JPH0236655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for recovering ruthenium from wastewater containing metal ruthenium or its oxides.

[Conventional technology]

Waste containing ruthenium or its oxides in the metallic state is waste from the production of catalysts, electrodes, and electronic parts, defective and used products, work waste from processing processes such as cutting and polishing, and waste during electrolytic refining. It is included in the slime etc. that is generated.

Conventionally, as a method for dissolving ruthenium from waste containing ruthenium metal or its oxide, sodium peroxide was used as described in JP-A-60-65730 and JP-A-60-92433. Alternatively, a method is used in which the material is melted using a mixture of an oxidizing agent such as potassium nitrate and an alkali hydroxide, and then water is added to dissolve the material.

These tailings often contain carbon or organic substances, and oxidative roasting is usually performed as a pretreatment to remove carbon and organic substances.

However, graphite carbon, e.g. SiC
If it contains metal carbides such as WC or WC, it cannot be decomposed and removed by normal roasting, and melting using the above-mentioned oxidizing alkaline flux carries the risk of ignition or explosion. Therefore, it could not be implemented.

In addition, in recent years, industrial production of sodium peroxide has been stopped due to the dangers of handling it, and the price has soared.

As another method, JP-A-58-194745 describes a method in which ruthenium metal is dissolved using hypochlorite. However, although this method is quite effective when the ruthenium content is high, there is a problem in that the dissolution rate is low when the ruthenium content is relatively low.

[Problem that the invention seeks to solve]

The present invention solves the above problems and provides a method for dissolving ruthenium in waste containing metal ruthenium or its oxides safely, at low cost, and at a high extraction rate.

[Means for solving problems]

In order to achieve this object, the present invention oxidizes and roasts waste containing at least one of metal ruthenium and ruthenium oxide, melts the roasted product together with an alkali hydroxide, and converts the solidified product to a waste containing free chlorine. The objective is to recover ruthenium by extraction with an aqueous alkali hydroxide solution.

In this specification, ruthenium metal and slag containing at least one of ruthenium refer to waste from the production of catalysts, electrodes, electronic parts, etc., defective products, used products thereof, and unused products. work scraps from cutting, polishing, etc.
This refers to everything that needs to be recovered from ruthenium, such as slime generated during electrolytic refining.

The water content in waste slag is first evaporated, and then carbon, excluding graphite, is removed.
Oxidative roasting is performed in air to oxidatively decompose and remove organic compounds and to oxidize ruthenium in a metallic state. The roasting temperature and time are sufficient as long as they can oxidize carbon, organic compounds other than graphite, and ruthenium in the metallic state, and they vary depending on the target waste, but in general, roasting is carried out at, for example, The roasting can be carried out at a roasting temperature of 400 to 600°C and a roasting time of 30 minutes to 2 hours.

If this roasting process is incomplete and carbon and organic compounds other than graphite remain, some of the ruthenium that has been dissolved will be removed when extracted with an alkali hydroxide aqueous solution containing free chlorine after alkali melting. It may be re-reduced and precipitated, resulting in poor extraction efficiency.

When the waste slag to be treated is powder, the roasted material is often sintered and becomes lumpy, so in order to improve the reaction efficiency after that, the roasted material that has become lumpy is -40
It is preferable to grind it to a mesh size.

The roasted product is then mixed with alkali hydroxide and melted. As the alkali hydroxide, sodium hydroxide is usually used, but other alkali hydroxides can also be used. The amount of alkali hydroxide added cannot be specified depending on the shape of the roasted product, but it may be sufficient as long as the roasted product can be immersed in the melt when heated and melted. 3 parts by weight
~5 parts by weight is preferred.

The material of the container used for melting is iron, nickel,
Any material used for ordinary melting of alumina or the like may be used, but a tray made of iron plate is the most economical. The roasted material and alkali hydroxide are placed in this container, mixed, and then melted. Generally, the mixture of roasted material and alkali hydroxide is melted by gradually increasing the temperature, for example, at 500 to 700℃.
This can be done by holding it for 15 minutes or more.

