JP2018087114A - Method for producing scorodite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing stable scorodite reduced in the elution amount of arsenic at a high conversion ratio.SOLUTION: Provided is a method for producing scorodite characterized in that a ferric compound is added to an arsenic-containing solution obtained by subjecting a copper-arsenic-containing matter to alkali oxidation treatment with a sodium-containing solution and removing a copper component therefrom to generate iron-arsenic precipitates, which is subjected to solid-liquid separation, and the precipitates are made into an acid solution with a pH of 0.5 to 1.0, which is subjected to heating to generate crystalline scorodite, in which an Fe/As molar ratio in the acid solution is controlled to 1.0 to 1.25 and a sodium concentration therein is controlled to 2.5 g/L, and scorodite having an arsenic elusion concentration of 0.15 mg/L or lower is generated at a conversion ratio of 95% or higher, and, more preferably, the sodium concentration is controlled to 3.0 to below 4.0 g/L, and scorodite having an arsenic elusion concentration of 0.07 mg/L or lower is generated at a conversion ratio of 98% or higher.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing scorodite capable of producing scorodite efficiently and stably.

At the time of electrolytic refining of copper, a part of impurities such as arsenic contained in the copper anode accumulates in the electrolytic solution. Therefore, a part of the electrolytic solution is generally subjected to a copper removal electrolytic treatment as a cleaning treatment. In this process, slime containing copper arsenide (such as Cu ₃ As) is generated as a smelting intermediate product. Since this copper arsenide-containing slime contains, for example, copper 40-60 mass%, arsenic 20-40 mass%, lead, tin, antimony, bismuth, etc. (each 0.5-5 mass%), Generally, this is returned to the copper smelting process and repeatedly processed. Alternatively, a method is also known in which arsenic and copper in a copper arsenide-containing slime are separated, and thereafter, arsenic is fixed to a stable compound and removed from the copper smelting system.

As a method for removing arsenic from the system, there is a scorodite method in which arsenic and copper contained in a slime are separated, and then arsenic is reacted with iron to generate a stable iron arsenic compound (scorodite: FeAsO ₄ .2H ₂ O). Are known.

  For example, divalent iron ions are added to a solution containing pentavalent arsenic so that the molar ratio of iron to arsenic (Fe / As) in the solution is 1 or more and less than 1.5, and an oxidizing agent is added and stirred. However, there is known a method of synthesizing crystalline scorodite by heating to 70 ° C. or higher (Japanese Patent No. 4087433, Japanese Patent No. 4149488, and Japanese Patent No. 4615561).

  However, the method of synthesizing scorodite by adjusting the molar ratio of iron to arsenic (Fe / As) to 1 to less than 1.5 is performed by removing copper from alkali leaching of copper arsenide or the like and then removing Na. Ca is added to a solution containing arsenic to form a Ca arsenic compound, which is separated from Na. This arsenic-containing liquid is used in which Ca is dissolved in sulfuric acid and Ca is removed by gypsum. The removal process is complicated.

Further, a method of synthesizing crystalline scorodite by heating after adjusting the molar ratio of trivalent Fe to pentavalent As contained in the acidic aqueous solution to 0.9 or more and less than 1.0 is known ( Japanese Patent No. 4538481). However, this method uses a sulfuric acid leaching solution of electrolytically precipitated copper produced in the copper smelting process as an acidic aqueous solution containing arsenic, so that the copper concentration in the solution is high and Cu is mixed in the scorodite by 1 to 2 wt%. There is.

  As a method of solving the problems of the conventional method, the copper arsenic-containing material is alkaline oxidatively leached with a sodium hydroxide solution, and a ferric compound is added to the arsenic-containing solution from which copper has been removed to produce an iron arsenic starch, There has been proposed a method in which a sulfuric acid slurry having a pH of 0.7 to 1.2 is formed and heated to produce crystalline scorodite (Japanese Patent Laid-Open No. 2014-208581). This method has the advantage that the treatment process is simple, Cu contamination is small, and scorodite with a large particle size can be produced, and the capacity of iron arsenic starch is greatly reduced with respect to arsenic leachate. doing.

