RU2793685C1 - Materials and methods for extraction of precious metals - Google Patents

Abstract

FIELD: extracting precious metals.

SUBSTANCE: group of inventions relates to methods for extracting precious metals, such as gold or silver, from ore raw materials, enrichment waste, waste, including electronic waste. The method includes treating an article containing a precious metal or a composition containing a precious metal with an oxidizing agent composition under conditions suitable for oxidizing the precious metal present in said article or composition to obtain a composition comprising a salt of the precious metal. The resulting composition is brought into contact with the sorbent under conditions in which the sorbent is capable of adsorbing at least a portion of the precious metal salt to obtain a sorbent containing the adsorbed material. At least a portion of the precious metal is recovered from the sorbent containing the adsorbed material. The oxidizing agent composition includes at least one halide ion source and at least one electrophilic halogen source, wherein the electrophilic halogen source is selected from one or more groups consisting of hypochlorous acid, hypochlorous acid, hypobromite salts, hypochlorite salts, bromochlorodimethylhydantoin (BCDMH). Alternatively, the precious metal is recovered from the precious metal salt composition by chemical reduction, electrochemical reduction and/or chemical precipitation.

EFFECT: technical result consists in realizing the purpose of the invention.

12 cl, 20 dwg, 6 tbl, 17 ex

Description

This application claims priority to Australian Provisional Patent Application AU 2019901135 entitled "Materials and Processes for Recovering Precious Metals (MATERIALS AND PROCESSES FOR RECOVERING PRECIOUS METALS)", filed April 3, 2019, the contents of which are hereby incorporated by reference in their entirety.

FIELD OF TECHNOLOGY

The present invention relates to compositions and methods for recovering precious metals such as gold and silver from ores, tailings, waste streams, electronic waste (ie, waste electrical and electronic equipment), and similar streams.

PRIOR ART

Gold mining and recovery are economically important activities in mining and e-waste recycling worldwide (Commercial Aspects of Gold Applications: From Materials Science to Chemical Science. C. W. Corti and R. J. Holliday. Gold Bull. 2004, 37, 20; Recovery of gold from secondary sources - A review S. Syed Hydrometallurgy 2012, 115-116, 30-51). Significant limitations exist in both of these areas of activity, forcing the choice of environmentally friendly methods of extracting gold that can minimize harm to mining workers and the environment (A Review of Environmental Considerations on Gold Mining and Production. A. Muezzinoglu. Critical Reviews in Environmental Science and Technology 2010, 33, 45-71). Accordingly, there is an increasing need to find materials that can replace mercury and cyanides, which are widely used toxic reagents for efficient gold recovery (The Mercury Problem in Artisanal and Small-Scale Gold Mining. L. J. Esdaile and J. M. Chalker. Chem. Eur. J. 2018, 24, 6905-6916). A significant contribution to this field of technology has been made by the use of leaching methods using thiosulfate (Thiosulfate leaching of gold - A review. M. G. Aylmore and D. M. Muir. Minerals Engineering 2001, 14, 135-174) and halogens (Bromine leaching as an alternative method for gold dissolution R. Sousa, A. Futuro, A. Fiuza, M. C. Vila, and M. L. Dinis Minerals Engineering, 2018, 118, 16-23 Environmentally Benign, Rapid, and Selective Extraction of Gold from Ores and Waste Electronic Materials, C. Yue, H. Sun, W.-J. Liu, B. Guan, X. Deng, X. Zhang, and P. Yang. Angew. Chem. Int. Ed. 2017, 56, 9331-9335). Despite the promise of the results available, they have little applicability on a large scale for both formal and informal mining or e-waste processing. In addition, these techniques often require careful control of recovery conditions, which include pH maintenance and the use of a co-oxidant (Thiosulfate leaching of gold - A review. M. G. Aylmore and D. M. Muir. Minerals Engineering 2001, 14, 135-174), or these techniques require the use of expensive reagents (Bromine leaching as an alternative method for gold dissolution. R. Sousa, A. Futuro, A. Fiuza, M. C. Vila, and M. L. Dinis. Minerals Engineering, 2018, 118, 16-23) or corrosive solvents (Environmentally Benign , Rapid, and Selective Extraction of Gold from Ores and Waste Electronic Materials, C. Yue, H. Sun, W.-J. Liu, B. Guan, X. Deng, X. Zhang, and P. Yang, Angew, Chem Int. Ed. 2017, 56, 9331-9335).

Accordingly, there is a need to provide methods for extracting gold or other precious metals from minerals, electronic waste, etc., which would solve one or more of the problems associated with existing methods and/or provide an alternative to existing methods.

SUMMARY OF THE INVENTION

The first aspect of the present invention relates to a method for extracting precious metal from a precious metal containing article or precious metal containing composition, wherein the method comprises:

- treating a precious metal containing article or precious metal containing composition with an oxidizing agent composition under conditions suitable for oxidizing the precious metal present in the precious metal containing article or precious metal containing composition, resulting in a composition comprising a salt precious metal;

bringing the composition comprising the precious metal salt into contact with the sorbent under conditions in which the sorbent is capable of adsorbing at least a portion of the precious metal salt, resulting in a sorbent containing the adsorbed material; And

- extracting at least part of the precious metal from the sorbent containing the adsorbed material.

In some embodiments of the first aspect, the sorbent may selectively adsorb at least a portion of the precious metal salt, resulting in a sorbent containing the adsorbed material.

The second aspect of the present invention relates to a method for extracting precious metal from a precious metal containing article or precious metal containing composition, wherein the method comprises:

treating an article containing a precious metal, or a composition containing a precious metal, with an oxidant composition comprising at least one source of a halide ion and at least one source of an electrophilic halogen, under conditions suitable for oxidizing the precious metal in the article containing a precious a metal, or a composition containing a precious metal, resulting in a composition comprising a salt of a precious metal; And

- extracting at least a part of the precious metal from the composition comprising the salt of the precious metal.

In some embodiments according to the first and second aspects, the precious metal is recovered from a sorbent containing an adsorbed material, or a composition comprising a precious metal salt, by chemical reduction, electrochemical reduction, and/or chemical precipitation.

The third aspect of the present invention relates to a sorbent containing a salt of a precious metal adsorbed by it obtained by the method according to the first aspect.

A fourth aspect of the present invention relates to a precious metal recovered from a precious metal containing article or a precious metal containing composition by the method of the first aspect.

