JPS58197233A - Manufacture of high purity gold from intermediate treated liquid of slime generated in copper electrolysis - Google Patents

Abstract

PURPOSE:To recover high purity gold in a high yield from a gold soln. prepared by treating slime subjected to treatment for removing Cu and Se with chlorine by adding a reducing agent such as ferrous salt to the soln. and by specifying the end of the precipitate forming reaction. CONSTITUTION:Slime subjected to a treatment for removing Cu and Se is converted into an aqueous slurry, and gold is leached into the liq. to prepare a gold soln. by blowing gaseous chlorine. The soln. contains Cu, Se, Te, Pd, Pt, etc. besides gold. Ferrous salt, H2O2 or oxalic acid is added to the soln. to form a precipitate. At this time, the reducing agent is added so as to adjust the oxidation-reduction potential of the soln. to 600-800mV. Thus, the contamination of the gold precipitate due to especially Pd, etc. among the leached components can be prevented. The precipitate is separated from the soln., recovered, treated with nitric acid, and melted by heating to obtain high purity gold in a high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-purity gold from an aqueous solution in which gold is eluted from slime with chlorine.

The present inventors have made copper electrolytic anode slime (hereinafter referred to as slime), which has been decoppered and selenized, into an aqueous slurry and injected chlorine gas into it to quickly remove gold with a high yield.
We have developed a simple method for recovering gold from slime, and have already published the ``Method for recovering gold from copper electrolytic slime'' (Special Request Sho!; 3 -
11. , No. 2/33). The gold eluate thus obtained contains components such as copper, selenium, tellurium, palladium, and platinum in addition to gold, which is the main component.

It is also known that reducing agents such as ferrous salts, hydrogen peroxide, oxalic acid, etc. are added to reduce gold from a gold-containing liquid and precipitate it as gold particles. If such a reducing agent is simply added to a solution containing various components other than gold (hereinafter referred to as gold solution), the various components mentioned above will be mixed with gold.
Because it precipitates to varying degrees and contaminates the precipitated gold particles? Ta. High purity gold of 97% by weight or more is difficult to obtain.

Therefore, when producing high-purity gold from a gold solution, a gold precipitate containing some impurities of 99.9% by weight or less, which was conventionally obtained by adding a reducing agent as described above, is heated and melted. The advantage of early extraction of gold from copper electrolytic slime can be fully utilized by electrolyzing the gold precipitate for several days using it as an anode, or redissolving the gold precipitate in nitric acid, aqua regia, etc. by applying a large amount of heat, and purifying it. There wasn't.

In view of the drawbacks of the prior art, the present invention has been developed as described above, which allows gold recovery to be carried out easily and quickly without requiring days or special equipment unlike full electrolysis. It is an object of the present invention to provide a method capable of producing high purity gold of 79.99% by weight or more, which has not been previously obtained, by employing a method of adding a reducing agent. That is, the present invention involves selectively using ferrous salts, hydrogen peroxide, and oxalic acid from conventional reducing agents that precipitate gold from all solutions, and adjusting the end point of this precipitation reaction to the gold solution. The oxidation-reduction potential is 00~g00mV.
(A silver chloride electrode, hereinafter this will be omitted and expressed simply in mV.) 99. After generating a precipitate of about 100% by weight, this precipitate is treated with nitric acid and heated and melted to ensure the production of high purity gold of 99.99% by weight or more. .

The present invention will be explained in more detail below.

The gold solution used in the method of the present invention is obtained by making copper- and selenium-removed slime into an aqueous slurry and blowing chlorine gas into it. Copper, selenium, tellurium, palladium, platinum, silver, lead, etc. are also eluted. The composition of these gold solutions varies depending on the composition of the slime, but usually copper and selenium are less than /g and /l of gold iog7t, respectively.
Tellurium n g/l.

Palladium Q, n ~ n g/l, platinum 0. θn〜0
．． ng/11 silver 0.00n z/l or less, ship 0. On
, g/l.

By adding ferrous salt, hydrogen peroxide, or oxalic acid (hereinafter referred to as the present reducing agent) to such a gold solution as a reducing agent, eluted components other than the above-mentioned gold (hereinafter referred to as eluted components) can be removed. Of these, selenium, platinum, etc. are difficult to co-precipitate. In addition, when using this reducing agent, the oxidation-reduction potential of the gold solution is 600~g00mV.
By adding so as to complete the entire precipitation reaction, it is possible not only to prevent contamination of the gold precipitate by palladium among the eluted components, but also to improve the yield of gold in the gold solution. Can be separated and recovered.

If the end point of the gold precipitation reaction is set to a redox potential lower than AOOmV, the formation of precipitates, especially palladium, in the gold solution becomes active, contaminating the gold precipitate, and causing a high concentration of 99.97% by weight or more during subsequent purification treatment. It becomes difficult to obtain pure ingots. On the other hand, if the end point is also set to a higher potential than goθmV, then 9
Although a gold precipitate with a high purity of 9.99% by weight or more can be obtained,
Gold recovery as a precipitate is reduced. As described above, from the viewpoint of contamination of the gold precipitate and gold recovery rate, the end point of the gold precipitation reaction needs to be 600 to 700 mV, preferably 600 to 700 mV.

Furthermore, other eluted components such as lead, rhodium, tellurium, copper, silver, iron, antimony, and bismuth are less likely to co-precipitate with gold, or their content in the gold solution is below the target grade of the total precipitate produced. It's just not so large that it has an impact.