Japanese Patent No. 4087433 Japanese Patent No. 4149488 Japanese Patent No. 4615561 Japanese Patent No. 4538481 JP 2014-208581 A

  In the production method of Patent Document 5, the arsenic elution amount of scorodite is suppressed to 0.2 ppm, which is compatible with the elution standard of 0.3 ppm (waste disposal method / special management waste), but arsenic is a toxic substance. Therefore, it is preferable that the amount of arsenic eluted is as small as possible. Moreover, although the manufacturing method of patent document 5 has a processing example whose conversion rate to scorodite is about 90%, a higher conversion rate is preferable in order to increase the productivity of scorodite. Furthermore, if the conversion rate to scorodite increases, the arsenic concentration of the drainage decreases, and the burden of the drainage treatment can be reduced.

  The production method of the present invention solves the problems of further reduction of the arsenic elution amount and improvement of the scorodite conversion rate in the production method of Patent Document 5, and scorodite with less arsenic elution amount than the production method of Patent Document 5 Is produced at a high conversion rate of 95% or more.

The present invention is a method for producing scorodite having the following configuration.
[1] An iron arsenic starch is formed by adding a ferric compound to an arsenic leachate obtained by removing copper from an alkali oxidation leaching of a copper arsenic-containing substance with a sodium-containing solution, and solid-liquid separation is performed. In a method of producing crystalline scorodite by heating to an acidic solution having a pH of 1.5 or less, the Fe / As molar ratio of the acidic solution is 1.0 to 1.25 and the sodium concentration is 2.5 g. A method for producing scorodite, characterized by producing scorodite having an arsenic elution concentration of 0.15 mg / L or less at a conversion rate of 95% or more.
[2] The method according to [1], wherein scorodite having an arsenic elution concentration of 0.07 mg / L or less is generated at a conversion rate of 98% or more by setting the sodium concentration to 3.0 g / L or more and less than 4.0 g / L. To produce scorodite.
[3] A sodium hydroxide solution is added to a copper arsenic-containing material, and alkaline oxidation leaching is performed under heating to separate a residue containing copper oxide. Then, a ferric compound is added to the leaching solution containing arsenic to add iron arsenic starch. The method for producing scorodite according to the above [1] or [2], wherein a product is produced, solid-liquid separated, and the starch is used.

[Specific description]
Hereinafter, the present invention will be specifically described together with examples.
In the production method of the present invention, an iron arsenic starch is formed by adding a ferric compound to an arsenic leachate obtained by removing copper by oxidative leaching of a copper arsenic-containing substance with a sodium-containing solution, and solid-liquid separation is performed. In the method of producing an acidic solution having a pH of 1.5 or less and heating to produce crystalline scorodite, the Fe / As molar ratio of the acidic solution is 1.0 to 1.25 and the sodium concentration is 2 The scorodite production method is characterized in that scorodite having an arsenic elution concentration of 0.15 mg / L or less is generated at a conversion rate of 95% or more at a rate of 0.5 g / L or more.

The production method of the present invention uses an iron arsenic starch produced by adding a ferric compound to an arsenic leachate obtained by removing copper from a copper arsenic-containing material by alkali oxidation treatment with a sodium-containing solution. The copper arsenic-containing material is, for example, a copper removal electrolytic slime containing copper arsenide (Cu ₃ As, Cu ₅ As ₂ ). An example of the process of producing iron arsenic starch from decoppered electrolytic slime containing copper arsenide and the treatment process of producing scorodite from the iron arsenic starch are shown in FIG.