BRIEF DESCRIPTION OF GRAPHICS

The embodiments of the present invention are discussed with reference to the accompanying drawings, in which:

On FIG. 1 shows the spectrum in the UV and visible region obtained by carrying out the reaction between TCCA (trichloroisocyanuric acid) and NaBr in water;

On FIG. 2 shows the dependence of the concentration of gold (III) on time, obtained in Example 4;

On FIG. 3 is a scanning electron microscopy (SEM) micrograph showing gold metal nanoclusters formed on the polysulfide polymer in Example 4;

On FIG. 4 shows the results of energy dispersive X-ray spectral (EDX) analysis of gold metal nanoclusters formed on the polysulfide polymer in Example 4;

On FIG. 5 is a photograph of the metallic gold recovered in Example 5.2;

On FIG. 6 shows the results of energy dispersive x-ray (EDX) analysis of the gold metal recovered in Example 5.2;

On FIG. 7 shows the results of energy dispersive x-ray (EDX) analysis of the gold metal recovered in Example 7;

On FIG. 8 shows the results of energy dispersive x-ray (EDX) analysis of the gold metal recovered in Example 8;

On FIG. 9 shows a plant with a retort for the wet recovery of sulfur dioxide from polymer combustion;

On FIG. 10 is an ion chromatogram showing that sulfate was detected in the scrubbing solution; this indicates that the gaseous sulfur dioxide that forms when the polymer is burned can be easily captured using the same oxidizers that were used in the oxidation of gold:

On FIG. 11 is an SEM micrograph of gold particles obtained by treating the leach solution with ascorbic acid (Example 14);

On FIG. 12 shows the results of X-ray spectral (EDX) analysis of gold particles obtained by treating the leach solution with ascorbic acid (Example 14), indicating that the particles are composed of high purity gold;

On FIG. 13 is an SEM micrograph of gold particles obtained by treating the leach solution with hydrogen gas (Example 15);

On FIG. 14 shows the results of X-ray spectral (EDX) analysis of gold particles obtained by treating the leach solution with hydrogen gas (Example 15), indicating that the particles are composed of high purity gold;

On FIG. 15 is a SEM micrograph of gold leached from ore concentrates and recovered with a polymer sorbent during post-burning (Example 16);

On FIG. 16 shows the results of an X-ray spectral (EDX) analysis of gold leached from ore concentrates and recovered with a polymeric sorbent during subsequent combustion (Example 16), and the results indicate that the material is gold;

On FIG. 17 is an SEM micrograph of gold recovered with a polysulfide polymer in post-burning (Example 17);

On FIG. 18 shows the results of X-ray spectral (EDX) analysis of gold recovered with a polysulfide polymer in post-burning (Example 17);

On FIG. 19 is an SEM micrograph of gold recovered by reductive precipitation with ascorbic acid (Example 17); And

On FIG. 20 shows the results of X-ray spectral (EDS) analysis of gold recovered by reductive precipitation with ascorbic acid (Example 17).

INFORMATION CONFIRMING THE POSSIBILITY

IMPLEMENTATION OF THE INVENTION

Unless otherwise indicated, all terms used in the description of the invention, including technical and scientific terms, have the meanings generally known to those skilled in the art to which the present invention pertains. As an additional guide and for a better understanding of the essence of the present invention, the definitions of the terms are given below.

According to the present invention, the following terms have the following meanings:

The use of the singular in this work refers to both the singular and the plural, unless the context makes it clear otherwise.

For example, the term "oxidizing agent" refers to one or more than one oxidizing agent.

As used herein, the term "approximately" referring to a measurable value such as a parameter, an amount, a length of time, and the like includes magnitude variations of +/-20% or less, preferably +/-10% or less, preferably +/-5% or less, more preferably +/-1% or less, and more preferably +/-0.1% or less of the specified value, provided that these variations do not interfere with the implementation of the present invention. However, it should be understood that the value to which the modifier "approximately" refers is also included in the scope of the invention.

As used herein, the terms "comprise", "including", "included" and "includes" are synonymous with the terms "comprise", "comprising" and "comprises" and have a non-exclusive or modifiable meaning that indicates the presence of the following entities, for example, components, and does not exclude or prevent the presence of additional, unnamed components, features, elements, details, steps known in the art or described in this work.

Unless otherwise indicated, as used herein and in the description, the term "wt % (wt %)" refers to the relative weight of the respective component based on the total weight of the composition or the respective element.

Limitations of numerical ranges include all numbers and decimals contained within the range, as well as the specified limits, unless expressly stated or otherwise indicated.

The present inventors have surprisingly found that certain sorbents, such as polymeric polysulfides, can be used to selectively recover precious metals, such as gold and silver, from certain compositions and articles that contain precious metal. Precious metals can be recovered by metal oxidation, which results in the formation of a precious metal salt, followed by selective adsorption of the precious metal salts by the sorbent. Surprisingly, it has been found that the precious metal can be recovered from the sorbent directly and in an environmentally friendly manner. In addition, the present inventors have surprisingly found that certain polysulfide polymer sorbents not only selectively adsorb some precious metal salts from solution, but also reduce precious metal salts to precious metals in situ.

Accordingly, the first aspect relates to a method for recovering a precious metal from a precious metal containing article or precious metal containing composition. The method includes treating a precious metal containing article or precious metal containing composition with an oxidizing agent composition under conditions suitable for oxidizing the precious metal present in the precious metal containing article or precious metal containing composition, resulting in a composition comprising a salt. precious metal. The composition comprising the precious metal salt is then brought into contact with the sorbent under conditions in which the sorbent is capable of adsorbing at least a portion of the precious metal salt, resulting in a sorbent containing the adsorbed material. At least a portion of the precious metal is then removed from the sorbent containing the adsorbed material.

The second aspect relates to a method for extracting precious metal from a precious metal containing article or precious metal containing composition. The method includes treating an article containing a precious metal, or a composition containing a precious metal, with an oxidant composition comprising at least one source of a halide ion and at least one source of an electrophilic halogen, under conditions suitable for oxidizing the precious metal present in the article, containing a precious metal, or a composition containing a precious metal, resulting in a composition comprising a salt of a precious metal; and recovering at least a portion of the precious metal from the composition comprising the precious metal salt.

A precious metal can be any naturally occurring metallic chemical element of great economic importance. Precious metals include gold, silver, ruthenium, rhodium, palladium, osmium, iridium and platinum. In some specific embodiments of the present invention, the precious metal is gold. In some other specific embodiments of the present invention, the precious metal is silver.

The present inventors have found that certain polysulfide polymers (described in more detail below) can adsorb gold ions from solution with greater selectivity than other metal ions that can typically be found in gold ores and tailings, such as ions Al ³⁺ , Cu ²⁺ , Zn ²⁺ , Fe ³⁺ , As ⁵⁺ , Cd ²⁺ and/or Pb ²⁺ .

The precious metal containing article or precious metal containing composition may be any of the solid, liquid or gaseous precious metal containing materials. The method of the present invention is particularly suitable for the extraction, recovery, separation and/or purification of precious metals present in ores, mining waste, electronic waste and other secondary sources of precious metals. Used in this work, the term "extraction (extraction)" means the extraction, separation and/or purification.

