JPS61235520A - Method for leaching noble metal - Google Patents

Abstract

PURPOSE:To easily leach and recover noble metals from a substance contg. noble metals without using a strong acid such as aqua regia by treating the substance with an aqueous HCl soln. in the presence of nitrogen oxide as a catalyst in a vessel isolated from the air. CONSTITUTION:A precipitate produced by the electrolysis of copper or a purified precipitate such as a pretreated waste catalyst is pulped with an aqueous HCl soln. contg. optionally a metallic chloride such as NaCl, and the resulting pulp is charged into a reaction vessel 1 isolated from the air. Gaseous oxygen is substituted for the vapor phase in the vessel 1, the vessel 1 is kept at a prescribed temp., and a substance contg. NOx such as NaNO2 and one or more kinds of bi-quatervalent metals is added as an oxidation catalyst from a hole 5. A reaction is caused by stirring with a stirrer 7 to transfer noble metals such as Au, Pt and Pd from the precipitate to the soln. By this method, leaching is completed in a short time.

Description

[Detailed Description of the Invention] The present invention is directed to materials containing precious metals such as gold and/or platinum, such as steel electrolytic precipitates, waste catalysts from automobiles and petroleum refineries, and scraps from electronic equipment, etc. The present invention also relates to a method for recovering precious metals from substances obtained by pre-treating these metals.

Regarding the treatment of electrolytic precipitates from sail steel treated with moxibustion, various studies have been conducted for a long time, and the methods described below are the mainstream. That is, first, copper and arsenic in the precipitate are oxidized and leached out with air in an aqueous sulfuric acid solution, and then the residue is oxidized and roasted to remove selenium.
It is vaporized and removed as at.

The roasted precipitate is further added with soda salt and a reducing agent and melted, resulting in soda powder containing tellurium and noble lead containing precious metals. Noble lead is removed in an oxidation furnace to become crude silver containing precious metals. The crude silver thus obtained is cast into a plate shape and subjected to electrolytic refining treatment as an anode. Silver is deposited and recovered on the cathode surface, and gold and platinum group metals accumulate in the electrolytic cell as anode mud. This anode mud is subjected to a perching treatment to remove contaminants. The residue is mainly gold, which is made into an anode by casting and becomes pure gold through electrolytic refining. In this method, each precious metal is separated one after another, so it takes about a month to finally obtain gold, and there are problems such as the use of highly concentrated acids and environmental measures.

Therefore, in recent years, various hydrometallurgical smelting methods have been proposed for the treatment of raw copper electrolytes. The main method among these is to oxidize gold and platinum group metals using aqua regia or chlorine gas, leaching them out as chloro complexes, and leaving silver as chloride in the residual liquid. However, aqua regia is extremely oxidizing and corrosive, and there are problems in selecting the material for the reaction vessel and in treating exhaust gas containing harmful substances. In the case of chlorine gas, the same problem as in the case of aqua regia occurs because the blown chlorine gas turns into hypochlorous acid and hydrochloric acid. Furthermore, in either case, the concentration of hydrochloric acid cannot be lowered, and a portion of the silver becomes a chloro complex and exists in large amounts in the aqueous solution, which is also unfavorable in terms of separation of silver and noble metals.

As for the treatment of the spent catalyst, the above-mentioned wet treatment method or treatment with an aqueous sodium hydroxide solution has been proposed.

The former has the same problems as mentioned above, and the latter has problems in terms of process and cost since a large amount of alumina carrier is dissolved.

For scraps such as electronic equipment parts, the above-mentioned method is usually applied after combustible materials are burned and removed as necessary.

In view of these problems, the present inventors conducted intensive research on a method for easily leaching these precious metals from substances containing gold and/or platinum, etc. without using aqua regia, etc., and as a result, they have made the following invention. reached.

- The present invention provides a method for leaching precious metals, etc. from a substance containing at least a precious metal such as gold or platinum, in which the substance is leached with a nitrogen oxide containing one or more of divalent, trivalent, or tetravalent. The present invention relates to a method for leaching noble metals, using an oxidation catalyst and oxygen as an oxidizing agent, and treating in a hydrochloric acid aqueous solution or a hydrochloric acid aqueous solution containing a metal chloride in a reaction vessel isolated from the atmosphere.

Further, in an embodiment of the present invention, the usual reaction temperature is 70°C.
There are noble metal leaching methods that are ~95°C.

Another embodiment is a process for leaching noble metals in which the pressure within the typical reaction vessel is less than 10'Pa g.

In yet another embodiment, in the gas phase in one reaction vessel,
The oxygen partial pressure is 5 for gases excluding the partial pressures of nitrogen oxides and water vapor.
There is a method for leaching precious metals that is 0% or more.

l Soybean standing human blood n plate The target processed material of the present invention is a substance containing precious metals such as gold and/or platinum.For example, raw materials for copper electrolysis, waste catalysts from automobiles and petroleum refining, and even electronic equipment, etc. For example, when copper electrolytic raw materials are treated according to the present invention, such as scraps and materials obtained by pre-processing these materials, the present invention can be applied as is, but the valuable metals are ultimately separated and recovered. Therefore, it is desirable to remove substances that can be removed in advance by a known method.5 In order to maximize the effects of the present invention, it is preferable that the shape of the precious metal-containing substance is small, so pretreatment methods are recommended. When using the dry method as
It is preferable to carry out treatments such as pulverization before carrying out the method of the present invention.

Copper and arsenic contained in the copper electrolyte raw material are, for example, 200 g/l.
It is easily removed by repulping with an aqueous sulfuric acid solution and blowing pure oxygen or air at 50 to 80°C. Then, if this residue is subjected to the method using Nox-Os-o, so+ disclosed in Japanese Patent Publication No. 52-134124, most of selenium, tellurium and silver are leached and separated. The case where the present invention is applied to the raw material treated in this way (hereinafter referred to as the purified raw material) will be explained.

