RU2443791C1 - Conditioning method of cyanide-containing reusable solutions for processing of gold-copper ores with extraction of gold and copper and regeneration of cyanide - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves treatment of solutions with water-soluble sulphide with addition of acid and deposition of copper sulphide. After the deposition there performed is filtration on a press filter with extraction of copper sulphide and treatment of filtrate with alkali solution. Copper sulphide deposition and cyanide regeneration is performed prior to gold extraction. At that, addition of sulphide and acid till pH-3.5-4.5, as well as treatment of filtrate with alkali solution is performed at normal pressure with further extraction of gold from filtrate.

EFFECT: simplifying the implementation of the process.

3 ex

Description

The invention relates to the field of hydrometallurgy, in particular to technologies for conditioning working solutions in the processing of gold-copper ore materials and organizing recycled water supply.

In the process of processing gold-copper ore materials by the planning method, a large amount of copper in the form of cyanide complexes is transferred to the technological solution along with noble metals. Additional cyanide is expended on the dissolution of copper. The reuse of such solutions in the circulating water supply system leads to a cumulative increase in the concentration of dissolved copper, which binds cyanide into an inactive form and negatively affects the processes of gold recovery. In some cases, the active dissolution of copper makes the processing of gold-copper ore materials unprofitable due to the high cost of reagents for processing raw materials and waste disposal, as well as because of the low recovery rates of precious metals.

A known method for the extraction of copper from copper ores and concentrates by cyanide solutions using precipitation of dissolved copper by treatment with water-soluble sulfide and precipitation of copper sulfide at pH below 5.0 with distillation of hydrocyanic acid in the form of gas with air or steam from acidified solutions and subsequent capture of distilled hydrocyanic acid with alkali solutions of sodium or calcium hydroxide for reuse (US No. 1050303, C22b 15/08, 12/07/1966).

The disadvantages of the method are: - the presence of the operation of distillation of hydrocyanic acid with its subsequent capture makes this method difficult, both in hardware and in operation; - the conversion of hydrocyanic acid (a highly toxic compound) into the gas phase makes the process potentially dangerous.

The closest, in technical essence to the claimed solution, is the prototype method for removing copper, possibly gold and silver, by leaching oxidized and sulfide-containing materials with cyanide-containing solutions, including processing solutions that have passed the stage of gold and silver adsorption on activated carbon with a water-soluble sulfide component (sulfide sodium or sodium hydrosulfide) with the addition of acid to achieve a pH of 1.5-2; and the deposition of metal sulfides at a pressure above atmospheric pressure of 1.5-15 bar, filtering on a press filter with the separation of metal sulfides, treating the filtrate with an alkaline solution at an elevated pressure of 1.5-15 bar using an alkali-treated filtrate in leaching cycles ( US No. 4587110, C01G 3/12, 05/06/1986).

The disadvantages of this method:

1. Operations are carried out on solutions that have passed the stage of adsorption of gold and silver on a sorbent - activated carbon. Accordingly, in the previous adsorption operation of gold and silver on activated carbon, a solution with a high copper content is supplied. In the process of adsorption on activated carbon, not only gold is extracted, but also copper. Depending on the concentration of copper in the initial solution, the copper capacity for copper can be an order of magnitude or more higher than the capacity for gold. At the same time, the capacity of the sorbent for gold decreases, the process of desorption of gold from a saturated sorbent is complicated (two stages of desorption are carried out, the first is desorption of copper, the second is desorption of gold to reduce the high residual coal capacity for gold), the quality of the cathode deposits obtained by electrolytic metal deposition is deteriorating from eluates (low fineness of precipitation, problems of closure of plate cathodes with a high copper content in eluates, etc.).

2. The addition of an acid to the treated solution to a pH of 1.5–2 creates the possibility of the precipitation of the toxic compound CuCN (copper cyanide) and this toxic compound contaminates the resulting precipitate of copper sulfide. Gold that is not extracted to activated carbon is also removed into the resulting copper sulfide precipitate, which, when the treated solution is recycled, is a loss of a valuable product.

3. The operations of the reagent treatment and deposition of metal sulfide, the treatment of the filtrate with an alkaline solution are carried out at a pressure of 1.5-15 bar, which requires the use of apparatuses operating under pressure and quite difficult to operate and manage.

4. The above operations with hydrocyanic acid solutions under pressure are dangerous from the point of view of safety. The depressurization during the transfer of such solutions to planning operations carried out at normal pressure can lead to the release of dissolved hydrocyanic acid into the atmosphere of the workshop. To eliminate this, it is necessary to implement special measures that complicate the process.

The objective of the invention is to remedy these disadvantages due to the technical result, which consists in creating conditions that can improve the quality of the process.