The oxidizing agent composition includes at least one halide ion source and at least one electrophilic halogen source. The present invention is based at least in part on the discovery made by the present inventors, which is that a number of readily available and relatively environmentally friendly oxidizing agents, such as trichloroisocyanuric acid (English trichloroisocyanuric acid, abbreviated TCCA), can be combined with some readily available and relatively environmentally friendly halogen salts such as sodium bromide to form an oxidizing agent that can react with gold metal and extract the gold into water. To the knowledge of the present inventors, this is the first example of the combined use of sodium bromide and SCCA in a reaction with gold. The present inventors have also found that a variety of different halide ion sources and electrophilic halogen sources can be used to oxidize the precious metal to form a water-soluble salt of the precious metal.

As used herein, the term "oxidation of a precious metal in a precious metal-containing article or precious metal-containing composition" means that at least a portion of the precious metal in a precious metal-containing article or precious metal-containing composition is oxidizes, but the oxidation reaction may not result in complete oxidation of the entire precious metal.

In some embodiments, the halide ion source includes chloride ions. In these embodiments, the halide ion source can be one or more of sodium chloride, potassium chloride, and hydrogen chloride.

In some other embodiments, the halide ion source includes bromide ions. In these embodiments, the halide ion source may be one or more of the following: sodium bromide, potassium bromide, and hydrogen bromide.

In other embodiments, the halide ion source includes iodide ions. In these embodiments, the halide ion source may be one or more of the following: sodium iodide, potassium iodide, and hydrogen iodide.

The halide ion source may also be a combination of any of the halide ion sources mentioned above.

The electrophilic halogen source may be selected from one or more of the group consisting of hypobromous acid, hypochlorous acid, hypobromite salts, hypochlorite salts, bromochlorodimethylhydantoin (abbreviated as BCDMH), sodium dichloroisocyanurate (abbreviated as SDIC) , dichloroisocyanuric acid, trichloroisocyanuric acid (English trichloroisocyanuric acid, abbreviated TCCA), sodium dibromisocyanurate, dibromisocyanuric acid and tribromisocyanuric acid.

In some specific embodiments, the halide ion source is sodium bromide and the electrophilic halogen source is trichloroisocyanuric acid. Sodium bromide and trichloroisocyanuric acid react with gold metal in a one-pot reaction to form a water-soluble salt, gold bromide, and cyanuric acid. Cyanuric acid is non-toxic and biodegradable, and thus the effluents and/or waste streams from this process are less toxic than the mercury or cyanide containing effluents typically produced from gold processing operations. In addition, trichloroisocyanuric acid is commonly used as a swimming pool disinfectant and is therefore readily available and considered less toxic than competing gold leach reagents such as mercury and cyanide.

Under the oxidizing conditions created, the precious metal present in the precious metal containing article or precious metal containing composition is oxidized, resulting in the formation of a composition comprising a salt of the precious metal. The oxidation reaction can be carried out at a temperature of from about 10°C to about 100°C, such as 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°С, 18°С, 19°С, 20°С, 2GS, 22°С, 23°С, 24°С, 25°С, 26°С, 27°С, 28°С, 29°С, 30°C, ZGS, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55° С, 56°С, 57°С, 58°С, 59°С, 60°С, 61°С, 62°С, 63°С, 64°С, 65°С, 66°С, 67°С, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80° С, 81°С, 82°С, 83°С, 84°С, 85°С, 86°С, 87°С, 88°С, 89°С, 90°С, 91°С, 92°С, 93° C., 94° C., 95° C., 96° C., 97° C., 98° C., 99° C., or 100° C. In some embodiments, the oxidation reaction is carried out at a temperature of from about 20° C. to about 60°C, such as from about 50°C to about 60°C.

Oxidizing conditions may include the use of methods to increase the rate of the oxidation reaction, such as sonication or sonication in conjunction with heating. The effect of ultrasound on the oxidation reaction can be carried out using any suitable type of transducer, such as a conventional ultrasonic transducer known in the art. Variables that can be adjusted with sonication include, without limitation: frequency of sonication applied, power level of sonication applied, duration of sonication applied, location of the transducer in the oxidation reaction vessel, and so on. In most embodiments, the applied energy is ultrasonic energy, ie. having a frequency of 17 kilohertz (kHz) or more.

The oxidation reaction can be carried out at a pH of about pH 1.0 to about pH 12.0, such as 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1, 6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4, 1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6, 6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9, 1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.1, 11.2, 11.3, 11.4, 11.5, 11, 6, 11.7, 11.8, 11.9 or 12.0. In some embodiments, the oxidation reaction is carried out at a pH of about pH 4.0 to about pH 8.0.

The oxidized and water-soluble precious metal can be recovered in a variety of ways, examples of which include, without limitation, electrochemical reduction, chemical reduction, chemical precipitation, activated carbon adsorption, and polymer sorbent adsorption.

In some embodiments, the oxidized and water-soluble precious metal is recovered by adsorption onto a suitable sorbent. In some of these embodiments, the sorbent is a polysulfide polymer. The polysulfide polymer can be produced by any of the methods discussed in International Patent Application WO 2017/181217, the contents of which are incorporated herein by reference. Briefly, according to these methods, a polysulfide polymer is prepared by reacting a fatty acid composition that includes at least one unsaturated fatty acid or derivative thereof with sulfur in a weight ratio of 9:1 to 1:9 under reflux conditions. vulcanization, which leads to the formation of a polymeric polysulfide, and at least 50% of the fatty acids or their derivatives in the composition based on fatty acids are unsaturated.

The fatty acid composition may be a glyceride-containing composition. The glyceride-containing composition may include either a triglyceride or a diglyceride or both a triglyceride and a diglyceride in substantially pure form. In some embodiments, the glyceride-containing composition comprises either a mixture of triglycerides, or a mixture of diglycerides, or a mixture of triglycerides and diglycerides. In some embodiments, either a triglyceride or a diglyceride or both a triglyceride and a diglyceride comprise at least one fatty acid having 8 to 24 carbon atoms in the chain, and examples of fatty acids include, without limitation: a-linolenic acid, stearidonic acid, stearic acid, ricinoleic acid, dihydroxystearic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, γ-linolenic acid, dihomo-γ-linolenic acid, arachidonic acid, docosatetraenoic acid, palmitoleic acid, vaccenic acid, paullic acid, oleic acid, elaidic acid, 11-eicosenoic acid, erucic acid, nervonic (aceterucic) acid or midic acid.