  In the illustrated processing example, a sodium hydroxide solution is added to a copper removal electrolytic slime containing copper arsenide, and air or oxygen, for example, is blown as an oxidant, and oxidative leaching (oxidation with an alkaline solution) is performed at 50 ° C. to 60 ° C. The arsenic is eluted by leaching: alkali leaching), and the copper content is made into copper oxide to form a residue, which is separated into solid and liquid to recover the arsenic leachate. An iron arsenic starch is produced by adding a ferric compound such as ferric sulfate to the recovered arsenic leachate. The iron arsenic starch is a starch in which arsenic ions are adsorbed on iron hydroxide, and a part of arsenic may exist as amorphous iron arsenate.

  In the production method of the present invention, the iron arsenic starch is washed by solid-liquid separation, and if necessary, dissolved by adding sulfuric acid or the like to a pH of 1.5 or less, preferably a pH of 0.5 or more and 1.0 or less. In the method of forming an acidic solution (iron arsenic starch solution) and heating to produce crystalline scorodite, the Fe / As molar ratio of the acidic solution is 1.0 to 1.25 and the initial sodium concentration is This is a method for producing crystalline scorodite at 2.5 g / L or more.

  When the pH of the acidic solution of iron arsenic starch is higher than 1.5, the starch hardly dissolves, and when the pH is less than 0.5, scorodite is hardly generated. An acidic solution having a pH of 1.5 or less, preferably a pH of 0.5 to 1.0 is heated to 90 ° C. or more to produce crystalline scorodite.

  In the production method of the present invention, scorodite is produced in a range where the Fe / As molar ratio of the solution is 1.0 or more and 1.25 or less. Since the Fe / As molar ratio is the Fe / As molar ratio of iron arsenic starch, when ferric sulfate is added to arsenic leachate or the like to produce iron arsenic starch, the Fe / As molar ratio of Fe The amount of ferric sulfate is adjusted according to the arsenic concentration so that the / As molar ratio is 1.0 or more and 1.25 or less, and iron arsenic starch having the Fe / As molar ratio is generated. This iron arsenic starch may be used.

  If the Fe / As molar ratio is less than 1.0, the amount of arsenic in the liquid becomes excessive, it is difficult to generate stable scorodite, and the amount of arsenic eluted from the generated scorodite increases. On the other hand, when the Fe / As molar ratio exceeds 1.25, the conversion rate to scorodite decreases and the operation efficiency decreases.

  In the production method of the present invention, the Fe / As molar ratio of the solution is in the above range, and the initial sodium concentration of the solution is in the range of 2.5 g / L or more, preferably from 3.0 g / L to 4.0 g / L. Generate scorodite in the range below. Since the sodium concentration is derived from the alkaline oxidation leaching of arsenic, the sodium concentration of the solution may be in the above range by the sodium remaining in the iron arsenic starch recovered from the arsenic leaching solution.

  When an iron arsenic starch is formed by adding a ferric compound to an arsenic leachate obtained by adding sodium hydroxide solution to a slime containing copper arsenide and oxidative leaching with alkali, this iron arsenic starch contains arsenic. Sodium from the leachate remains. Usually, the amount of deposits such as sodium ions and sulfate ions can be adjusted or removed by washing the solid-liquid separated and recovered iron arsenic starch.

  In the production method of the present invention, when the iron arsenic starch is an acidic solution having a pH of 1.5 or less, preferably 0.5 to 1.0, and heated to produce crystalline scorodite, It has been found that the initial sodium concentration has a significant effect on scorodite stability and conversion. Specifically, the arsenic elution amount is 0.15 mg by generating scorodite with an Fe / As molar ratio in the range of 1.0 to 1.25 and an initial sodium concentration of 2.5 g / L or more. / L or less crystalline scorodite can be produced with a conversion rate of 95% or more.

  Further, by controlling the initial sodium concentration within the range of the Fe / As molar ratio to 3.0 g / L or more to less than 4.0 g / L, the scorodite having an arsenic elution concentration of 0.07 mg / L or less can be increased to 98% or more. Can be generated at a conversion rate of When the initial sodium concentration is 4.0 g / L or more, the conversion rate to scorodite is about 95.0% to about 97.5%. Therefore, to produce scorodite with a high conversion rate of 98% or more. The initial sodium concentration of the iron arsenic acid solution is preferably in the range of 3.0 g / L to less than 4.0 g / L.