The purified raw material is repulped in an aqueous solution containing hydrochloric acid or an aqueous hydrochloric acid solution containing a metal chloride and placed in a reaction tank. Here, metal chlorides include NaCl, KCl, CaCl, and the like. The gas phase of the tank was replaced with pure oxygen gas.

While maintaining the temperature at a predetermined temperature, a substance containing nitrogen oxide (NOX) is added. Substances containing nitrogen oxides include, for example, NaNO, No, NzO*, etc.It is preferable that oxygen consumed as the reaction progresses be automatically supplied to maintain a set pressure. However, the added NOx (other than Nl) is easily dissolved in an aqueous solution and reacts with the metal to become -No. Since its solubility in water is /l\\, it comes out in the gas phase. Since oxygen is present in the gas phase, N is easily water-soluble under the conditions of the present invention.

3 and is used repeatedly. The reaction rate will be faster if the amount of NOx added is large, but even a small amount will cause a sufficient reaction, so it cannot be determined unambiguously.The oxygen to be supplied may be a mixture with an inert gas (for example, air) for the reaction. However, pure oxygen is preferable if degassing is not required in order to fully utilize NOx, but when using a mixed gas, the oxygen content in the gas phase is reduced due to the above reasons. It is preferable that the pressure is 60% or more of the gas excluding the partial pressure of the vapor.

The reaction temperature is 1. The higher the temperature, the better.If the reaction is carried out at atmospheric pressure or slightly higher pressure, the temperature should be around 95°C, since the partial pressure of water vapor will increase and oxygen supply will deteriorate, which is undesirable. be.

However, if a pressurized container is used, the temperature may exceed 100°C.

The amount of hydrochloric acid used for leaching varies depending on the amount of leachable material. If it is desired to reduce the amount of impurities mixed into the leachate, it is better to use as little amount of hydrochloric acid as possible.

Furthermore, although titanium was used for a part of the stirrer, no corrosion was observed even at the end of this experiment. Examples will be shown and explained below.

Mizudan Shyun By implementing the present invention, the following effects are produced.

(1) Precious metals can be easily leached and recovered from materials containing precious metals.

(2) Strong acids such as aqua regia are not used.

It can be carried out with a simple device.

(3) The processing time is extremely short, about 1 month compared to the conventional one month.
The process will be completed in about a week.

It's 叉凰五! One embodiment of the present invention was carried out using the apparatus shown in FIG.

Steel, arsenic, silver,
Purified raw material with selenium and tellurium removed (Au 3.87
%, Pt O, 046%, Pd O, 10%) were charged into a reaction tank (1), repulped to 70 g/l with a 3N HCl solution, and kept at 80 °C in a thermostat (2).
) is replaced with pure oxygen from the oxygen introduction pipe (3),
A water column manometer (
4).

NaN0. as a NOx source. 0.5 equivalent of the noble metal was added through the injection hole (5), stirred with a stirrer (7) to react, and samples were taken from the sampling hole (6) at intervals to analyze the residue. The temperature was measured with a thermometer (8). The results are shown in Table-1.

Table-1 It can be seen that most of the samples were leached out within 15 minutes.

1jLl The amount of purification plate used in Example 1 was 100 g/l.

Leaching was carried out in the same manner as in Example 1 for 1 hour using hydrochloric acid concentrations of 3N, IN, and 0.5N. The residue analysis values are shown in Table 2.Table 2 In the case of 0°5NHC1, although the noble metal grade in the residue is slightly higher in N, it can be seen that all are well leached out.

Further, the impurity concentration in the leachate at this time was as shown in Table 3.

Table 3 It can be seen that leaching of these impurities can be suppressed by lowering the concentration of hydrochloric acid.

Next ffi Platinum-based waste catalyst pellets (PTO) for automobile exhaust gas treatment.

19%) was put into a glass column as unpulverized, and after replacing the gas phase with pure oxygen, a 3N HCl solution containing 0.2 equivalents of NO□ relative to platinum was circulated through the column using a pump for 3 hours. . After the reaction, the temperature was 60° C., the pellet was taken out, washed with water, and analyzed. It was found that 0.014% of platinum was contained, and most of it was leached out.

After incinerating electronic material component scrap containing gold to remove organic matter, the same treatment as in Example 1 was performed for 2 hours. The total grade in the residue was less than 0.001%.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the apparatus used in the present invention. 1 is a reaction tank, 2 is a constant temperature bath, 3 is an oxygen introduction pipe, 5 is an input hole, and 6 is a sampling hole.

Claims (4)

[Claims] (1) In a method of leaching precious metals, etc. from a substance containing at least a precious metal such as gold or platinum, the substance is divalent,
Treated in a hydrochloric acid aqueous solution or a hydrochloric acid aqueous solution containing a metal chloride in a reaction vessel isolated from the atmosphere using a nitrogen oxide containing one or more of trivalent or tetravalent oxides as an oxidation catalyst and oxygen as an oxidizing agent. A method for leaching precious metals. (2) The method for leaching noble metals according to claim 1, wherein the normal reaction temperature is 70 to 95°C. (3) The pressure inside the normal reaction vessel is 10^ in gauge pressure.
A method for leaching noble metals according to claim 1, characterized in that the pressure is less than 5 Pa. (4) Leaching of noble metals according to claim 1, wherein the oxygen partial pressure of the gas phase in the reaction vessel is 50% or more of the gas excluding the partial pressures of nitrogen oxides and water vapor. Method.