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INVENTION
Patent of the Russian Federation RU2176279

METHOD OF PROCESSING SECONDARY GOLD-CONTAINING RAW MATERIALS
IN CLEAN GOLD (OPTIONS)

The name of the inventor: Doronicheva LA; Dzegylenok VN; Kryschenko K.I .; Bulanov VV; Lenshin ID; Tertiary AI; Obrezumov VP; Neiland AB; Nikolsky AA; Kryschenko I.K .; Bulanov Yu.V .; Vorontsov AA; Sosner EM; Kutepov A.N.
The name of the patent holder: Konstantin Konstantin; Dzegylenok Vadim Nikolaevich; Neiland Anatoly Borisovich
Address for correspondence: 123631, Moscow, ul. Isakovsky, 25-1, ap.163, V.N. Dziegilenka
The effective date of the patent: 2001.03.23

The invention relates to the hydrometallurgy of noble metals, in particular to processes for extracting gold from concentrates, wastes from the electronic and jewelry industries to produce high purity gold. In the proposed method, including the extraction of gold and its purification, all the gold recovery processes are carried out in one technological operation by electrolysis, charging the raw material into a titanium anode basket coated with a catalyst and adding to the electrolyte the salts of the metals of variable valence and the complexing agent. Gold precipitates out of the electrolyte, and the remaining metals are deposited on the cathode. In the first embodiment, the purification is carried out by any known method. In a second embodiment of the invention, purification is carried out by anodic dissolution of gold recovered in the first stage in an aqueous solution of hydrochloric acid under the application of a variable asymmetric current with deposition of pure gold to the cathode, silver chloride to the bottom of the cell, accumulation of impurities in the electrolyte, and extraction from the electrolyte with a part of gold An additional cathode equipped with an anionic or porous diaphragm. The concentration of gold and chlorides in the electrolyte is regulated by the fraction of the current passing through the additional cathode, and the precipitate from the additional cathode is returned to the first stage of gold recovery. To eliminate the deposition of gold on the bottom of the cell during the purification process, the anodes are placed in a titanium basket coated with a catalyst. The method provides environmentally safe processing of gold-bearing raw materials to produce a product with a high degree of purification with minimal metal losses, energy consumption and reagent consumption.

DESCRIPTION OF THE INVENTION

The invention relates to the hydrometallurgy of noble metals, in particular to processes for extracting gold from concentrates, wastes from the electronic and jewelry industries to produce high purity gold.

A method is known for extracting gold and silver from concentrates and dispersed secondary materials containing gold and silver, and chromium, aluminum, iron, copper, silicon, which consists in processing the raw material with a solution with a concentration of thiocyanates of 10-200 g / dm ³ and concentration Trivalent iron 0.1-5.0 g / dm ³ at a pH of 0.5-4.0 and a direct current of 0.1-10.0 A / dm ² . As the salt of ferric iron, sulfate or nitrate is used. The separation of gold and silver on the cathode, separated from the leachate by the filter membrane, is conducted simultaneously with the leaching. After the extraction of gold and silver, the solution is returned to the process. The metal precipitate is mechanically removed from the cathode and refined in any way to separate silver and gold. The degree of gold recovery is 97.8% , and silver 99.5% / 1 /.

The disadvantage of the known method is a low degree of extraction of precious metals, a low concentration of gold obtained, the use of a filter membrane.

A method for obtaining high purity gold from black gold containing impurities of silver, copper, iron, palladium, etc. is known, based on its extraction from hydrochloric acid solutions with tributyl phosphate at a molar ratio of extractant to gold (3.0-4.0): 1 s By washing the extract with a solution of sulfuric acid. The subsequent isolation of the metal is carried out by known methods. The obtained gold has a high degree of purity - 99.99% / 2 /.

The disadvantage of the method lies in the fact that , due to the large gold distribution coefficient, the reextraction of gold into the aqueous phase requires the presence of strong complexing agents (CN ^- , OH ^- ) in the aqueous phase, in particular, this method proposes reextraction to alkali, which can lead to the formation of Insoluble precipitation by some impurities. A large gold distribution coefficient leads to dilution of gold-containing solutions during the stripping process.