In some embodiments, the glyceride-containing composition includes at least one oil derived from natural sources or a synthetic oil. In some embodiments, the glyceride-containing composition comprises or is derived from at least one oil derived from acai berry oil, avocado oil, brazil nuts, canola, castor oil, corn oil, cottonseed oil, grape seed oil, hazelnut (hazelnut) oil ), linseed oil, mustard oil, peanut oil, olive oil, rice bran oil, safflower oil, soybean oil, or sunflower oil.

Preferably, the glyceride-containing composition may be a used natural or synthetic oil composition, such as oil that has already been used in food production. It is then used to produce a relatively inexpensive and/or environmentally acceptable glyceride-containing composition.

In some other embodiments, the fatty acid composition is a fatty acid ester composition. The fatty acid ester composition may include esters of one or more unsaturated fatty acids. The ester may be an alkyl ester such as a methyl ester, an ethyl ester or a propyl ester. Fatty acid esters can be prepared by fatty acid esterification or transesterification of a glyceride-containing composition or a fatty acid derivative such as a fatty acid amide. In some embodiments, the fatty acid contains from 8 to 24 carbon atoms in the chain, inclusive. The fatty acid may be selected from one or more groups, which include, without limitation: α-linolenic acid, stearidonic acid, stearic acid, ricinoleic acid, dihydroxystearic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, γ-linolenic acid, dihomo- γ-linolenic acid, arachidonic acid, docosatetraenoic acid, palmitoleic acid, vaccenic acid, paullic acid, oleic acid, elaidic acid, 11-eicosenoic acid, erucic acid, nervonic (aceterucic) acid, or midic acid.

The fatty acid ester can be derived from natural oil or synthetic oil. In some embodiments, the fatty acid ester is derived from at least one oil selected from acai berry oil, avocado oil, Brazil nut oil, canola oil, castor oil, corn oil, cottonseed oil, grape seed oil, hazelnut (hazelnut) oil, linseed oil, mustard oil, peanut oil, olive oil, rice bran oil, safflower oil, soybean oil or sunflower oil.

In some embodiments, the weight ratio of fatty acid composition to sulfur is between 9:1 and 1:9. For example, 8:1, 7:1, 6:1, 5:1, 5:2, 2:1, 3:2, 1:1, 2:3, 1:2, 2:5, 1:5, 1:6, 1:7 or 1:8. Accordingly, in some embodiments in which the fatty acid composition is an oil, such as canola oil, the weight ratio of canola oil to sulfur may be 1:1. In some embodiments, the weight ratio of the amount of glyceride-containing composition to the amount of sulfur can be suitably changed.

In some embodiments, sulfur includes elemental sulfur. In some embodiments, sulfur includes at least one allotropic form of sulfur, such as S5, S6, S7, or S8. In some embodiments, S8 is at least one of the following forms: alpha sulfur (commonly referred to as sulphur), beta sulfur (or crystalline sulphur), or gamma sulphur (also referred to as pearlescent sulphur). In some embodiments, sulfur includes any poly-S reagent, intermediate, or product derived from sulfide (such as sodium sulfide), sodium chloride, or hydrogen sulfide.

The polysulfide polymer may be a solid. In some embodiments, the polysulfide polymer is rubber. In some embodiments, the polysulfide polymer is elastic and cold deformable at temperatures up to about 150°C, i.e. up to the temperature at which the polysulfide polymer begins to decompose. In some embodiments, the polysulfide polymer begins to degrade at temperatures greater than about 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240 , 245 or 250°С. The temperature at which the polysulfide polymer begins to decompose can be increased, for example by increasing the sulfur content.

In alternative embodiments, the polysulfide polymer is a liquid material. Liquid polysulfide polymers can be prepared by reacting fatty acid esters with sulfur in reactant weight ratios ranging from 9:1 to 1:9.

The polysulfide polymer is produced by reacting a fatty acid composition with sulfur under reverse cure conditions. Reverse curing involves adding a fatty acid composition to liquid sulfur in a relatively high weight percentage. This is in contrast to classical vulcanization, which involves the addition of relatively low weight percentages of sulfur to the hot fatty acid composition.

The composition comprising the precious metal salt is brought into contact with the sorbent under conditions in which the sorbent is capable of adsorbing at least a portion of the precious metal salt, resulting in a sorbent containing the adsorbed material.

Optionally, the precious metal salt composition may be pre-treated before being brought into contact with the sorbent. For example, the pH of the composition may be changed prior to bringing the composition comprising the precious metal salt into contact with the sorbent. In some embodiments, prior to bringing the composition comprising the precious metal salt into contact with the sorbent, the composition comprising the precious metal salt is filtered to remove solids. This step can be important in the processing of ore and tailings, which contain a large amount of insoluble fragments, since solids can block the reactive surface of the sorbents during the extraction of precious metals.

A composition comprising a precious metal salt may be brought into contact with more than one sorbent. If the precious metal salt composition is contacted with more than one sorbent, then each of the sorbents may be contacted with the precious metal salt composition sequentially (in turn) or non-sequentially.

The sorbent may be brought into contact with the precious metal salt composition in any suitable manner. In some embodiments, the sorbent is brought into contact with a composition comprising a precious metal salt in a container, such as a beaker, test tube, tube, bottle, flask, balloon, bucket, bath, reservoir, in any other suitable container known in the art. , or in any other means for storing, containing or moving a composition comprising a salt of a precious metal. In some embodiments, contact of the sorbent with a composition comprising a precious metal salt is carried out in a batch or continuous manner.

Optionally, upon contact of the sorbent with the composition comprising the precious metal salt, agitation may be performed. Any suitable mixing method may be used, including shaking, agitation, swirling, magnetic stirring, and sparging.

The amount of time required for the precious metal salt composition to contact the sorbent depends on a variety of factors, which include: sorbent composition, temperature, agitation, and any other relevant factors. In some embodiments, the contact time of the precious metal salt composition with the sorbent is from 1 minute to 24 hours.

Preferably, the oxidation and recovery and subsequent production of the precious metal can be carried out in one vessel. For example, sodium bromide and trichloroisocyanuric acid can be added to the gold source, after which selective adsorption can be carried out on the surface of the polymer. In the case of a polysulfide polymer, the polymer may be added to the gold solution directly, or it may be added in a protected form.

