JP2019085321A - Manufacturing method of scorodite - Google Patents

Abstract

To provide a manufacturing method of scorodite extremely high in conversion rate of arsenic to scorodite, and largely less in residual arsenic concentration of a scorodite synthesis post liquid.SOLUTION: There is provided a manufacturing method of scorodite for synthesizing crystalline scorodite by heating an acidic slurry of iron arsenic deposition generated by adding a ferric compound to an arsenic exudate by alkali oxidation exudating copper arsenic-containing article by a sodium-containing solution and removing copper component, in which the scorodite is synthesized by adjusting pH of the acidic slurry to 1.1 to 1.6, sodium concentration to 10 to 40 g/L, and initial arsenic concentration to 20 to 50 g/L.SELECTED DRAWING: Figure 1

Description

  The present invention is a method for producing scorodite from arsenic leachate of copper arsenic-containing material such as copper arsenide-containing slime, the conversion rate of arsenic to scorodite is extremely high, and the residual arsenic concentration in the solution after scorodite synthesis is significantly low. The present invention relates to a method of manufacturing scorodite.

In electrolytic refining of copper, a part of the impurities such as arsenic contained in the copper anode is accumulated in the electrolytic solution, so a part of the electrolytic solution is purified (de-copper electrolytic treatment). During this process, a slime containing copper arsenide (such as Cu ₃ As) is generated. The copper arsenide-containing slime contains, for example, 40 to 60% by mass of copper, 20 to 40% by mass of arsenic, lead, tin, antimony, bismuth and the like (each 0.5 to 5% by mass). It is common to return this to a copper smelting process and to process it repeatedly. In addition, arsenic contained in copper arsenide-containing slime is finally separated from copper, then the arsenic is immobilized on a stable compound and removed from copper smelting outside the system.

As a method of removing arsenic out of the system, there is a scorodite method in which arsenic and copper contained in slime are separated, and then arsenic is reacted with iron to form 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 oxidant is added and stirred. However, there is known a method of synthesizing crystalline scorodite by heating at 70 ° C. or higher to react (Japanese Patent No. 4087433, Japanese Patent No. 4149488, Japanese Patent No. 465561).

  However, the above-mentioned method is a method of synthesizing scorodite from an arsenic-containing solution, and after alkaline oxidation leaching of copper arsenide or the like to remove copper, Ca is added to a solution containing Na and arsenic to add Ca arsenic compound. An arsenic-containing solution is used which is produced and separated from Na, and this Ca-arsenic compound is dissolved in sulfuric acid to remove calcium as gypsum to remove the complex of Na and Ca.

  There is also known a method of synthesizing crystalline scorodite by adjusting the molar ratio of trivalent Fe to pentavalent As contained in the acidic aqueous solution to be 0.9 or more and less than 1.0 (heating Patent No. 4538481 gazette). However, since this method uses a sulfuric acid leaching solution of electrolytically precipitated copper produced in the decoppering electrolytic step as an acidic aqueous solution containing arsenic, the concentration of copper in the solution is high, and 1 to 2 wt% of Cu is mixed in scorodite There's a problem.

  As a method of solving the problems of the conventional method, alkaline arsenic leaching of copper-arsenic containing material with sodium hydroxide solution, ferric compound is added to the arsenic-containing solution from which copper content has been removed to form iron-arsenic sediments; A method has been proposed in which this is converted to a sulfuric acid acidic slurry of pH 0.7 to 1.2 and heated to form crystalline scorodite (Japanese Patent Laid-Open No. 2014-208581). This method has an advantage that the process is simple, Cu contamination is less, and scorodite having a large particle size can be manufactured.

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

In the manufacturing method of Patent Document 5, since the residual arsenic concentration of the solution after scorodite synthesis is as high as 1.8 to 7.5 g / L, the burden of drainage treatment is large. Moreover, in this production method, there is a treatment example in which the conversion rate to scorodite is about 90%, but the residual arsenic concentration of the solution after synthesis is high, and there is a limit to increase the conversion rate to scorodite. Further, in this manufacturing method, arsenic elution amount from the scorodite is suppressed to 0.2 ppm, but less than the elution standard 0.3Pp m based on Wastes Disposal and Public Cleaning Law, the amount of elution of the arsenic because arsenic is a toxic substance Further reduction is preferable.

  The production method of the present invention is a further improvement of the production method of Patent Document 5, and the conversion rate to scorodite is extremely high, so the residual arsenic concentration in the solution after scorodite synthesis is significantly low, and the burden of drainage treatment Provide less manufacturing method. Furthermore, it is preferable to provide a method of production in which the amount of elution of arsenic from scorodite is small.