Such a gold precipitation reaction does not need to be allowed to proceed at a particularly limited temperature, and usually may be allowed to proceed at room temperature without any particular heating.

The gold precipitate thus produced and separated into solid and liquid is in powder form and has a total grade of about 99.93% to 97.99% by weight.

The remaining total solution from which most of the gold has been precipitated can be fed, for example, to a platinum group recovery process.

The resulting total precipitate is then repulped into nitric acid.

The amount of nitric acid used may be approximately the same as the volume of the precipitate, and its concentration is usually 20 to 60% by weight. The higher the temperature of nitric acid treatment, the more efficient it is.

Depending on the amount of components contained, the treated nitric acid solution can be appropriately supplied to a recovery step for these components, or can be directly subjected to normal wastewater treatment.

Reference examples and examples will be described below.

Reference Example/ A copper electrolytic slime subjected to decopper removal and selenium removal treatment was repulped with water, and chlorine was blown into the slime to dissolve gold, thereby obtaining a gold solution having the following composition and physical property values.

Au / /-, 2g7'l z Ou, 0-3
5 gel 1'Te 2-70 g/'%
Pd0-7'l g/lXP70-/9 g/7%
A, g (0-00/g/lpH 0.9g% Redox potential 900 mV To this total solution 330me, ferrous chloride solution (Fe/30 gel) and hydrogen peroxide solution (30% heavy N) were added as reducing agents. Either of these was added to make solutions exhibiting various redox potentials, and total precipitates were generated at room temperature. The palladium quality in all the produced precipitates was analyzed.The results are shown in Table 1.

Table 1 - (7) The following can be seen from Table 1. As for fgll, as ferrous chloride and hydrogen peroxide are added to the total solution and the redox potential of the total solution decreases, the total concentration in the remaining total solution decreases rapidly. , the gold precipitation reaction occurs rapidly. And its redox potential is 1.30~
At 700 mV, the total concentration in the gold solution is several tens of mg/
1 or less. When the addition of the reducing agent is continued to reduce the redox potential of the entire solution, the precipitation reaction of dissolved palladium begins to occur and becomes more rapid. For example, at a redox potential of AOOmV, in Example 6/Reference Example/in which about 90 ppm of palladium is mixed into the gold precipitate, a ferrous chloride solution is added as a reducing agent to bring the redox potential of the entire solution to A'13 mV. (required time: 5 minutes), solid-liquid separation (residual liquid volume: approximately 33A; ml),
Approximately 3.4 g of gold powder was obtained by washing with water and drying. Approximately 2 g of this gold powder was then boiled in nitric acid, filtered, and then heated and melted to obtain gold particles. The analytical values of the whole powder in each process were as shown in Table Ω.

(8) Table 2 Example 2 Copper-removed and selenium-removed copper electrolytic slime 233.2 ~
was repulped with water and chlorine was blown in to elute the gold to obtain a total solution having the following composition and physical properties.

Au! ;-2gel, Qu 0-1I3 gel
N Te 3-20 gel N PdO, A7 g
7'l SPt 00 (77gel XAg <0-0
0/g7'1pH/, θ3, redox potential 900 m
After adjusting the pH of this entire solution to 7.20 with caustic soda, about 20% of 30% hydrogen peroxide was added as a reducing agent using OC, and the redox potential was brought to A30 in about 2 hours.
It was lowered to mV. After that, filter it to 11M! 0
3 g of gold powder was obtained.

Next, this gold powder was boiled in 2.31% concentrated nitric acid for 7 hours, filtered, and then heated and melted to obtain an ingot. The analytical values of the gold powder area in each process are as shown in Table 3. In addition, the total concentration in the remaining total solution obtained by filtering the generated precipitate is /, g mg
It was 7 tons.

Table 3 ■ (Note) - indicates those not observed in spectroscopic analysis Next, add formic acid to this residual gold solution, and increase the redox potential by approximately 2 θm.
Palladium, platinum, etc. were precipitated as V. In the solution obtained by solid-liquid separation, palladium is 7m9/11 platinum is 0.
3 mti/l, and two analyzes of the precipitate revealed pdl, 8%, Pt 10%, Au/, 2%, OuO
, //%, Te 3. The results were obtained: Bi%, Bi/, 2% (both weight%).

Example 3 A total of about 3 kg of sodium oxalate crystals were added as a reducing agent little by little to the total solution SOt of Reference Example/, and the oxidation-reduction potential of the total solution was set to A! A whole ingot was obtained in the same manner as in Example except that the ingot was lowered to OmV. As a result of analyzing this ingot, the overall grade was 97% by weight.

In addition, when reducing the redox potential of the entire solution by the method of the present invention, the object of the present invention can also be achieved by appropriately using the present reducing agent in combination.

As is clear from the above results, the present invention can easily produce high-purity gold without requiring special equipment, and moreover, can produce high-purity gold quickly.

Claims (1)

[Claims] (1) In a method of recovering gold from an eluate in which copper-removed and selenium-removed copper electrolytic slime is made into an aqueous slurry and chlorine gas is blown into the solution, the eluate is oxidized. Ferrous salt, hydrogen peroxide, or oxalic acid was added so that the reduction potential was AOO~g00mV (vs. silver chloride electrode), the resulting precipitate was separated and collected from the eluate, and then the product was treated with nitric acid. A method for producing high-purity gold from a copper electrolytic slime intermediate treatment solution, which is characterized by heating and melting a precipitate.