JPS6056030A - Method for recovering high purity gold - Google Patents

Abstract

PURPOSE:To recover easily and surely high purity gold by subjecting reduced gold obtd. by a solvent extraction method to oxidation blowing, adding soda ash, melting them, forming a gold plate, and refining the plate by electrolysis. CONSTITUTION:A precipitate produced in a stage for electrolyzing copper is slurried after removing copper and arsenic from the precipitate as required, and gaseous chlorine is blown into the slurry to prepare a soln. contg. leached gold and other valuable metals. The soln. is brought into contact with a solvent such as diethylene glycol-n-butyl ether to obtain reduced gold by the selective extraction of gold. The reduced gold is subjected to oxidation blowing, soda ash is added, and they are melted. The melt is cast into a gold plate of >=about 99.5% gold grade. This plate is refined by electrolysis to recover high purity gold of >=about 99.999% purity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refining method for easily and quickly commercializing reduced gold obtained by a solvent extraction method in the form of high-purity gold. The reduced gold obtained by back-extracting and reducing the gold in the leached liquid produced by the chlorine gas leaching method using gold as a starting material is subjected to dry IW processing by oxidation blowing and soda ash melting, and then electrolytically refined. Related to high-purity gold recovery methods.

Gold is recovered not only by smelting whole ores, but also as a byproduct of smelting copper, lead, zinc, etc., and various refining methods are used depending on the raw material. Generally, these methods recover the gold bullion only after passing through several long and complicated processing steps, and they involve many problems as described below. In relatively recent years, a method has been proposed in which gold in an aqueous solution is concentrated into an organic phase using a solvent extraction method, and gold is back-extracted and reduced from there. This method alone is by no means satisfactory when applied to the treatment of substances.

Therefore, it is desired to establish a method to easily, reliably, and quickly recover gold from raw materials that coexist with various impurities in the form of high-purity gold of 99.999% or higher, but conventional methods Each has its advantages and disadvantages, and no method that is completely satisfactory has yet been found.

To explain specifically the example of copper electrolyte deposits, copper electrolyte deposits, also called anode mud, are deposited at the bottom of an electrolytic tank during the copper electrolytic refining process. This copper electrolytic precipitate contains gold, silver,
Because it contains valuable elements such as platinum group elements, selenium, and tellurium, recovering these in a short period of time with good yield and at low cost not only helps improve the profitability of the smelter, but also
This is extremely desirable for our country, which is poor in resources.

Gold is the most expensive of these valuable elements, and rationalization of the recovery method for gold is most strongly desired.

The conventional method for processing copper electrolytic materials in Japan is to collect precious metals into coarse silver metal by dry refining the copper electrolytic materials from which most of the hooks and selenium have been removed. A method of performing a branching process is being implemented, but since it is a smelting of a complex aggregate of compounds,
Since the direct extraction rate varies and smelting of the repeated material is unavoidably required, it is disadvantageous not only in terms of yield and cost but also in terms of interest rate because it takes a long time to recover. Therefore,
Recently, the chlorine gas leaching method has been attracting attention as an alternative method. In the chlorine gas leaching method, copper electrolysis materials or decoppered materials obtained by decoppering and dearsenization are made into a slurry, and chlorine gas is blown into the slurry, and gold and other valuable metals are eluted into the leachate, and silver is mixed with AgCl. The leach residue is separated from the fixed leaching residue in the form of The chlorine gas leaching method uses an aqueous slurry as the slurry into which chlorine gas is blown, a method in which the material is slurried in an aqueous solution of hydrochloric acid, and a method in which chlorides of metals of Groups 1 and 2 of the periodic table (NaCl, MgCl
2 etc.) to make the material into slurry,
The last method proposed by the applicant can reduce the amount of gold in the cargo by appropriately selecting the conditions.
It is superior to the former two in that it can elute 9.5% or more into the leaching solution and at the same time confine 995% or more of the silver in the conveyed material into the leaching residue as AgCl. In any case, the leachate in the chlorine gas leaching process is an important source of gold recovery. In addition to gold, this leachate contains Pb.

