JP5062111B2 - Method for producing high-purity arsenous acid aqueous solution from copper-free slime - Google Patents

Description

  The present invention relates to a method for producing high-purity arsenous acid by separating arsenic and other impurities from a mixture containing arsenic, copper and antimony, for example, copper-free slime generated by copper smelting.

  In copper smelting, ore such as copper sulfide with a copper grade of about 1% mined in the mine is crushed, and the concentrate is concentrated to a copper grade of about 30%. This copper concentrate is processed in a smelting process using a flash smelting furnace, converter, etc. to produce crude copper having a purity of about 99%, and the resulting crude copper is used as an anode for electrolytic purification, thereby purifying the purity on the cathode. 99.99% or more of electrolytic copper is obtained.

  In the above-mentioned series of smelting processes, many impurities other than copper contained in the ore are separated and removed from copper as gangue, slag, dust, exhaust gas, etc. by beneficiation and smelting processes. Impurities such as antimony, bismuth and lead are contained in the crude copper at a certain ratio. Precious metals and impurities contained in crude copper are various such as those that elute into the electrolyte like arsenic by electrolytic refining, those that precipitate as electrolytic slime like precious metals and lead, and those that distribute to both like antimony and bismuth Separated from copper.

  The electrolytic slime is treated in a separate noble metal treatment process to separate the noble metal and impurities. The removed impurities are repeated in the smelting process, or discharged out of the smelting process to be commercialized. On the other hand, the impurities eluted in the electrolytic solution accumulate in the solution if left as they are, and there is a risk of contaminating the copper. Therefore, the electrolytic solution is periodically withdrawn and sent to the cleaning process to remove the impurities. . For example, in the case of arsenic, antimony, and bismuth, it is electrolyzed using an electrolytic tank different from the electrolytic purification, co-deposited with copper in the electrolytic solution and precipitated at the bottom of the electrolytic solution, and removed from the electrolytic solution as decoppered slime. .

  Since this decopperized slime contains toxic arsenic, it cannot be sold as a product as it is, or it cannot be subjected to final treatment such as landfilling. Therefore, it is often repeated in the smelting process and put into a furnace. Part of the impurities contained in the copper removal slime repeated in the smelting process is distributed to slag and dust, and part is distributed again to crude copper.

  It is known that impurities distributed in the slag are difficult to elute from the slag. This is thought to be because impurities are confined in a crystal lattice having a glass structure composed of silica and calcium, which are the main components of slag, and are difficult to ionize. Slag in which impurities are stably sealed and fixed can be used for cement, asphalt concrete, etc. in addition to landfill treatment, and has been conventionally used as a method for treating impurities.

  As described above, slag can stably fix impurities such as arsenic. However, as impurities in copper sulfide ore, especially arsenic, have been increasing as in recent years, the concentration of arsenic in the copper concentrate also increases accordingly. The arsenic quality in the slag will also increase. There is a limit to the amount of arsenic that can be fixed in the slag crystal lattice, and there is a limit to increasing the amount of slag generation to fix arsenic. It was done.

  As a method for stably fixing arsenic, for example, there is a method as disclosed in Japanese Patent Application Laid-Open No. 2008-105921 (Patent Document 1). In this method, an oxidant is added to an aqueous solution containing arsenic ions and divalent iron ions and the precipitation reaction of the iron arsenic compound proceeds while stirring, and the precipitation is completed when the pH of the solution is in the range of 0 to 1.2. It is a method to make it. Specifically, arsenic that exists in the form of metals and sulfides in repeated products in the system such as decopperized slime is oxidized and leached in a sulfuric acid solution, and arsenous acid is generated from the obtained leachate. By adding divalent iron ions to an aqueous arsenous acid solution and oxidizing it, an arsenic iron compound with good crystallinity is produced, and arsenic is fixed therein and discharged out of the system.

  However, when arsenic is fixed using this method, if impurities other than the target arsenic are present in the leachate, the crystallization of the compound of iron and arsenic is inhibited in the resulting product. It is known that the fixation of arsenic becomes unstable and arsenic is eluted from the product. Therefore, in order to obtain a product made of a compound with good crystallinity in which arsenic and iron are stably fixed, it is necessary to use a high-purity arsenous acid aqueous solution containing little impurities other than arsenic.