A method is known for purification of gold , comprising anodic dissolution of the starting material in a halogen-containing electrolyte in an electrolytic cell containing anode and cathode chambers separated by a diaphragm, followed by separation of insoluble impurities by filtration, precipitation of metallic gold from the solution by treating the solution with a reducing agent and recovering it from the solution. In this case, dissolution of the starting material is carried out in an electrolyte containing iodine and / or an iodide compound. Before removal of insoluble impurities, soluble impurities are precipitated, their removal from the solution is carried out simultaneously (together) with insoluble impurities. The reduction of the iodide compound of gold to precipitate gold is carried out at a pH of at least 12 by introducing an alkali metal hydroxide obtained by electrolysis in the cathode chamber. After separation of precipitated gold, the solution is returned to the cell for its reuse. Gold yield is 95-98% at a purity of 99.91-99.999% (3).

The disadvantage of the known method lies in the impossibility of purifying gold containing more than 1% impurities, since At a higher content (for example, silver and copper) they will be deposited on the surface of the particles of the raw material in the form of insoluble iodides and inhibit the dissolution of gold. In addition, the known method requires the use of reagents to impart soluble impurities to the sediment for their joint removal with insoluble impurities from the solution.

A method is known for processing secondary gold-bearing raw materials into pure gold , including extraction by complete dissolution of the raw material in an acidic chloride medium in the presence of an oxidizer, followed by selective precipitation of gold and subsequent purification. The realization of this method consists, for example, in dissolving raw materials in aqua regia with heating to 80-90 ^° C and intermittent mixing. Dissolution proceeds by reaction

Au + 4HCl + HNO ₃ = HAuCl ₄ + NO + 2H ₂ O

The resulting solution is decanted and settled for 4-6 hours to coagulate AgCl . The filtered AgCl precipitate is dried and routed to a melt. Gold from the clarified solution is isolated by precipitation with hydrochloric acid hydrazine or ferrous sulphate

4HAuCl ₄ + 3N ₂ H ₄ (HCl) ₂ = 4Au + 3N ₂ + 22HCl

The resulting gold-containing sludge is washed with hot deionized water and then with 10% NH ₄ OH solution for washing with AgCl to form a water-soluble complex

AgCl + 2NH ₄ OH = Ag (NH ₃ ) ₂ Cl + H ₂ O

The precipitate is then washed with a 5-10% H ₂ SO _{4 solution} for washing away iron and copper. Washing of slime from silver, copper and iron is carried out twice. The resulting slurry is dried at 150-200 ^° C , melted with nitrate at 1250 ^° C and poured into ingots, which are sent to electrolysis for cleaning / 4 / (prototype of option 1).

However, the known method of gold extraction requires the consumption of reagents (oxidants and reducing agents) and is associated with the formation of harmful and difficult to recycle waste, such as hydrochloric acid vapor, acidic aqueous solutions of metal salts, incl. With organic impurities, etc.

A method is known for processing secondary gold-bearing raw materials in pure gold , including extracting gold by completely dissolving the raw material in an acidic chloride medium in the presence of an oxidizer followed by selective gold precipitation and subsequent purification, consisting in electrolysis of gold chloride hydrochloric acid, in which the anode is an alloy of gold with impurities Ag, Cu, Fe, Pt, Pd, etc. ), and the cathode is a pure gold plate or plate of titanium. The process is carried out on a constant or alternating asymmetric current with its specific density. In the process of electrolysis, pure gold is deposited on the cathode, silver falls to the bottom of the cell as a chloride, and the remaining impurities are concentrated in the electrolyte. Polluted electrolyte is processed, recovering and returning gold to production. In the process of electrolysis, all the current on the cathode is spent on the precipitation of gold, and at the anode is spent on dissolving gold and impurities. As a result, the electrolyte is depleted in gold, and to maintain its concentration during electrolysis, it is necessary to add the hydrochloric acid (5) (prototype of variant 2) to the solution.

