JPS5919048B2 - How to separate thallium from thallium-containing substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for selectively separating thallium from thallium-containing substances, and in particular to a method for recovering metallic thallium using various thallium-containing substances produced in non-ferrous smelting processes as starting materials. The present invention relates to a method for selectively leaching thallium for the purpose of leaching thallium.

Although the thallium-containing starting material concomitantly contains arsenic, the main object of the present invention is to suppress the leaching of arsenic and selectively leached only thallium.

Lead electrolytes, clean slag generated from cadmium smelting processes, and other residues and waste from non-ferrous smelting processes include:
Depending on the source, thallium can be contained in a large number to about 20 thallium.

If thallium is discharged without being recovered from such dathallium-containing materials, thallium will accumulate during circulation within the smelting system, and if acceptable limits are exceeded, it will adversely affect various process steps.

Furthermore, there has been an increasing demand for thallium recovery for the purpose of commercialization, and from this point of view as well, it is necessary to selectively recover thallium from the above-mentioned thallium-containing substances.

Although there have been few attempts to selectively separate thallium from thallium-containing substances, there have been no attempts to prevent arsenic, which is contained together with thallium in thallium-containing substances, from being accompanied by thallium during recovery. .

If arsenic and thallium are packaged together, arsine gas (H3As) will be generated when spongy thallium is deposited from the separated and recovered thallium by replacing the thallium with zinc plates, which is extremely dangerous.

Therefore, it is necessary to develop a method that can selectively separate only thallium without accompanying arsenic.

With the above purpose in mind, the present inventor conducted extensive studies on a method for selectively separating thallium from thallium-containing substances, and as a result,
It has been found that arsenic leaching can be suppressed by adopting an alkali leaching method and adjusting the value to 9 or more.

At the same time, leaching of zinc and cadmium contained in the impurity-containing IJ '7' substance is also suppressed.

Although the method itself is simple, its arsenic suppression effect is surprising, and by applying this method, it is possible to produce highly pure metallic thallium extremely efficiently without the generation of arsine gas. Ru.

Thus, the present invention provides a thallium separation method characterized by alkaline leaching of a substance containing thallium and arsenic at a pH of 9.0 or higher and recovering a thallium-containing leachate.

As mentioned above, the thallium-containing substances targeted by the present invention are intermediates and residues produced in the nonferrous metal smelting process, such as lead electrolyte and slag generated from the cadmium smelting process. .

Here, as a representative example, thallium slag in which thallium is concentrated at a high concentration, called "deliminated cake", generated in the cadmium smelting process will be explained for reference.

In cadmium smelting, cadmium-containing raw materials including Cottrell dust, smoke ash, cleaning slag, etc. are sulfated and roasted, and then subjected to a leaching operation using hot water. is separated into cleaning liquid and cleaning slag.

The cleaning solution is sent to the cadmium ingot manufacturing process.

Until now, clean slag has been repeatedly used in the process and reused as a raw material, but as mentioned above, thallium accumulates during cyclic use, so thallium-free operations have recently been implemented to remove thallium from the clean slag outside the system. .

The cleaned slag generally contains 10% to 20% thallium, but by subjecting it to S02 leaching treatment and chlorination treatment, a cake in which 80% to 90% of the thallium in the cleaned slag is concentrated can be obtained.

This is called a thallium-free cake.

In addition to thallium, the deliminated cake contains several tres of arsenic, zinc,
Contains cadmium, lead, etc.

In the derium cake, thallium is present in the form of thallium chloride (TICI).

One specific example of the present invention is selectively leaching and separating only thallium from such a thallium-free cake.

According to the present invention, the denatured cake or other thallium-containing material is subjected to an alkaline leaching operation at a pH of 9.0 or higher in a leaching tank.

In the case of a thallium-free cake, water is added to form a pulp and the cake is subjected to a leaching operation.

The leaching operation is carried out with stirring at a temperature of room temperature to 80°C, preferably 50 to 60°C, by adding sodium hydroxide, potassium hydroxide, sodium carbonate, etc.

After alkali leaching, the liquid and cake are separated by a filtration operation, and the cake is repeatedly subjected to the leaching operation.

