JP7325363B2 - Method for treating mixtures containing selenium and tellurium - Google Patents

Description

The present invention relates to a method of treating mixtures containing selenium and tellurium. In particular, it is suitable for application to smelting intermediates of selenium and tellurium generated in the electrolytic sediment treatment process of copper smelting.

In copper pyrometallurgical refining, copper concentrate is melted, converted into 99% or higher blister copper in a converter and a refining furnace, and then refined copper with a purity of 99.99% or higher is produced in an electrolytic refining process. In recent years, metal scraps containing precious metals derived from electronic components have been put into converters as recycled raw materials, and valuables other than copper precipitate as slime during electrolytic refining.

This slime is enriched with precious metals, rare metals, and selenium and tellurium contained in copper concentrates at the same time. These elements are separately separated and recovered as copper smelting by-products. Hydrometallurgical methods are often applied to treat this slime. For example, Patent Document 1 discloses a method of recovering silver from slime with hydrochloric acid-hydrogen peroxide, recovering dissolved gold by solvent extraction, and then successively reducing and recovering other valuables with sulfur dioxide.

In the method of recovering valuables using sulfur dioxide, the valuables are reduced and recovered sequentially after dissolution. Platinum and palladium precipitate first. If the raw material is copper electrolytic slime, it is recovered as a mixture with selenium because it contains a large amount of selenium. Selenium is then reduced, and finally tellurium is reduced.

In reducing and recovering selenium, the reaction is stopped when the selenium concentration reaches about 3 g/L in order to prevent contamination with tellurium. Therefore, a large amount of selenium is mixed in the tellurium that is reduced in the post-process and recovered as a precipitate. Tellurium and selenium are separated from this mixed precipitate.

For the separation of these two elements, a method is generally known in which tellurium is dissolved in a strong alkali and then neutralized to separate tellurium as tellurium dioxide (Patent Document 2). The liquid after separation of tellurium dioxide contains selenium, and in order to recover this selenium, the precipitate is recovered as simple selenium using a reducing agent.

JP-A-2001-316735 JP-A-5-311264

The liquid after precipitation and separation of tellurium dioxide still contains about 10 to 500 mg/L of tellurium. When crude selenium is reduced and recovered from this liquid, tellurium is mixed. This crude selenium can be further distilled to increase its purity, but if crude selenium containing tellurium is distilled, tellurium will be brought into the still.

Since the tellurium brought into the distillation kiln remains without volatilization, it is necessary to remove the tellurium by regular cleaning of the kiln. Since the production of selenium also stops during the cleaning, it is better that the cleaning frequency is low. It is necessary to reduce the amount of tellurium brought in, and in reality, to lower the grade of tellurium in the crude selenium.

However, the tellurium mixed in the crude selenium is generally separated by repeating the reaction of precipitating tellurium dioxide by alkali dissolution or oxidative dissolution and neutralization, and an inexpensive and efficient method for separating this is known. not

An object of the present invention is to provide a method for efficiently isolating tellurium from a mixture containing selenium and tellurium at low cost.

