JPS6246497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an arsenic solution with a high arsenic concentration, and in particular, an arsenic solution containing an arsenic sulfide-containing aqueous solution containing As ⁺⁵ and a precipitate containing arsenic sulfide are produced for the main purpose of producing arsenous acid. The present invention relates to a method for producing an arsenic-containing solution with a high arsenic concentration through the interaction of

Arsenic recovery methods include a dry method and a wet method, but the dry method involves a roasting process, resulting in high equipment costs and problems in terms of environmental management, so it is not currently used. Regarding the wet method, arsenic in various aqueous solutions is relatively simply precipitated as arsenic sulfide by the addition of a sulfiding agent. However, arsenic sulfide is not marketable, and therefore attempts are underway to recover arsenic sulfide as a marketable arsenic acid. Therefore,
It is desired to establish a method for efficiently producing a marketable arsenic acid using a wet process from arsenic sulfide.

The currently promising wet production method for arsenous acid basically involves the interaction of a copper sulfate-containing aqueous solution containing As ⁺⁵ with an arsenic sulfide-containing precipitate to produce copper sulfide and an arsenic-containing solution. The arsenous acid is crystallized and recovered by reducing, concentrating and cooling the arsenic solution. In order to efficiently recover arsenous acid in this method, it is necessary to generate an arsenic solution with a high arsenic concentration and to crystallize and recover arsenous acid using this solution as a starting material. Furthermore, in order to recover high quality arsenous acid, it is also necessary to reduce impurities in the arsenic solution as much as possible. Many studies have been made to more efficiently produce higher quality arsenous acid.

Both the copper sulfate-containing aqueous solution and the arsenic sulfide-containing precipitate used as raw materials for producing arsenous acid are mainly obtained using products from non-ferrous smelting processes, and therefore inevitably contain some impurities. These impurities are likely to be mixed into the arsenic solution produced by mutually reacting these raw materials, and the arsenous acid produced using this as a starting solution contains copper, sulfur, these compounds, antimony, and other impurities. Easy to contaminate and difficult to obtain high purity products. Among these impurities, especially when the raw material contains antimony, antimony is likely to be mixed into the arsenic acid product. Both the copper sulfate-containing aqueous solution and the arsenic sulfide-containing precipitate as raw materials are derived from intermediate products from nonferrous smelting plants, and therefore often contain antimony. Therefore, it is impossible to produce arsenous acid of stable quality unless a method for removing antimony is established.

As a result of previously searching for an efficient method for removing antimony, the applicant of the present application discovered that if the conditions of the mutual reaction are controlled to a condition that keeps the copper concentration of the arsenic solution produced as a liquid after the reaction low, it is possible to remove antimony. They discovered that the antimony concentration in arsenic solutions could also be kept extremely low, and filed a patent application. In summary, the method involves producing a copper sulfide and arsenic solution by interacting an arsenic sulfide precipitate with a copper sulfate-containing aqueous solution containing As ⁺⁵ , reducing, concentrating, and cooling the arsenic solution. Particularly, in the method for crystallizing and recovering arsenous acid, the copper concentration in the arsenic solution is set to 3 g/or less, thereby obtaining an arsenic-containing purified solution with a low antimony concentration. It is. This method has made it possible to produce arsenous acid with a purity of 99.5% or higher even when the raw material contains antimony.

As a result of subsequent research, when an arsenic solution is generated through the above interaction, if the copper concentration in the arsenic solution is extremely reduced, As ⁺⁵ in the arsenic solution is reduced by the added arsenic sulfide. Therefore, it has been recognized that arsenous acid crystallizes during subsequent solid-liquid separation, resulting in a decrease in the total arsenic concentration in the arsenic-containing solution after solid-liquid separation. A decrease in the total arsenic concentration in the arsenic solution leads to a deterioration in arsenous acid production efficiency.

As a result of continuing research aimed at solving this problem, we found that when a copper sulfate-containing aqueous solution containing As ⁺⁵ is reacted with an arsenic sulfide-containing precipitate, the copper concentration in the arsenic solution rapidly decreases at the end of the reaction. It has been found that by setting this as the front, As ⁺³ can be displaced and eluted while As ⁺⁵ is maintained at a high concentration, and the total arsenic concentration can be maintained at a high level. Generally, the end point of the reaction is a copper concentration of 0.05 g/or more.