The drawback of the method for extracting gold (a prototype) is described above.

The drawbacks of the known method of gold purification are : its very high energy intensity, the need for frequent changes in the gold-containing electrolyte, the accumulation of impurities in which can precipitate them on the cathode and thereby lead to a reduction in the target product, the need to return a large amount of pure gold to the process to resume the electrolyte and Preparation of a concentrate of gold chloride hydrochloric acid, periodically added to the electrolyte during electrolysis. A large amount of contaminated electrolyte requires its processing in order to return to the production of gold contained in it. Separated into a precipitate in the form of chloride, silver is contaminated (up to 10% ) with gold, which reduces the yield of gold as a commodity (target) product and complicates the processing of silver chloride. Wastes obtained in the process of gold extraction and subsequent purification are hardly soluble acid solutions of metal salts.

The task, the solution of which is directed to the invention, is to create an environmentally friendly energy-saving method for processing secondary gold-bearing raw materials to produce high purity gold with the maximum yield of the final product.

The technical result of the invention consists in increasing the degree of extraction of high purity gold from any secondary gold-bearing feedstock by excluding industrial effluents and harmful gas emissions and associated loss channels for precious metal, and by reducing the return of pure gold to processing. The technical result, which consists in improving the ecology of the process, is ensured by the creation of a closed cycle without effluents at the gold extraction stage, a decrease in the volume of industrial effluents and a decrease in the content of harmful components in the purification stage, and by a reduction in harmful gas emissions in both stages. The technical result consists in simplifying the process and saving electricity by eliminating the casting of anodes at the extraction stage, and by reducing the energy costs associated with the return of gold to production.

This technical result is achieved by two variants of the method for processing secondary gold-bearing raw materials into pure gold.

Option 1
In a process involving the recovery of gold by dissolving the raw material in an acidic aqueous chloride solution, the selective precipitation from the metal gold solution and the subsequent purification by the reductant according to the invention is carried out by electrolysis by loading it into a titanium anodic basket coated with a catalyst, Chlorides of variable valence metals with a complexing agent to convert insoluble metal compounds into solutes with precipitation of impurity metals on the cathode. The process is carried out by eliminating the stirring of the electrolyte, while the electrolyte is used many times, and the purification is carried out by any known method. As metals of variable valence, iron, copper, and titanium are used in concentrations from 0.01 to 0.3 mol / l .

Option 2
In a process involving the recovery of gold by dissolving the feed in an acidic aqueous chloride solution, selective precipitation with a reducing agent from a solution of metallic gold and subsequent purification consisting in the production of anodes from recovered gold, electrolysis by anodic dissolution when an alternating asymmetric current is applied in an electrolyte containing an aqueous solution of gold chloride Acid, the precipitation of pure gold to the cathode with the accumulation of silver in the form of chloride at the bottom of the cell, and the remaining impurities in the electrolyte, in the periodic replacement of the electrolyte with the accumulation of impurities therein, and in the recovery of gold from the spent solution, according to the invention, the dissolution of the raw material is electrolyzed by its charging into Titanium anodic basket coated with a catalyst, a solution of variable-valence metal chlorides with a complexing agent is used as a chloride solution to convert insoluble metal compounds to soluble metals, with precipitation of impurity metals on the cathode. The process is carried out by preventing the electrolyte from stirring, while the electrolyte is used repeatedly. As metals of variable valency, iron, copper or titanium in concentrations of 0.01 to 0.3 mol / l is used . When gold is purified by electrolysis, the replacement of the electrolyte and the recovery of the spent gold electrolyte is carried out by moving a part of the electrolyte into a porous or anionic diaphragm with an additional cathode, previously removing from it the gold-free and chloride-depleted solution, the electrolyte is filled with distilled water in the electrolyte outside the diaphragm. During electrolysis, hydrogen, gold and other metals are released on the additional cathode placed in the diaphragm, and the precipitate from the secondary cathode is periodically returned to the primary stage of gold recovery. Anodes made from recovered gold are placed in a titanium basket coated with a catalyst. The gold content of the electrolyte during the purification is controlled by the amount of current passing through the additional cathode.