At least a portion of the precious metal is then removed from the sorbent containing the adsorbed material. The method for extracting a precious metal from a sorbent containing an adsorbed material includes separating the sorbent containing the adsorbed material from a composition containing a precious metal salt. The precious metal can be obtained from the sorbent containing the adsorbed material by converting the salt of the precious metal into elemental precious metal by chemical reduction, electrochemical reduction, chemical precipitation, adsorption on activated carbon, and adsorption on polymeric sorbents. Thus, the method includes the reduction of at least a portion of the salt of the precious metal adsorbed on the sorbent, which leads to the formation of the precious metal. Thus, the present inventors have found that, at least in the case of gold, the precious metal salt is reduced in situ by the polysulfide polymer described above, forming metallic gold on the polymeric sorbent. In other cases, the precious metal salt adsorbed on the sorbent can be reduced by reaction with a suitable reducing agent known in the art, such as zinc metal, sodium borohydride, hydrogen gas, ascorbic acid, electrochemical precipitation, and other conventional reducing agents. Alternatively, the precious metal salt adsorbed on the sorbent can be recovered by electrochemical reduction.

In some embodiments, an oxidizing agent is used to oxidize and convert the precious metal to a water-soluble salt of the precious metal. The resulting solution is then filtered and separated from the remaining solid. Then, a reducing agent such as ascorbic acid or hydrogen gas is added to the precious metal salt composition. The precious metal is recovered and precipitated as elemental precious metal. If copper is present in the solution, a copper-binding ligand such as ethylenediaminetetraacetic acid (EDTA) or water-soluble amino acids and diamines that bind to copper can be added to bind copper. The precious metal can then be selectively reduced and precipitated by adding ascorbic acid or hydrogen gas. At this stage, ascorbic acid or hydrogen will also remove any excess oxidizing agent. The required amount of ascorbic acid or hydrogen gas depends on the amount of oxidant used in the first stage. As a minimum, an equimolar ratio of reducing agent to oxidizing agent must be maintained plus an additional molar equivalent must be added to react with the precious metal.

Preferably, the methods described herein can be used to selectively separate gold from tailings or similar compositions containing other metals. For example, tailings containing gold and other metals including mercury can be contacted with an oxidant composition under conditions suitable to oxidize most of the gold present in the tailings. Under the conditions described in this paper, gold (>99%), mercury (>99%) and nickel (>99%) leach into solution faster than some other metals such as copper and iron. A sorbent can then be used to recover the gold. It has been shown that the polysulfide polymer described in this paper removes gold from the leach solution faster than any other component of this solution. In addition, it shows that the oxidant composition can also be used to remove mercury from tailings by stripping. Mercury can be removed from the leach solution by adding more polysulfide polymer or by adding activated carbon. The use of an oxidizer solution to eliminate mercury also applies to the removal of mercury from soil, sludge and other mixed waste and solid waste. The oxidant solution oxidizes the mercury, making it soluble, and the polymer or activated carbon or other similar sorbent can remove the mercury from the water.

The use of a leach solution to eliminate mercury also applies to the removal of mercury from soil, sludge and other mixed waste and solid waste. This must be stated specifically. The leaching solution oxidizes the mercury, making it soluble, and the polymer or activated carbon or other similar sorbent can remove the mercury from the water.

The precious metal is separated from the sorbent. The method for separating the precious metal from the sorbent may include destroying the sorbent. The sorbent may be destroyed by chemical, thermal and/or physical means. For example, if the sorbent is the polysulfide polymer described above, then the polysulfide polymer can be destroyed by dissolution in pyridine. Alternatively, if the sorbent is a polysulfide polymer as described above, then the polysulfide polymer may be destroyed by incineration. For example, if the gold is associated with a polysulfide polymer, then the gold can be recovered by burning the polymer. In this process, gases such as sulfur dioxide are released, which are preferably captured, wetted or decomposed. This can be carried out in a kiln equipped with a lime scrubber or by other methods commonly used for flue gas desulfurization. The combustion of the polymer can also be carried out on a small scale in a retort in which the off-gases given off by the polymer to be burned are bubbled through an aqueous solution of trichloroisocyanuric acid. Thus, components also contained in the leach solution can be used to convert sulfur dioxide to sulfate.

The third aspect relates to a sorbent containing a precious metal salt adsorbed by it, obtained by the method according to the first aspect.

The fourth aspect relates to a precious metal recovered from a precious metal-containing article or composition by the method of the first aspect.

One skilled in the art will appreciate that the above aspects of the present invention need not be limited to the description of each individual aspect, but may include features of other aspects, for example, the use according to the fourth aspect may include features of the method according to the third aspect.

DESCRIPTION OF EXAMPLES OF CARRYING OUT THE INVENTION

Example 1

Synthesis of solid polysulfide polymer

Sulfur (technical grade, 20.0 g) was placed in a 100 ml round bottom flask, which was then melted with stirring by heating to 180°C. Canola oil (20.0 g) was then added dropwise over 3-5 minutes, resulting in a biphasic mixture. The mixture was vigorously stirred to effectively mix the two phases. The mixture began to look single phase after about 10 minutes. Heating was continued for the next 10 minutes at 180°C. During this time, a rubbery solid product was formed. Then, the material was removed from the flask and stirred for 3 minutes (rotating paddle size 8.5 cm) to obtain rubber particles whose diameter was 0.2 to 12 mm and the average diameter was 2 mm. The particles were then transferred to a 250 ml round bottom flask and filled with enough 0.1 M NaOH to completely cover the particles (approximately 60 ml). The resulting mixture was stirred for 90 minutes at room temperature to remove residual hydrogen sulfide. After this time, the particles were recovered by filtration and then washed on the filter with deionized water (3 x approximately 50 ml). The particles were then removed from the filter and dried in air at room temperature and pressure for 24 hours. Typically, after this procedure, the final weight of the washed and dried polysulfide polymer particles was between 38 and 40 g (95-99% yield).

Example 2

Oxidation and dissolution of gold

Prepared a solution of the oxidant (100 mg) in water (15 ml). An additional reagent (HCl and/or NaBr) was added so that all solutions had the same total molar concentration of halide. Gold wire (1 mg) was placed in the solutions, and all solutions were kept for 8 hours at 25°C, after which the undissolved gold was removed and weighed. All prepared solutions effectively dissolved the gold. Gold dissolved most rapidly in solutions of hypochlorous acid and chlorine at pH less than 3.0 (Experiments 3, 4, 5 and 8). Although dissolution was slower in Run 7, it proceeded most efficiently at higher pH and did not require the addition of corrosive acids. In addition, TCCA is non-toxic and biodegradable, and the reagents (TCCA and NaBr) are conveniently transported as solids.

The following oxidizers were used:

The results are shown in Table 1 below:

Example 3

Preparation of Hypochlorous Acid in Situ from Trichloroisocyanuric Acid and Sodium Bromide

TSCA and NaBr were dissolved in water in a molar ratio of 1:3 and the resulting spectrum was recorded in the UV and visible region (Fig. 1). The reaction of TCCA with NaBr produces a substance having an absorption maximum at 264 nm, indicating in situ formation of hypochlorous acid (HOBr).