Various impurities such as Se+Te, BIHSb, Fe and others coexist. In order to efficiently recover gold from the leachate, a method with excellent selectivity for gold, such as DBC (
Solvent extraction methods may advantageously be used, such as contacting with a solvent such as (diethylene glycol-n-butyl ether). However, in the solvent extraction method, in addition to gold, impurities such as Te, Fe, and Pb are inevitably extracted simultaneously with the extract, so these impurities are also present in the reduced gold that is precipitated by adding a reducing agent to the extract. A part of this is unavoidably accompanied. Therefore, in order to make it possible to produce gold with a high purity of 99,999% or more by casting reduced gold into a raw metal plate and electrolytically refining it, Te y Fe, pb
It is necessary to take some measures to prevent impurities such as those from entering the raw metal plate. Thus, there is a desire to establish a method for simply and efficiently separating impurities from counterfeit gold obtained by solvent extraction, and this is an object of the present invention. The above is related to the process of copper electrolyte waste via chlorine gas leaching, but many of the other recovery methods currently in use also end up at the stage of obtaining reduced gold through solvent extraction. As a result, it is also necessary to remove impurities from the reduced gold in subsequent steps.

This situation 1c! As a result of many studies, the inventors have found that it is most advantageous to process the reduced gold obtained by solvent extraction using a dry process in which the reduced gold is oxidized and then melted with the addition of soda ash, followed by electrolytic treatment. I found out that this is a very effective method.

By removing Te in particular through a dry process, a raw metal plate with a total quality of over 995% can be created.
This makes purification of the gold electrolyte much easier, virtually eliminates the risk of gold contamination, and produces gold of 99.999% or higher quality with high reliability.

The above method is also particularly suitable for use in combination with the previously described method of chlorine gas leaching of the copper electrolyte followed by solvent extraction. This combination makes it possible to recover high-purity gold from copper electrolytic materials simply and quickly with high reliability. During solvent extraction, free hydrochloric acid from the leachate was extracted at α5-3N.

Preferably, it is adjusted to around 1N, and 'l'e, Fe,
In addition to minimizing the contamination of impurities such as Pb into the organic solvent, it is preferable to scrub the organic solvent carrying the extracted gold at least once to prevent contamination during extraction.
It is beneficial to wash out significant amounts of impurities such as e, Fe, and Pb. This minimizes the amount of impurities introduced during the extraction process and efficiently removes them during the subsequent dry process, making the dry process easier and more effective and ensuring the highest quality of the final gold product. The reliability of the system will also be even higher.

The advantages of the present invention compared to conventional methods can be summarized as follows.

1) Impurity management can be performed easily and reliably.

2) The entire recovery process is speeded up.

3) Since the content of impurities contained in the raw metal plate is extremely low, control of the electrolyte in the electrolysis process is extremely easy.

4) There is no need to worry about passivation of the anode.

5) Reliability of final quality is ensured.

The present invention will be explained in detail below. First, a method for leaching copper electrolyte materials with chlorine gas will be described as an example of a prerequisite step to the present invention.

Since the copper electrolytic materials still contain a considerable amount of steel and are heated at ℃, they are generally subjected to decopper removal and arsenization treatment. Various methods have already been established for copper removal, including sulfuric acid leaching, sulfated roasting, and acid leaching.

Alternatively, a method such as Fe3+ ion addition leaching may be used even if the temperature difference is ℃. Depending on the source and processing method, decoppered materials may contain Au, Ag, Cu, As, Se, Te,
Pb.

13i, Fe, Sb, S, 5tQ2, etc. in various ranges. As mentioned above, the most important target to be considered in a system for recovering these valuable elements is total recovery.

The copper electrolytic material or the decoppered material, preferably the decoppered material, is leached with chlorine gas in a slurry state in a chlorine gas leaching step. As mentioned above, water, hydrochloric acid solution, and aqueous chloride solutions of metals from Groups MI to II of the periodic table have been proposed as media for slurrying copper electrolyte materials or decopper materials. When hydrochloric acid is used, the elution rate of gold and the fixation rate of scissors are poor, so an aqueous chloride solution of metals from Groups 1 to 2 of the periodic table, such as NaCl and MgCl2, is used to slurry the material. It is convenient to measure. For example, when a hydrochloric acid slurry is used, a significant amount of the silver chloride is redissolved, reducing the total concentration in the leachate and the Ag
The silver recovery rate as a C1 residue is limited to 98.2X at the maximum, whereas when NaCl slurry is used, it is 98.2X.
A leachate in which 95% or more of gold has been eluted and a residue in which 99.5% or more of silver has been fixed as AgCl can be produced.