  By the way, when leaching decopperized slime with sulfuric acid, the contained bismuth and lead are hardly leached, and almost the entire amount is distributed to the residue, so that it can be separated from the leached arsenic. However, copper contained in a large amount in the copper removal slime is leached with sulfuric acid. Antimony ions have essentially no solubility in water in both trivalent and pentavalent forms, but have a specific property that antimony is leached when the arsenic concentration in the sulfuric acid solution is high.

  Therefore, when recovering arsenic from the leachate obtained by leaching the decoppered slime with sulfuric acid, it is necessary to separate the contained copper, antimony and arsenic. For separation of copper, for example, hydrogen sulfide can be blown into the leachate and precipitated as sulfide. However, arsenic and antimony are also precipitated as sulfides at the same time as copper, and there is a high possibility that mutual separation will be insufficient, and handling and cost will be required.

  As for the separation of arsenic and antimony, there is a method in which a leachate obtained by leaching decopperized slime with sulfuric acid and activated carbon are brought into contact with each other, and antimony ions are adsorbed on the activated carbon and separated from the leachate. As described in (Patent Document 2), a method has been proposed in which a chelate resin or an ion exchange resin is brought into contact with a leaching solution so that only antimony ions are selectively adsorbed on the resin and separated from the leaching solution.

  However, the above-described separation method using activated carbon, ion exchange resin, or the like is effective when the antimony concentration of the leachate is low, such as less than 1 g / l, but the antimony concentration exceeds, for example, 1 g / l. In such a case, the required amount of activated carbon and ion exchange resin increases, the scale of equipment expands and the cost increases, and excessive labor and cost are required as the amount of chemicals used and wastewater treatment increase. The possibility of an inefficient processing method is high.

JP 2008-105921 A JP-A-60-050192

  In view of the above-described conventional circumstances, the present invention easily and inexpensively separates copper and antimony from a sulfuric acid acidic solution containing copper, antimony and arsenic leached from a copper smelting slime in copper smelting. Another object of the present invention is to provide a method for obtaining a highly pure arsenous acid aqueous solution.

In order to achieve the above object, a method for producing an arsenous acid aqueous solution provided by the present invention is a method for obtaining an arsenous acid aqueous solution by separating each from a mixture containing arsenic, copper and antimony,
(A) a leaching step of adding and mixing a sulfuric acid solution to a mixture containing arsenic, copper and antimony, separating into a leaching solution and a leaching residue containing arsenic, copper and antimony, and filtering the leaching residue to recover the leaching solution;
(B) While maintaining the leachate at a liquid temperature of 60 ° C. or higher and 100 ° C. or lower, a reducing agent is added to maintain the redox potential of the leachate within the range of 240 mV or higher and 560 mV or lower with a standard hydrogen electrode. And a reduction step of producing a reduced precipitate mainly composed of antimony and collecting the reduced precipitate by filtration;
(C) The reduced precipitate is added to and mixed with warm water maintained at 60 ° C. or more and 100 ° C. or less to separate the arsenous acid aqueous solution and the undissolved residue containing antimony, and the undissolved residue is separated by filtration to separate arsenic and antimony. A separation step of separating
It is characterized by providing.

In the method for producing an arsenous acid aqueous solution according to the present invention , the reducing agent used in the reduction step is preferably at least one of hydrogen gas, sulfurous acid gas, sodium sulfite, and sodium hydrogensulfite . Furthermore, in the reduction step, the temperature of the leachate is desirably maintained at 70 ° C. or higher and 80 ° C. or lower.

  According to the present invention, from a leachate obtained by leaching a mixture containing arsenic, copper and antimony, such as decopperized slime, with sulfuric acid, without requiring a special device such as an adsorption device or an ion exchange device, reduction precipitation and By a simple means of dissolving in hot water, a high-purity arsenous acid aqueous solution containing no copper and antimony can be obtained.