As a result of intensive research to solve the above problems, the present inventors dissolved a mixture of selenium and tellurium with an alkali, neutralized it to separate tellurium dioxide, adjusted the solution to pH 11 or higher again, and added a reducing sugar. We have found that the above problems can be solved by reducing and removing tellurium. Embodiments of the invention are specified as follows.
(1) A dissolution step of pouring an alkaline solution into a mixture containing selenium and tellurium and heating at 70° C. or higher while supplying air to prepare a solution of selenium and tellurium;
A tellurium dioxide recovery step of separating tellurium dioxide by solid-liquid separation of a precipitate formed by adding an acid to a solution of selenium and tellurium to adjust the pH to less than 5, and
A tellurium removal step of adding alkali to the solution after tellurium dioxide separation, adjusting the pH to 11 or higher again, adding reducing sugars and heating to 60° C. or higher to precipitate and remove tellurium in the solution;
A method of treating a mixture containing selenium and tellurium containing
(2) The method for treating a mixture containing selenium and tellurium according to (1), wherein the amount of the reducing sugar added is at least 2 times the mass of tellurium.
(3) The method for treating a mixture containing selenium and tellurium according to (1) or (2), wherein the reducing sugar is fructose or glucose or a mixture thereof.
(4) The reducing sugar is fructose, and in the tellurium removal step, when the fructose is added to precipitate tellurium, the pH is adjusted to 12 to 13 for reduction according to any of (1) to (3). A method for treating a mixture containing selenium and tellurium according to claim 1.
(5) Acid is added to the liquid from which tellurium has been precipitated and removed in the tellurium removal step to adjust the pH to 3 or less, and the liquid is heated to 70°C or higher and sulfur dioxide is blown in to precipitate selenium. A method for treating a mixture containing selenium and tellurium according to any one of (1) to (4) to be recovered.

According to the embodiments of the present invention, it is possible to provide a method for inexpensively and efficiently isolating tellurium from a mixture containing selenium and tellurium.

FIG. 10 is a time-dependent change in the concentration of selenium according to Example 3 of the present invention; FIG.

<Mixture containing selenium and tellurium>
Platinum group elements and chalcogen elements are concentrated in electrolytic slime produced in the electrorefining process of non-ferrous metal smelting, especially copper smelting. Platinum group elements and chalcogen elements are not smelted independently, but are recovered as by-products of other metals or recovered from recycled raw materials such as waste catalysts. Therefore, the method of treating mixtures containing selenium and tellurium according to embodiments of the present invention can also be applied to recycling from waste.

In the electrolytic refining process of copper smelting, hydrochloric acid and hydrogen peroxide are added to dissolve electrolytic slime, but silver forms chloride ions and insoluble silver chloride precipitates immediately after dissolution. A solution containing an oxidizing agent and chlorine, such as aqua regia or chlorine water, dissolves precious metals and separates silver as silver chloride. Since it is a chloride bath, platinum group elements, rare metal elements, selenium, and tellurium are distributed in the pregnant leach liquor (PLS).

Precious leach liquor (PLS) is cooled once to precipitate and separate chlorides of base metals such as lead and antimony. The gold is then separated into the organic phase by solvent extraction. A widely used extractant for gold is dibutyl carbitol (DBC).

Valuables can be precipitated and recovered by reducing PLS after extracting gold, but the order of precipitation is naturally determined because the oxidation-reduction potential differs depending on the element. Gold, platinum and palladium are precipitated first, then chalcogens such as selenium and tellurium, and then inert precious metals.

Reducing sulfur is used as a reducing agent from the viewpoint of cost and efficiency. Among them, sulfur dioxide is most suitable because it can be supplied in large quantities and at low cost by roasting of converter gas or sulfide ore.

After recovering selenium with sulfur dioxide, tellurium is recovered by blowing sulfur dioxide in the same manner, but at this time, a considerable amount of unrecovered selenium is mixed. This selenium-contaminated tellurium is suitable as a target.

The mixture to be treated in the method for treating a mixture containing selenium and tellurium according to the embodiment of the present invention may be a mixture of selenium and tellurium. When tellurium is mixed as tellurium dioxide, the effect is even higher.

<Method for treating mixture containing selenium and tellurium>
In the method for treating a mixture containing selenium and tellurium according to an embodiment of the present invention, an alkaline solution is poured into the mixture containing selenium and tellurium, and heated at 70 ° C. or higher while supplying air to dissolve selenium and tellurium. A dissolution step of adjusting the liquid, a tellurium dioxide recovery step of separating tellurium dioxide by solid-liquid separation of the precipitate formed by adding acid to the solution of selenium and tellurium to adjust the pH to less than 5, and dioxide A tellurium removal step is included in which alkali is added to the tellurium-separated liquid to adjust the pH to 11 or higher again, reducing sugars are added, and the solution is heated to 60°C or higher to precipitate and remove tellurium in the solution.