SUMMARY OF THE INVENTION CONCLUDES IN THE FOLLOWING

In the process of extracting gold from gold-bearing raw materials, dissolution and separation of metals lead to a single technological operation - electrolysis in an acidic aqueous chloride solution by introducing variable valence ( Fe, Cu, Ti ) and a complexing agent into the electrolyte of metals. At the same time, all metal components of the raw materials are transferred to the solution. On the cathode all metals are precipitated, except gold, and at the same time the oxidized form of the metal of variable valence is restored. In the electrolyte volume, selective gold precipitation occurs due to the oxidation of the reduced form of a variable valence metal, the concentration of which is selected so that other metals do not precipitate in the absence of mixing. When there is a lack of variable valence in the electrolyte of metals, a gold "breakthrough" occurs and precipitation of it together with impurity metals on the cathode. With an excess of these metals, the concentration of silver, copper and other impurities precipitated in the electrolyte volume together with gold increases, which worsens the quality of the extracted gold and complicates the subsequent purification. To prevent electrolyte mixing, it is possible in various ways: by setting the cathode and anode at a given distance from each other, placing a partition between them, etc.

The presence of the complexing agent in the electrolyte eliminates the precipitation together with gold of insoluble compounds of other metals, for example, silver chlorides.

The presence of an anode basket made of titanium coated with a catalyst makes it possible to generate an oxidizer inside the basket and in the space near it to maintain a redox potential that excludes the dissolution of metals to form compounds capable of self-oxidation-reduction to release metal powders in the bulk of the electrolyte, for example



In this case, after switching off the current, unloading the gold deposited in the electrolyte volume and removing the cathode deposit containing the remaining metals, the electrolyte is recyclable without any treatment.

The washing water from the washing of the gold powder recovered in the first stage and the cathode deposit is fully used to compensate the evaporation of water during the electrolysis process.

When gold is purified by electrolysis in hydrochloric acid (known methods), gold and metal impurities dissolve at the anode (anodes) to form chlorides, and on the cathode (cathodes), only gold is deposited, which results in a depletion of the solution in gold. The use of an additional cathode (variant 2 of claim No. 5), in a porous or anionic diaphragm that excludes the flow of gold from the electrolyte outside the diaphragm to the additional cathode, ensures that some of the current on the cathode is consumed to release hydrogen and precipitate metals. As a result, the amount of gold entering the solution from the anode becomes equal to the amount of purified gold deposited on the main cathodes. The gold content in the electrolyte does not change, there is no need to add to it a concentrate of gold chloride and, consequently, the cost of pure gold for the preparation of the chloride of hydrochloric acid.

When accumulation of impurities in the electrolyte exceeds the permissible norm, some of it is transferred to the diaphragm, from which a gold-free and chloride-depleted solution is previously removed, and distilled water is added to the electrolyte, whereas in the known methods the electrolyte is completely replaced, and a large portion of the electrolyte is consumed The amount of gold, labor and electricity. At the same time, the content of impurities in the electrolyte decreases. The gold content in the electrolyte, falling, remains within the permissible norm. When the electrolysis continues, all the metals from the electrolyte portion placed in the diaphragm are deposited on the cathode. After that, hydrogen evolution is resumed on it, and the chlorine ions return to the electrolyte through the diaphragm. If, at the same time, the proportion of the current passing through the additional cathode is increased, then the concentration of gold in the electrolyte will be restored to its original value by exceeding the dissolution of the anodes over the precipitation of pure gold to the main cathodes. When dissolved on the silver anode, it is deposited on the bottom of the cell in the form of silver chloride, contaminated with gold powder, formed in the volume of the electrolyte according to reaction



In the presence of an anodic titanium basket coated with a catalyst, oxidized forms of chlorine are formed near the anode, oxidizing the monovalent gold to a trivalent one, which excludes the formation of a gold powder.

