JPH02197532A - Method for recovering ru from metallic electrode - Google Patents

Abstract

PURPOSE:To efficiently recover Ru by peeling off an Ru-containing coating layer from an electrode base material, oxidizing the peeled matter by means of heating, reducing precipitated ruthenium oxide, and then separating the resulting metallic ruthenium by dissolution in a solution of sodium hypochlorite. CONSTITUTION:A peeled matter peeled off from a titanium base material electrode and containing ruthenium dioxide is heated up to 800-1200 deg.C in an oxidizing atmosphere, by which the associated base material composed of titanium, etc., is oxidized and also ruthenium oxide is precipitated. After cooling, the above peeled matter is heated up to 700-1200 deg.C in a reducing atmosphere and the above ruthenium oxide is reduced into metallic ruthenium, and the above is put into an alkaline sodium hypochlorite solution to dissolve metallic ruthenium and separate it by filtration, by which ruthenium liquor is recovered. By this method, ruthenium can be separated and recovered from the metallic electrode in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The method of the present invention involves peeling off a coating layer containing Ru and/or its oxide, and subjecting the resulting peeled product to 800°C in an oxidizing atmosphere.
heated to ~1200°C, then heated to 700°C in a reducing atmosphere.
This method involves reducing ruthenium oxide to metal ruthenium at 200° C., and then dissolving and separating Ru in an alkaline sodium hypochlorite solution to recover Ru from a metal electrode.

(Prior art and its problems) In recent years, insoluble electrodes in which an oxide such as titanium, ruthenium, or ruthenium oxide coating is provided on a metal substrate such as titanium have been used in various fields of electrochemistry, particularly in the salt electrolysis industry. It is widely used as an electrode.

Although such metal electrodes have a fairly long lifespan, the electrode coating gradually wears out and becomes less active during use.
When a certain level of performance cannot be maintained, it is necessary to replace the electrode with a new one.

A considerable amount of expensive ruthenium still remains in the coating of these used metal electrodes, and it is industrially important to recover and effectively utilize this.

Conventionally, as related to this type of technology, Japanese Patent Application Laid-Open No. 51-
No. 68493 discloses a method for recovering Ru by treating a poorly soluble substance containing Ru or a compound thereof.

However, these methods require complicated and time-consuming processes for the alkali molten salt treatment and oxidizing solution dissolution steps for the peeled material.

Furthermore, when separating ruthenium and metal oxides, metal hydroxides precipitate, resulting in poor efficiency and cannot be said to be an industrially optimal ruthenium recovery method.

(Objective of the Invention) The present invention was made in view of the above circumstances, and its object is to provide a method for simply and efficiently recovering ruthenium from a metal electrode.

(Structure of the Invention) The present invention provides a method for recovering Ru, in which a coating layer containing Ru and/or its oxide is peeled off on a metal electrode substrate, and the resulting peeled product is heated at 800 to 1200°C in an oxidizing atmosphere.
After heating at 700 to 1200 °C in a reducing atmosphere to oxidize the metal electrode substrate such as titanium that accompanies the peeled material and precipitate ruthenium oxide from the titanium oxide, it is heated at 700 to 1200 °C in a reducing atmosphere to convert the ruthenium oxide into metal. This method is characterized by recovering ruthenium by reducing it to ruthenium, dissolving it in an alkaline sodium hypochlorite solution, and separating it.

When the peeled product is heated to 800 to 1200° C. in an oxidizing atmosphere, the titanium of the electrode base accompanying the peeled product is oxidized, and ruthenium oxide is precipitated from the titanium oxide.

The reason why the titanium in the electrode base that accompanies the peeled material is oxidized by heating in an oxidizing atmosphere is that if the peeled off material containing metallic titanium is directly treated in a reducing atmosphere, the metallic titanium will reduce the titanium oxide. and Ti0z +
A reaction similar to 'ri-27'io occurs, making the crystal structure of titanium oxide a hexagonal structure similar to that of ruthenium metal, and ruthenium is eluted during subsequent melting.

The precipitation of ruthenium oxide from titanium oxide is caused by TiO□
It can be inferred that the precipitation is due to the phase equilibrium of -RuO7.

The temperature is preferably 700 to 1200°C. This is because at temperatures below 700°C, oxidation reaction of titanium metal occurs, but precipitation of ruthenium oxide does not occur. This is based on an experimental result that the ruthenium recovery rate is lower when heated at 1200°C or higher.

Examples and conventional examples will be described below.

(Example) 500 g of a peeled material containing ruthenium dioxide (Ru 3.60 wt%) peeled off from a titanium-based electrode was placed in a refractory crucible and heated at 1000° C. for 1 hour in the atmosphere.

After cooling to room temperature, it was heated at 950°C for 1 hour in an H2 atmosphere.

The removed product was placed in a NaOH-NaCJO mixture to dissolve metal ruthenium.

When the Ru solution was separated from the residue by filtration and recovered, the recovery rate was 94%.

Other results (recovery rate) are shown in Table-1.

(Left below) Table 1 (Conventional example) Composite oxide of Ru dioxide and titanium dioxide (Ru5, 02
When 5kg (wt%) was melted at 800°C using KOH+KNO, KOH8.4kg5KNO30,
It required 9 kg and the recovery rate of Ru was 86%.

As is clear from the above examples and conventional examples, the method of the present invention has a recovery rate of 86 to 94%, which is higher than that of the conventional examples.

Further, the conventional method requires complicated and long-time processing such as a molten salt treatment step and an acidic solution dissolution step.

(Effects of the Invention) As detailed above, according to the present invention, it is possible to separate and recover Ru from a metal electrode with higher efficiency than in the past, and it does not require complex and long-term processing as in the past. In order not to
It has the effect of being economical and can be recovered in a short time.

Applicant: Tanaka Kikinzoku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. Peel off the coating layer containing ruthenium and/or its oxide on the metal electrode substrate, heat the peeled product at 800 to 1200°C in an oxidizing atmosphere, and remove metals such as titanium that accompany the peeled product. After oxidizing the ruthenium oxide and precipitating ruthenium oxide from the titanium oxide, heating at 700 to 1200°C in a reducing atmosphere to reduce the ruthenium oxide to metal ruthenium, and then adding an alkaline sodium hypochlorite solution. A method for recovering Ru from a metal electrode, the method comprising dissolving and separating Ru.