In the dissolution step, an alkaline solution is poured into the mixture containing selenium and tellurium, and the mixture is dissolved by heating at 70° C. or higher while supplying air. From the viewpoint of solubility, the alkali that can be used in the alkaline solution is preferably sodium hydroxide or potassium hydroxide, and the concentration is preferably 1N or higher, more preferably 1.5N or higher, and even more preferably 2N or higher. Moreover, the heating temperature at this time is preferably 70 to 80° C. from the viewpoint of reactivity.

In the dissolution process, the reaction efficiency is improved by supplying air as an oxidant during heating. The selenium in the mixture dissolves as selenous acid and the tellurium as telluric acid. Thus, a solution of selenium and tellurium can be prepared.

In the tellurium dioxide recovery step, an acid is added to the solution of selenium and tellurium to adjust the pH to less than 5, and the resulting precipitate is subjected to solid-liquid separation to separate tellurium dioxide. Acids added to the solution of selenium and tellurium include hydrochloric acid and sulfuric acid. The pH adjusted by adding an acid is more preferably 1 to 4. By adjusting the pH to such a range, white tellurium dioxide precipitates.

Tellurium can be recovered as tellurium dioxide by solid-liquid separation of the precipitate formed by adjusting the pH to less than 5.

In the tellurium removal step, an alkali is added to the tellurium dioxide separated liquid to adjust the pH to 11 or more again, and a reducing sugar is added and heated to 60° C. or more to precipitate and remove tellurium in the solution. . Since a certain amount of tellurium remains in the solution after solid-liquid separation, the solution is again adjusted to alkalinity, and tellurium is selectively reduced with reducing sugars.

From the viewpoint of solubility, the alkali to be added is preferably sodium hydroxide or potassium hydroxide, and the concentration is preferably 1N or more, more preferably 1.5N or more, and even more preferably 2N or more. Moreover, the heating temperature at this time is preferably 60 to 80° C. from the viewpoint of reactivity.

Saccharides, lower aldehydes and the like are known to exhibit a reducing action under alkaline conditions. Tin (II) salts, copper, and base metals reduce tellurium even under acidic conditions, but there is a risk of contamination with selenium as impurities. Therefore, in embodiments of the present invention, tellurium is selectively reduced with reducing sugars.

Any reducing saccharide can be used as the reducing saccharide of the present invention. In particular, a ketose having a large equilibrium constant is preferred in view of the ring-opening equilibrium of the ring structure. Saccharides have a cyclic structure, which is hydrolyzed into a linear structure. The linear and ring shapes are in equilibrium with each other, and this is called open ring equilibrium.

The reducing sugar is preferably fructose or glucose, or a mixture thereof, which is versatile in terms of cost. Fructose is most preferred as it is a ketose.

The amount of reducing sugar added is preferably at least 2 times the mass of tellurium. Tellurium can be removed more satisfactorily when the amount of reducing sugar added is 2 times or more by mass that of tellurium. Moreover, if too much reducing sugar is added, it causes an increase in cost and an increase in COD (Chemical Oxygen Demand) of the solution. It also reduces selenium. From this point of view, the amount of reducing sugar added is more preferably 2-10 times the mass of tellurium.

The reduction temperature by reducing sugars is controlled at 60° C. or higher. If the temperature is low, there is a problem that the reaction is slow, or the precipitated tellurium particles become fine and solid-liquid separation becomes difficult. Therefore, it is preferable that the reduction temperature by the reducing saccharide is 70° C. or higher. Before adding the reducing sugar, the solution after removing tellurium dioxide is adjusted to pH in the alkaline range. Since saccharides have ring-opening equilibrium in the carbonyl portion, the pH is adjusted to 11 or higher. In addition, when the alkalinity becomes strong, the sugar ring opens and a reducing aldehyde is generated. Here, when the pH exceeds 13, it becomes extremely highly alkaline. At this time, the once precipitated tellurium is likely to re-dissolve over time. Therefore, when fructose is added as a reducing sugar to precipitate tellurium, it is preferable to adjust the pH to 12-13 for reduction.