Thus, the present invention involves reacting a copper sulfate-containing aqueous solution containing As ⁺⁵ with an arsenic sulfide-containing precipitate to produce a copper sulfide and arsenic-containing solution, in which case an antimony-free copper sulfate-containing aqueous solution and arsenic sulfide are reacted. Using the arsenic-containing precipitate, the reaction is allowed to proceed with the copper concentration in the arsenic solution being 3 g/or less, and the reaction is stopped when the copper concentration is 0.05 g/or more, and after solid-liquid separation, the high arsenic concentration is removed. Provided is a method for producing an arsenic-containing solution with a high arsenic concentration, which is characterized in that the arsenic-containing solution is obtained.

The present invention will be explained in detail below.

As mentioned above, the method of the present invention can be mainly applied as part of the arsenous acid manufacturing process. Figure 1 shows a basic arsenous acid production flow sheet. Using a copper sulfate-containing aqueous solution containing As ⁺⁵ and an arsenic sulfide precipitate as starting materials, copper sulfide and an arsenic solution are produced through their mutual reaction, and the arsenic solution is reduced, concentrated, and cooled. Arsenous acid is then crystallized and recovered. The object of the present invention is to obtain this arsenic-containing solution with a high arsenic concentration and high purity.

In order to keep the copper concentration in the arsenic solution low, the interaction formula As ₂ S ₃ +3CuSO ₄ +4H ₂ O=
The reaction must be carried out while maintaining an excess of arsenic and a deficiency of copper relative to the equivalent amount of 3CuS + 2HAsO ₂ + 3H ₂ SO ₄ . Therefore, when the reaction is carried out in one stage, it is unavoidable that the arsenic content in copper sulfide will be somewhat high, and the direct recovery rate of the arsenous acid product will therefore be somewhat low. To solve this problem, as shown in the flow sheet in Figure 2, a two-step reaction is carried out: an arsenic elution step in which the reaction is carried out in an excess of copper and an arsenic deficiency, and a decopper removal step in which the reaction is carried out in an excess of arsenic and an insufficient amount of copper. It is better.

The copper sulfate-containing aqueous solution containing As ⁺⁵ may be an aqueous solution in which crude copper sulfate or purified copper sulfate is dissolved, or a hydrometallurgical process liquid, such as a copper sulfate production process liquid from copper electrolytic waste liquid, but crude copper sulfate crystallization may be used. When applying to the present invention an aqueous solution in which electrolytically precipitated copper, which is an electrolytic deposit produced when the after-liquid is electrolyzed to remove copper, is applied to the present invention.
Since the copper and arsenic in the aqueous solution are also separated at the same time, the effect of killing two birds with one stone can be obtained.

Arsenic sulfide-containing precipitates are precipitates generated by adding a sulfiding agent to the process liquid of a non-ferrous smelting factory, such as waste sulfuric acid generated from a non-ferrous smelting flue gas sulfuric acid manufacturing factory, or the process liquid of a hydrometallurgical smelting process. be.

The mutual reaction between the two is carried out at a temperature of 70 to 90°C and a slurry concentration of about 10 to 15%, with mechanical stirring.

According to the present invention, the end point of the interaction is determined by the copper ion concentration in the arsenic solution, and the stirring is stopped before the copper ion concentration drops rapidly to stop the reaction, followed by solid-liquid separation. By doing so, an arsenic-containing solution with a high arsenic concentration can be obtained.

FIG. 3 is a graph showing the relationship between copper concentration and arsenic concentration in an arsenic solution. It can be seen that when the copper concentration decreases, the arsenic concentration decreases rapidly. In the present invention, the total arsenic concentration is set as a target of 60 g/or more, and the reaction end point copper concentration in the arsenic solution is set as 0.05 g/
The above was selected.