  Therefore, using the high-purity arsenous acid aqueous solution obtained by the present invention as a raw material, for example, using the method of Patent Document 1, an iron arsenic compound with good crystallinity can be generated and arsenic can be stably treated. Furthermore, it can be used as a raw material for producing high-purity arsenous acid or arsenic metal.

  The high-purity arsenous acid aqueous solution according to the present invention is made from a mixture containing arsenic, copper and antimony, for example, copper-free slime produced in the electrolytic refining process of copper smelting. According to the method of the present invention, antimony, copper, and the like contained in the mixture are processed through three steps of a leaching step, a reduction step, and a separation step in order to separate copper and antimony from arsenic. A pure arsenous acid aqueous solution can be obtained.

  Hereinafter, a method for producing a high purity arsenous acid aqueous solution according to the present invention will be described in detail with reference to FIG. In the process diagram of FIG. 1, copper removal slime is illustrated as a mixture containing arsenic, copper, and antimony.

  In the first leaching step (a), a sulfuric acid solution is added to and mixed with the decoppered slime so that arsenic (As), copper (Cu), and antimony (Sb) are leached into the solution, and the leaching residue is filtered to collect the leachate. . In this leaching step, as conventionally performed, the sulfuric acid concentration of the sulfuric acid solution is preferably 50 to 100 g / l at the start, and the slurry concentration is preferably in the range of 50 to 150 g / l.

  In the leaching step (a), air is preferably blown in order to increase the dissolution rate during leaching. The dissolution rate can also be increased by adding an oxidizing agent such as hydrogen peroxide and leaching as an oxidizing atmosphere having a redox potential of 700 mV or higher. The liquid temperature during leaching is preferably 60 ° C. or higher and 100 ° C. or lower in order to promote the reaction.

  When leaching copper removal slime with a sulfuric acid solution, copper contained in a large amount in the copper removal slime is likely to be leached by sulfuric acid, but almost all of bismuth and lead are distributed to the residue without being leached. Antimony ions have essentially no solubility in water, but are leached when the arsenic concentration in the sulfuric acid solution is high. The mechanism by which antimony is leached is not known, but as a result of studies by the present inventors, it has been found that antimony ions are considered to be leached by forming a complex with pentavalent arsenic ions.

  In the next reduction step (b), the leaching solution collected in the leaching step (a) is maintained at 60 to 100 ° C., and a reducing agent is added to reduce arsenic ions and antimony ions. Precipitate as diantimony. On the other hand, since copper ions remain in the leachate, copper can be separated from arsenic and antimony by collecting the reduced precipitates by filtration.

The principle of this reduced precipitation of arsenic and antimony is considered as follows. That is, according to the study by the present inventors, it is considered that arsenic ions are dissolved in a pentavalent form in a leachate obtained by leaching decopperized slime with sulfuric acid. Here, as can be seen from the solubility of arsenic in the equilibrium state shown in FIG. 2, the solubility of trivalent arsenic ions is only a fraction of that of pentavalent arsenic ions. For this reason, when pentavalent arsenic ions in the leachate are reduced to trivalent using a reducing agent, the solubility of arsenic ions decreases and supersaturated arsenic ions are precipitated as crystals of arsenous acid (As ₂ O ₃ ). . Further, since pentavalent arsenic ions are reduced, antimony ions are destroyed in a complex with arsenic ions and precipitated in the form of diantimony trioxide (Sb ₂ O ₃ ) having low solubility.

  The liquid temperature during the reduction is in the range of 60 to 100 ° C. When the liquid temperature is less than 60 ° C., the reaction rate of the reduction with sulfur dioxide gas is extremely reduced, and it takes time to reach the equilibrium state of FIG. In order to obtain a good reaction rate, the liquid temperature is preferably 70 ° C. or higher. On the other hand, if the liquid temperature exceeds 100 ° C., expensive equipment such as a pressurized container is required, which increases the cost and is not preferable. Furthermore, as shown in FIG. 2, the difference in solubility between trivalent and pentavalent arsenic is large in the range of 30 ° C. to 80 ° C., and it can be expected that a larger amount of arsenous acid precipitates after reduction can be obtained. For this reason, it is most preferable to reduce at a liquid temperature between 70 ° C. and 80 ° C. from the viewpoint of reaction rate and solubility difference.

