JP2021025069A - Method of treating seleno sulfate solution - Google Patents

Abstract

To provide a method of treating a seleno sulfate solution that selectively reduces selenium oxonium ions in a seleno sulfate solution to separate tellurium from the seleno sulfate solution.SOLUTION: A method of treating a seleno sulfate solution includes the step of adding a reducing sugar to a seleno sulfate solution containing tellurium oxonium ions with its pH controlled to 10 or more, and heating it to 60°C or higher for precipitating tellurium.SELECTED DRAWING: None

Description

The present invention relates to a method for treating a selenosulfuric acid solution.

In the copper pyrometallurgy, copper concentrate is melted to obtain 99% or more blister copper in a converter and a refining furnace, and then electrolytic copper having a purity of 99.99% or more is produced in the electrolytic refining process. In recent years, metal scraps containing precious metals derived from electronic parts have been introduced as recycling raw materials in converters, and valuable resources other than copper are precipitated as slime during electrolytic refining.

The slime is also enriched with precious metals, rare metals, and selenium and tellurium contained in copper concentrate. These elements are separated and recovered individually as copper smelting by-products. A hydrometallurgy method is often applied to the treatment of this slime. For example, Patent Document 1 discloses a method in which silver is recovered from slime with hydrochloric acid-hydrogen peroxide, the dissolved gold is recovered by solvent extraction, and then other valuable resources are sequentially reduced and recovered with sulfur dioxide.

Japanese Unexamined Patent Publication No. 2001-316735

In the method of recovering valuable resources using sulfur dioxide, the valuable resources are sequentially reduced and recovered after dissolution. First, platinum and palladium precipitate. 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. Iridium, ruthenium, and rhodium have relatively low redox potentials and are not easily reduced. The liquid after collecting platinum, palladium, and selenium is further reduced and recovered as a mixture with chalcogens.

Further separation from selenium is required in the platinum group or the element group having a relatively low redox potential. For separation from selenium, a method of oxidatively dissolving again and then extracting the solvent is common.

The inventor of the present application has found that it is possible to separate selenium as selenium sulfate by adding sulfite or sulfite to separate selenium. Selenium sulfate precipitates selenium by adjusting the acid concentration of the solution to be acidic, and simple selenium can be easily recovered. Specifically, it has been found that the selenosulfate solution can be obtained by bringing elemental selenium into contact with an aqueous sulfite solution or a solution obtained by absorbing sulfur dioxide in an alkaline solution and heating it to 40 ° C. or higher. In this method, the solution is brought into contact with an alkaline solution, and when the target valuable group contains tellurium dioxide, the selenosulfate solution contains tellurium oxonium ions as impurities.

To prevent tellurium contamination, it is conceivable to elute tellurium dioxide with a strong alkaline solution before recovering it as selenosulfuric acid. However, such methods require several elution operations and washes to completely remove tellurium.

In addition, when an acid is added to a selenosulfuric acid solution containing tellurium oxonium ions, the tellurium content also precipitates as tellurium dioxide or elemental tellurium. When treating the selenium sulfuric acid solution, if the recovery of selenium is also taken into consideration, the mixing of tellurium into the simple substance selenium becomes a problem.

Therefore, an object of the present invention is to provide a method for treating a tellurium solution capable of separating tellurium from the selenosulfuric acid solution by selectively reducing selenium oxonium ions in the selenosulfuric acid solution. And.