  When the iron arsenic starch produced and recovered by adding a ferric compound to the arsenic leachate obtained by adding sodium hydroxide solution to the slime containing copper arsenide and alkaline leaching is dissolved without washing, about 8 to Since a liquid containing 30 g / L of sodium is obtained, the iron arsenic starch is washed and the sodium concentration is 2.5 g / L or more, preferably 3.0 g / L or more, more preferably 3.0 g / L. It may be set to be above-less than 4.0 g / L.

  On the other hand, the production method of the present invention can be used without washing the recovered iron arsenic starch. In this case, the sodium concentration of the solution is about 8 to 30 g / L.

  The scorodite produced by the production method of the present invention is crystalline. This scorodite can be recovered, and a part thereof can be returned to the iron arsenic starch production step and used as a seed crystal.

  According to the production method of the present invention, the Fe / As molar ratio of the acidic solution of iron arsenic starch is set in the range of 1.0 to 1.25 and the initial sodium concentration is controlled to 2.5 g / L or more. Thus, scorodite having an arsenic elution concentration of 0.15 mg / L or less can be produced at a high conversion rate of 95% or more.

  Furthermore, according to the production method of the present invention, the Fe / As molar ratio of the acidic solution is in the range of 1.0 to 1.25 and the initial sodium concentration is 3.0 g / L to 4.0 g / L. By controlling to less than scorodite having an arsenic elution concentration of 0.07 mg / L or less can be produced at a conversion rate of 98% or more.

  As described above, the production method of the present invention has a high conversion rate to scorodite, so that the arsenic concentration of the drainage after production is low, and therefore the burden of the drainage treatment can be reduced.

Process drawing which shows an example of the manufacturing method of this invention

Examples of the present invention are shown below together with comparative examples. Arsenic leachate was prepared, and Examples and Comparative Examples were carried out using this arsenic leachate. The results of Examples are shown in Table 1, and the results of Comparative Examples are shown in Table 2. ICP-AES was used for the measurement of arsenic, iron and sodium. The produced scorodite was washed and an elution test based on Circular 13 was conducted. The result of this dissolution test was shown as As dissolution concentration (mg / L). The conversion rate of scorodite was shown. The conversion rate of scorodite was obtained by the following equation.
Conversion rate% = 100- (final arsenic concentration (g / L) / initial arsenic concentration (g / L) × 100)

[Preparation of arsenic leachate]
400 g (As 25 mass%) of slime mainly composed of copper arsenide and 2 L of water were made into a slurry, and sodium hydroxide was added to the NaOH / As molar ratio of about 1.6 while stirring to prepare a slurry. This slurry was heated to 50 ° C. to 60 ° C., and air was introduced at a flow rate of 1 L / min for about 6 hours to perform oxidative leaching. As leaching progressed, the slurry changed from black to brown (Cu ₂ O color). Here, the stirring was stopped, and the slurry was filtered to recover the arsenic leachate. This arsenic leachate had a pH of 8.5, As 40 g / L, Na 24.5 g / L, and Cu of 2 ppm or less.

[Example 1]
Heat 600 ml of the arsenic leachate to 50 ° C. to 60 ° C., add 121-127 ml of polyferric sulfate solution (Nittetsu Mining Co., Ltd. product: Polytetsu, Fe concentration 160 g / L), and stir for 60 minutes to stir iron arsenic. Product was produced. Thereafter, about 220 g of wet starch (water content: about 70% by mass) was collected by suction filtration and washing. About 100 ml of concentrated sulfuric acid is mixed with 100 g of this starch, and the Fe / As molar ratio is 1.08 to 1.13, the initial sodium concentration is 3.12 g / L to 3.74 g / L, and the initial pH is 0.71 to 0.78. A solution was prepared. This solution was heated to 93 ° C. ± 3 ° C., 6 g (50 g / L) of crystalline scorodite was added as a seed material, and heating and stirring were continued for 6 hours. Thereafter, the produced scorodite was recovered by solid-liquid separation. Production conditions and results are shown in Table 1 (Sample 1 to Sample 4).