By alkali melting, ruthenium changes to a state where it can be easily dissolved in an aqueous alkali hydroxide solution containing free chlorine. This is thought to be because the ruthenium oxide becomes hydrated by the alkali hydroxide, swells, and becomes porous.

After the melt is cooled and solidified, it is heated in an aqueous alkali hydroxide solution containing free chlorine in a suitable container to extract and dissolve ruthenium. As an aqueous alkali hydroxide solution containing free chlorine, it is common to use commercially available sodium hypochlorite (12% free chlorine) as it is or diluted with water. It is also possible to use a material that has absorbed gas. Extraction and dissolution conditions vary depending on the shape and properties of the target molten solidified material, but even if it is a powder, extraction and dissolution will take place at a liquid temperature of 60 to 80°C.
This can be carried out with stirring for 5 hours.

According to one example, the relationship between the concentration of free chlorine in an aqueous alkali hydroxide solution and the extraction rate of ruthenium is that when the concentration of free chlorine is 1%, the extraction rate is 41%, and when the concentration of free chlorine is 1.5% and 2%, the extraction rate is 41%. are 86% and 99% respectively.
, the concentration of free chlorine is at least 1.5%,
The content is preferably 2% or more.

Through this step, ruthenium oxide is extracted into the liquid as an alkali salt of ruthenic acid. According to the present invention, it is possible to extract 99% or more of the ruthenium content in the raw material waste.

The extract may contain undissolved residue, or after separating the residue, ruthenium can be converted to ruthenium chloride using a known method such as distillation with a yield of 99%.
Separation, purification and recovery can be carried out in the above manner.

〔Example〕

Example 1 In this example, a test was conducted to extract ruthenium using waste slag containing ruthenium, which cannot be decomposed by oxidative roasting and contains metal carbide, in which it has been extremely difficult to dissolve ruthenium. Namely carbon (activated carbon) 49.8%, SiC27.5%, Ru22.7
(each weight)% of waste slag was placed in 3 trays of 3.0 g each and oxidized and roasted at approximately 600°C for 2 hours.
The obtained 1.8 g of roasted material was crushed into 40 meshes or less, 9 g of sodium hydroxide was added to each, mixed, transferred to the original tray, and heated at 600°C, 650°C, respectively in an electric furnace.
It was held at 700°C for 30 minutes to melt. After cooling, transfer the molten mass together with the tray to a 500ml beaker, and add 3 ml of free chlorine.
% sodium hypochlorite aqueous solution was added until the entire tray was submerged and dissolved at 70 to 80°C for 5 hours. After separating the insoluble matter from the aqueous solution, the extraction rate was calculated by determining the ruthenium content in the solution.
In all cases, values of 99% or higher were obtained.

Comparative Example 1 The same waste slag as in Example 1 was used, and after being oxidized and burned under the same conditions as in Example 1, the roasted product was directly treated with an aqueous sodium hypochlorite solution containing 3% free chlorine without alkali melting. When extracted under the same conditions as in Example 1, the extraction rate of ruthenium was 53%.

Comparative Example 2 The same waste slag as in Example 1 was used, and after oxidative roasting under the same conditions as in Example 1, ruthenium was reduced to a metallic state using hydrogen in the roasted product. 70-80℃ using 5% sodium hydroxide aqueous solution adjusted to contain sodium chlorite
After extraction at a temperature of 5 hours, the extraction rate of ruthenium was 77%.

Example 2 10 g of a used catalyst in which 0.46% by weight of ruthenium was supported on spherical SiC with a diameter of 5 mm was placed in an aluminum crucible and oxidized and roasted at 400° C. for 30 minutes to obtain 7.9 g of roasted product. The roasted product was mixed with 24 g of sodium hydroxide without being crushed, and melted at 550° C. for 15 minutes. After cooling, the molten mass was transferred together with the crucible to a 500 ml beaker, and an aqueous solution of sodium hypoxite containing 3% free chlorine was added until the crucible was completely immersed, and dissolved at 70 to 80°C for 2 hours. After separating the insoluble matter from the aqueous solution, the ruthenium content in the solution was determined. The extraction rate of ruthenium was 96%.