Example 4

Extraction of gold

The sulfur-containing polymer was obtained by reverse curing of sulfur and canola oil in accordance with Example 1 and/or previously published procedures [Chem. Eur. J. 2017, 23, 16219-16230 and WO 2017181217]. This polymer was used as a sorbent for gold ions in solution. Accordingly, a cotton tea bag (2×9 cm) containing 1 g of the polysulfide polymer was placed in the centrifuge tube solution containing 5 ppm Au ³⁺ (AuCl ₃ ). The tube was centrifuged at 25 rpm, removing aliquots (1.9 ml) of the Au ³⁺ solution for analysis after 2, 4, 6, 8 and 10 hours. After 10 hours, >99.9% of the gold was recovered from the solution and was bound to the polymer (FIG. 2).

Scanning electron microscopy (SEM) of polymer-bound gold

The polysulfide polymer used to extract gold from solution had redox activity and reduced gold ions to metallic gold. The SEM micrograph (FIG. 3) shows gold metal nanoclusters on the polymer. The composition of gold was confirmed by energy dispersive x-ray analysis (Fig. 4).

Example 5

Recovery of gold from polymer

Example 5.1: 1.0 g of a polysulfide polymer was placed in 50 ml of a 500 ppm AuCl ₃ solution for 9 hours. The polymer and associated gold were then recovered by filtration. After drying, the polymer was dissolved in pyridine (5 ml) by sonication (10 minutes). Solid metallic gold was recovered by filtration and was identified by energy dispersive X-ray analysis.

Example 5.2 Gold bound to a polysulfide polymer (1 g of polymer bound 42 mg of gold) was removed and placed in a crucible. The polymer was then burned using either a Fischer burner or an oven (>600°C). Metallic gold was recovered from the crucible in >95% yield. The recovered gold shown in Fig. 5 was identified by energy dispersive X-ray analysis (FIG. 6).

Example 6

Selective extraction of gold from a mixture of metal salts

Example 6.1: A 50 ml solution was prepared in a test tube of polymeric material, in which the final concentration of each of the following salts: AuCl ₃ , AlCl ₃ , CuBr ₂ , ZnSO ₄ , FeCl ₃ was 5 ppm. A polysulfide polymer (1 g) placed in a cotton tea bag was added to the resulting mixture of ions. The metal ion concentration was measured, after 7 hours and then again after 72 hours, by the ICP-MS (Inductively Coupled Plasma Mass Spectrometry) method. The absorption of metals is presented in the tables below, in which each of the values given represents the concentration of the metal remaining in solution (average of three repetitions of the experiment). The results obtained show that the polymer selectively extracts gold from water, while the degree of extraction of Al ³⁺ , Cu ²⁺ , Zn ²⁺ and Fe ³⁺ under the described conditions is negligible.

Table 2.

Example 6.2: A 50 ml solution was prepared in a test tube of polymeric material in which the final concentration of each of the following salts: AuCl ₃ , As ₂ O ₅ , Cd(NO ₃ ) ₂ and Pb(NO ₃ ) ₂ was 5 ppm. A polysulfide polymer (1 g) placed in a cotton tea bag was added to the resulting mixture of ions. The metal ion concentration was measured, after 7 hours and then again after 72 hours, by the ICP-MS method. The absorption of metals is presented in the tables below, in which each of the values given represents the concentration of the metal remaining in solution (average of three repetitions of the experiment). The results obtained show that the polymer selectively extracts gold from water, while the degree of extraction of As ⁵⁺ , Cd ²⁺ and Pb ²⁺ under the described conditions is negligible.

Table 3

Example 7

Full cycle of extraction and production of gold

Metallic gold (50 mg) was placed in 20 ml of a solution of TCCA (0.1 M) and NaBr (0.3 M) and kept in a tube of polymeric material without stirring for 6 days at 25°C. During this period, the gold was completely oxidized and dissolved. Then, 30 ml of water was added, followed by the addition of 1 g of a sample of canola oil derived polysulfide polymer placed in a cotton tea bag. The polymer and leach solution were mixed by inverting the container at 20 rpm. within 4 days. At the end of this time, the polymer and the sachet were removed from the solution, after which they were burned in the crucible using a Fischer burner. Pure gold (45 mg), which was identified by energy dispersive X-ray analysis (FIG. 7), was recovered in 90% yield.

Example 8

Extraction of gold from ore

The gold ore was mined from a mine in Kalgoorlie, WA, Australia. The ore was ground to a particle size of approximately 30 microns, and then 750 mg of the ore was poured into a test tube of polymeric material with 20 ml of a solution of TCCA (0.1 M) and NaBr (0.3 M) and inverted at a speed of 20 rpm. on an overturn mixer for 8 days at 25°C. After the leaching was completed, the substance was left to settle to the bottom of the tube. According to inductively coupled plasma mass spectrometry (ICP-MS), the final concentration of gold in water was 30-40 parts per million (three repetitions of the experiment). Then, 1 g of the canola oil-derived polysulfide polymer contained in a cotton bag was directly placed in the solutions, and the gold recovery rate of the polymer was determined over a period of 13 days. During this time, >97% of gold was recovered from the solution in all three samples. The presence of gold on the polymer was confirmed by energy dispersive x-ray analysis (FIG. 8).

Example 9

Oxidation of gold when exposed to ultrasound

Metallic gold (10 mg) was placed in a 25 ml round bottom flask along with 25 ml of a solution containing trichloroisocyanuric acid (290 mg) and sodium bromide (385 mg). The flask was immersed in an ultrasonic bath maintained at a temperature of 60°C. The concentration of gold leached into solution throughout the reaction was monitored using AAS (atomic absorption spectrophotometry). After 2 hours under the described conditions, >98% gold was leached into the solution, and no solid gold was visually observed in the solution at the end of the leaching procedure.

Example 10

Selective reduction and precipitation of gold in solutions containing copper and gold

Copper metal (2.00 g) and gold metal (1.00 g) were immersed in 400 ml of water, and then trichloroisocyanuric acid (8.08 g) and potassium bromide (0.95 g) were added to the solution. The solution was stirred at room temperature to oxidize and dissolve all of the copper and all of the gold. After all the copper and all the gold had dissolved, ethylenediaminetetraacetic acid (EDTA, 18.41 g) was added to the solution. The color of the solution turned from green to blue as a result of the binding of EDTA with copper. Then, ascorbic acid (1.79 g) was added to the solution, and the solution was immediately filtered to remove gold-free solids (such as precipitated trichloroisocyanuric acid or cyanuric acid). As gold was reduced with ascorbic acid in the filtered solution, metallic gold precipitated in the beaker, while copper remained in solution as a blue complex of copper with EDTA. Gold can be scraped off the surfaces of the beaker and recovered by filtration. Additional ascorbic acid may be added for complete recovery and recovery of gold.

