JPH01230733A - Manufacture of high purity thallium - Google Patents

Abstract

PURPOSE:To effectively recover high purity Tl by subjecting Tl to leaching and oxidizing from Tl-contg. material in the use of an acid and an oxidizing agent, adding a reducing agent to the filtrate in which residue is filtered out to reduce Tl, furthermore adding Cl thereto, precipitating TlCl and reducing it. CONSTITUTION:Tl-contg. material such as smoke ash in lead refining is subjected to leaching and oxidizing in the use of an acid such as sulfuric acid and an oxidizing agent to filter out the residue. The reducing agent such as hydrazine hydrochloride and the source of chlorine are added to the filtrate and tervalent Tl is reduced into monovalent one to convert it to TlCl and it is selectively precipitated to separate. The molten solution is filtered to recover Tl from the filtrate by reduction depositing. The recovered Tl is dehydrated, is thereafter melted into coarse Tl and is furthermore subjected to melt refining. By this method, high purity Tl can effectively be manufactured by a simple process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing highly pure metallic thallium from a thallium-containing substance. In particular, 99.999% of all thallium materials produced in non-ferrous smelting are used as starting materials.
The present invention relates to a method capable of recovering high-purity thallium.

Thallium is present in a few percent in lead flue ash, lead electrolyte, clean slag generated from the cadmium wire manufacturing process, zinc smelting smoke ash, and other by-products generated from various treatments in the non-ferrous smelting process.
Contains about 20%. If thallium is left unrecovered and removed from such thallium-containing materials, thallium will accumulate in the smelting system, and if the allowable limit is exceeded, various adverse effects will occur in each processing step. In addition, thallium is an optical fiber,
Demand for high-purity thallium has increased in recent years, as it is used in special optical fields such as copier lenses and for sealing phototubes and transistors.

[Conventional technology and problems]

Conventional methods have been proposed for recovering high-purity thallium from thallium-containing materials. In JP-A No. 56-136941, thallium-containing material is immersed in sulfuric acid to which a reducing agent such as sodium sulfite has been added to dissolve thallium as thallium hydroxide, and the a solution is changed to an alkaline solution to precipitate the inclusions. After removal, zinc powder is added again as an acidic solution of sulfuric acid to reduce it and precipitate metal thallium. In addition, in Japanese Patent Publication No. 61-34494, thallium-containing substances were
After leaching and converting this into an alkaline solution to precipitate and remove contaminants, the solution is again converted into an acidic sulfuric acid solution, and metal thallium is reduced and precipitated on a zinc plate in the presence of hydrogen peroxide. In addition, special public relations show 6
No. 1-34495 proposes a method in which a step of adding sodium chloride to the SO2 leaching slurry is added, and hydrogen peroxide is omitted in the thallium precipitation step.

However, each of the above methods has problems. That is, in the method of JP-A-56-136941, since zinc powder is used in the step of reducing and precipitating thallium,
There is a risk that zinc dust will be mixed into the product, and a large amount of thallium will precipitate as sulfide during thallium precipitation, causing problems in refining metallic thallium.

Next, Special Publication No. 61-34494 and No. 61-3449
In all methods No. 5, thallium is leached out while reducing the raw material with SO2, so in the case of raw materials containing chlorine, hardly soluble thallium chloride is produced and is difficult to be leached out. In addition, in these methods, the leach slag is subjected to alkali dissolution to remove contaminants by precipitation.
Since almost no arsenic is removed and thallium may precipitate, the yield of thallium may be less than 80% in the alkaline purification process, which also poses a problem in terms of yield. Furthermore, in both of the above methods, after leaching thallium, it is made into an alkaline solution, and then this is further changed to an acidic solution to replace the zinc plate, making the adjustment of the treatment solution cumbersome.

[Knowledge related to problem solving]

The present inventor discovered that by adding an oxidizing agent to oxidize thallium to trivalent thallium during leaching of thallium, it is possible to secure an extremely high leaching rate even for raw materials containing chlorine, and that the leaching solution is not made alkaline but acidic. It was discovered that not only zinc and cadmium but also arsenic can be separated by adding a reducing agent and chlorine.