The solution extracted from the diaphragm does not contain gold and is depleted in other metals and chlorides, therefore it does not require additional purification operations, while extraction of gold from the spent electrolyte, utilization and disposal of the spent electrolyte in the known methods is a multistage technology associated with the costs of reagents And losses of gold and other metals.

Analysis of the proposed invention for compliance with the condition of the inventive level showed the following.

A hydrometallurgical method for extracting gold is known in which a scrap containing gold alloys with non-noble metals and articles of base metals made of gold is treated in an inert atmosphere with a leaching solution in which an oxidizer containing metal ions capable of being present in at least two valence The number of metal ions should be sufficient for the oxidation of base metals. The solution also contains a complexing reagent, which includes a source of halide ions in an aqueous solution to dissolve the non-noble metal from the gold-containing scrap. As a result of treatment remains a gold-enriched solid metallic precipitate, which is collected mechanically. The ions of the oxidizing metal consist mainly of copper or iron ions. To accelerate the dissolution of base metals, agitation of the leach solution and / or its heating is used. The method may include an additional step of regenerating the oxidant ions into the higher valence form (Claim 13 of the invention), which is not included in the gold recovery process ( US Patent No. 4,668,289, NCI 75-118, published May 26, 1987 ).

The difference between the proposed method and the known method ( US Pat. No. 4,668,289 ) is that the process is carried out by electrolysis with complete dissolution of the feed, including gold and impurities, while in the known method gold does not dissolve but remains as a solid residue. The use in the known method of an oxidizer containing metal ions of variable valency in the higher form of valency is necessary for the dissolution of only impurity (ignoble) metals. The concentration and quantity of metals of variable valency is selected (as described in the US patent specification) from the consideration of dissolution of base metals without dissolving gold. Excess of the oxidant content will cause dissolution and loss of gold, and a disadvantage - reduces the gold content in the concentrate. In the proposed method, there is a complete dissolution of the raw materials, including gold, both due to metals of variable valence in the oxidized (higher) form of valence, and due to the anodic process, but also due to oxidants generated on the surface of the titanium basket coated with a special catalyst for this purpose.

Simultaneous use of both a chemical method (as in the US patent) and electrochemical with the simultaneous generation of an oxidizing agent makes it possible to achieve complete dissolution of the feed at the minimum concentrations of the substances entering the electrolyte. In the known method, the amount of oxidant equivalent to the amount of the soluble feed is required, whereas in the process of the invention the oxidant is continuously regenerated, which requires its minimum quantity and concentration.

In the proposed method, the dissolution of gold does not lead to its loss. Gold is precipitated from the electrolyte volume, selectively recovering the lower form of the variable valence metal, since in the absence of stirring of the electrolyte between the anode and the cathode, a gradient of the redox potential is established, at which the anode completely dissolves the raw materials, all metals other than gold are precipitated on the cathode, and the ions Gold can not reach the cathode, since they are chemically precipitated by a reducing agent-ions of metals of variable valence in the lower form of valency. The constancy of the concentration of these ions is maintained due to their continuous regeneration at the cathode. As a result of the fact that gold passes through the stage of dissolution and selective chemical deposition, a high degree of pre-treatment is achieved at the extraction stage, which facilitates subsequent purification.

In the method according to the invention, the impurity metals are recovered in the metal form, and in the known method, in the form of salts, which requires their further processing.

In the US patent method, a separate production step is required to regenerate the oxidant ions, and in the process according to the invention both the oxidizing agent and the reducing agent are different forms of the same variable valence metal regenerated at different electrodes.

Thus, the distinctive feature of the invention - the content of metals of variable valency in an acidic aqueous chloride solution - is not identical to the known and proposed methods, since both forms of metals of variable valence are involved in the process of gold extraction, which are continuously regenerated, whereas in the known - only one (the highest).

In connection with the foregoing, it can be concluded that the proposed method for processing the secondary gold-containing feed corresponds to the condition of the inventive step of the invention.