The technical result is achieved by the fact that in the method of conditioning cyanide-containing working solutions with the extraction of gold and copper and the regeneration of cyanide, including treating the solutions with water-soluble sulfide with the addition of acid and precipitating copper sulfide, filtering on a press filter with separation of copper sulfide, treating the filtrate with an alkaline solution, according to The invention deposition of copper sulfide and the regeneration of cyanide is carried out before the extraction of gold, while adding sulfide and acid to a pH of 3.5-4.5, as well as processing ltrata alkaline solution is carried out at normal pressure, followed by extraction of gold from the filtrate.

The essence of the method is as follows. The reverse gold-containing technological solution enters the contact tanks for treatment with solutions of sodium sulfide and sulfuric acid to a pH of 3.5-4.5. Next, a solution containing a precipitate of copper sulfide enters the press filter. The filtrate is sent to the contact vat, where it is alkalized to the desired pH (10.5-11.0) with sodium hydroxide solution or lime. The alkalized solution is fed to the gold extraction operation, and then used in the water recycling system.

The difference of the proposed method from the prototype is that the process is carried out on gold-containing cyanide solutions, at normal atmospheric pressure they are treated with sulfide ions with the simultaneous introduction of mineral acid to reduce the pH value of 3.5-4.5, decomposition of metal cyanide complexes with the formation of precipitate poorly soluble copper sulfides and hydrocyanic acid (HCN) remaining in solution:

The resulting mixture of solution and precipitate was separated by filtration.

Filtration cake consists mainly of copper sulfide and is a high-quality copper concentrate. It is recommended to implement it as a marketable product.

The filtrate containing dissolved hydrogen cyanide is made alkaline to the required pH (10.5-11.0) with sodium or calcium hydroxide. In this case, free cyanide suitable for dissolving ore gold is generated from dissolved hydrogen cyanide:

The alkaline filtrate is sent to a gold recovery operation. The anhydrous solution is circulating and reused in the process of gold leaching, if necessary, having strengthened with cyanide.

The claimed processing regimes (pH 3.5-4.5, normal pressure) make it possible to obtain a precipitate of copper sulfide without impurities of simple copper cyanide (the toxicity of cake obtained as a commercial product is reduced) and without precipitated gold (loss of valuable precious metal is excluded).

The advantages achieved by the application of the claimed invention:

1. The conditioning operation before the extraction of gold can significantly improve the performance of the subsequent extraction of precious metal. When dissolved copper is removed, gold is extracted from decoupled solutions and the interfering effect of dissolved copper cyanide complexes on the processes of precious metal extraction by sorption methods on ion-exchange resins or activated carbons, by cementation, direct electrolysis is eliminated.

2. The addition of an acid to the treated solution to a pH of 3.5-4.5 eliminates the possibility of the formation of a highly toxic precipitate of copper cyanide and contamination of the copper sulfide obtained as a commercial product. Precipitation of dissolved gold is also eliminated - the possibility of losing this expensive metal is eliminated. Acid consumption for acidification and alkali operations for alkalization is reduced.

3. The elimination of the need for technological operations (adding sulfide and acid, processing the filtrate with an alkaline solution) under pressure allows the use of equipment conventional for hydrometallurgical production, and simplifying its maintenance. The absence of pressure drops during the transfer of conditioned working solutions to the gold recovery operation increases the industrial safety of the technology as a whole.

The method is illustrated by the following examples.

Example 1 (Prototype).

The technological solution (composition: Cu - 810 mg / L, CNtotal - 1110 mg / L, CNsav. - 95 mg / L, Au - 4.8 mg / L) was desalted by sorption on activated carbon. Along with noble metals, copper was adsorbed onto coal. In total, 97.1% of gold and 9.9% of copper were extracted from coal, the content in the working solution decreased Au to 0.14 mg / L, Cu to 730 mg / L. The coal capacity for gold was 3.5 mg / g, for copper - 60.1 mg / g.

Na ₂ S solution was added to the anhydrous solution in the first mixer under a pressure of 2 bar. Then, H ₂ SO _{4 was} added to the first mixer under pressure until a pH of 1.8 was reached. The resulting copper sulfide is separated by filtration on a press filter. The filtrate is directed to a second mixer. In this mixer, NaOH solution was added under a pressure of 2 bar until a pH of 10.5 was reached. The reagent consumption amounted to: Na ₂ S - 0.65 g / l, H ₂ SO ₄ - 3.2 g / l, NaOH - 3.15 g / l.

The filter cake contains: Cu - 65.1%, including in the form of simple copper cyanide 7.6%, Au - 0.1 kg / t.

The working solution after alkalization contains: Cu - 9.8 mg / l, CNtotal. - 920 mg / l, CNsvob. - 910 mg / l, Au - 0.03 mg / l.