Example 3 In Example 2, the melting time was 30 minutes and the dissolution temperature with the sodium hypochlorite aqueous solution was 60 to 70 minutes.
The same procedure as in Example 2 was carried out except that the temperature was changed to .degree. C., and the extraction rate of ruthenium was 99%.

Example 4 Example 2 was carried out in the same manner as in Example 2, except that the melting time was 500°C and the melting time was 30 minutes, and the extraction rate of ruthenium was 95%.

Example 5 Example 2 was carried out in the same manner as in Example 2, except that the roasting temperature was 500°C, the roasting time was 60 minutes, and the melting temperature was 500°C. The extraction rate of ruthenium was 79%. Ta.

Comparative Example 3 Example 2 was carried out in the same manner as in Example 2 except that the melting temperature was changed to 400°C, and the extraction rate of ruthenium was 10%.

Comparative Example 4 Example 2 was carried out in the same manner as in Example 2, except that the roasting temperature was 500°C and the melting temperature was 400°C, and the extraction rate of ruthenium was 8%.

Comparative Example 5 10 g of the same used catalyst used in Example 2 was placed in an aluminum crucible and roasted at 400°C for 30 minutes. The roasted product was transferred to a 300 ml beaker, and 100 ml of a 5% by weight solution of sodium hydroxide in an aqueous sodium hypochlorite solution containing 2% free chlorine was added and dissolved at 60 to 70°C for 2 hours. After separating the insoluble matter from the aqueous solution, the ruthenium content in the solution was determined. The extraction rate of ruthenium was 0.4%.

Example 6 The undissolved residue obtained in Comparative Example 5 was once dried and then treated in substantially the same manner as in Example 2 using 24 g of sodium hydroxide, and the extraction rate of ruthenium was 99%. Ta.

Example 7 A used catalyst in which 5% by weight of ruthenium was supported on activated carbon was roasted at 600°C for 2 hours. When the ruthenium content of this roasted product was determined, the ruthenium content was 51.1% by weight.

1.00 g of this roasted material was placed in an aluminum crucible, 5 g of sodium hydroxide was added thereto, mixed, and melted at 700° C. for 30 minutes. After cooling, transfer the molten mass together with the crucible to a 500 ml beaker, add 200 ml of pure water and 70 ml of sodium hypochlorite aqueous solution containing 12% free chlorine, and heat at 70 to 80℃.
It was dissolved for 2 hours.

After separating the insoluble matter from the aqueous solution, the ruthenium content in the solution was determined. Ruthenium extraction rate is 95.3
It was %.

Comparative Example 6 1.00 g of the roasted product used in Example 7 was placed in a magnetic crucible and reduced with hydrogen at 750°C for 30 minutes. Transfer the reduced sample to a 500ml beaker with the boat, and
% sodium hydroxide aqueous solution 70ml and free chlorine 12%
Add 20ml of sodium hypochlorite aqueous solution containing 70ml
Dissolved at ~80°C for 2 hours.

After separating the insoluble matter from the aqueous solution, the ruthenium content in the solution was determined. Ruthenium extraction rate is 16.8
It was %.

〔effect〕

According to the method of the present invention, when recovering ruthenium from waste containing ruthenium metal or ruthenium oxide, the conventional method of melting with an alkaline oxidizing agent or the direct extraction method with an aqueous alkali hydroxide solution containing free chlorine Since it is possible to obtain a much higher ruthenium extraction rate than that of conventional methods, its industrial value is great.

Claims (1)

[Scope of Claims] 1. After oxidizing and roasting waste containing at least one of metal ruthenium and ruthenium oxide, and melting the roasted product with an alkali hydroxide, the solidified product is treated with an aqueous alkali hydroxide solution containing free chlorine. A method for recovering ruthenium characterized by extraction. 2. The method for recovering ruthenium according to claim 1, wherein the amount of alkali hydroxide used for melting the roasted product is 3 to 5 times the weight of the roasted product. 3 The free chlorine concentration in the aqueous alkali hydroxide solution is 2
The method for recovering ruthenium according to claim 1, characterized in that the amount is at least % by weight.