  Examples of the reducing agent to be used include hydrogen gas, hydrazine, sulfurous acid gas (sulfur dioxide gas), sodium sulfite, and sodium hydrogensulfite. It is preferable to use sulfurous acid gas. The reason for this is that sulfurous acid gas is produced in large quantities in the copper smelting process, so it can be used inexpensively and easily, and since it becomes sulfuric acid after being blown into the liquid as a reducing agent, it affects the treatment process. This is because there is an advantage that it is less.

  The reduction with a reducing agent such as sulfurous acid gas is desirably maintained so that the redox potential (ORP) is in the range of 240 to 560 mV at the standard hydrogen electrode. After ORP is stabilized, stirring is continued for about 1 hour. After completion of the reduction, the leachate is cooled to room temperature and the reduced precipitate is collected by filtration.

In the separation step (c), the reduction precipitate obtained in the reduction step (b) is added to warm water at 60 to 100 ° C. and mixed with stirring, whereby arsenous acid (As ₂ O ₃ ) and dioxide trioxide are mixed. Arsenous acid in the reduced precipitate containing antimony (Sb ₂ O ₃ ) is selectively dissolved to obtain an aqueous arsenous acid solution. At that time, since diantimony trioxide having a low solubility remains in the undissolved residue, a high-purity arsenous acid aqueous solution can be recovered by filtering off the undissolved residue.

  As the temperature of the hot water for dissolving the reduced precipitate, the higher the temperature, the faster the dissolution rate, and the more efficiently it can be handled. However, if the temperature exceeds 100 ° C., expensive equipment such as a pressurized container is required. On the other hand, if the temperature of the hot water is less than 60 ° C., the dissolution rate is slow and the dissolution time is long, which is not efficient. Therefore, the temperature of hot water for dissolving the reduced precipitate is set to 60 to 100 ° C, preferably 70 to 90 ° C. In addition, since the slurry density | concentration of the reduction | restoration deposit with respect to warm water will require a long time for melt | dissolution when it exceeds 50 g / l, or an undissolved residue will increase and it will become difficult to handle, it is preferable to set it as 50 g / l or less. .

  The high-purity arsenous acid aqueous solution obtained by the above-described method of the present invention can precipitate a crystalline iron arsenic compound by adding an iron source and oxidizing according to the method shown in Patent Document 1 described above. The precipitated crystalline iron arsenic compound can be used as a new method for fixing arsenic. Also, using the high-purity arsenous acid aqueous solution obtained by the present invention as a raw material, arsenous acid powder and arsenic metal can be obtained and used as chemicals and semiconductor materials.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by an Example. The chemical analysis of each component of the leachate, the reduced precipitate, the reduced solution, and the aqueous arsenous acid solution was performed by ICP emission spectrometry.

[Example 1]
30 g of copper removal slime produced at the operation site of the copper smelting electrolytic refining process was added and mixed with 300 ml of sulfuric acid solution with a sulfuric acid concentration of 75 g / l so that the slurry concentration became 100 g / l, and air was blown in while heating to 85 ° C. The leaching was carried out by oxidation , and the leaching residue was filtered off to obtain 300 ml of a leachate having the composition shown in Table 1 below.

Take 200 ml of this leachate and keep the temperature at 70 ° C., blow 100% industrial sulfurous acid gas (SO ₂ gas) into the liquid, before blowing redox potential (ORP; standard hydrogen electrode). Was reduced from 850 mV to maintain 400 mV. After the ORP was stabilized, the SO ₂ gas was continuously blown for 1 hour, and then the gas blowing was stopped. The reduced precipitate obtained by cooling to room temperature was filtered and separated into 200 ml of post-reduction liquid and 7.8 g of reduced precipitate.

