SU1766998A1 - Method of gold extraction from iodide solutions - Google Patents

Abstract

This invention relates to hydrometallurgy in the regeneration of iodine pickling solutions. 18 n. Are introduced into the solution of iodide trawler containing 280 mg of gold. sodium hydroxide solution to pH 12.8, then 0.75 ml of 30% hydrogen peroxide solution is poured to create concentration. The mixture is stirred, heated to boiling, kept at boiling for 0.5 h. The gold precipitate is separated by filtration. The gold precipitation rate is 100% with an analysis accuracy of ~ 0.1%.

Description

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This invention relates to gold hydrometallurgy and can be used to extract gold and regenerate iodide etchants.

A known electrochemical method for the extraction of gold from an iodide etching solution with simultaneous regeneration of iodine. The process is carried out with insoluble anodes at pH 4-12.8, voltage 4-5 V and temperature 50-60 ° C. The duration of the process is 2.5-6 hours. The degree of gold extraction is 99.2-99.8%, the degree of regeneration of the etchant, in terms of molecular iodine, is 99.4%) (see I F Hulkov et al. Secondary non-ferrous metals metallurgy , M: Metallurgists, pp. 449- 451).

This method has the following disadvantages:

due to the high aggressiveness of oxygen and iodine formed at the anode, strong equipment corrosion occurs (this requires special materials for the electrode to implement the method)

the losses of gold and iodine are respectively 0.2-0.8 and 0.6%;

process duration 2.5-6 hours

waste generation (alkaline or weakly acidic solutions containing potassium salts, i.e. the method allows to regenerate the main component of the pickling solution, and not the solution itself).

There is also known a method of extracting gold from solutions after etching electronic elements containing gold (0.001-0.002%) in the form of complex iodide by adding a solution to sulfuric acid in the ratio (4-10) 1. The resulting mixture is heated to boiling (150 ° C) and you are kept at this temperature for 2 hours until the iodide complex is dissolved. As a result, the reaction releases gold, submits iodine, and deposits on the walls of the refrigerator. The mixture is then cooled to ambient temperature, metallic gold is separated from the solution. Iodine is removed from the walls of the refrigerator. The degree of extraction VI o o o o o

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nor gold and iodine, respectively, 99.9 and 90% (see Polish Patent No. 115387)

The method has the following disadvantages

high energy intensity of the process (solution heating temperature 150 ° C, at least 2 h),

the complexity of the implementation of the method (the aggressiveness of elementary 12 and especially hot H2SO / I solutions imposes high requirements on the instrumentation of the method);

low degree of regeneration of iodine 90%;

pickling solution destruction and waste generation

The closest technical solution to the present invention is a method of purifying gold, including dissolving crude gold in iodide solution, removing insoluble particles from the solution and reducing the gold to metallic by adjusting the pH to at least 12 (see EP EP 0253783)

The disadvantages of the method include the low degree of gold recovery of 95-98% (139-1800 g of gold remain in the solution) and the process duration is up to 80 h

The purpose of the invention is to increase the degree of gold recovery and accelerate the process.

The goal is achieved in the method of extracting gold from iodide solutions, which involves treating the solutions with alkali metal hydroxide with stirring followed by separation of the gold deposit by introducing alkali metal hydroxide, in contrast to the prototype, to achieve a pH of 12 8 and carry out treatment in the presence of hydrogen peroxide in the amount 1-20 g / dm3 at a temperature of at least 90 ° C

It is known that an alkaline solution of potassium iodide restores gold. The method is used for the qualitative determination of gold.

walks by the equation.

KAul4 + 3KOH Au + 1/2 CUy + 7/2 KI + 3 / 2Ng X

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According to the data of the prototype and the experimental results obtained, the deposition of gold is not quantitative (92-98%). Perhaps this is due to the reversibility of the reaction (1) or the formation of unknown gold compounds.

It was established experimentally that hydrogen peroxide in an amount of 1-20 g / dm3 at pH 12.8 accelerates the process of gold extraction, allows quantitatively planting gold from the iodide of the etchant while virtually eliminating the loss of iodine. In the proposed method, hydrogen peroxide plays the role of accelerating catalyst process (1) reduction of gold with iodide ion The degree of gold deposition does not depend on the initial concentration of hydrogen peroxide (does not affect the H2U2 Au ratio) When the amount of hydrogen peroxide increases, when it is restored impressive properties (25-60 g / l) the degree of gold deposition decreases, the precipitate is fine. At 8, the gold deposition is incomplete.