Tellurium precipitated by reduction is recovered by solid-liquid separation by an appropriate method. It is also possible to add an acid to the solution from which the tellurium content has been removed to adjust the liquid property to be acidic, and to further add a reducing agent such as sulfur dioxide to reliably recover the selenium.

Acid is added to the liquid after precipitating and removing tellurium in the tellurium removal step to adjust the pH to 3 or less, and the liquid is heated to 70° C. or higher and sulfur dioxide is blown in to precipitate and recover selenium. can. Examples of the acid to be added include hydrochloric acid and sulfuric acid. Selenium can be more favorably precipitated by adjusting the pH adjusted by adding an acid to 3 or less.

After adjusting the pH to 3 or less by adding an acid, by heating to 70° C. or more and blowing in sulfur dioxide, the reactivity becomes good and selenium can be well precipitated. A heating temperature of 80° C. or higher is more preferable.

Examples of the present invention are described below, but the examples are for illustrative purposes and are not intended to limit the invention.

(Example 1)
Electrolytic slime recovered from copper smelting was treated with sulfuric acid to remove copper, then concentrated hydrochloric acid and 60% hydrogen peroxide solution were added to dissolve the slime, followed by solid-liquid separation to obtain PLS. The PLS was then cooled to 6° C. to precipitate and remove base metals.

Next, the PLS and DBC (dibutyl carbitol) are mixed to extract gold, and a mixed gas of sulfur dioxide and air (sulfur dioxide concentration: 5 to 20%) is blown into the extracted PLS at 70° C. to extract precious metals. Solid-liquid separation was performed on the precipitates formed by the sequential reduction of selenium.

Next, the liquid after solid-liquid separation was heated again to 80° C. to 85° C., and a mixed gas of sulfur dioxide and air was blown thereinto. When the tellurium concentration became 30 mg/L or less, the reaction was stopped and solid-liquid separation was performed. A 1 mol/L (1N) sodium hydroxide solution was poured into the precipitate and heated to 80° C. while aeration. After heating for 12 hours, the mixture was filtered, and the filtrate was used as an experimental liquid.

Sulfuric acid was poured into the liquid to be tested to adjust the pH to 3-4. A white precipitate of tellurium dioxide was formed and was filtered off. 200 ml of the filtrate was weighed out, and an attempt was made to separate tellurium from the liquid using the additives and conditions shown in Table 1. After the resulting precipitate was separated by filtration, sulfuric acid was added until the pH reached 1 or less, the mixture was heated to 65-70°C, and a mixture of sulfur dioxide and air was blown in for 90 minutes to recover the precipitate of selenium.

The concentrations of selenium and tellurium in the liquid after separating tellurium and after separating selenium (liquid after selenium precipitation) were quantified. After filtration, 2 ml of the sample liquid was collected, and hydrochloric acid was added. A precipitate formed and was dissolved by adding 2 ml of 25% hydrogen peroxide. Next, each concentration of Se and Te was quantified by ICP-OES (SPS3100 manufactured by Seiko) after adjusting to 50 ml. The raw material liquid had a Te concentration of 23 mg/L and a Se concentration of 17.6 g/L. Table 1 shows the test results.

Table 1 shows that saccharides are effective in reducing tellurium. Tin sulfate and copper powder, which are typical reducing agents, can also be used to precipitate tellurium, but this is not preferable because the recovered tellurium may be contaminated with heavy metals.

(Example 2)
1N sulfuric acid was added to solid selenium and hydrogen peroxide (35%) was slowly added. After stirring, selenium remaining undissolved was filtered off. The filtrate was neutralized by adding sodium hydroxide (10 g/L) solution. Further, tellurium dioxide dissolved in 1N sodium hydroxide solution was added. After mixing well, the supernatant was used as an experimental solution.

