extracted from ore using halogens, comprising: the oxidation-reduction potential of the rich liquid is reduced by mixing the rich liquid and the reducing agent on the surface of the silicon bed, and flowing the mixture through the silicon bed.

Also provided is a system for recovering gold and silver from a pregnant solution used in leaching gold from an ore with a halogen, comprising a silicon bed, a feeder for controlling the pregnant solution and a reductant feed to direct a mixture having an ORP of less than 550mV to a surface of the silicon bed, and a collector for receiving a barren solution from the silicon bed after the mixture has flowed through the silicon bed.

Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

Drawings

In the drawings:

fig. 1 is a schematic diagram of a system according to an embodiment of an aspect of the present invention.

Detailed Description

The invention is illustrated in further detail by the following non-limiting examples.

In a precious metal recovery process based on precious metal precipitation of a pregnant solution (S1) resulting from leaching of gold and silver ores with hypohalite, and having an ORP in the range of about 1100mV to about 900 mV. The ORP of the pregnant solution drops below 550mV and the precious metals are released as metallic species with gold usually accompanied by traces of silver.

Using a BET specific surface area of about 1m²The silicon particles in g allow the metal species to be collected on a slurry of these silicon particles without significant loss on the reactor wall. However, when ferrous sulfate or sodium sulfite is used as the reducing agent, the duration of the operation is highly variable between 1 and 10 hours; furthermore, process losses occur during the process.

Surprisingly, it was found that using a collector in the form of silica gel mounted in a static bed in the column instead of slurried silicon in a rich liquor as known in the art, and feeding a reducing agent to the top of the column of silica gel with the rich liquor mixed thoroughly so that a small amount of silicon collects a large amount of gold, increasing the gold content of the silicon collector up to 17% while releasing a lean liquor with less than 0.02ppm gold. Thus rich solutions with as low as 2ppm gold can be treated with a silica gel bed with a contact time of less than 10 minutes. To ensure proper permeability of the silica gel bed, it may be mixed with a solid diluent (solid diluent), which may be, for example, of specific surface area of about 1m²Fine crystalline silicon per gram.

When loading of the silica gel with gold was completed as evidenced by the black color of the bed surface, the silica gel was recovered and melted with a flux to release the gold/silver value.

FIG. 1 illustrates a system according to an embodiment of an aspect of the invention. A rich liquid (S1) produced by leaching gold and silver ores with hypohalite and having an ORP in the range between about 1100mV to about 900mV, and a reducing agent (R) are fed to the surface of the silica gel static bed (B). The feed rates of the rich liquid (S1) and the reducing agent (R) were controlled using metering pump 12 and metering pump 14, respectively, to produce a solution (S2) having an ORP of less than about 550mV to the surface of the silica gel static bed (B).

As shown in fig. 1, the silica gel bed (B) is located in a tube 16 that receives a mixture of rich liquid (S1) and reductant (R), in a sleeve 18 over a filter medium 20 within the tube 16. The perforated collector 22 below the filter media 20 leads to a collector 24.

The flow rate of the solution (S2) from above the silica gel bed (B) through the perforated collector 22 to the receiver 24 was controlled by applying a controlled vacuum (see arrow (V)) on the receiver 24 to maintain the level (L) of the solution (S2) within the tube 16 at the top of the silica gel bed (B) near a steady value. As described in us patent 9,206,491B2, the lean liquid (S3) collected in the receiver 24 may be pumped out (see pump 26) for recovery by oxidation for further extraction of gold.

Therefore, when the solution (S2) was flowed through the silica gel bed with a very short contact time, gold was deposited on the silica gel bed (B). Once the silica gel bed (B) is saturated, it can be recovered by removing the filter media 20 of the support sleeve 18 and forming a disposable meltable container and containing the saturated silica gel bed (B) from the system.

The BET specific surface area of silicon was varied from 1m in the experiments by replacing crystalline silicon with silica gel²The/g is increased to 450m²(ii) in terms of/g. Using ferrous sulphate as the reducing agent, it was noted that the time required to achieve complete precipitation of gold with crystalline silicon was approximately twice that with silica gel.

Sodium metabisulphite as reducing agent so that after 30 minutes on silica gel (BET specific surface area 450 m)²Per g), whereas ferrous sulfate takes 100 minutes to achieve the same result. Sodium sulfite was 50 minutes, slightly slower than metabisulfite. The contact time is adjusted according to the amount of silicon and the volume of the pregnant solution to be treated, so as to collect the gold value.

In the experiment, silicon (in the form of crystalline silicon (BET specific surface area of 1 m)²Per g) or silica gel (BET specific surface area 450 m)²Form/g)) and ORP 1121The mV of pregnant solution was contacted at a ratio of 1g silicon/1300 g pregnant solution. The remaining gold in the solution was determined by ICP-AES analysis. The silicon used is AlfaAesar^tm60。

The results in table 1 below show the time required for complete adsorption of gold on silica:

TABLE 1

In another experiment, 500ml of a solution of gold having a concentration of 1266mg/l Au and an ORP of 980mV was mixed with 500ml of a sodium sulfite solution (12g/l) in a reaction vessel using 5.0g of silica gel (450 m)²Per g) and 5.0g of crystalline silicon (1 m)²/g) was circulated over the bed made up for 2 hours at a fixed rate. The mixing of the two liquids is performed at the surface of the bed as discussed above with respect to fig. 1. The duration of contact of the solution with the silica column was 1 minute. It was noted that the precipitated gold formed a black layer on the top surface of the silicon bed. The barren solution at the bottom of the column, which contained 0.78mg/L gold, showed substantially complete recovery of gold (99.9%).