The present invention is a method of manufacturing scorodite having the following configuration.
[1] Alkaline oxidation leaching of copper arsenic containing material with sodium containing solution to remove copper content Arsenic leachate formed by adding ferric compound to arsenic leaching solution is heated, and crystalline scorodite is heated. Is characterized in that the pH of the acidic slurry is adjusted to 1.1 to 1.6, the sodium concentration is adjusted to 10 to 40 g / L, and the initial arsenic concentration is adjusted to 20 to 50 g / L to synthesize scorodite. How to make scorodite.
[2] The method for producing scorodite according to the above [1], wherein the conversion rate of arsenic to scorodite is 99% or more and the residual arsenic concentration of the solution after scorodite synthesis is 0.4 g / L or less.
[3] Sodium hydroxide solution is added to copper arsenide-containing slime, and alkaline oxidation leaching is performed by heating in the presence of an oxidizing agent to separate a residue containing copper oxide, and then ferric compound is added to a leachate containing arsenic. To form an iron-arsenic precipitate of Fe / As molar ratio of 1.0 to 1.25, and using the acidic slurry of the iron-arsenic precipitate, the production of scorodite described in the above [1] or [2] Method.

[Specific description]
Hereinafter, the present invention will be specifically described with examples.
According to the production method of the present invention, an acidic slurry of iron arsenic precipitate formed by adding a ferric compound to an arsenic leaching solution from which copper arsenic has been removed by alkaline oxidation leaching a copper arsenic containing substance with a sodium containing solution is heated In the method of synthesizing crystalline scorodite, it has been found that the pH and sodium concentration of the acidic slurry have a great effect on the arsenic conversion of scorodite synthesis and the residual arsenic concentration of the solution after synthesis, and the pH and sodium concentration of the acidic slurry The present invention provides a scorodite manufacturing method in which the conversion rate of arsenic is extremely high and the residual arsenic concentration in the solution after synthesis is significantly reduced by adjusting the initial arsenic concentration to a certain range.

  More specifically, the production method of the present invention is the acidity of iron arsenic precipitate formed by adding a ferric compound to an arsenic leaching solution from which copper arsenic is removed by alkaline oxidation leaching a copper arsenic containing material with a sodium containing solution. In the method of heating a slurry to synthesize crystalline scorodite, the pH of the acidic slurry is in the range of 1.1 to 1.6, the sodium concentration is in the range of 10 to 40 g / L, and the initial arsenic concentration is in the range of 20 to 50 g / L. It is a manufacturing method of scorodite characterized by synthesizing to scorodite by adjusting to.

The production method of the present invention uses an acidic slurry of iron arsenic precipitate formed by adding a ferric compound to an arsenic leaching solution in which copper arsenic is removed by alkaline oxidation treatment of a copper arsenic containing material with a sodium containing solution. . The copper-arsenic inclusion is, for example, a decoppered electrolytic slime containing copper arsenide (Cu ₃ As, Cu ₅ As ₂ ). An example of the process of producing iron arsenic deposit from decoppered electrolytic slime containing copper arsenide and the process of producing scorodite from the iron arsenic deposit are shown in FIG.

  In the processing example shown, a sodium hydroxide solution is added to decoppered electrolytic slime containing copper arsenide, and air or oxygen, for example, is blown as an oxidizing agent, and oxidative leaching under heating at 50 ° C to 60 ° C (oxidation by alkaline solution) The leaching is referred to as alkaline oxidation leaching to elute the arsenic, and the copper content is converted to copper oxide residues, which are solid-liquid separated to recover the arsenic leachate. By adding a ferric compound such as polyferric sulfate to the arsenic leachate, an iron arsenic deposit is formed. The formed iron-arsenic precipitate is a precipitate in which arsenate ion is adsorbed to iron hydroxide, and a part of arsenic may be present as non-crystalline iron arsenate.

  In the production method of the present invention, the above-mentioned iron-arsenic sediment is made into an acidic slurry, which is used for synthesis of scorodite. Specifically, for example, an iron-arsenic precipitate obtained by alkaline oxidation treatment of a copper-arsenic containing material with a sodium-containing solution to separate and remove a leaching residue containing copper by solid-liquid separation, and adding ferric sulfate to an arsenic leachate The product is separated into solid and liquid, and sulfuric acid etc. is added to this to make acidic slurry with pH 1.1 to 1.6, sodium concentration 10 to 40 g / L, initial arsenic concentration 20 to 50 g / L for synthesis of scorodite Use.

  Instead of solid-liquid separation after formation of iron arsenic precipitate, an acidic slurry may be used at the time of formation of iron arsenic precipitate. Specifically, for example, a pH 1.1 to 1.6, a sodium concentration 10 to 40 g / L, and an arsenic concentration 20 to 50 g / L in an arsenic leachate obtained by alkali leaching with a sodium-containing solution An amount of concentrated sulfuric acid and ferric polysulfate in the range of (1) may be added to form the above-mentioned iron-arsenic sediment to form an acidic slurry. This acidic slurry is used in the synthesis of scorodite.