Example 1
The electrolyzer with a capacity of 14 dm ³ with 3 titanium cathode matrices and 2 anodes (titanium baskets coated with a catalyst) is loaded with 5 kg of jewelry scrap of the following composition:

• Mass fraction of gold 58.33%
• Mass fraction of silver 5%
• Mass fraction of copper 30%
• Mass fraction of zinc 6.67%

And a solution containing up to 10 g / dm ^{3 of} ferric iron, 10 g / dm ^{3 of} concentrated hydrochloric acid and a complexing agent in an amount of up to 50 g / dm ^{3 is} poured.

The process of dissolving the jewelry scrap is carried out by preventing mixing, for which a grid of chemical dielectric is placed between the anode and the cathode. The process is carried out at room temperature and a current density of 15 A / dm ² until 4/5 of the loaded jewelry scrap is dissolved. In the process of electrolysis, a secondary gold powder of 2.908 kg is precipitated to the bottom of the cell. Silver is deposited on the cathode - 0.24 kg , copper - 1.49 kg , zinc - 0.33 kg .

The composition of the electrolyte remains unchanged during the electrolysis process. The gold powder released at the bottom of the cell is washed with hot distilled water, a 10% solution of NH ₄ OH and a 10% solution of H ₂ SO ₄ . Flushing water is returned to the cell. The powder is dried to constant weight. As a result, 2.908 kg of powder with a mass fraction of gold of 98.5-99.0% are obtained in terms of 100% gold, and with the subsequent electrochemical purification - up to a mass fraction of gold of 99.99-99.999% .

Example 2
In an electrolyzer with a capacity of 14 dm ³ with 3 titanium cathode matrices and 2 anodes (titanium baskets coated with a catalyst), dissolve 5 kg of jewelry scrap of the following composition:

• Mass fraction of gold 75%
• Mass fraction of silver 15%
• Mass fraction of copper 10%

And pour the solution containing 8 g / dm ^{3 of} cupric copper, 10 g / dm ³ hydrochloric acid and a complexing agent up to 50 g / dm ³ . At the anode all metal components of the jewelry scrap pass into the solution. The process of dissolving the jewelry scrap is conducted at a temperature of 50-60 ^o C and a current density of 15 A / dm ² before dissolving 4/5 of the jewelry scrap. During the electrolysis, 3.743 kg of gold powder falls to the bottom of the cell, and 0.75 kg of silver and 0.5 kg of copper are deposited on the cathode. The composition of the electrolyte during electrolysis is unchanged. The gold powder deposited on the bottom of the cell is rinsed with hot distilled water, 10% NH ₄ OH, 10% H ₂ SO ₄ and dried to constant weight. In a recalculation for 100% gold, 3.743 kg of gold powder with a 98.5-99.0% gold mass fraction, and with the subsequent electrochemical purification, up to a mass fraction of 99.99-99.999% gold.

Example 3
In an electrolyzer of 14 dm ³ capacity with 3 titanium cathode matrices, 2 anodes (titanium baskets coated with a catalyst) and an additional cathode in an anionite diaphragm, which is filled to 2 dm ³ 18% hydrochloric acid, dissolve 5.0 Kg of gold concentrate in the form of cast plates prepared as described in Example 1 with a 98.5-99.0% gold content , and a solution containing 100 g / l gold and 80-100 g / l HCl is poured . The temperature of the electrolyte is maintained within the thermal resistance of the diaphragm, the total current density is 100-300 A / dm ² . When the concentration of copper chloride reaches 50 g / l in the solution, the solution from the diaphragm is pumped out, a part of the electrolyte is poured into the diaphragm, and the volume of the electrolyte is brought up with distilled water and the electrolysis continues. Gold and impurity metals, from a portion of the solution placed in the diaphragm, are extracted and deposited onto an additional cathode, and the chlorine ions through the diaphragm enter the main volume of the electrolyte. Increasing the proportion of current flowing through the additional cathode, bring the concentration of gold chloride hydrochloric acid to the original one. This operation with the replacement of the solution in the diaphragm is repeated many times than the preservation of the permissible concentration of impurity metals in the volume of the electrolyte and the extraction of the impurity metals by an additional cathode are achieved. The sediment from the additional cathode returns to the first stage of gold recovery. At the main cathodes, gold is deposited with a mass fraction of 99.99-99.999% . There is no need for additional equipment and technological operations for processing contaminated electrolyte.