In the above-mentioned chlorine leaching method using metal chlorides, NaCl and MgCl2 are typically used as metal chlorides.
, BeCI 2 may also be suitably used. The metal chloride concentration is generally 1-5N, preferably 25-5.5N.

In an open or closed container, the slurry IJ- is blown with chlorine gas at a temperature of 60-80°C. The slurry is stirred by stirring blades installed in the container, for example,
It is preferable to stir at a stirring speed of 0 to 1000 rpm. The amount of chlorine gas blown is an appropriate amount to bring about the specified total elution, but it is possible to fix 99.5% or more of silver into a residue by blowing at a rate of 200 to 1500 cc/min/l slurry for 5 to 7 hours. It is possible to elute more than 99% of gold and other valuable metals. It has been found that a preferred method of blowing is to blow 15 to 3 times more into the first half than the second half. For example, 400-6 for the first 2-4 hours.
It is preferable to make the slurry 00 CC/min/l and half the amount for the remaining 1 to 4 hours. Slurry concentration is 200~4oo
g/l. If the slurry concentration is too low, the pH of the solution will drop, making it easier for silver and lead to be eluted.

In this way, chlorine gas is blown into the slurry for a predetermined period of time.
The residues retained as AgCl are converted into solid-liquid separations, and then subjected to post-processing to recover the valuable elements contained therein. The chlorine leaching method is advantageous in that it obtains the gold as a highly concentrated leachate and the silver as a concentrated leach residue in the form of AgCl from the feed early in the process. Another notable advantage is that the separation rate between gold and silver is good.

In the post-leaching solution obtained in this way, more than 99.5% of the gold contained in the material is eluted, but at the same time, Pbl
Se%Te, Bi, Sb, Fe and other impurities are also present. The leached solution is then processed by a solvent extraction method using a solvent with good selectivity for gold.

DBC (diethylene glycol-n-butyl ether) is typically used as the solvent, but methyl isobutyl ketone or a mixture thereof with isoamyl acetate may also be used. Solvent extraction is carried out by thoroughly mixing the post-leaching solution and the solvent at room temperature at an A10 ratio of 1 to 2, and then allowing it to stand to separate the organic phase and the aqueous phase,
The gold present in the leaching solution in the form of chlorides migrates to the organic phase. At this time, impurities such as Te, Fe, and Pb are also transferred.

It has been found that during extraction, the rate at which impurities are extracted together with gold is largely dependent on the free hydrochloric acid concentration of the leached solution. That is, the concentration of free hydrochloric acid in the normal solution after leaching is 6 to 8N, but this can be diluted to 0.5 to 3N, preferably 1N.
It has been found that when subjected to solvent extraction after pre-treatment, a significant amount of impurities remain unextracted. FIG. 1 is a graph showing the relationship between the extraction rate of several elements and the concentration of free hydrochloric acid. The test solution composition was 59/lAu
, 2.4 ill Fe, 100.011/lSe
, 79/lPb, 2.4 g/13 Sb and 6.
5 g/It Fe and the test was carried out at room temperature using DBe solvent at 0/A = 1/2. It can be seen that the selectivity to gold improves on the low hydrochloric acid concentration side. Free hydrochloric acid can be diluted as appropriate by methods such as partial neutralization with NaOH, adjustment to a target hydrochloric acid concentration by diluting the leachate with water, and ion dialysis.

The extracted liquid from which gold has been extracted in this way may be directly reduced and precipitated using a reducing agent such as oxalic acid, but it has been found that a considerable amount of extracted impurities can be removed by scrubbing after the extraction process. It was done. By incorporating the scrubbing step, a considerable amount of impurities are removed, which facilitates the subsequent reduction step with a reducing agent, and also has the advantage of saving the amount of reducing agent consumed for impurities. Scrubbing is performed using water or 0.5-2N hydrochloric acid at a ratio of 0/A=1 to 2, usually around 0/A=1/1. It is preferable to use dilute hydrochloric acid since phase separation is poor when using only water.