  The pH of the acidic slurry is preferably in the range of 1.1 to 1.6. If the pH is less than 1.1, the conversion rate of arsenic to scorodite (hereinafter referred to as "arsenic conversion rate") is only about 95% to 98%, and it is difficult to further increase the arsenic conversion rate. When the pH exceeds 1.6, the slurry concentration becomes high during scorodite synthesis, which is not preferable because it is difficult to stir the slurry. The pH of the acidic slurry can be adjusted by the amount of sulfuric acid used when adding sulfuric acid and ferric polysulfate to the arsenic leaching solution.

  The sodium concentration of the acidic slurry is preferably in the range of 10 to 40 g / L, and more preferably in the range of 15 to 30 g / L. If this sodium concentration is less than 10 g / L, it is difficult to increase the arsenic conversion to 96% or more in the above pH range. Further, if the sodium concentration of the acidic slurry is higher than 40 g / L, the filterability of the synthesized scorodite is unfavorably lowered.

  The sodium concentration of the acidic slurry can be adjusted by measuring the sodium concentration in the arsenic leachate obtained by subjecting the copper-arsenic content to alkaline oxidation treatment with a sodium-containing solution. When the sodium concentration in the arsenic solution is in the range of 10 to 40 g / L, ferric compounds and sulfuric acid are added to form an iron arsenic deposit, and the acid arsenic slurry is not separated from the solid solution. It can be used as

  When the sodium concentration of the acidic slurry exceeds 40 g / L, dilute the acidic slurry or, since most of the sodium is contained in the liquid, separate a part of the liquid from the above acidic slurry and extract it. The excess sodium can be removed and the water (mainly water) can be added to the acidic slurry after solid-liquid separation to adjust to the above sodium concentration range. In addition, the sodium contained in the filtrate recovered by this solid-liquid separation can be used by returning the filtrate to an iron arsenic precipitate acid slurry process or the like. In addition, since the sodium concentration of the arsenic leachate obtained by subjecting the copper-arsenic containing material to alkaline oxidation treatment with a sodium-containing solution is approximately 10 g / L or more, it is not usually necessary to replenish sodium.

  The initial arsenic concentration of the acidic slurry may be in the range of 20 to 50 g / L, preferably in the range of 25 to 40 g / L. When the initial arsenic concentration is less than 20 g / L, the amount of scorodite formed decreases, and the scorodite production efficiency decreases. If the initial arsenic concentration exceeds 50 g / L, the slurry concentration during scorodite synthesis will increase, making stirring difficult. When the pH is less than 1, stirring is possible even if the initial arsenic concentration exceeds 50 g / L, but as described above, it is difficult to increase the arsenic conversion to 99% when the pH is less than 1.

  The molar ratio of iron to arsenic (Fe / As molar ratio) contained in the acidic slurry is preferably in the range of 1.0 or more and 1.25 or less. If the Fe / As molar ratio is less than 1.0, stable scorodite is difficult to form, and the amount of elution of arsenic from the generated scorodite may be large. On the other hand, when the Fe / As molar ratio exceeds 1.25, the scorodite formation efficiency decreases. This Fe / As molar ratio is such that the Fe / As molar ratio is in the range of 1.0 or more and 1.25 or less when ferric sulfate is added to the arsenic leachate to form an iron-arsenic sediment. The addition amount of ferric sulfate may be adjusted according to the arsenic concentration of the arsenic leachate.

  The above acidic slurry is heated, preferably a small amount of scorodite crystals is added as seed crystals to synthesize scorodite. The heating temperature is preferably 90 ° C. to less than 100 ° C., and preferably 90 ° C. to 96 ° C. The scorodite synthesized is crystalline and can be recovered and used as the seed crystal.

According to the production method of the present invention, scorodite can be produced with a high arsenic conversion rate (conversion rate to scorodite) of 99% or more. Therefore, the production efficiency of scorodite can be greatly enhanced.
In addition, since the production method of the present invention has a high conversion rate of arsenic, the residual arsenic concentration in the solution after scorodite synthesis is extremely low, and is less than 0.4 g / L, preferably less than 0.1 g / L. Can significantly reduce the burden of
Furthermore, in the pH range of 1.1 to 1.6, the sodium concentration of 10 to 30 g / L, and the initial arsenic concentration of 20 to 40 g / L of the acidic slurry, the arsenic conversion is 99% or more, and the scorodite A stable scorodite having an arsenic elution amount of 0.15 mg / L or less and a significantly reduced arsenic elution amount can be efficiently produced.