200 ml of test solution was taken. Sodium hydroxide was added until the pH was above 12. It was heated to 70° C. and the sugars shown in Table 2 were added. The precipitate formed after stirring for 30 minutes was filtered off. Sulfuric acid was added to the filtrate to adjust the pH to 1 or less, the mixture was heated to 65-70° C., and a mixture of sulfur dioxide and air was blown thereinto. The reaction was stopped after 60 minutes. Quantitative solution samples were taken after the addition of reducing sugar and when the reaction was stopped. The quantitative analysis operation conforms to Example 1.

According to Table 2, it can be seen that only tellurium was selectively reduced by the addition of reducing sugars. In addition, it can be seen that reducing sugars show an effect from about 2 times the mass of tellurium (addition of 0.2 g of fructose), and the effect is high when adding at least 5 times the mass of tellurium (addition of 0.5 g of each).

(Example 3)
200 ml of the same experimental solution as in Example 2 was taken. The pH was adjusted to 12.5 or 13.2 with sodium hydroxide, and the liquid temperature was heated to 70°C. 0.5 g or 1 g of fructose was added and stirred. Samples were taken at predetermined time intervals, and the concentrations of selenium and tellurium in the filtered solution were quantified. The quantification method conforms to Example 1. The evaluation results of Example 3 are shown in FIG. In FIG. 1, the solid line indicates the tellurium concentration and the dashed line indicates the selenium concentration.

In all experimental examples, the tellurium concentration decreased immediately after the addition of fructose, but turned to increase after a certain period of time. It is considered that the once precipitated tellurium dissolved again after the fructose disappeared. To prevent redissolution, it is effective to reduce the reaction rate with sugars. For fructose, less than 80°C is preferred. If the temperature is too low, the reaction will not occur, so 60° C. or higher is preferable.

It can be seen that if the pH is too high, the balance of fructose is biased toward the reduced form, and selenite is also reduced. This was the same when the amount of fructose added was 1 g. Increasing the amount added and pH decreases the tellurium reduction selectivity.

When fructose is used as a reducing sugar, the pH is preferably 12 to 13, and the amount to be added is preferably 5 times the mass of tellurium. Reducing sugars change this optimum.

These phenomena are presumed to be the same even when sugars other than fructose are used, and if the reaction is unavoidably prolonged, or if the pH is high, the precipitation can be precipitated once by adding glucose, which has a slow reaction rate. Redissolution of tellurium could be prevented.

Claims (5)

A dissolution step of pouring an alkaline solution into a mixture containing selenium and tellurium and heating at 70° C. or higher while supplying air to prepare a solution of selenium and tellurium;
A tellurium dioxide recovery step of separating tellurium dioxide by solid-liquid separation of a precipitate formed by adding an acid to a solution of selenium and tellurium to adjust the pH to less than 5, and
A tellurium removal step of adding alkali to the solution after tellurium dioxide separation, adjusting the pH to 11 or higher again, adding reducing sugars and heating to 60° C. or higher to precipitate and remove tellurium in the solution;
A method of treating a mixture containing selenium and tellurium containing 2. The method for treating a mixture containing selenium and tellurium according to claim 1, wherein the amount of the reducing sugar added is two times or more by mass that of tellurium. 3. The method for treating a mixture containing selenium and tellurium according to claim 1 or 2, wherein the reducing sugar is fructose or glucose or a mixture thereof. 4. The reducing sugar is fructose, and in the tellurium removal step, when the fructose is added to precipitate tellurium, the pH is adjusted to 12 to 13 for reduction according to any one of claims 1 to 3. of a mixture containing selenium and tellurium. An acid is added to the liquid from which tellurium has been precipitated and removed in the tellurium removal step to adjust the pH to 3 or less, the liquid is heated to 70°C or higher, and sulfur dioxide is blown in to precipitate and recover selenium. Item 5. A method for treating a mixture containing selenium and tellurium according to any one of Items 1 to 4.