In another experiment, a 1 liter sample of 1266mg/l Au gold solution (ORP 980mV) was divided into 10 100ml portions. Each part in turn co-operating with 4.0450 m in the column²The bed is contacted with silica gel for 1 hour, and the lean solution is removed after each contact. After these ten exposures to the gold solution, the silicon was fire tested and showed a gold content of 170700g/t Au in the silicon, which corresponds to a gold recovery of 99.94% in the starting solution and a gold concentration on the silicon of 17% (w/w).

According to one aspect of the invention, the halogen (Cl) is selected from₂、Br₂) The method for recovering gold and silver from the pregnant solution from extraction of gold and silver comprises using sodium metabisulfite (Na)₂S₂O₅) As reducing agent, in a BET specific surface area of at least 350m²The/gm silicon static bed precipitates noble metals from the rich liquor by reducing the OPR of the rich liquor from 1100-900mV to less than 550mV on the surface.

The deposition of the precious metals is complete within minutes and the barren solution can be recycled for further extraction of gold. I.e. a rich solution containing as little as 2ppm gold, can also accumulate gold in amounts exceeding 15% w/w on a static silicon bed.

The pregnant solution may be concentrated up to about 1000ppm Au, or diluted to about 2ppm Au.

Since in the method and system of the invention the silicon collector is static, as opposed to for example circulating slurry, the saturated bed is transferred to the melt with its vessel as described above, avoiding gold losses due to filtration or other processing operations.

This method allows the continuous deposition of gold on a given silica gel bed using concentrated (1000ppm Au) or diluted (2ppm Au) pregnant solutions with very short contact times and avoids process gold losses. The results show that gold precipitation is optimal. Thus, having a layer of gold particles on top of the silicon bed allows for efficient and complete deposition.

In accordance with one aspect of the invention, a method for recovering gold and silver from a pregnant solution produced from a chlorine extract of gold includes reducing the ORP of the pregnant solution from a range of about 1100 to about 900mV to less than about 550mV by mixing the pregnant solution with a reducing agent solution over the surface of a silicon bed and circulating a mixture of the solutions across the surface of the silicon bed.

Selecting a BET specific surface area above about 350m²In g, e.g. above about 400m²In g, e.g. above about 450m²Per g of silica gel. Silicon of high BET surface area, e.g. BET surface area greater than about 450m²The silicon may be mixed with a solid diluent (e.g. having a BET specific surface area of about 1 m)²Fine silicon/g) to improve permeability and allow adjustment of the contact time of the solution with the mixture of silicon to be in the range of about 1 minute to about 10 minutes.

The reducing agent is one of ferrous sulfate, sodium sulfite and sodium metabisulfite.

The gold precipitation on the silicon bed can be carried out in a disposable fusible container, for example made of glass fibre, borosilicate glass or recycled glass, preventing the loss of gold-loaded silicon.

The scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims

1. A method of recovering gold and silver from a pregnant solution using halogens to extract gold from ore, comprising: the oxidation-reduction potential of the rich liquid is reduced by mixing the rich liquid and a reducing agent on the surface of a silicon bed, and flowing the mixture through the silicon bed.

2. The method of claim 1, comprising decreasing the oxidation-reduction potential of the pregnant solution from a range of 1100mV to 900mV to less than 550 mV.

3. The method of claim 1, wherein the silicon bed comprises a specific surface area of at least 350m²Per g of silica gel.

4. The method of claim 1, wherein the silicon bed comprises a specific surface area of at least 400m²Per g of silica gel.

5. The method of claim 1, wherein the silicon bed comprises a specific surface area of at least 450m²Per g of silica gel.

6. The method of claim 1, wherein the silicon bed comprises a specific surface area of at least 350m mixed with a solid diluent²Per g of silica gel.

7. The method of claim 1, wherein the silicon bed comprises a specific surface area of at least 350m mixed with crystalline silicon²Per g of silica gel.

8. The method of claim 1, wherein the silicon bed comprises a silicon material having a specific surface area of about 1m²A specific surface area of at least 350m for a crystalline silicon mixture/g²Per g of silica gel.

9. The method of claim 1, wherein the reducing agent is one of ferrous sulfate, sodium sulfite, and sodium metabisulfite.

10. The method of claim 1, wherein the reducing agent is sodium metabisulfite.

11. The method of claim 1 including the step of depositing gold on a silicon bed within a disposable fusible container.

12. A process as claimed in claim 1, comprising installing the silica bed in a column and feeding a mixture of rich liquid and reducing agent to the top of the silica column.

13. The method of claim 1, comprising recovering the barren solution and recycling the barren solution for further extraction of gold.

14. A system for recovering gold and silver from a pregnant solution in which gold is leached from ore with halogens includes a silicon bed, a feeder and a collector,

the feeder is used to control the rich liquor and reductant feed to direct a mixture having an ORP of less than 550mV to the surface of the silicon bed,

the collector is for receiving a lean liquid from the silicon bed after the mixture flows through the silicon bed.

15. The system of claim 14, wherein the silicon bed is located in a vessel made of one of fiberglass, borosilicate glass, and recycled glass, and is removable from the system.

16. The system of claim 14, wherein the silicon bed is disposed in a vessel that is removable from the system.

17. The method of claim 14Wherein the silicon bed comprises a specific surface area of at least 350m²Per g of silica gel.

18. The system of claim 14, wherein the silicon bed comprises a specific surface area of at least 350m mixed with a solid diluent²Per g of silica gel.

19. The system of claim 14, wherein the silicon bed comprises a specific surface area of at least 350m mixed with crystalline silicon²Per g of silica gel.

20. The system of claim 14, wherein the silicon bed comprises a silicon surface area of about 1m²A specific surface area of at least 350m for a crystalline silicon mixture/g²Per g of silica gel.