[Structure of the invention]

The present invention involves the steps of leaching and oxidizing thallium from a thallium-containing material using an acid and an oxidizing agent, filtering off the residue, adding a reducing agent to the filtrate to reduce thallium, and adding a chlorine source to convert thallium chloride. A method for producing high-purity thallium is provided, which comprises a step of precipitating and separating, and a step of reducing the thallium chloride and recovering it as metal thallium.

An example of the method according to the invention is shown in a flow sheet.

The thallium-containing substances that are the starting materials of the present invention include lead briquette ash, button electrolyte, clean slag generated from the cadmium smelting process, zinc smelting ash, and other by-products produced in various steps in the non-ferrous smelting process. It is a residue.

The present invention leaches and oxidizes thallium from thallium-containing materials using an acid, primarily sulfuric acid, and an oxidizing agent. As the oxidizing agent, hydrogen peroxide, ozone, etc. can be used. Thallium is 3
oxidized to valence (TI2'') and dissolves in the leachate. -valence TQ+ compounds are difficult to dissolve.

Thallium-containing substances usually contain impurities such as tin, zinc, cadmium, and arsenic. Sulfuric acid and oxidizing agents precipitate lead as lead sulfate, but most of the other elements are leached out. The leaching temperature is preferably about 60°C or higher from the viewpoint of increasing the solubility of thallium.

After separating the precipitate mainly consisting of lead sulfate by filtration, a reducing agent and a chlorine source are added to the filtrate to reduce trivalent thallium to monovalent thallium.
It is selectively precipitated and separated as thallous chloride (TQCQ). Note that since thallium chloride (TQCQ) does not precipitate, it is necessary to add a chlorine source together with a reducing agent.

Chlorine sources include HCQ, CQ2, NaCQ, etc.
Any material that forms Q ions may be used.

Reducing agents include FeSO4, FeCQ2, Cu CQ
2. Hydrazine hydrochloride (N2H6CI22) and the like can be used. Especially FeCQ, CuCl2. Hydrazine hydrochloride and the like can be used both as a reducing agent and as a chlorine source. Zinc and arsenic in the liquid remain in the filtrate and are separated from the thallium chloride precipitate5. Therefore, in the subsequent cementation process, arsenic is not present and the generation of dangerous arsine (AsH,) gas is prevented. Can be done. Several percent of cadmium is thallous chloride (TQ).
, Cl2), but most of it is dissolved in the filtrate and can be removed by filtration. More than 90% of thallium becomes thallium chloride (TQCQ). Filtered thallium chloride (
TffCQ) is subsequently dissolved in sulfuric acid. Melting temperature is 8
A temperature of about 0°C is preferable.

There is no need to add hydrogen peroxide when dissolving the thallous chloride (Tff(I2)). Therefore, most of the cadmium co-precipitated with the thallium chloride remains as a precipitate. is reduced and precipitated and recovered. The reduction and recovery step can be performed by a known method.

For example, after adjusting the pH of the filtrate to 2 to 3, it is loaded onto a zinc plate, and thallium is reduced and precipitated as sponge thallium and recovered. After dehydrating the recovered sponge thallium at 80-100°C in a reducing or inert atmosphere, it was heated at 350 °C in the same container.
Melt at ~400°C to obtain crude thallium.

Crude thallium is melted and purified using NaOH flux9
9.999% metallic thallium is obtained. NaOH bath is 35
The temperature is 0 to 400°C.

In addition, instead of cementation using zinc as mentioned above,
Electrolytic refining may also be performed.

[Examples and comparative examples]

Example 1 100g of smoke ash from lead smelting (TU 12.2%, Pb 5
,1.3%, As0.4%, Cd4.2%, ZnO
, 5%, 85.0%, Cl215.4%) for 1000 m
Place in a beaker of I2, add 10 mQ of sulfuric acid, 400 mQ of water,
+(,0220ml was added and leached for 2 hours at 60°C.

When the sediment was filtered and the filtrate was analyzed, the leaching rates were TQ 94% (11.5 g/Q), Pb O, 7%, and A.
s 70%, Cd 95%, and Zn 92%.

Next, hydrazine hydrochloride Log was added to the leachate to reduce Tρ to T.
Precipitated as QCfl. The precipitation rate of TI2 is 93.0
%Met. As and Zn did not precipitate, but 5.0% of Cd precipitated.

