JPS627609A - Method for recovering tellurium from anode slime produced by electrolysis of tellurium - Google Patents

Abstract

PURPOSE:To recover TeO2 with high efficiency by adjusting the pH of extracted liquid obtd. by treating anode slime with mineral acid to adjust the pH to a specified value, and adding a specified amt. of sodium sulfite to form precipitate. CONSTITUTION:Anode slime is deposited on the surface of an insoluble anode when tellurium is obtd. by electrowinning of electrolytic liquid of sodium tellurite. The anode slime is treated with mineral acid (e.g. H2SO4) and the solid is separated from the liquid to prepare extracted liquid, and alkali (e.g. NaOH) is added to the extracted liquid to adjust the pH to 4-8. The extracted liquid is stirred while maintaining the pH, and 0.7-1.5 times weight (basing on the amt. of tellurium contained in the extracted liwuid) of sodium sulfite is added and the mixture is stirred for ca.2-3hr. The temp. at this stage is held at below ca.30 deg.C. The liquid is then allowed to stand or filtered and generated precipitate is separated. Thus, TeO2 having high purity is recovered at high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for recovering tellurium from anode mud produced during electrowinning of tellurium using telluric acid (IJ) as an electrolyte.

[Conventional technology]

When collecting sodium tellurate as an electrolyte using the tellurium decomposition method, an insoluble electrode made of stainless steel, titanium, etc. is used as the anode, but when this electrolysis operation progresses to a certain extent, the insoluble anode is removed, which is thought to be a phenomenon of anodic oxidation. A defective conductor is deposited on the surface of the

The above-mentioned defective conductor is referred to as tellurium anode mud. Conventionally, the methods for recovering tellurium from the anode mud are as follows: 1) The anode mud is treated with sulfuric acid, sulfur dioxide gas is blown into the resulting extract, and the resulting tellurium grains are repeatedly subjected to the precipitate treatment step. 2) Copper powder is added to the sulfuric acid extract obtained by the same treatment as in 1), and copper telluride grains are precipitated. 3) Same as in 1). After neutralizing the sulfuric acid extract obtained by adding an alkali to the sulfuric acid extract, sulfur dioxide gas is blown in to recover tellurium as tellurium oxide (presented by Japan Mining Industry at the Autumn Conference of the Japan Mining Association in 1988). Practical or proposed.

However, methods 1) and 2) above: - Approximately 3
Approximately 0% by weight becomes tellurium metal and is repeated in the grain processing process, and methods 1) to 3) also use sulfur dioxide gas, which is environmentally unfavorable.

[Problem that the invention seeks to solve]

The object of the present invention is to provide a method for separating and recovering tellurium from tellurium anode mud without the above-mentioned drawbacks.

[Means for solving problems]

In order to achieve this object, the present invention treats tellurium anode mud with mineral acid, adds alkali to the resulting extract, and
H2-8 Preferably, the pH is set to 4-8, and while stirring while maintaining this pH, 0.7-1.5 times the amount of IJ sulfite is added by weight to the amount of tellurium contained in the extract. It is preferably added in the form of a powder, and preferably after continued stirring for 1 to 3 hours, it is allowed to stand and the supernatant liquid is removed, or it is filtered to efficiently recover the generated tellurium dioxide (TθO). It is something.

[Effect]

In the present invention, any mineral acid can be used as the mineral acid for extracting tellurium from tellurium anode mud as long as it does not generate harmful gas in this operation or interfere with the precipitation of tellurium dioxide in the next step. However, during the extraction operation, sulfuric acid is most preferable because it accelerates the extraction process with reaction heat, etc.
Otherwise, hydrochloric acid is preferred. The reason why the pH of the extract obtained in the first step is adjusted to 2 to 8, preferably 4 to 8 with an alkali is because if the pH of this extract is low, sulfur dioxide gas will be generated when sodium sulfite is added. This is because the reduction reaction does not proceed quantitatively. Moreover, no particular advantage is observed even if the pH is increased further.