[Example 2]
For samples 5 to 16, iron arsenic starch solutions were prepared in the same manner as in Example 1 except that the initial pH, initial sodium concentration, and Fe / As molar ratio shown in Table 1 were adjusted. After these solutions were heated to 93 ± 3 ° C., crystalline scorodite was added as a seed crystal so as to be 50 g / L, and heating and stirring were continued for 6 hours. The produced scorodite was recovered by solid-liquid separation. Production conditions and results are shown in Table 1.

  As shown in Table 1, sample Nos. 1 to 16 having Fe / As molar ratios of 1.05 to 1.18 and initial sodium concentrations of 3.12 g / L to 26.38 g / L are all scorodite arsenic elution. The amount is 0.15 mg / L or less, scorodite is stable, and the conversion rate to scorodite is as high as 95% or more. Furthermore, among these, sample Nos. 1 to 4 having an initial sodium concentration of 3.12 g / L to 3.74 g / L have a scorodite arsenic elution amount of 0.07 to 0.03 mg / L, which is markedly higher. Both are low and the conversion rate to scorodite is 98% or more, indicating a remarkably high conversion rate.

[Comparative Example 1]
An iron arsenic starch solution was prepared in the same manner as in Example 1 except that the initial pH, initial sodium concentration (less than 2.5 g / L), and Fe / As molar ratio were adjusted as shown in Table 2. After these solutions were heated to 93 ± 3 ° C., crystalline scorodite was added as a seed crystal so as to be 50 g / L, and heating and stirring were continued for 6 hours. The produced scorodite was recovered by solid-liquid separation. Production conditions and results are shown in Table 2 (Samples 20 to 30).

[Comparative Example 2]
The same procedure as in Example 1 was conducted except that the initial pH, initial sodium concentration (3.9 g / L to 13.4 g / L), and Fe / As molar ratio (less than 1.0) shown in Table 2 were adjusted. Thus, an iron arsenic starch solution was prepared. After these solutions were heated to 93 ± 3 ° C., crystalline scorodite was added as a seed crystal so as to be 50 g / L, and heating and stirring were continued for 6 hours. The produced scorodite was recovered by solid-liquid separation. Production conditions and results are shown in Table 2 (Samples 31 to 35).

[Comparative Example 3]
The same as Example 1 except that the initial pH, initial sodium concentration (3.91 g / L to 4.9 g / L), and Fe / As molar ratio (1.25 or more) were adjusted as shown in Table 2. Thus, an iron arsenic starch solution was prepared. After these solutions were heated to 93 ± 3 ° C., crystalline scorodite was added as a seed crystal so as to be 50 g / L, and heating and stirring were continued for 6 hours. The produced scorodite was recovered by solid-liquid separation. Production conditions and results are shown in Table 2 (Samples 36 to 38).

  As shown in Table 2, most of the samples 20 to 30 of Comparative Example 1 having a low initial sodium concentration have a large amount of arsenic, low scorodite stability, and a low conversion rate to scorodite of 90% or less. It is. In addition, Samples 31 to 35 of Comparative Example 2 having a low Fe / As molar ratio have a high conversion rate to scorodite, but a large amount of arsenic is eluted, and scorodite stability is low. On the other hand, in the samples 36 to 38 of Comparative Example 3 having a high Fe / As molar ratio, the arsenic elution amount is less than 0.2 mg / L, so the stability of the colloid is good, but the conversion rate to scorodite is significantly low. .

