JP3212875B2 - Arsenic recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous solution containing arsenic.
It relates to a process for the recovery of arsenic as calcium arsenate, to a method for recovering Seineri intermediate and electrolytically precipitated copper Karahisan calcium sulfide containing arsenic occurring in a copper smelting by further such recovery process.

[0002]

2. Description of the Related Art Arsenic (As) is relatively widely distributed in the earth's crust and mostly exists in the form of sulfide, but rarely exists alone and coexists with copper sulfide and lead sulfide. Often. Normally, arsenic is not collected alone, but various intermediates are generated during the kneading of copper or the like in the non-ferrous kneading process of copper or lead, but copper, zinc,
A major feature is that it contains arsenic together with bismuth and the like. On the other hand, in recent years, high-purity As has been required to be used as a material of a compound semiconductor such as GaAs or InAs or a photoconductor such as AsSe.

[0003] However, in the dry method, a kneading intermediate is oxidized and roasted, and arsenic acid (H ₃ AsO ₄ ) is volatilized as arsenous acid (As ₂ O ₃ ). Handling arsenous acid in a dry state by the method of separating and recovering as arsenic acid causes difficulties in the working environment, and it is difficult to reduce the cost due to the large-sized equipment for preventing pollution to the atmosphere. It is. In addition, smoke ash contains 20 to 40% of arsenous acid.
About 5% of crude arsenous acid was obtained and further reduced to produce metal arsenic (As), which was then purified by various methods to obtain high-purity arsenic.

On the other hand, in the wet method, when recovering various metals, it is common to repeat these in a purification process such as electrolytic refining. However, since the oxidation-reduction potential of arsenic is close to that of copper, In addition, it is difficult to separate arsenic. Therefore, if arsenic is not separated, arsenic is concentrated and accumulated in a kneading intermediate, so that it is necessary to separate and remove arsenic. Therefore, a commonly used method for separating arsenic from various aqueous solutions containing arsenic and copper generated in the copper electrolytic smelting process is to first recover copper in the form of sulfide by a sulfidation method, and then Arsenic is removed by a sulfurization method. However, such a method requires a solid-liquid separation step for arsenic-containing sulfides as well as a solid-liquid separation step for copper sulfide, and two solid-liquid separation steps cause an increase in processing cost. In the wet method, not only the target metal is kneaded and refined, but also the waste acid sulfide generated when treating sulfide ore such as copper accompanied by arsenic sulfide and the electrolytic extraction generated during electrolytic purification of copper. It is often the case that sintering intermediates such as sulfides contain arsenic in the form of sulfides together with valuables, and it has long been required not only to improve the purity of the target metal but also to separate highly useful arsenic into high purity. Was.

The following techniques have been proposed as means for avoiding the arsenic separation / recovery problem. JP-A-54-1
No. 60590 discloses calcium arsenate (Ca ₃ (As
A method for producing a stable arsenic compound such as O ₄ ) ₂ ) has been proposed. The present proposal proposes that a leachate obtained by alkaline leaching of a purified intermediate in the form of sulfide is led to a process of synthesizing calcium arsenate with slaked lime in a form containing trivalent arsenic ions (As ³⁺ ), and the precipitate is recovered. It is. Also, Japanese Patent Application Laid-Open No.
No. 60914 discloses a method in which arsenous acid containing As ³⁺ leached with sulfuric acid is oxidized by aeration in the presence of copper ions to form arsenic acid containing As ⁵⁺ , which is then converted to sulfur dioxide gas or the like. To precipitate and recover arsenous acid.

[0006]

However, the above proposal has the following problems. JP-A-54-160
No. 590, leaching treatment is performed while adjusting the pH to 5 to 8 by adding alkali while blowing air into the sulfide-containing kneading intermediate containing arsenic, thereby converting arsenic into acidic arsenate. Compared with the dry method, it does not require a large-scale air pollution control device, but requires a large device because the arsenic leaching rate is extremely slow. Therefore, there is a problem that a large amount of energy such as steam is involved. Furthermore,
It contains a large amount of unstable calcium arsenite, which hinders practical use.