Example 11

Extraction and recovery of gold from e-waste

In a 250 ml polymeric container, trichloroisocyanuric acid (2.91 g) and sodium bromide (43 mg) were dissolved in 125 ml of water. One contact of RAM (random access memory, eng. Random Access Memory, abbr. RAM) was cut into several pieces, which were then placed in a solution of an oxidizing agent. Then, the polymer material container was immersed in a sonication water bath and heated at 50-60° C. under sonication. Usually gold visually disappeared from the RAM contact after 2-5 hours. Analysis by atomic absorption spectrophotometry (AAS) versus dissolution in aqua regia, which quantitatively dissolves all of the gold, indicated that >95% of the gold was typically leached into the solution. To recover gold, gold can be bound with a polymeric sorbent or precipitated with ascorbic acid. According to the first method, 500 mg of a polymer obtained from sulfur and castor oil by reverse vulcanization was fixed on a porous mesh, added to the solution and aged for at least one day. The polymer was then taken out of solution, washed with water and then burned to produce gold. To reduce and precipitate gold with ascorbic acid, the solution was filtered, and EDTA was added to stabilize the copper in solution, and then ascorbic acid was added at room temperature. EDTA was added in an amount to ensure the presence of 1-3 molar equivalents in relation to the dissolved copper, the amount of which was determined by the AAS method. The amount of ascorbic acid must be at least equimolar with respect to the total amount of gold and active chlorine. The gold metal usually precipitates as gold metal or black particles and can be recovered by filtration. The yield of gold recovered by any of these methods is typically >90%.

Example 12

Combustion of a polymeric sorbent containing a precious metal and wet scrubbing of exhaust gases

5 g of the polymer sorbent of Example 1 was placed in a simple retort (Fig. 9). As the polymer was heated, it decomposed as a result of pyrolysis, and the exhaust gases left the retort. The end of the retort was immersed in a saturated solution of trichloroisocyanuric acid in water (approximately 500 ml). Trichloroisocyanuric acid (TCCA) was the same reagent as the one added to the leach solution. As the off-gases passed through the scrubbing solution, sulfur dioxide was converted to sulfate, as confirmed by ion chromatography (FIG. 10). This is a convenient and simple method of wet cleaning, which uses the same oxidizers as in the leaching of precious metal.

Example 13

Extraction and production of gold from enrichment waste

The tailings used in this Example were obtained from a historic pulp mill that used mercury to produce gold amalgam. The tailings, also referred to as crushed sand in this paper, contain a complex mixture of elements (whose composition after chemical leaching was determined by a combination of spectroscopic analysis methods, which included X-ray fluorescence analysis and inductively coupled plasma optical emission spectrometry (abbreviated OES-ICP)), as shown in the tables below.

Table 4

Table 5

Table 6

A sample of crushed sand (5.0 g) was placed in a container of polymeric material along with sodium bromide (3.0 g), trichloroisocyanuric acid (2.32 g) and water (100 ml). The mixture was stirred for 72 hours at room temperature, and then the composition of the leach solution was analyzed by the OES-ICP method. The main components of the leach solution were gold, copper, iron, mercury and nickel. The percentages of elements leached from tailings were as follows: gold (>99%), copper (13%), iron (19%), mercury (>99%) and nickel (>99%). Then, a polymeric sorbent obtained by copolymerization of sulfur (50%) and castor oil (50%) was used to extract gold. Accordingly, 1.0 g of the polysulfide polymer of Example 1 was added to the filtered solution and kept for 72 hours. 88% of the gold was recovered from the solution and bound to the polymer. The concentrations of other elements in the solution did not change. This indicates that the leach solution effectively oxidizes and leaches gold, mercury, and nickel, and some oxidizes copper and iron. It also shows that the polysulfide polymer recovers gold faster than the other components of the leach solution. The amount of oxidizer has not been optimized as this experiment was conducted to demonstrate the potential selectivity for gold leaching and recovery from complex tailings. In addition, this experiment shows that a trichloroisocyanuric acid leach solution can also be used to clean mercury from tailings. Mercury can be removed from the leach solution by adding more sulfur-containing polymer or by adding activated carbon. This method can also be used to leach mercury from soil, sludge and other mixed water and solid wastes.

Example 14

Recovery and precipitation of gold from a leaching solution under the action of ascorbic acid

Metallic gold (531 mg) was added to water (300 ml) containing trichloroisocyanuric acid (5.92 g) and sodium bromide (9.0 g). The mixture was stirred at room temperature until all gold was oxidized and dissolved. Then a 50 ml aliquot of the gold solution (1770 ppm gold) was treated with 50 ml of an aqueous solution of ascorbic acid (0.2 M). After the addition of ascorbic acid, a black precipitate formed within a few minutes. The color of the leach solution also changed from orange to light yellow as the excess oxidant was converted to halide salts and cyanuric acid. The black solid was recovered by filtration and analyzed by scanning electron microscopy (FIG. 11) and X-ray spectrum analysis (EDS) (FIG. 12). The black solid was identified as gold particles.

Example 15

Recovery and precipitation of gold from the leaching solution under the action of hydrogen gas

Metallic gold (531 mg) was added to water (300 ml) containing trichloroisocyanuric acid (5.92 g) and sodium bromide (9.0 g). The mixture was stirred at room temperature until all gold was oxidized and dissolved. Hydrogen gas was then bubbled into a 50 ml aliquot of the gold solution (1770 ppm gold) for 2 hours, during which time a black precipitate formed. A black solid was recovered by filtration and analyzed by scanning electron microscopy (FIG. 13) and X-ray spectrum analysis (EDS) (FIG. 14). The black solid was identified as gold particles.

Example 16

Extraction of gold from ore concentrates

The ore was ground in a ball mill, and fine gold particles were concentrated using an ore washing trough and a vibrating sorting table. Based on ore grade analysis by smelting, the resulting concentrates contained 75 grams of gold per tonne of concentrate (75 ppm gold in concentrates). A sample of the concentrate (246 g) and 150 ml of water were placed in a 5 L bucket of polymeric material. Magnets have been used to remove magnetic material that can react with an oxidizing agent, such as magnetite. Trichloroisocyanuric acid (4.85 g) and potassium bromide (0.285 g) were then added, and the solution was stirred with a stirrer equipped with an overhead paddle agitator coated with a polymeric material. After 24 hours, atomic absorption spectrophotometric (AAS) analysis showed that 90% of the gold was leached into solution. Another dose of oxidizing agent (1.76 g trichloroisocyanuric acid) was added to complete the oxidation and the leach solution was stirred for the next 24 hours. According to the AAS, after this time, >99% of the gold was leached into the solution. The leach solution was then filtered to remove solids and the separated liquid was treated with a polysulfide polymer derived from canola oil (9.5 g). The gold concentration was monitored by the AAS method over several days until at least 97% of the gold was recovered from the solution. This procedure has not been optimized and the gold recovery could be increased by adding more polymer. After binding with gold, the polymer was recovered by filtration and burned to give gold (FIGS. 15 and 16). Typically, gold extracted from ore by this method, after burning the polymer-gold complex, looks like an orange powder.