As a result of diligent research to solve the above problems, the present inventor has found that selenoxonium ions in a selenosulfate solution are selectively reduced by a reducing sugar and precipitated. The present invention has been completed based on such findings. Embodiments of the present invention are specified as follows.
(1) A selenosulfuric acid solution having a step of adding a reducing sugar to a selenosulfuric acid solution containing tellurium oxonium ions adjusted to pH 10 or higher and heating to a temperature of 60 ° C. or higher to precipitate tellurium. Processing method.
(2) The method for treating a selenosulfuric acid solution according to (1), wherein the reducing sugar is added to the selenosulfuric acid solution so as to be 2 mol times or more the amount of tellurium.
(3) The method for treating a selenosulfuric acid solution according to (1) or (2), wherein the reducing sugar is any or a mixture of fructose and glucose.
(4) The selenosulfuric acid solution is characterized in that it is a solution prepared by adding sulfite to a precipitate formed by reducing an acid-dissolved solution of selenium and tellurium (1) to (3). How to treat any of the selenosulfate solutions.
(5) Treatment of the selenosulfuric acid solution according to any one of (1) to (4), which comprises adding oxalic acids to the selenosulfuric acid solution to generate fine particles of tellurium before adding the reducing sugar. Method.
(6) Any of (1) to (5), wherein the selenosulfuric acid solution is a solution obtained by adding sodium sulfite to a solution containing selenium in an electrolytic slime treatment step in a copper smelting step. How to treat the selenosulfuric acid solution.
(7) It is characterized by having a step of adding a reducing sugar and heating to 60 ° C. or higher when the contents of simple selenium and tellurium dioxide are brought into contact with an alkaline sulfite ion-containing solution to dissolve selenium as selenium sulfuric acid. How to treat seleno sulfuric acid solution.

According to the embodiment of the present invention, it is possible to provide a method for treating a seleno-sulfuric acid solution capable of separating tellurium from the seleno-sulfuric acid solution by selectively reducing selenium oxonium ions in the seleno-sulfuric acid solution. ..

[Serenosulfuric acid solution]
Platinum group elements and chalcogen elements are concentrated in the electrolytic slime produced in the electrolytic refining 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 based on recycled raw materials such as waste catalysts. Therefore, this method can also be applied to recycling from waste.

Hydrochloric acid and hydrogen peroxide are added to dissolve the electrolytic slime, but silver forms an insoluble silver chloride precipitate with chloride ions immediately after dissolution. If it is a solution containing an oxidizing agent and chlorine, for example, aqua regia or chlorine water, the precious metals can be dissolved and silver can be separated as silver chloride. Since it is a chloride bath, platinum group elements, rare metal elements, selenium, and tellurium are distributed in the leachate noble liquid (PLS).

The leached noble liquid (PLS) is cooled once to precipitate and separate chlorides of base metals such as lead and antimony. After that, the gold is separated into an organic phase by solvent extraction. Dibutyl carbitol (DBC) is widely used as a gold extractant.

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

Reducing sulfur is used as the reducing agent in terms of price and efficiency, and sulfur dioxide is most suitable because it can be supplied in large quantities and at low cost by roasting linz-Donaw gas or sulfide ore.

Sulfur dioxide also partially reduces selenium when reducing platinum and palladium. Reduction is carried out until palladium and platinum are almost absent in the liquid, but selenium is also mixed in and the amount is 40 to 70% by mass.

The recovered mixture of platinum, palladium, and selenium is eluted again with hydrogen peroxide-hydrochloric acid, but selenium consumes a large amount of hydrogen peroxide when it is dissolved. In order to selectively remove selenium, sulfite or sulfite water is added and eluted. Since selenium is contained as a simple substance, it reacts with sulfite ion to form selenosulfate ion (Equation 1).
Se + SO ₃ ^2- → SSeO ₃ ^2- (Equation 1)

In the lower process, after selenium is recovered by sulfur dioxide, sulfur dioxide is continuously blown to recover tellurium, but unrecovered selenium is mixed at this time. Equation 1 described above can be used for the selective removal of the mixed selenium.

However, since 80% or more of the recovered tellurium is recovered as tellurium dioxide, it dissolves in an alkaline solution. The aqueous solution of sulfites required for the reaction of formula 1 is alkaline. Furthermore, the solution needs to be alkaline as selenosulfate is stable only in alkaline. Therefore, tellurium derived from tellurium dioxide is inevitably mixed in the selenosulfuric acid solution.