The present invention is a method for producing scorodite having the following configuration.
[1] An iron arsenic starch is formed by adding a ferric compound to an arsenic leachate obtained by removing copper from an alkali oxidation leaching of a copper arsenic-containing substance with a sodium-containing solution, and solid-liquid separation is performed. In an acidic solution having a pH of 0.5 to 1.0 and heating to produce crystalline scorodite, the Fe / As molar ratio of the acidic solution is 1.0 to 1.25 and sodium. A method for producing a scorodite, characterized in that a scorodite having a concentration of 2.5 g / L or more and an arsenic elution concentration of 0.15 mg / L or less is produced at a conversion rate of 95% or more.
[2] The method according to [1], wherein scorodite having an arsenic elution concentration of 0.07 mg / L or less is generated at a conversion rate of 98% or more by setting the sodium concentration to 3.0 g / L or more and less than 4.0 g / L. To produce scorodite.
[3] A sodium hydroxide solution is added to a copper arsenic-containing material, and alkaline oxidation leaching is performed under heating to separate a residue containing copper oxide. Then, a ferric compound is added to the leaching solution containing arsenic to add iron arsenic starch. The method for producing scorodite according to the above [1] or [2], wherein a product is produced, solid-liquid separated, and the starch is used.

[Specific description]
Hereinafter, the present invention will be specifically described together with examples.
In the production method of the present invention, an iron arsenic starch is formed by adding a ferric compound to an arsenic leachate obtained by removing copper by oxidative leaching of a copper arsenic-containing substance with a sodium-containing solution, and solid-liquid separation is performed. In the method of making this an acidic solution having a pH of 0.5 or more and 1.0 or less and heating to produce crystalline scorodite, the Fe / As molar ratio of the acidic solution is 1.0 or more and 1.25 or less, And a scorodite production method characterized in that scorodite having an arsenic elution concentration of 0.15 mg / L or less is produced at a conversion rate of 95% or more with a sodium concentration of 2.5 g / L or more.

In the production method of the present invention, the iron arsenic starch is solid-liquid separated and washed, and if necessary, dissolved by adding sulfuric acid or the like, and an acidic solution (iron arsenic starch) having a pH of 0.5 to 1.0. In the method of producing a crystalline scorodite by heating, the Fe / As molar ratio of the acidic solution is set to 1.0 to 1.25 and the initial sodium concentration is set to 2.5 g / L or more. This is a method for producing crystalline scorodite.

When the pH of the acidic solution of iron arsenic starch is higher than 1.5, the starch hardly dissolves, and when the pH is less than 0.5, scorodite is hardly generated . Preferably, an acidic solution having a pH of 0.5 to 1.0 is heated to 90 ° C. or higher to form crystalline scorodite.

  In the production method of the present invention, when the iron arsenic starch is converted to an acidic solution having a pH of 0.5 to 1.0 and heated to produce crystalline scorodite, the initial sodium concentration of the solution is stable scorodite. It was found to have a significant effect on sex and conversion. Specifically, the arsenic elution amount is 0.15 mg by generating scorodite with an Fe / As molar ratio in the range of 1.0 to 1.25 and an initial sodium concentration of 2.5 g / L or more. / L or less crystalline scorodite can be produced with a conversion rate of 95% or more.

Claims (3)

A ferric compound was added to an arsenic leachate obtained by alkaline oxidation leaching of a copper arsenic-containing material with a sodium-containing solution to remove the copper content, thereby producing an iron arsenic starch and solid-liquid separation. In a method for producing an acidic solution of 5 or less and heating to produce crystalline scorodite, the acidic solution has a Fe / As molar ratio of 1.0 to 1.25 and a sodium concentration of 2.5 g / L or more. And producing a scorodite having an arsenic elution concentration of 0.15 mg / L or less at a conversion rate of 95% or more. The scorodite production according to claim 1, wherein the scorodite having an arsenic elution concentration of 0.07 mg / L or less is produced at a conversion rate of 98% or more by setting the sodium concentration to 3.0 g / L or more and less than 4.0 g / L. Method. Add sodium hydroxide solution to copper arsenic containing material, perform alkaline oxidation leaching under heating, separate the residue containing copper oxide, add ferric compound to the leaching solution containing arsenic to produce iron arsenic starch The method for producing scorodite according to claim 1 or 2, wherein the starch is used after solid-liquid separation.

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