Next, the amount of sodium sulfite added was set to 0 based on the weight of tellurium.
．． The reason for setting the amount in the range of 7 to 1.5 times is that if it is less than 0.7 times, it is difficult to reduce hexavalent tellurium to tetravalent tellurium, and if it is used more than 1.5 times, tellurium will be reduced. If the reaction progresses too much, some metallic tellurium precipitates and becomes a mixture with tellurium dioxide, which not only complicates subsequent operations but also tends to increase the tellurium concentration in the supernatant liquid, as shown in Table 1. This is because it shows. The temperature for carrying out the above reduction is 30 C.
The following are desirable.

Approximately 70% of the tellurium in the supernatant liquid separated in this process is recovered by the known cementation method by adding copper powder, and then discharged. According to the present invention, PbX5.
Tellurium can be recovered as high-purity tellurium dioxide at a yield of 99% by weight or more from tellurium anode mud containing .

〔Example〕

Examples will be described below.

Example I 9 to 1 part each of tellurium anode mud containing t% of each weight of To42.2, Se O,03, Pb O,03 balance water, Na, etc.
, 722% by weight (182g/l, specific gravity 1.63)
+7) 500 at each of sulfuric acid was added, and after waiting for the reaction to settle down, 2.7 to 4.61 at of ion water was gradually added, and the exothermic reaction was utilized to leaching valuables.

The slurry concentration at the time of leaching was around 200g/200g, and suction filtration and washing were carried out after a total of 1 hour without any particular heating or cooling, and the slurry was adjusted to a predetermined pH value of 48%.
Add 0 g/l of sodium hydroxide aqueous solution, and then add To
The concentration is 70-120 g/l, and the liquid volume of each sample is 200 g/l.
After adjusting by adding ionized water so that the amount is 1.0 m, add 0.5 to 2.0 times the amount of tellurium by weight (1.0 times is approximately 1 equivalent) to the amount of tellurium in the above aqueous solution. The pH of the aqueous solution was maintained and the solution was added while gently stirring with a propeller stirrer. After 1 to 3 hours, the tellurium concentration in the supernatant was determined by atomic absorption method, and the tellurium in the precipitate was determined by chemical analysis. Quantitated.

The results are shown in Table 1 in comparison with those outside the scope of the present invention.

Table 1 shows the relationship between the addition ratio of sodium sulfite and the tellurium concentration of the supernatant after each treatment.

The treatment temperature was room temperature 25C.

As is clear from Table 1, experiments and
In all cases other than No. 1, A7, and A12, tellurium was recovered as high-purity tellurium dioxide with a yield of 99% by weight or more.

However, a small amount of 5eXPb contained in the tellurium anode mud could not be removed.

Example 2 Tellurium dioxide was precipitated in the same manner as in Example 1, except that the tellurium anode mud used in Example 1 was treated with concentrated hydrochloric acid of grade 1 reagent. The overall results were almost the same, with a slight increase in lead content in the product.

In Examples 1 and 2, there were no problems such as formation of metallic tellurium together with tellurium dioxide, generation of gas, or difficulty in solid-liquid separation, but as seen in Experiment &6 and Boil 11 in Table 1,
If a large amount of IJum is added and the solution is left for a long time after reduction, the tellurium concentration in the supernatant will increase, so care must be taken.

〔Effect of the invention〕

Since the process steps of the present invention are short, there is less loss of tellurium.

Advantages include the ability to obtain extremely pure tellurium dioxide with simple equipment.

Claims (1)

[Claims] (1) In a method for recovering tellurium from the anode mud that adheres to the surface of an insoluble anode when tellurium is electrowinning using sodium tellurite as an electrolyte, the anode mud is treated with a mineral acid and then solid-liquid separated. Then, add an alkali to the obtained extract to adjust the pH to 2 to 8, and while maintaining this pH and stirring, add sodium sulfite in an amount of 0.7 to 1.5 times the amount of tellurium in the extract, A method for recovering tellurium from anode mud generated during tellurium electrolysis, which is characterized by separating the generated precipitate.