The method proposed in Japanese Patent Application Laid-Open No. 57-160914 has a low rate of conversion from arsenous acid to arsenic acid, and precipitates other valuable materials together at the expense of part of arsenous acid. You have to make it inefficient. Further, in the case of an alkali leaching solution, it has been considered that application to alkali leaching is difficult because copper ions are neutralized and cannot exist as copper ions.

Accordingly, the present invention has been made to solve the above-mentioned disadvantages, and has as its object to provide a method for efficiently recovering only arsenic from an aqueous solution containing arsenic. An arsenate of high purity can be obtained without containing unstable arsenous acid. Another object of the present invention is to provide a method for efficiently recovering calcium arsenate as arsenate from sulfide containing arsenic discharged in copper smelting and electrolytically precipitated copper with high purity.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 occurs in copper smelting.
Waste arsenic sulfide which is to be discharged
~ 90 ° C, pH 5.5 ~ 7.5 alkaline leaching, the leachate
At least electrolytic precipitated copper generated in copper refining.
And the solution temperature is 50 ° C to 90 ° C, pH10.5 with sodium hydroxide.
Oxidized by air as ~ 11.5, then solid-liquid separation
And reacting the clarified liquid with slaked lime before it is generated in copper smelting
From the smelting intermediates containing the two types of arsenic, high-purity arsenate
This is an arsenic recovery method for recovering arsenic. The present invention relates to electrolytic precipitation generated in copper refining from an aqueous solution containing arsenic.
At least copper is added and oxidized with an oxidizing agent at a pH of 10.5-11.5 to produce arsenic acid (As ⁵⁺ ) and produce arsenic (A
s). When arsenic is leached into solution, trivalent ions (As ³⁺ ) and pentavalent ions (As ³⁺ )
⁵⁺ ) coexist at a certain rate. Therefore, an oxidizing agent is added to the solution to promote the oxidation reaction of arsenic ions by utilizing the catalytic action of copper and copper oxide or copper or copper oxide in the electrolytically precipitated copper, and the presence of pentavalent arsenic ions The ratio can be increased. By using the arsenic ions obtained thereby, arsenic can be easily and efficiently recovered.

At this time, the copper oxide is represented by the following reaction formula: As ³⁺ + 2Cu0 → As ⁵⁺ + Cu ₂ O Cu ₂ O + 1 / 2O ₂ → 2CuO Trivalent arsenic ion is converted to divalent copper oxide. Is oxidized and the copper oxide itself is reduced to monovalent copper oxide as pentavalent arsenic ions. It is presumed that the reduced copper oxide is oxidized to divalent copper oxide by oxygen as an oxidizing agent and promotes the oxidation of arsenic ions again. Therefore, the presence of the copper oxide makes it possible to promote the generation of pentavalent arsenic ions. Further, even a simple substance of copper is oxidized in an alkaline leaching solution to become copper oxide and cuprous oxide, and performs the same reaction as described above to exhibit the same effect. The same applies to copper and copper oxide.

As the oxidizing agent for the oxidation, an oxygen-containing gas such as air or pure oxygen gas can be used. Preferably, air is good. It is inexpensive and easy to obtain. When air is used, the amount used depends on the amount of arsenic ions (As ³⁺ ) in the solution, the amount of copper and copper oxide or copper or copper oxide in the electrolytically precipitated copper.
1.2 L / min is preferred. Examples of the method for recovering arsenic include a method in which the solution temperature is lowered to precipitate arsenic acid, a method using a chelate resin, and the like.

[0012] The sulfide containing arsenic, copper sulfide containing arsenic, lead sulfide ore such as zinc sulfide, beneficiation is a pretreatment of ore, tailings produced by roasting or the like, Susuhai like,
It refers to mats, spices, soot and the like generated as exhaust gas, and residues and precipitates generated by electrolytic refining when these ores are kneaded in a flash furnace or a converter. The present invention suppresses the leaching of valuable metals other than arsenic by alkali leaching, and enables trivalent arsenic ions to be pentavalent after solid-liquid separation and to be efficiently recovered. As an alkali for alkali leaching, an alkali which forms an insoluble salt with arsenous acid or arsenic acid is not suitable. Therefore, sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia hydroxide and the like are suitable. The alkali is also used for pH adjustment. As the alkali actually used, sodium hydroxide is preferable in terms of cost and ease of use. Was made alkaline leaching, the copper Seineri intermediate is to prevent as much as possible copper, zinc, from being leached into the solution until these because it contains bismuth. This is a major difference from acid leaching with sulfuric acid or the like.