Tellurium dioxide may be eluted with a strong alkaline solution such as caustic soda solution before preparing the selenosulfuric acid solution. However, when applied to a platinum-palladium mixture, the amount of tellurium contained is small, and alkali elution is not cost-effective. On the contrary, the tellurium recovered precipitate has a large content of tellurium and is difficult to completely remove, and a small amount of contamination is unavoidable.

[Treatment method of selenosulfuric acid solution]
Tellurium is mixed as an oxonium ion in the recovered selenosulfuric acid solution. To remove this, reducing sugar is added and heated. Commonly used reducing agents are base metals and salts thereof, such as tin (II) chloride, iron powder, iron (II) sulfate, etc., but unreacted components remain as impurities or hydroxide precipitates. There is a problem that it is generated and becomes an impurity. On the other hand, reducing sugars can be easily removed as carbon dioxide after decomposition.

Sugars, oxalic acids, formic acids, phenols, lower aldehydes and the like are known to exhibit a reducing action under alkaline conditions. In the selenosulfuric acid solution, those capable of selectively reducing tellurium oxonium are sugars and oxalic acids.

Any sugar that exhibits reducing properties can be used as the reducing sugar of the present invention. In particular, ketose having a large equilibrium constant is preferable because of the ring-opening equilibrium of the ring structure. In terms of cost, it is preferably any or a mixture of fructose and glucose, which are versatile. Fructose is most suitable because it is ketose.

To the selenosulfuric acid solution, add 2 mol times as much reducing sugar as tellurium and heat. If too much reducing sugar is added, the cost will increase and the COD (Chemical Oxygen Demand) of the solution will increase. If it is too small, tellurium cannot be removed sufficiently.

The reduction temperature with the reducing sugar is controlled to 60 ° C. or higher. If the temperature is low, the reaction is slow, or the precipitated tellurium particles become fine and solid-liquid separation becomes difficult. The reduction temperature with the reducing sugar is preferably 70 ° C. or higher. Before adding the reducing sugar to the selenosulfuric acid solution containing the tellurium oxonium ion, the selenosulfuric acid solution is prepared to an alkaline pH. The pH is preferably pH 10 or higher. Since the saccharide has a ring-opening equilibrium in the carbonyl portion, the pH is more preferably 11 or more.

Even with oxalic acids, reduction of teluruoxonium in selenosulfate is easy. However, oxalic acid is highly reactive and autolyzes when the liquid temperature is high. When the tellurium concentration is low, the autolysis and the reduction reaction become concerted and the reduction efficiency decreases. It is preferable to add tellurium to the selenosulfuric acid solution to generate fine particles of tellurium before adding the reducing sugar, because the precipitation of tellurium is promoted.

The precipitated tellurium is recovered by solid-liquid separation by an appropriate method. The selenium sulfuric acid solution from which tellurium has been removed produces selenium by adding an acid to adjust the liquid property to acidic. After recovering selenium with an acid, it is also possible to add a reducing agent such as sulfur dioxide to reliably recover selenium.

When a substance containing elemental selenium and tellurium dioxide (precipitate of valuable resources) is brought into contact with an alkaline sulfite ion-containing solution to dissolve selenium as selenosulfate, a reducing sugar may be added to the solution. Tellurium dioxide once dissolved undergoes reduction and precipitates. If the selenium dissolution condition at this time is a temperature of 60 ° C. or higher and the amount of reducing sugar added is 2 mol times or more that of tellurium, a seleno sulfate solution having a low tellurium content can be obtained.

The embodiment of the present invention is particularly suitable for a selenosulfuric acid solution obtained from a selenium-containing substance produced in a slime treatment step generated in an electrolytic refining step in copper refining. That is, the selenosulfuric acid solution may be a solution obtained by adding sodium sulfite to a solution containing selenium in the electrolytic slime treatment step in the copper smelting step.

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

After removing copper by treating the electrolytic slime recovered from copper smelting with sulfuric acid, concentrated hydrochloric acid and 60% hydrogen peroxide solution were added and dissolved, and solid-liquid separation was obtained to obtain PLS. Next, the PLS was cooled to 6 ° C. to precipitate and remove the base metal component.