It was established that, in addition to the pH and consumption of hydrogen peroxide, the degree of gold deposition depends on the time and temperature at which the process is carried out. At room temperature, gold deposition takes 8-40 hours. At 90 ° C, complete gold deposition takes 1 hour, including heating and cooling The effect of these parameters and the deposition of gold from the iodide solution is illustrated in the table

As a result of the implementation of the proposed method, after the deposition of gold, the solution contains iodide, iodate and alkali metal hydroxide. When mineral acid is added to a similar solution (after neutralizing the alkali), the following interaction occurs:

5G + + ZN20. (2)

This leads essentially to regeneration of the pickling solution.

The method is carried out as follows.

An alkali metal hydroxide solution is added to a pickling pickling solution until a pH of 12.8 is created, and then a hydrogen peroxide solution is added to create a concentration of 1-20 g / dm3. Heat to 90 ° C (or until boiling). Maintained at this temperature for 30 min, defend 0 min and filtered. The precipitate is dried. The concentration of gold is calculated in the filtrate and sediment. The degree of precipitation of gold is calculated.

In the examples, an iodide stabilizer containing g / dm3; iodine 20; one potassium 40; sodium chloride 6; gold 1.12.

Example A 250 ml beaker was placed with 250 ml of herbal iodide containing 280 mg of gold. PH meter brought pH 18 n. with a solution of NaOH up to 12.8 and then poured 0.72 ml of 30% hydrogen peroxide solution (1 g / dm3 before creating the concentration of H2O2), mixed and heated to boiling. Procippe 0.5 hours, 0.5 hours spaced

Gold precipitate was filtered. No gold was detected in the filtrate. 280 mg of gold were found in the sediment. Gold deposition degree 100%

Concentrated hydrochloric acid was added to the remaining portion of the filtrate with stirring until a pH of 6.8 was obtained. In the filtrate, the total concentration of iodine was determined - 49.6 g / dm3. The degree of regeneration of iodine is 98%. Determined the rate of etching of the gold plate. In the initial solvent, the etching rate is 11.2 mg / cm-h, in the regenerated etchant, the etching rate is 11 mg / cm2 h.

The remaining winners are similar. Information about the conditions of their implementation and the effect achieved is given in the table. Examples t.3-5, 8, 10, 13. 14 illustrate the implementation of the method using all the features indicated in the claims in the claimed HzOa consumption range. pH and temperature. Examples 2, 6. 9, 15, 16, 17 illustrate the results of an experiment in the implementation of the method with modes other than the claimed interval. Examples 10-12 show the effect of temperature. Examples 15-17 show gold deposition in accordance with the prototype. Due to the absence of the effect of pH and consumption of 1 gold deposition

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In the prototype, which are more specific than the process parameters (time, temperature), experiments were conducted under conditions close to the proposed method.

Thus, the proposed method of extracting zolbt from iodide solutions in comparison with the prototype, has the following advantages:

gold recovery rate increases from 95-98 to 99.9-100%;

The residual concentration of gold in the solution does not exceed 1 mg / l: the duration of the process decreases by 2-10 times;

As a result of the implementation of the method, no waste is generated, conditions are created for the regeneration of the pickling solution.

Claims (1)

The invention of the method of extracting gold from iodide solutions, which include treatment of solutions with an alkali metal hydroxide with stirring followed by separation of the gold precipitate, characterized in that, in order to increase the degree of gold recovery and accelerate the process, the alkali metal hydroxide is introduced until pH 12.8 is reached and treated in the presence of hydrogen peroxide in the amount of 1 -20 g / dm3 at a temperature of at least 90 ° C. degree of hydrogen oxide iodide hermit h thirty zo thirty zo thirty zo zoo zo zo zoo thirty 100.0 95, A 100.0 99.9 98.0 96.3 93.7 100.0 ten 99.6 90.6 95.9 100.0 100.0 95.0 92.0 98.0 Part of the sediment is fine - Precipitate is fine