USED ​​BOOKS

1. Patent of the Russian Federation No. 2,077,789 of the IPC S 25 S 1/20, publ. 20.04.1997 - formula and description.

2. Patent of the Russian Federation N 2113523 IPC From 22 V 11/00, publ. 06/20/1998.

3. The patent of the Russian Federation N 2020192 МПК With 25 With 1/20, publ. 30.09.1994.

4. "Metallurgy of precious metals" - Ed. Chugaeva L.V. - M., "Metallurgy", 1987, pp. 346-350 - prototype of variant 1.

5. "Metallurgy of precious metals" - Ed. Chugaeva L.V. - M., "Metallurgy", 1987, pp. 346-350, 328-331 - prototype of the variant 2.

CLAIM

1. A method for processing secondary gold-bearing raw materials in pure gold, including extracting gold by dissolving the raw material in an acidic aqueous chloride solution, selectively precipitating the reducing agent from a solution of metallic gold and then purifying it, characterized in that dissolving the raw material is electrolyzed by charging it into a titanium anode basket coated Catalyst, a solution of variable-valence metal chlorides with a complexing agent is used as a chloride solution to convert insoluble metal compounds into solutes with precipitation of impurity metals on the cathode, while the process is conducted preventing the stirring of the electrolyte.

2. The process according to claim 1, characterized in that iron, copper or titanium are used as valence metals in concentrations from 0.01 to 0.3 mol / l .

3. The method according to claim 1 or 2, characterized in that the electrolyte is used repeatedly.

4. A process according to any one of claims 1 to 3, characterized in that the purification is carried out by any known method.

5. A method for processing a secondary gold-containing feedstock into pure gold, including extracting gold by dissolving the feed in an acidic aqueous chloride solution, selectively precipitating the reducing agent from a solution of metallic gold, and then purifying, including producing anodes from the recovered gold, electrolysis by anodic dissolution in an electrolyte containing an aqueous solution of gold chloride Acid with the application of variable asymmetric current, with the deposition of gold on the cathode and the accumulation of silver in the form of chloride at the bottom of the cell, and the remaining impurities in the electrolyte, the periodic replacement of the electrolyte with the accumulation of impurities in it and the recovery of gold from the spent solution, Electrolysis by charging it to a titanium anodic basket coated with a catalyst, a solution of variable-valence metal chlorides with a complexing agent is used as a chloride solution to convert insoluble metal compounds into soluble metal compounds with precipitation of impurity metals on the cathode, while the process is conducted, preventing electrolyte mixing, during gold purification Replacement of the electrolyte and recovery from the spent electrolyte of gold is carried out by moving a part of the electrolyte into a porous or anionic diaphragm with an additional cathode, a gold-free and chloride-depleted solution is extracted from it first, distilled water is added to the electrolyte outside the diaphragm, additional hydrogen, gold and Other metals, and the precipitate from the secondary cathode is periodically returned to the gold recovery stage.

6. A process according to claim 5, characterized in that iron, copper or titanium in concentrations of 0.01 to 0.3 mol / l is used as the metals of variable valence.

7. The method according to claim 5 or 6, characterized in that the electrolyte is repeatedly used in the gold recovery step.

8. A process according to any one of claims 5 to 7, characterized in that the anodes made of recovered gold are placed in a titanium basket coated with a catalyst.

9. The method according to any one of claims 5 to 8, characterized in that, during purification, the gold content in the electrolyte is controlled by the amount of current passing through the additional cathode.

print version
Date of publication 01.12.2006гг

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