Example 2 (claimed invention)

A Na ₂ S solution was added to the gold-containing solution (composition: Cu - 810 mg / L, CNtotal - 1110 mg / L, CNvol. - 95 mg / L, Au - 4.8 mg / L) in the first mixer at normal pressure. Then, H ₂ SO _{4 was} fed into the first mixer at normal pressure until a pH of 3.5 was reached. The precipitate of copper sulfide formed is separated by filtration on a press filter. The filtrate is directed to a second mixer. In this mixer, at normal pressure, a NaOH solution was added until a pH of 10.5 was reached. The reagent costs were: Na ₂ S - 0.65 g / l, H ₂ SO ₄ - 2.5 g / l, NaOH - 2.52 g / l.

The filtration cake contains: Cu - 66.8%; gold and simple copper cyanide were not found in its composition.

The composition of the solution after separation of the precipitate: Cu - 10.2 mg / L, Au - 4.8 mg / L.

This solution was desalted by sorption on activated carbon.

The gold capacity of coal is 4.6 mg / g, the copper capacity is 0.9 mg / g.

The composition of the solution after dehydration: Cu - 9.3 mg / l, CNtotal. - 1090 mg / l, CNsvob. - 1080 mg / l, Au - 0.02 mg / l.

Example 3 (claimed invention)

A Na ₂ S solution was added to the gold-containing solution (composition: Cu - 810 mg / L, CNtotal - 1110 mg / L, CNvol. - 95 mg / L, Au - 4.8 mg / L) in the first mixer at normal pressure. Then, H ₂ SO _{4 was} fed into the first mixer at normal pressure until a pH of 4.5 was reached. The precipitate of copper sulfide formed is separated by filtration on a press filter. The filtrate is directed to a second mixer. In this mixer, at normal pressure, a NaOH solution was added until a pH of 10.5 was reached. The reagent consumption was: Na ₂ S - 0.65 g / l, H ₂ SO ₄ - 2.1 g / l, NaOH - 2.18 g / l.

The filtration cake contains: Cu - 66.9%; gold and simple copper cyanide were not found in its composition.

The composition of the solution after separation of the precipitate: Cu - 10.1 mg / L, Au - 4.8 mg / L.

This solution was desalted by sorption on activated carbon.

The coal capacity for gold is 4.5 mg / g, the copper capacity is 0.8 mg / g.

The composition of the solution after dehydration: Cu - 9.2 mg / l, CNtotal. - 1100 mg / l, CNsvob. - 1090 mg / l, Au - 0.02 mg / l.

The implementation of the process according to the proposed method allows to eliminate the disadvantages of known technologies, including the prototype method, to improve the performance of conditioning technologies for recycled water and gold recovery using this recycled water:

1. Significantly reduce the concentration of copper in the solutions supplied to the operation for the extraction of gold, and thereby increase the performance of this operation. So, in the case of using gold extraction with activated carbon, the capacity of saturated coal for copper decreases by ~ 60-70 times with a simultaneous increase in its capacity for gold and an increase in the degree of solution deoxidation, the regeneration of coal and the electrolysis of the resulting eluates are simplified, and the quality of cathodic deposits is improved. With the extraction of dissolved gold by other processes - ion exchange resins, cementation, direct electrolysis, the technologies are also simplified, the performance also improves due to a significant decrease in the concentration of copper competing with gold.

2. To obtain a precipitate of copper sulfide, which is a highly liquid commercial product - high-quality copper concentrate, without impurities of simple copper cyanide. To eliminate the phenomenon of the transition of gold into a copper sulfide precipitate - when recycled use of conditioned solutions, the presence of gold in a copper precipitate is a loss of an expensive precious metal.

3. Eliminate the need to add reagents and conduct operations under pressure. This greatly simplifies the design of the equipment used and makes it cheaper, and maintenance is also simplified. The use of equipment operating at normal pressure increases the industrial safety of the process.

4. To reduce the costs of sulfuric acid and alkali in the conditioning process to optimally sufficient. Increase the content of free cyanide suitable for gold recovery in solutions.

Claims (1)

A method for conditioning cyanide-containing recycled solutions of gold-copper ore processing with gold and copper recovery and cyanide recovery, comprising treating solutions with water-soluble sulfide with the addition of acid and precipitating copper sulfide, filtering on a press filter with separation of copper sulfide, treating the filtrate with an alkaline solution, characterized in that copper sulfide and cyanide regeneration is carried out before gold recovery, while the addition of sulfide and acid to a pH of 3.5-4.5, as well as alkaline filtrate treatment th solution is carried out at normal pressure, followed by extraction of gold from the filtrate.