In the present invention , arsenic acid caused by pentavalent arsenic ions can be recovered as a precipitate of high-purity calcium arsenate (Ca ₃ (AsO ₄ ) ₂ ) by adding slaked lime (Ca (OH) ₂ ). It is.

The slaked lime for producing calcium arsenate preferably has a molar ratio to arsenic ion (As ⁵⁺ ) in the range of 1.8 to 2.2. This is because when slaked lime is large, it is mixed as an impurity during solid-liquid separation, so that high purity of calcium arsenate cannot be maintained.

The smelting intermediate containing arsenic refers to tailings, soot and the like generated by beneficiation, roasting, and the like, which are pretreatments of sulfide ores, and occurs when these ores are smelted in a flash furnace or a converter. Mats, spices, soot and the like generated as exhaust gas, and residues and precipitates generated by electrolytic refining. In the present invention,
In copper smelting, waste that is part of the above exhaust gas treatment process
Waste acid arsenic sulfide generated from acid process and electrolytic refining process
And at least electrolytically precipitated copper.

As a reactor for carrying out the present invention, a Develo type stirring device, a dollar type stirring device, or the like can be appropriately used. Although the necessity of using an autoclave is small, it is possible to use an autoclave. Also, for copper refining
As the electrolytically precipitated copper generated in the process, at least copper powder and copper oxide powder generated during anode casting, electrolytically purified copper precipitated obtained in a purification process during electrolytic purification , and electrolytically precipitated copper leaching Copper oxide or the like contained in the residue may be used as appropriate.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, in the step of leaching waste arsenic sulfide with sodium hydroxide, the treatment temperature is 5 ° C.
A range from 0 to 90C is preferred. This is to increase the leaching speed. The pH is preferably in the range of 5.5 to 7.5. 5.5
In the following, it is because the leaching speed is low. In addition, pH7.
If it is 5 or more, the oxidation of S to SO ₄ may be promoted or other elements may be leached. In addition, de power
In the step of oxidizing by adding at least dissolving copper ,
When the pH of the solution is in the range of 10.5-11.5 and the temperature is 5
It is preferable to blow air in the range of 0 to 90 ° C. The pH is for enhancing the catalytic action of copper or the like. Also, the higher the temperature, the faster the reaction proceeds. However, in order to increase the reaction rate, it has conventionally been necessary to raise the temperature of the solution to 100 ° C. or higher using an autoclave or the like.

It is assumed that the reaction according to the method of the present invention is represented by the following reaction formula when sodium hydroxide is used. _{As 2 S 3 + 3 / 2O} 2 + H 2 O → 2HAsO 2 + 3S (1) As 2 S 3 + 6O 2 + 4H 2 O → 2HAsO 2 + 3H 2 SO 4 (1 ') Haisande arsenic sulfide in the reaction according to the equation the arsenic sulfide in an alkali leaching solution is extracted as trivalent ions of arsenite. At this time, the following reaction partially occurs. HAsO ₂ + 1 / 2O ₂ + NaOH → NaH ₂ AsO ₄ (2) HAsO ₂ + 1 / 2O ₂ + 2NaOH → Na ₂ HAsO ₄ + 4H ₂ O (3) According to the above formula, arsenate (NaH ₂ AsO ₄ , Na ₂ HA)
sO ₄ ) is produced, but the arsenate is soluble in water,
Form acids as pentavalent arsenic ions. The partition coefficient of this ion is mainly determined by the pH of the solution. Thus, the present invention makes it possible to increase the distribution coefficient of arsenic acid by utilizing the catalysis of copper and copper oxide or copper or copper oxide in electrolytically precipitated copper .

Hereinafter, the contents of the present invention will be specifically described. (Example 1) As sulfide containing arsenic, waste acid-derived arsenic sulfide, which is a kneading intermediate in the form of copper sulfide, was used. This results from the waste acid process which is part of the gas treatment process when kneading copper sulfide in a flash furnace. This was alkali leached with sodium hydroxide. The leaching conditions were as follows: the blowing rate of air was 200 L / min per 1 m ^{3 of} the solution, and the temperature of the solution was 60 ° C.
The pH of the solution was adjusted to 6.5. The leaching treatment was performed for 10 hours.

