JP3286212B2 - Method for purifying gold electrolyte containing Pd - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying a gold electrolyte, and more particularly to a method for purifying a gold electrolyte containing a relatively large amount of Pd at a low Pd concentration every time. The present invention relates to a method for purifying a gold electrolyte solution that can easily remove Pd from a solution after each electrolysis.

[0002]

2. Description of the Related Art In the electrorefining of gold, anode slime from electrolysis of silver is treated with nitric acid to dissolve Ag, Pd, etc.
u: 95 to 98%, Ag: 1 to 3% is used as a raw metal plate for the anode, and a thin plate of pure gold or electric gold is used as a cathode to perform electrolysis by a so-called “Wholwill” method. It is carried out by precipitation. The gold deposited on the cathode is called electric gold. As the gold electrolyte, a solution prepared by dissolving crude gold in concentrated hydrochloric acid by a liquid electrolysis method or by using concentrated hydrochloric acid and aqueous hydrogen peroxide is diluted and used. The free hydrochloric acid concentration is between 50 and 200 g / l.

A gold electrolyte generally contains about 100 g / l of gold and, as impurities, Pd, Pt, Te, Ti, Fe, C
u and the like. The impurity concentration often depends on the grade of the ore used. The electrolytic solution of gold is performed using this electrolytic solution. As the electrolysis proceeds, impurities such as Pd and Pt contained in the anode elute, and the impurity concentration in the electrolytic solution gradually increases. This leads to a situation where the purity is deteriorated.

[0004] In recent years, depending on the ore used, the Pd content may increase in some cases.
0.3 to 0.9 g / l of P is contained in the post-electrolysis solution after the second electrolysis.
d, in which case the Pd content of the electric gold is around 5 ppm, and the post-electrolysis solution after the second electrolysis has a Pd content of 0.1 ppm.
6 to 1.8 g / l of Pd, in which case P
The d-content reaches around 10 ppm and is no longer above the permissible limit.

[0005] Therefore, in the conventional method, in order to prevent contamination of electric gold due to an increase in the Pd concentration in the electrolytic solution, the entire amount of the electrolytic solution is treated after the completion of the second electrolysis. FIG. 3 shows a flow sheet of a step of reducing the entire amount of the post-electrolysis solution with copper powder after the completion of the second electrolysis according to the conventional method (also referred to as a Cu replacement liquid purification method). Here, after the completion of the second electrolysis, the entire amount of the post-electrolysis solution was reduced by adding copper powder, separated by filtration and washing into reduced gold and a filtrate, and the reduced gold was subjected to nitric acid parchmentation, dissolved anodized, and subjected to gold electrolysis. Then, while the product is produced as electric gold, the filtrate separated from the reduced gold is reduced with zinc and separated into a reduced product containing Pd and a filtrate. The reduced product is returned to the refinement process, and the filtrate is discarded after iron reduction. It had been. Further, the filtrate generated by the nitric acid parchmenting of the reduced gold is put into a Pd recovery step to produce it. These steps take a number of days in total, for example around a week, and this work has to be performed every two electrolysis ends, which has resulted in considerable stagnation rates.

As another method for purifying a gold electrolytic solution, for example, Japanese Patent Application Laid-Open No. 1-127691 discloses a method in which chlorine gas is blown into an electrolytic solution continuously extracted from an electrolytic cell and ammonium carbonate or the like is removed from the electrolytic solution. Free hydrochloric acid concentration of 80 to 140
g / l, and the temperature of the resulting slurry is 3
It describes that after the impurities such as platinum, palladium and silver are separated into solid and liquid by lowering the temperature to 0 ° C. or lower, the obtained purified liquid is repeatedly used in an electrolytic cell. However, this method
It was necessary to blow chlorine gas into the electrolyte and lower the temperature of the slurry once to 30 ° C. or lower, and it was not necessarily effective in the case of an electrolyte having a high Pd content.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to reduce the stagnation interest rate and to improve the quality of electric money every time by setting a low P.
An object of the present invention is to establish a simple method for purifying a gold electrolyte, which enables electrolysis at a concentration of d.