Thereafter, a reducing agent, typically oxalic acid, is added to the extracted solution and the mixture is sufficiently shaken to reduce and precipitate gold. When oxalic acid is used, by shaking at 60 to 80°C, preferably around 70°C for 2 to 4 hours, all of the gold is reduced and precipitated, and the residual gold in both the solvent phase and the aqueous phase becomes substantially zero.

The solvent extraction step is thus completed, and the obtained reduced gold is subjected to oxidation blowing and soda ash melting treatment to further remove impurities such as 'l'e, Fe, and Pb contained therein.

In oxidation blowing, reduced crude gold is melted in a heat-resistant crucible with little metal solution penetration, such as a graphite crucible, and an appropriate amount of air is blown onto the surface of the hot metal to cause an oxidation reaction, until no white smoke is produced. It is carried out by continuously blowing air. The general conditions for oxidation blowing are as follows: Air blowing amount 20-50 l/min/kg Furnace temperature 1200
~1300°C Time: 05 to 3 hours After that, a soda ash melting process is performed in which an appropriate amount of soda ash (Na2CO5) is added and maintained at a predetermined temperature until a molten slag is formed. Te migrates to slag as Na2Te03. The general conditions for soda ash melting treatment are as follows: Addition of soda ash 12 to 2 equivalents to Te (usually 15 equivalents t) Furnace temperature 1200 to 1300°C (slag solidifies at 1150°C) Time 0. After removing the molten slag for 5 to 3 hours, the entire molten metal is cast as a raw metal plate.

A raw metal plate with a total quality of 995% or more can be obtained.

Finally, the raw metal sheet is processed by electrolytic refining known as the Wohlwill process. This method uses a pure gold plate as a shade and a raw metal plate as an anode to prevent the anode from becoming passivated and making it difficult for the gold to dissolve, to improve the surface smoothness of deposited gold, and to maintain the liquid temperature. Therefore, the general electrolysis conditions are as follows: Electrolyte composition All 150-400 9/1) IC1
50 to 200 11/1 Electrolyte temperature Room temperature to 65°C Current density 300 A/m2 Superimpose alternating current on direct current (110
%) Electrolysis time: 72 hours Electrodeposited gold has a high purity of 99.999'X or higher.

Because the amount of impurities in the raw metal plate is small, it is very easy to purify the electrolyte and control the current conditions, and the possibility of contamination is also minimized. These effects make it possible to produce high-purity gold as described above. easily and reliably obtained.

Reference examples and examples are shown below.

Reference Example (Chlorine Gas Leaching from Copper Electrolyte) Copper electrolyte by-produced during copper wire cutting was 1) decoppered with e3+ ions to obtain a decoppered product having the chemical composition shown in Table 1.

(7) The decoppered material was made into a slurry with a slurry concentration of 375 g/l using 1 to 5N NaCl, and chlorine leaching was performed by blowing chlorine gas into the slurry.

The leaching temperature was fixed at 60°C and the leaching time was fixed at 6 hours. The amount of chlorine gas blown is 500CC/min/l for the first 3 hours.
The slurry was made into a slurry, and the remaining time was made into half the amount. The chemical composition of the leachate after treatment is shown in Table 2. The Ag concentration in the leachate is very low, indicating that Ag is fixed in the leach residue as AgCl. Incidentally, the leaching rate of Au is as high as 99% or more in the case of 3N NaCl. The NaCl concentration should be optimally selected depending on the slurry concentration, leaching conditions, etc.

As a representative chloride other than NacI, λ short from Group 1 of the periodic table was selected, and a rug leaching test using an aqueous MgC+2 solution slurry IJ- was conducted. Here, the decoppered material was slurried using a 3 N MgCl2 solution to a concentration of 250 g/73. Raise the leaching temperature to 80℃ and add C12 gas to 6
It blew continuously for hours. The amount of injection is 1 for the first half of the day from 0 to 3 hours.
1/min/l slurry and the latter 3 to 6 hours a, 51/
min/l slurry. The obtained leaching rates are shown in Table 3.