Example 17

Recovery of gold from mixed laboratory waste

The walls of a laboratory ion sputterer, regularly used to coat gold, silver, and chromium samples, were cleaned with mild detergent, a hard sponge, and paper towels. Metals were removed by cleaning materials from the walls of the device in the form of small metal particles. Then, used sponges and paper towels, as well as 600 ml of water, 13.92 g of trichloroisocyanuric acid (TCCA) and 1.14 g of potassium bromide were placed in a container of polymeric material with a capacity of 500 ml. The solution was kept without stirring for two days. After this time, metal particles were not visually detected. The rate of oxidation and dissolution of the metal can be increased by heating and/or sonication. The solution was then filtered to recover a liquid containing oxidized and dissolved gold. Gold can be recovered by bonding with a polysulfide polymer or by reductive precipitation with ascorbic acid, as described below. Polymer-assisted gold recovery: A portion of the leach solution (265 ml) was mixed with a total of 10 g of the polysulfide polymer of Example 1, with stirring for at least 24 hours, or until the gold concentration, according to the AAS, was reduced by >98%. The polymer was then recovered by filtration and burned on an open flame or in an oven to give gold which was isolated in 97% yield (FIGS. 17 and 18). Extraction of gold by the action of ascorbic acid: Part of the leaching solution (265 ml) at room temperature and stirring was mixed with 50 mg of ascorbic acid. After 5 minutes, the gold precipitated as a black solid (according to AAS, >98% gold was removed from the solution). The gold was recovered by filtration, and the yield of recovered gold was 93%.

Any reference in this work to the prior art is not, and should not be construed as an admission that such prior art is part of the common knowledge.

Those skilled in the art will appreciate that the use of the invention is not limited to the particular use described. In addition, the present invention is not limited to the preferred embodiments in terms of specific elements and/or features described or illustrated in this work. It should be understood that the invention is not limited to the exemplary embodiment or exemplary embodiments discussed, but may include numerous permutations, modifications and substitutions that do not depart from the scope of the invention as defined by the following claims.

Claims (20)

1. A method for extracting precious metal from an article containing precious metal or from a composition containing precious metal, including: - treating a precious metal containing article or precious metal containing composition with an oxidizing agent composition under conditions suitable for oxidizing the precious metal present in the precious metal containing article or precious metal containing composition to obtain a composition comprising a salt of the precious metal , - bringing the composition comprising the precious metal salt into contact with the sorbent under conditions in which the sorbent is capable of adsorbing at least a portion of the precious metal salt to form a sorbent containing the adsorbed material, and - extracting at least part of the precious metal from the sorbent containing the adsorbed material, wherein the oxidant composition comprises at least one halide ion source and at least one electrophilic halogen source, and wherein the electrophilic halogen source is selected from one or more of the groups consisting of hypochlorous acid, hypochlorous acid, hypobromite salts, hypochlorite salts, bromochlorodimethylhydantoin (BCDMH). 2. The method of claim 1 wherein the precious metal is gold or silver. 3. The method of claim 1 or 2, wherein the halide ion source is selected from one or more of the group consisting of sodium chloride, potassium chloride, hydrogen chloride, or one or more of the group consisting of sodium bromide, potassium bromide and hydrogen bromide, or one or more substances of the group consisting of sodium iodide, potassium iodide and hydrogen iodide. 4. The method according to any one of paragraphs. 1-3, in which the sorbent is a polymeric polysulfide obtained by the reaction of a composition based on fatty acids, including at least one unsaturated fatty acid or its derivative, with sulfur, at a mass ratio of 9:1 to 1:9, under reverse cure conditions to form a polymeric polysulfide, wherein at least 50% of the fatty acids or their derivatives in the fatty acid composition are unsaturated, preferably the fatty acid composition is a glyceride-containing composition. 5. The method of claim 4, wherein the process of recovering at least a portion of the precious metal from the sorbent containing the adsorbed material comprises reducing at least a portion of the precious metal salt adsorbed on the sorbent to form the precious metal. 6. The method of claim 5, wherein the process of recovering at least a portion of the precious metal from the sorbent containing the adsorbed material comprises separating the precious metal from the sorbent by chemically destroying the sorbent or physically destroying the sorbent. 7. The method of claim 5, wherein the process of recovering at least a portion of the precious metal from the sorbent containing the adsorbed material comprises separating the precious metal from the sorbent by thermally breaking the sorbent. 8. The method of claim 7, further comprising wet scrubbing of off gases resulting from thermal degradation of the sorbent polymer, wherein the wet scrubbing comprises passing the off gases through a scrubber containing lime or through a solution of the oxidant composition. 9. The method according to any one of paragraphs. 1-8, in which the article or composition containing a precious metal additionally includes mercury, which is oxidized with an oxidizing agent composition to form a composition including a salt of a precious metal and additionally including salts of mercury, and the sorbent selectively removes salts of precious metals from the composition, including a salt of a precious metal , with the formation of a sorbent containing adsorbed material, and a leaching solution containing a mercury salt. 10. The method of claim 9, further comprising removing mercury from the leach solution with a mercury sorbent, preferably the mercury sorbent comprising a polysulfide polymer and/or activated carbon. 11. A method for extracting precious metal from a product containing precious metal, or a composition containing precious metal, including: - treating an article containing a precious metal, or a composition containing a precious metal, with an oxidant composition comprising at least one source of a halide ion and at least one source of an electrophilic halogen, under conditions suitable for oxidizing the precious metal in the article containing precious metal, or in a composition containing a precious metal, to obtain a composition comprising a salt of a precious metal, wherein the electrophilic halogen source is selected from one or more of the groups consisting of hypochlorous acid, hypochlorous acid, hypobromite salts, hypochlorite salts, bromochlorodimethylhydantoin (BCDMH), and - removing at least a portion of the precious metal from the composition comprising the salt of the precious metal by chemical reduction, which includes treating the composition comprising the salt of the precious metal with ascorbic acid or hydrogen gas under conditions conducive to the reduction and precipitation of the precious metal. 12. The method of claim 11 further comprising adding to the precious metal salt composition a copper-binding ligand to bind copper, if present, prior to treating the precious metal salt composition with ascorbic acid or hydrogen gas, preferably the ligand copper-binding is selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), copper-binding water-soluble amino acids, and copper-binding diamines.

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