[0008]

The present inventors have noticed that dimethylglyoxime chelate (hereinafter abbreviated as DMG) forms a complex with Pd and is used as a reagent for quantifying Pd. And examined the feasibility of applying gold electrolyte containing various components to the purification site. As a result of the examination,
It was confirmed that Pd can be removed by adding dimethylglyoxime in the form of a powder or an ethanol solution to a Pd-containing gold electrolyte and reacting it. Based on this finding, the present invention provides a Pd-containing gold electrolyte solution to which dimethylglyoxime is added in the form of a powder or an ethanol solution to cause a reaction, precipitates a generated Pd complex, and removes the precipitate from the gold electrolyte solution. P characterized by separating
A method for purifying a gold electrolyte containing d. Practically, it is carried out by adding dimethylglyoxime in the form of a powder or ethanol solution, reacting with stirring, and then ripening the precipitate. Specifically, a gold electrolyte containing Pd is a post-electrolysis solution each time, and a post-electrolysis solution obtained by separating a precipitate is used for each electrolysis. Excess DM
When G is added, there is a danger that Au in the liquid will also precipitate. Therefore, it is preferable to add 1 to 1.2 equivalents of Pd of DMG. The sediment has a fine particle, so
It is recommended to separate with a filter of 1.2 μm mesh, for example 1 μm mesh.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow sheet of a process for purifying an electrolytic solution each time according to the present invention. The gold electrolyte generally contains about 100 g / l of gold and Pd and P as impurities.
It contains t, Te, Ti, Fe, Cu and the like. The electrolytic solution of gold is performed using this electrolytic solution. As the electrolysis proceeds, impurities such as Pd and Pt contained in the anode elute, and the impurity concentration in the electrolytic solution gradually increases. This leads to a situation where the purity is deteriorated. In recent years, the content of Pd has been increasing due to the ore used. For example, the post-electrolysis solution after the first electrolysis contains 0.3 to 0.9 g / l of Pd. Has a Pd content of about 5 ppm. 0.6 to 1.8 g in the post-electrolysis solution after the second electrolysis
/ L of Pd, in which case the Pd content of the electrogold reaches around 10 ppm, which is no longer acceptable. Therefore, conventionally, after the second electrolysis, as shown in FIG.
After the electrolysis, the entire amount of the solution was reduced by adding copper powder, and separated by filtration and washing into reduced gold and a filtrate.The reduced gold was subjected to nitric acid parchmenting, dissolved anodized, gold electrolyzed, and commercialized as electric gold. However, it took many days. In the present invention, methylglyoxime (DMG)
Is used to purify the gold electrolyte and always maintain the Pd content of the gold electrolyte at the Pd level of 0 to 0.9 g / l after one electrolysis.

[0010] Each electrolysis solution is analyzed by, for example, atomic absorption spectrometry in order to quantify its Pd content. Then, the amount of dimethylglyoxime (DMG) to be added is determined from the Pd content. If excess DMG is added, Au in the solution may also precipitate, so it is preferable to add 1 to 1.2 equivalents of DMG to Pd.

DMG corresponds to diacetyldioxime or 2,3-butanedionedioxime, and is a white crystal. Although it is known as a quantitative reagent for Pd, Fe, etc., it requires a large amount of treatment, and it is unknown whether it can be used for Pd removal at a purification site of a gold electrolyte containing various components. Was. DMG is added to a gold electrolyte in the form of a powder or an ethanol solution and reacted with stirring to form a complex with Pd and precipitate and separate. Precipitation and aging of the Pd-DMG complex requires, for example, 10 to 20 hours, and this can be performed, for example, by keeping the mixture still at night.

Thereafter, the precipitate is separated into a Pd precipitate and a filtrate by filtration, the Pd precipitate is sent to a refining process, and the filtrate is subjected to an electrolysis process as a purified gold electrolytic solution. Thus, electrolysis is always performed while maintaining the Pd content within the Pd level of 0 to 0.9 g / l after one electrolysis. Pd
-DMG complex precipitates are very fine particles, easy to pass through the filtrate at the time of filtration, adhere to the electric gold when the precipitate enters the electrolytic solution, the Pd content in the product is high, the mesh size is small, For example, it is necessary to use a 0.8-1.2 μm mesh filter. For example, while filtering with two sheets of filter paper, cartridge filter (1μ)
m filter) can avoid such a situation.

The total time required for purification is generally 18 to 19 hours, depending on the throughput. Purification must be performed at room temperature. This is because when the temperature rises to about 60 ° C,
This is because Pd is re-eluted due to the decomposition of Pd-DMG. The conventional treatment using the total Cu replacement method may be performed once every six months (about 25 times of electrolysis). In this way, the purification using the DMG according to the present invention is carried out for each electrolysis, and the purification is carried out once every six months (about 25 times of electrolysis) by the Cu total replacement method, thereby reducing the stagnation interest rate and reducing the Pd of electric gold. By maintaining the content at 1 to 3 ppm, gold electrolysis can be effectively performed for a long time.