The arsenic-containing aqueous solution obtained by the leaching had the composition shown in Table 1 below.

[Table 1] This aqueous solution was subjected to solid-liquid separation, and the separated residue was returned to the flash furnace and reused.

[0021] The copper smelting factory in an aqueous solution 1.15m ³ that said separated
22.5 kg of electrolytically precipitated copper generated during the process was added. The electrolytically precipitated copper had the composition shown in Table 2 below.

[Table 2] While adjusting the pH to 11 with sodium hydroxide, air was blown at 600 L / min to oxidize for 4 hours. At this time, the temperature of the solution was set to 60 ° C. As a result, the concentration of As ^{3+ in} the post-oxidation solution was as extremely small as 10 g / L and 1.5 g / L before oxidation.
% Was As ⁵⁺ . Thereafter, solid-liquid separation was performed, and the residue was returned to the flash furnace and reused.

An extremely stable calcium arsenate could be obtained by reacting the separated clarified liquid with the slaked lime which was subsequently carried out. The processing conditions at this time were a temperature of 60 ° C. The added amount of slaked lime was 2. as a molar ratio to the total As amount.
It was set to 0. The treatment was performed for 60 minutes. After the treatment, precipitated calcium arsenate was recovered by solid-liquid separation. At this time, the amount of arsenic recovered as calcium arsenate was as high as 92.1% of the total amount of arsenic initially charged. The sodium hydroxide regenerated at the same time was reused as a leachate or the like. At this time, the regeneration rate of sodium hydroxide was 7
0.5%.

[0023] Contact copper refining (Example 2) Example 1 and similar arsenate-containing solution 1.15 m ³
Kicking copper powder 1 deposited on the turntable at the time of the anode casting
0 kg was added, and air was blown at 600 L / min at pH 11 with sodium hydroxide and oxidized for 3 hours. As a result, the concentration of As ^{3+ in} the post-oxidation solution was 1.8 g / L at 10 g / L before oxidation, and was 93% of the total arsenic.
% Was As ⁵⁺ . Calcium arsenate precipitated by treatment in the same manner as in Example 1 was recovered. At this time, the amount of arsenic recovered as calcium arsenate was as high as 91.2% of the total amount of arsenic initially charged. The sodium hydroxide regenerated at the same time was reused as a leaching solution or the like. At this time, the regeneration rate of sodium hydroxide was 70.
0%. As in Example 1, it was found that high-purity calcium arsenate can be produced and that a high arsenic recovery rate can be achieved.

[0024]

As described above, according to the present invention, the amount of pentavalent ions forming arsenic acid obtained by oxidizing and leaching an arsenic-containing kneading intermediate in the presence of sodium hydroxide is increased. As a result, stable calcium arsenate could be produced with high purity. Since the oxidation catalysis of copper can be used to a high degree, arsenic can be recovered efficiently and at a high yield from smelting intermediates. Therefore, in copper smelting
During the smelting of two types of arsenic that had previously been considered difficult to process
Extremely effective from waste arsenic sulfide and electrolytically precipitated copper
Calcium arsenate can be recovered efficiently.

Continuation of the front page (56) References JP-A-58-204826 (JP, A) JP-A-54-160590 (JP, A) JP-A-57-160914 (JP, A) JP-A-58-45115 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 28/02

Claims (1)

(57) [Claims] Claims: 1. Arsenic acid arsenic generated in copper smelting
The compound is treated with sodium hydroxide at a liquid temperature of 50 ° C to 90 ° C, pH 5.5.
Alkaline leaching at ~ 7.5, and the leachate contains a small amount of electrolytically precipitated copper generated in copper refining.
At least 50 ° C to 90 ° C, pH10.5 to 11.5 with sodium hydroxide.
Oxidized by air, then solid-liquid separated, and the clarified liquid is reacted with slaked lime .
Is characterized by recovering high purity calcium arsenate.
Method of recovering that arsenic.