The solution thus produced is a high thallium solution containing substantial amounts of arsenic and only trace amounts of zinc and cadmium.

The leaching reaction mechanism has not been completely elucidated, but by adding alkali to the slurry of the lithium-containing lithium cake, zinc and cadmium can be converted into hydroxides to suppress leaching, and arsenic can be added to these hydroxides. It is thought that the leaching of arsenic can be prevented by adsorption.

At this time, it seems that the u value has a subtle influence for some reason.

Thallium chloride (TICI) does not hydrolyze to form hydroxide precipitates even in basic solutions.

As the alkali used in the leaching operation, any alkali such as sodium hydroxide can be used, but when a mixed alkali of sodium hydroxide and sodium carbonate is used, both settling and filterability are extremely good. It was discovered that

Solid-liquid separation after alkali leaching can be performed only by the sedimentation method.

According to the invention, the arsenic concentration of the leachate is 1 i/l.

Below, the range is usually from o, i~/l to several hundredths of da/l, and the leaching of arsenic is almost completely suppressed.

With this level of arsenic concentration, there is no danger of arsine gas being generated when spongthallium is produced by replacing zinc plates.

On the other hand, the zinc and cadmium concentrations in the leachate are at pH 9,
At pH 0, it is several tens of ■/l, but at pH 10.0, it is several tens of ■/l.
Furthermore, at pH 11.0, it drops to several tenths of m from 1.0.
It decreases to the order of 9/l.

Therefore, it can be seen that in the present invention, not only the leaching of arsenic is suppressed, but also the separation of zinc and cadmium can be achieved very well.

The liquid after alkali leaching is used to produce metallic thallium.

Several methods are known for producing thallium metal, and one of the typical methods is a substitution method.

After adjusting the pH to around 3 by adding sulfuric acid, spongy thallium is produced by suspending a zinc plate in the liquid.

After being sent to each house, the collected crude sponge thallium undergoes a purification process.

The purification treatment is carried out by dissolution treatment with the addition of sodium hydroxide, although the former may be omitted depending on the situation.

The dissolution treatment by adding sodium hydroxide is carried out at about 400°C, and the produced metallic thallium and soda chloride are separated.

The metallic thallium obtained has a high purity of 99.99% or more.

If the starting thallium-containing liquid contains lead, it is advisable to remove the lead either beforehand or separately after leaching.

Lead can be easily removed as lead sulfate by adding sulfuric acid, or by adding barium carbonate or strontium carbonate under sulfuric acid acidity to make it adsorbed on barium sulfate or strontium sulfate.

As described above, the present invention makes it possible to selectively extract thallium from thallium-containing substances by suppressing leaching of arsenic, zinc, and cadmium by an extremely simple method, and to produce extremely high-purity metallic thallium. This method has been established, and is particularly significant in that there is no danger of arsine gas being generated during the production of spongthallium.

Example 2 The leaching operation of the present invention was carried out using 74 g of thallium-free cake as a starting material.

The deliminated cake contained 49.8% thallium, 3.70% arsenic, 2.22% zinc, 2.24% cadmium, and 31.4% water.

This was repulped with water and hydroxylated) IJium was added to pH values of 9.0, 10.0 and 11.0.

Leaching was carried out for 1 hour while stirring at a liquid temperature of 50 to 60°C, and the leachate was filtered and separated into a cake liquid.

The component concentrations of the obtained filtrate were as follows.

The leaching filtrate thus obtained was adjusted to pH 3.0 by adding sulfuric acid.
After adjusting the zinc plate, spongthallium was produced by a substitution reaction.

Spongthallium production was carried out by suspending arsine gas detection paper (filter paper impregnated with 3% HgBr 2-alcohol solution) over a container, but no yellowing of the detection paper was observed.

Metal thallium was obtained by heating and melting sponge thallium with the addition of sodium hydroxide.

Shows the analysis value of metal thallium.

Claims (1)

[Scope of Claims] 1. A method for separating thallium, which comprises leaching a substance containing thallium and arsenic with an alkali at a pH of 9.0 or higher and recovering a thallium-containing leachate. 2. The method according to claim 1, wherein the alkali is a mixture of sodium hydroxide and sodium carbonate.