[0014]

EXAMPLE The results of a beaker test and an actual operation test are shown.

(Beaker test) In 500 ml of a simulated electrolyte having a Pd concentration of 253 mg / l,
The equivalent amount was added. The liquid temperature is 20 ° C. DM
G addition is as powdered DMG (solid DMG) and 1 g / g
(Liquid DMG) was carried out as C ₂ H ₅ OH solution 100 ml. The results are shown in the graph of FIG. The Pd concentration dropped sharply up to a reaction time of 20 minutes, after 20 minutes the Pd concentration dropped to 30 mg / l for solid DMG and to 38 mg / l for liquid DMG. It can be seen that the Pd concentration decreases dramatically. Subsequent changes in Pd concentration are small.

(Actual test) Gold concentration: 100 g / l, silver concentration: 0.1 g / l, platinum concentration: 0.1 g / l, palladium concentration: 0.2 g / l, free hydrochloric acid concentration: 100 g / l
Then, gold electrolysis was performed by using an electrolysis starting solution containing a trace amount of impurities such as Te, Ti, Fe, and Cu, using coarse gold as an anode and an electric gold thin plate as a cathode. The electrolysis conditions were as follows: the electrolysis current was +200 A on average, −50 A, using an unhealthy rectification with the −AC side partially cut, and the anode current density was 33%.
3 A / m ² , the cathode current density was 250 A / m ² , and the electrolysis temperature was 50 ° C. The energization time was 65 hours.

The Pd concentration of the electrolyzed solution after one electrolysis is 0.3 to 0.9 g / l on average, and the Pd concentration of
pm. By the way, Pd of post-electrolysis solution after double electrolysis
The concentration is 0.6-1.8 g / l on average and the Pd
The concentration was 10 ppm. To the post-electrolysis solution after one electrolysis, 1.1 equivalents of DMG powder were added while stirring, and the mixture was subjected to precipitation aging for 16 hours. The operation of filtering with two filter papers, performing filtration using a cartridge filter (1 μm filter), and performing electrolysis using the filtrate was repeated.
One purification operation required 18.5 hours. The Pd content of the post-electrolysis solution was maintained at 0 to 0.9 g / l, and the Pd content of electric gold was maintained at 3 to 6 ppm. After 10 months (50 times electrolysis) the content of impurities in the solution after electrolysis was as follows: Pt: 1.64 g / l, Te: 0.18 g / l, Ti:
0.003 g / l, Fe: 0.17 g / l, Cu: 0.
26 g / l As described above, when the purified solution according to the present invention is used for each electrolysis,
Even after 10 months of continuous use, the content of impurities in the post-electrolysis solution is very low.

[0018]

According to the present invention, the stagnation interest rate is reduced, and the Pd content of electric gold is maintained at 1 to 3 ppm, so that gold electrolysis can be effectively performed for a long time.

[Brief description of the drawings]

FIG. 1 is a flow sheet of a process for purifying an electrolytic solution each time according to the present invention.

FIG. 2 shows a Pd-containing electrolyte as powdered DMG (solid DM
G) and a graph showing the results of adding DMG (liquid DMG) as a 1 g / 100 ml C ₂ H ₅ OH solution.

FIG. 3 is a flow sheet showing a step of reducing the whole amount of the post-electrolysis solution with copper powder after the completion of two times of electrolysis according to a conventional method.

Continuation of front page (56) References JP-A-1-127691 (JP, A) JP-A-61-104095 (JP, A) JP-A-2-254191 (JP, A) JP-A-53-77827 (JP) , A) Japanese Patent Publication No. 55-1994 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25C 1/00-7/08

Claims (4)

(57) [Claims] 1. A reacted with dimethylglyoxime in hydrochloric acid gold electrolyte containing Pd was added and stirred in the form of a powder or an ethanolic solution to precipitate the Pd complex to produce, aged after which the precipitate gold A method for purifying a Pd-containing gold electrolyte, comprising separating a precipitate from the electrolyte. 2. The method for purifying a gold electrolyte according to claim 1, wherein the gold electrolyte containing Pd is a post-electrolysis solution each time, and the post-electrolysis solution obtained by separating a precipitate is used for each electrolysis. 3. The method of claim 1, wherein the dimethylglyoxime is composed of Pd.
2 solution purification process according to claim 1 or 2 gold electrolyte equivalents are added. Wherein the precipitate and separating a filter of 0.8~1.2μm mesh claim 1 or
3. The method for purifying a gold electrolyte according to any one of the above items 3 .