The results of analyzing the reduced precipitate and the solution after reduction are shown in Table 2 below. Arsenic and antimony are distributed in the reduced precipitate, but the other impurities are hardly distributed in the reduced precipitate. Further, as a result of identifying the reduced precipitate using X-ray diffraction (XRD), it was confirmed that arsenous acid (As ₂ O ₃ ) and diantimony trioxide (Sb ₂ O ₃ ) were produced.

Taking into account the analysis values and quantities in Table 2 above, the distribution ratio of antimony to the reduced precipitates in the SO ₂ gas reduction step was 90%. The distribution ratio of arsenic to the reduced precipitate was 64%.

  Next, 3 g of the reduced precipitate obtained in the reduction step was collected, added to 200 ml of 85 ° C. warm water, and stirred. The addition ratio of the precipitate to the warm water is 15 g / l. Thereafter, the reduced precipitate was dissolved over 6 hours, followed by filtration to obtain 0.5 g of an undissolved residue and 200 ml of a filtrate. The analysis results of the arsenous acid aqueous solution obtained as the filtrate are shown in Table 3 below.

  Using the grade and quantity of each impurity in Tables 1 to 3 above, the proportion of arsenic and antimony distributed to the solution or undissolved residue was estimated. As a result, 84% of arsenic was distributed in the arsenous acid aqueous solution, and only 16% was distributed to the undissolved residue. On the other hand, antimony was distributed only 3% in the arsenous acid aqueous solution, and 97% was distributed in the undissolved residue.

  By this example, it was confirmed that arsenic and antimony in the copper removal slime can be reliably separated. In addition, in the copper removal slime of actual operation, bismuth and lead may be contained in the copper removal slime. However, these impurities are separated from arsenic in each step of the present invention, and are hardly contained in the finally obtained arsenous acid aqueous solution.

[Example 2]
The same leaching solution of copper-free slime as in Example 1 was reduced to a redox potential of 260 mV (standard hydrogen electrode) with sulfurous acid gas. The obtained reduced precipitate had the same composition as in Table 2 above, and it was confirmed that a high-purity arsenous acid aqueous solution was obtained in the same manner as in Example 1.

[Example 3]
The same copper-free slime leachate as in Example 1 was reduced to a redox potential of 550 mV (standard hydrogen electrode) with sulfurous acid gas. The obtained reduced precipitate had the same composition as in Table 2 above, and it was confirmed that a high-purity arsenous acid aqueous solution was obtained in the same manner as in Example 1.

It is process drawing which shows the manufacturing method of the high purity arsenous acid aqueous solution by this invention. It is a graph showing the solubility in the equilibrium state of trivalent and pentavalent arsenic ions.

Claims (3)

A method for obtaining an aqueous arsenous acid solution by separating each from a mixture containing arsenic, copper and antimony,
(A) a leaching step of adding and mixing a sulfuric acid solution to a mixture containing arsenic, copper and antimony, separating into a leaching solution and a leaching residue containing arsenic, copper and antimony, and filtering the leaching residue to recover the leaching solution;
(B) While maintaining the leachate at a liquid temperature of 60 ° C. or higher and 100 ° C. or lower, a reducing agent is added to maintain the redox potential of the leachate within the range of 240 mV or higher and 560 mV or lower with a standard hydrogen electrode. And a reduction step of producing a reduced precipitate mainly composed of antimony and collecting the reduced precipitate by filtration;
(C) The reduced precipitate is added to and mixed with warm water maintained at 60 ° C. or more and 100 ° C. or less to separate the arsenous acid aqueous solution and the undissolved residue containing antimony, and the undissolved residue is separated by filtration to separate arsenic and antimony. A separation step of separating
A process for producing an aqueous arsenous acid solution, comprising: The method for producing an arsenous acid aqueous solution according to claim 1 , wherein the reducing agent used in the reduction step is at least one of hydrogen gas, sulfurous acid gas, sodium sulfite, and sodium hydrogensulfite . The method for producing an aqueous arsenous acid solution according to claim 1 or 2, wherein the temperature of the leachate is maintained at 70 ° C or higher and 80 ° C or lower in the reduction step.

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