After filtering and washing the precipitate, 80°C H2SO, IonΩ
was dissolved in a solution 112 containing The main component of the dissolved residue was Cd. After the residue was filtered off, it was diluted with water and adjusted to pl=2 to prevent TQ precipitation. The volume of the solution is 3Q,
The thallium concentration was 3.5 g/u.

A zinc plate measuring 5 mm x 55 mm x 90 mm was placed in this solution to precipitate thallium. The spongy thallium deposited was scraped off from the zinc plate and charged into a furnace. After drying in the furnace at 90°C in an Ar2 atmosphere for 12 hours, the furnace temperature was raised to 400°C.
℃ and melted thallium to obtain crude thallium. Subsequently, NaOH flux was added to the crude thallium, stirred, and then cooled to obtain 5 g of purified thallium metal lo.

The quality of purified thallium metal was 99.999%.

Example 2 100g of smoke ash from copper smelting (TQ 3.5%, Pb 20.
4%, As4.8%, CdO, 8%, Zn 2.2%
, 89.9%, CI 20.02%) was placed in a 10100O beaker, and sulfur filOm (1, 400ml of water, air with an ozone concentration of 10g/rn'' was supplied at 6n/min,
Leaching was carried out for 2 hours at 80°C. When the precipitate was filtered and the filtrate was analyzed, the leaching rates were TQ 94%, (3,
3g/U, As 75%, Cd 65%, Zn 91%
Met.

Next, 10 g of FeSO4 and 3.0 m of HCfl were added to the leachate.
I2 was added to precipitate TI2 as TQCQ. T
The precipitation rate of Q is 94%.

As and Zn did not precipitate, and 3% of Cd precipitated. After filtering and washing the precipitate, it was dissolved in solution IQ containing 8230410m+2 at 80°C. After filtering off the residue containing Cd as the main component, the pH of the solution was adjusted to 2, and 5 mm
A 55 mm x 90 mm zinc plate was charged, and thallium was deposited. The resulting spongy thallium was scraped off from the zinc plate.

It was charged into a furnace, and after drying in the furnace in an Ar atmosphere at 90° C. for 12 hours, the furnace temperature was raised to 400° C., and thallium was melted to obtain crude thallium. Approximately 400% crude thallium with NaOH flux
It was melted and purified at ℃ to obtain 3.1 g of purified thallium.

The quality of purified thallium was 99.999%.

Comparative Example 1 100g of the sample of Example 1 was mixed with 10mQ of sulfuric acid and 40ml of water.
When 0mQC was leached, Cd and Zn were leached out, but TQ was not leached out and Trl could not be recovered.

Comparative Example 2 Na0)15.
The p)l of the solution was adjusted to 12 by adding 5 g. Zinc and cadmium were converted to hydroxide and removed, but arsenic was removed at 70%.
It was dangerous to perform cementation in the subsequent recovery process because only 1.5% could be removed. Furthermore, the recovery rate of TQ was 80%, which was extremely low.

〔Effect of the invention〕

According to the method of the present invention, thallium with higher purity than thallium-containing substances can be produced efficiently and at low cost.

Since the method of the present invention uses an oxidizing agent during leaching, the leaching rate is better than that of conventional methods. In addition, since the alkalinization step is not performed, the process is simple, the actual yield is high, and it is advantageous in terms of cost. Further, in the process of dissolving thallium chloride (TQCρ), hydrogen peroxide is not required, so the separation effect from cadmium is good.

Furthermore, the arsenic removal effect is good in the thallium chloride precipitation process, and there is no risk of toxic arsine gas being generated during thallium cementation, making the treatment operation safe.

In the steps after recovering sponge thallium, drying and melting can be performed in the same furnace in a reducing or inert atmosphere, resulting in crude thallium, resulting in a high yield of thallium.

[Brief explanation of the drawing] The drawing is a flow sheet of the method of the invention.

Claims (1)

[Claims] 1. A step of leaching and oxidizing thallium from a thallium-containing material using an acid and an oxidizing agent, and filtering off the residue. After adding a reducing agent to the filtrate and reducing thallium, a chlorine source is added to precipitate and separate thallium chloride. A method for producing high-purity thallium, comprising a step of reducing the thallium chloride and recovering it as metal thallium.