In order to obtain a highly pure arsenic-containing solution, the reaction proceeds better if the copper concentration in the arsenic-containing solution is kept in a copper-deficient state, so the concentration is set at 3 g/or less and 0.05
A highly pure arsenic-containing solution with a high arsenic concentration can be obtained by terminating the reaction at a point where the arsenic content is higher than 100 g/g/g. This makes it possible to efficiently produce highly pure arsenous acid in the post-process.

For your reference, we will briefly explain the post-process for producing arsenous acid. First, a reducing agent is added to an arsenic solution to reduce pentavalent arsenic present in the arsenic solution to trivalent arsenic. The reducing agent in this case may be a relatively weak reducing agent, and SO ₂ -containing gas is used in non-ferrous smelting plants. Of course, liquid sulfite water may also be used. This is because when these reducing agents are used, it is advantageous that only sulfuric acid is produced as a by-product during the reaction. If there is no problem if alkali ions are mixed into the system, an aqueous solution of alkali sulfite or acidic alkali sulfite, such as sodium sulfite or acidic sodium sulfite, may be used. The reduced arsenic-containing solution is heated or concentrated by heating under reduced pressure and then cooled to crystallize arsenous acid and perform solid-liquid separation to recover high-purity arsenic acid. In the concentrated liquid before arsenous acid crystallization, the sulfuric acid concentration increases because the sulfuric acid derived from SO ₂ blown for reduction is added to the sulfuric acid derived from the raw material copper sulfate solution. A higher sulfuric acid concentration is preferable because the solubility of trivalent arsenic is lowered and the crystallization rate of arsenous acid is therefore higher. A sulfuric acid concentration of about 300 g/approx.

The liquid after crystallization of arsenous acid is dilute sulfuric acid that contains a small amount of arsenic, so it may be partially repeated into the system of this process, but if this is done, the sulfuric acid in the system will accumulate, so the process of dissolving intermediate products such as dust is necessary. Alternatively, it is reasonable to add it to a process that requires dilute sulfuric acid, such as a gas cleaning process.

Examples and comparative examples are shown below.

Example Electrolytically precipitated copper solution (As ⁺⁵ = 35.0g/, Cu ⁺²
=42g/)1.0 and arsenic sulfide mud (As=49.5%,
Add 110g of Cu = 0.3%) and heat to 80°C while stirring.
Displacement copper removal was carried out at a reaction temperature of , and stirring was stopped when the copper concentration in the arsenic solution reached 0.07 g/
An arsenic solution of 0.987 was obtained by filtration. The total arsenic concentration of the arsenic solution was as high as 62.6 g/.

Comparative Example Using the same raw materials and reaction conditions as in the example, the reaction was stopped when the copper concentration in the arsenic solution reached 0.02 g/. The total arsenic concentration of the obtained arsenic solution was 40.0 g/
It was nothing more than a simple thing.

As explained above, the present invention solves the problem related to the decrease in the total arsenic concentration of the arsenic solution as a solution after copper removal, and the total arsenic concentration in the arsenic solution can be maintained at a high concentration. This guarantees efficient and stable production of arsenous acid. The increased total arsenic concentration reduces the amount of liquid to be handled, allowing equipment to be made more compact.

[Brief explanation of the drawing]

Figures 1 and 2 show flow sheets for producing high purity arsenous acid from arsenic-containing materials, of which Figure 1 shows the case of a one-stage reaction, and Figure 2 shows the case of a two-stage reaction. FIG. 3 is a graph showing the relationship between arsenic concentration and copper concentration in an arsenic solution.

Claims (1)

[Claims] 1 Reacting a copper sulfate-containing aqueous solution containing As ⁺⁵ with an arsenic sulfide-containing precipitate to produce copper sulfide and an arsenic-containing solution,
In that case, a copper sulfate-containing aqueous solution containing no antimony and an arsenic sulfide-containing precipitate are used, and the reaction is allowed to proceed at a copper concentration of 3 g/or less in the arsenic-containing solution. A method for producing an arsenic-containing solution with a high arsenic concentration, characterized by stopping the reaction at a certain point, and then obtaining an arsenic-containing solution with a high arsenic concentration after solid-liquid separation.