Table 3 0 - - 15 99.70 G, 79 1 9B, 99 9.07 2 98.44 7952 3 9185 95.23 4 9798 99.87 6 98.27 99.90 Since the slurry concentration is as low as 2509773, AgC1 It appears that the re-solubility of . AgCl recovery can be increased by properly selecting the slurry concentration.

In any case, in the CI2/metal chloride system, group I of the periodic table (Na, K, l(b, etc.)
It has been demonstrated that good results can be achieved by selecting an appropriate element from Group II (13e, Mg%, etc.).

The leachate thus produced is one of the most suitable examples for treatment according to the present invention.

Example 1 The typical composition of the reduced gold produced when the decoppered material shown in the reference example was leached with chlorine gas, the leachate was subjected to solvent extraction with DBCK, and scrubbing was performed once was simulated.
Fe24% and pb = i% using high purity electrolytic gold
A gold alloy containing was first prepared. 204 g of this alloy was melted in a graphite crucible and subjected to oxidation blowing at 1200° C. for 45 minutes (10//ml). Next, 113% of soda ash was added to the molten gold. ! i' (15 equivalents relative to Te+Pb) was added and purification was performed at 1200° C. for 30 minutes. This was cast into a raw metal plate, liquid temperature 70'C1C0D, 240A/
77L2, when electrolytically refined using an anode box, 99,
More than 999% electrical gold was obtained. The overall quality of the raw metal plate is 99.76X, and the electrolyte used is 15-1
This is a field solution as described on page 6.

Example 2 A leached solution obtained by leaching the decoppered material shown in Reference Example with chlorine gas was diluted to have a free hydrochloric acid content of 15N. The composition is as follows: This leached solution was subjected to solvent extraction using an organic solvent DBC under the conditions of O/A=1 and room temperature for 15 minutes.

The composition of the organic phase and aqueous phase after extraction is shown.

The impurity level in the organic phase after extraction is 20LX relative to the total amount.
Since the gold was retained, scrubbing was omitted and reduced gold was generated by direct back extraction reduction treatment. If the impurity level is a little higher, it is effective to perform scrubbing at least once to reduce the impurity level to this level. Reduction treatment was carried out using 140g/l oxalic acid aqueous solution at 0/A=1.
．． The test was carried out at a temperature of 70° C. and a shaking period of 5 hours for 3 hours. The reduced gold was collected by filtration. The compositions of the reduced gold produced and the organic and aqueous phases after back extraction are as follows.

The gold quality of the returned gold was 978176X. 1 refund amount
Melt at 200℃, oxidation blowing (conditions, 1200℃) and soda ash melting treatment (conditions Na2Co3Te, ≦e
1.5 equivalents based on the amount were added at 1200°C).

As a result, the gold quality increased to 99.866%.

When molten gold was cast as a raw metal plate and electrolytically refined under normal on-site electrolysis conditions, electrodeposited gold with a quality of 99.999% or higher was obtained. Due to the small amount of Pd, the amount of Pd that accumulates in the gold electrolyte is significantly reduced, and therefore the solution is easier to purify compared to current methods.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1) Reduced gold obtained from a concentrated aqueous solution of gold by a solvent extraction method is subjected to liquefaction blowing and soda ash melting treatment, and then cast as a raw metal plate, and the raw metal plate is electrolytically refined. A method of recovering high-purity gold. 2) leaching copper electrolytic precipitate or decopper-removed dispersion obtained by decoppering and dearsenizing it with chlorine gas to produce a leached liquid enriched with gold;
The reduced gold obtained from the leached liquid by a solvent extraction method,
A method of recovering high-purity gold by casting a raw metal plate after oxidation blowing and soda ash melting treatment, and then electrolytically refining the raw metal plate. 3) The method according to claim 2, which is carried out by forming a slurry with an aqueous solution of a chloride of a metal belonging to Groups (1) to (2) of the periodic table, which is prone to leaching chlorine gas, and then blowing chlorine gas into the slurry. . 4) Prior to solvent extraction, the concentration of free hydrochloric acid in the post-leaching solution is t5.
3. The method according to claim 2, wherein the temperature is adjusted to 3N. 5) The method according to claim 2, wherein the reduced gold is produced by a subsequent operation of scraping the solvent-extracted extract (organic phase) at least once.