Next, the PLS and DBC (dibutyl carbitol) were mixed to extract gold. Next, the PLS after gold extraction was heated to 70 ° C., and a mixed gas of sulfur dioxide and air (sulfur dioxide concentration 5 to 20%) was blown to reduce the noble metal and separate it into solid and liquid. The precipitate obtained here is referred to as a precious metal-containing precipitate.

Next, after the solid-liquid separation, the liquid was further heated to 70 ° C., and a mixed gas of sulfur dioxide and air was blown in until the selenium became 3 g / L. Next, solid-liquid separation was performed again, and after the separation, the liquid was heated to 80 ° C. to 85 ° C. and a mixed gas of sulfur dioxide and air was blown into it. When the tellurium concentration became 30 mg / L or less, the reaction was stopped and solid-liquid separation was performed. The solid obtained here is called tellurium precipitation.

(Experimental Example 1)
40 g of each of the precious metal-containing precipitate and the tellurium precipitate were weighed. To this, twice the weight of sodium sulfite was added, and 1.5 L of sodium hydroxide 1 g / L solution was further added and heated to 70 ° C. After 1 hour, solid-liquid separation was performed to obtain a selenosulfate solution. The pH of the selenosulfate solution was 10.3.

120 ml of the obtained selenosulfate solution was taken up, and 0.6 g of D- (-) fructose or oxalic acid dihydrate was added. In each case, a special grade reagent manufactured by Wako Pure Chemical Industries, Ltd. was used. The temperature was increased to about 1 ° C. per minute, and 5 ml of a sample solution was collected every time the temperature increased by 10 ° C. At this time, 2 to 5 ml of pure water was occasionally added to compensate for the evaporation. After filtering the sample solution, 2 ml was collected and hydrochloric acid was added. Since precipitation occurred, 2 ml of 25% hydrogen peroxide was added to dissolve it. Next, the concentrations of Se and Te were quantified by ICP-OES (SPS3100 manufactured by Seiko Co., Ltd.) in an amount of 50 ml. The results are shown in Table 1.

From Table 1, it can be seen that tellurium oxonium is reduced in fructose at a temperature of 60 ° C. or higher. In particular, at 65 ° C., a black precipitate of tellurium was formed so that it could be visually confirmed. Since the ring-opening equilibrium changes depending on the alkali concentration, the temperature at which this reduction starts is expected to change depending on the conditions, but it can be considered to be approximately 60 ° C. or higher. Since no decrease in selenium concentration was observed, it can be seen that selenosulfate did not undergo sugar reduction.

It can also be seen that oxalic acid also effectively reduced tellurium oxonium. However, oxalic acid costs more than twice the price of fructose per unit weight. In terms of cost, it is not as good as sugar. Since the reaction proceeds rapidly when a black precipitate of tellurium occurs as described above (after 60 minutes of fructose), it is possible that the reaction time of fructose can be shortened by using oxalic acid as a tellurium seed crystal generating reagent.

(Experimental Example 2)
100 ml of the same solution as in Experimental Example 1 was collected, heated to 70 ° C., the reducing agent shown in Table 2 was added, and the mixture was stirred. 5 ml of the sample solution was collected at predetermined time intervals. From time to time, 2-5 ml of pure water was added to compensate for the evaporation. Next, 2 ml of the sample solution was collected after filtration, and hydrochloric acid was added. The subsequent quantitative analysis operation is the same as in Experimental Example 1.

After 60 minutes, the reaction was stopped and solid-liquid separation was performed by filtration. The solid content was washed in the order of water and alcohol, then dried at 50 ° C. overnight and weighed. In addition, an appropriate amount of the recovered residue was collected and dissolved in aqua regia. Next, the concentrations of Se and Te were quantified by ICP-OES (SPS3100 manufactured by Seiko Co., Ltd.) in an amount of 100 ml. The results are shown in Table 2.

According to Table 2, it can be seen that sugars act effectively. Compared with saccharides, glucose is cheaper than fructose but has lower reaction efficiency. Under conditions 2 and 5, the tellurium concentration may be further reduced if the reaction time is extended.