Process flow chart showing an example of the manufacturing method of the present invention

Hereinafter, examples of the present invention will be shown together with comparative examples. In each case, measurement of arsenic, iron and sodium in the acidic slurry was dissolved in concentrated hydrochloric acid and then ICP-AES was used. The generated scorodite was washed and subjected to a dissolution test according to No.13. The result of this elution test is shown as As elution concentration (mg / L). The arsenic conversion (conversion to scorodite) was determined by the following equation.
Arsenic conversion rate% = 100− (residual arsenic concentration (g / L) / initial arsenic concentration (g / L) × 100)

[Preparation of arsenic leachate]
A slurry was prepared by slurrying 400 g of a slime mainly composed of copper arsenide (25% by mass of As) and 2 L of water while stirring and adding sodium hydroxide to a molar ratio of about 1.6 of NaOH / As while stirring. The 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 carry out oxidative leaching. The slurry turned from black to brown (Cu ₂ O color) as the leaching proceeded. Agitation was stopped here and the slurry was filtered to recover the arsenic leachate. The arsenic leachate had a pH of 12, 40 g / L of As, and 24.5 g / L of Na.

Example 1
10 ml of concentrated sulfuric acid is added to 600 ml of the above arsenic leachate at room temperature, and further 127 ml of polyferric sulfate (Fe concentration 160 g / L, Nittetsu Mining Co., Ltd. product: Polytetsu) is added and stirred for 60 minutes to precipitate iron arsenic Acid slurry (pH 1.12). The acidic slurry is heated to 93 ° C. to 96 ° C., 36 g (50 g / L) of crystalline scorodite is added as a seed material, and heating and stirring are continued for 6 hours to form crystalline scorodite, and this scorodite is separated into solid and liquid Collected. The production conditions and the results are shown in Table 1 (Sample 1).

Example 2
The scorodite was synthesized in the same manner as in Example 1 except that the pH, initial arsenic concentration, sodium concentration, and Fe / As molar ratio of the acidic slurry were changed to the amounts shown in Table 1. The production conditions and the results are shown in Table 1 (Samples 2 to 8).

As shown in Table 1, the pH of the acid slurry is in the range of 1.12 to 1.56, the initial arsenic concentration is 20.5 to 39.0 g / L, and the sodium concentration is 13.2 to 27.7 g / L. By adjusting, scorodite can be generated at an arsenic conversion rate of 99% or more, and the residual arsenic concentration of the solution after synthesis can be reduced to 0.33 g / L or less.

Comparative Example
A scorodite was synthesized in the same manner as in Example 1 except that the pH, initial arsenic concentration, sodium concentration, and Fe / As molar ratio of the acidic slurry were changed to the amounts shown in Table 2. The production conditions and the results are shown in Table 2 (Samples 20 to 29).

As shown in Table 2, Samples 20 to 25 having an acidic slurry pH of less than 1 each had an arsenic conversion of 96.4 or less, and the residual arsenic concentration of the solution after synthesis was 1.20 g / L or more, The formation efficiency of scorodite is low, and the residual arsenic concentration of the solution after synthesis is high. In addition, although the arsenic conversion rate of the sample 29 in which the pH of the acidic slurry exceeds 1.6 is 99.9% or more, the arsenic elution amount of generated scorodite is 0.3 mg / L or more, which exceeds the environmental standard.
On the other hand, samples 26 to 28 in which the Na concentration of the acidic slurry is less than 10 g / L have an arsenic conversion rate of 96.8% or less, and the residual arsenic concentration of the solution after synthesis is 1.56 g / L or more. The residual arsenic concentration is 5 g / L or more and is very high.

Claims (3)

Alkaline oxidation leaching of copper arsenic content with sodium containing solution to remove copper content By adding ferric compound to arsenic leaching solution, an acidic slurry of iron arsenic precipitate formed is heated to synthesize crystalline scorodite In the method, scorodite is prepared by adjusting the pH of the acidic slurry to 1.1 to 1.6, the sodium concentration to 10 to 40 g / L, and the initial arsenic concentration to 20 to 50 g / L, and synthesizing scorodite. Manufacturing method.
The method for producing scorodite according to claim 1, wherein the conversion rate of arsenic to scorodite is 99% or more, and the residual arsenic concentration of the solution after scorodite synthesis is 0.4 g / L or less.
Sodium hydroxide solution is added to copper arsenide-containing slime, and alkaline oxidation leaching is performed by heating in the presence of an oxidizing agent to separate a residue containing copper oxide, and then a ferric compound is added to a leachate containing arsenic. The method for producing scorodite according to claim 1 or 2, wherein an iron-arsenic precipitate having an Fe / As molar ratio of 1.0 to 1.25 is formed, and an acidic slurry of the iron-arsenic precipitate is used.

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