Tellurous acid, which is a tellurium oxonium ion, receives 4 electrons and precipitates as a simple tellurium. Fructose may be added in an amount of 3 times by weight or more, that is, 2 mol times or more with respect to tellurium. Fructose theoretically donates up to 12 electrons, but it is thought that only 2 electrons of the carbonyl moiety are involved in the reaction. Tellurium can be selectively precipitated and removed with any sugar at a value close to the theoretical equivalent.

Tellurium oxonium could not be reduced with formate and formalin, which are typical aldehydes. The reducing action of saccharides is aldehyde reduction. This difference in reactivity is unknown, but it is considered to be a saccharide-specific reaction. Although we are experimenting with monosaccharides, it is presumed that disaccharides that show reducing properties and sugars that are hydrolyzed to become reducing monosaccharides also have the effect of selectively reducing tellurium.

In this experiment as well, the precipitation of black particles indicating the precipitation of tellurium was clear. It can be seen in Table 2 that the tellurium concentration drops sharply. It seems that they react sequentially when precipitation starts. As described above, a method of adding oxalic acid and simple tellurium powder, which have a rapid reaction, to saccharides as seed crystals or reaction initiators is also conceivable.

(Experimental Example 3)
10 g of the noble metal-containing precipitate was weighed, and 100 ml of NaOH was added. Next, when the temperature reached 70 ° C. by heating, 15 g of sodium sulfite and 0.5 g of the reducing sugar shown in Table 3 were added and stirred, and leaching was performed for 15 minutes. Next, the leachate was filtered off and the solids were leached again under the same conditions for 15 minutes. After solid-liquid separation, 2 ml of the solution was collected and neutralized with hydrochloric acid. Precipitation occurred when neutralized, so 2 ml of hydrogen peroxide solution (25%) was added to dissolve it. Next, the concentrations of Se and Te were quantified by ICP-OES (SPS3100 manufactured by Seiko Co., Ltd.) with Y as the internal standard, adjusting to 50 ml. The results are shown in Table 3.

The total of the first leaching and the second leaching shows that tellurium elution is small when sugar is added. Especially in the first leaching, the effect of sugar is large. When the temperature was high, the reducing effect was high, and when fructose was added at 70 ° C., tellurium did not elute. Even glucose has a great effect at 70 ° C.

It can also be seen that selenium was eluted as selenosulfite by sodium sulfite. None of the reducing sugars inhibited the production of selenosulfate.

Claims (7)

A method for treating a tellurium sulfuric acid solution, which comprises a step of adding a reducing sugar to a tellurium sulfate solution containing tellurium oxonium ions adjusted to pH 10 or higher and heating to a temperature of 60 ° C. or higher to precipitate tellurium. .. The method for treating a selenosulfuric acid solution according to claim 1, wherein the reducing sugar is added to the selenosulfuric acid solution so as to be 2 mol times or more the amount of tellurium. The method for treating a selenosulfuric acid solution according to claim 1 or 2, wherein the reducing sugar is any or a mixture of fructose and glucose. Any one of claims 1 to 3, wherein the selenosulfuric acid solution is a solution prepared by adding sulfite to a precipitate formed by reducing an acid-dissolved solution of selenium and tellurium. The method for treating a selenosulfite solution according to. The method for treating a selenosulfuric acid solution according to any one of claims 1 to 4, wherein oxalic acids are added to the selenosulfuric acid solution to generate fine particles of tellurium before the reducing sugar is added. .. The invention according to any one of claims 1 to 5, wherein the selenosulfuric acid solution is a solution obtained by adding sodium sulfite to a solution containing selenium in the electrolytic slime treatment step in the copper smelting step. How to treat selenosulfuric acid solution. A selenosulfuric acid solution characterized by having a step of adding a reducing sugar and heating to 60 ° C. or higher when dissolving elemental selenium and tellurium dioxide in contact with an alkaline sulfite ion-containing solution to dissolve selenium as selenosulfuric acid. Processing method.