JP2013095985A - Method for recovering arsenic from nonferrous smelting smoke ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method capable of recovering arsenic from nonferrous smelting smoke ash as a pentavalent arsenic solution without using a sulfating agent, and restraining copper from being mixed into the pentavalent arsenic solution.SOLUTION: The method for recovering arsenic from nonferrous smelting smoke ash includes: a step for slurrying the nonferrous smelting smoke ash; a step for performing primary leaching step with the pH value of the slurry being 0.5 or less; a neutralization step for causing the slurry after the primary leaching step to be subjected to solid-liquid separation, and adding a neutralizer to the obtained primary leaching solution to obtain a solution after neutralization; an oxidation step for obtaining an oxidized precipitate by causing the solution after neutralization to be subjected to solid-liquid separation after an oxidizing agent is provided to the solution after neutralization; and a step for slurrying the oxidized precipitate, performing secondary leaching, and obtaining a pentavalent arsenic solution for producing crystalline iron arsenate as the secondary leaching solution.

Description

  The technology for separating and recovering arsenic and metal elements other than arsenic from by-products and smoke ash containing metal elements such as arsenic (As), copper (Cu), iron (Fe), etc., especially non-ferrous smelting The present invention relates to a technique for recovering a liquid arsenic-containing solution suitable as a raw material liquid source liquid for producing crystalline iron arsenate from ash containing arsenic generated in the process.

  Arsenic is a substance with a large environmental load, and its stable treatment is important from the viewpoint of environmental conservation. In non-ferrous smelting, especially copper smelting, the arsenic content in the ore tends to increase in recent years, and it is an urgent task to establish a high-load operation system for arsenic. In order to establish this system, a large amount of arsenic is concentrated in the smelting furnace ash generated in the smelting process, so it is necessary to actively discharge the arsenic out of the system. For this reason, the discharge of arsenic is an important technical element. In this case, the discharged arsenic is preferably discharged as crystalline iron arsenate, which is the most stable compound, and managed and stored for environmental measures.

Regarding the arsenic treatment, the present applicant discloses Patent Document 1.
Patent Document 1 prepares a slurry by mixing non-ferrous smelting smoke ash and water, controlling the pH within a predetermined pH value range by adding an alkaline agent to the slurry, and leaching liquid containing copper and arsenic by leaching reaction. A leaching residue containing. Then, the leaching residue containing the arsenic is re-leached with an acid to obtain an arsenic solution, the arsenic solution is sulfided to collect arsenic as arsenic sulfide, and the arsenic sulfide is used as an arsenic raw material source for producing crystalline iron arsenate. It is what.

JP 2009-161803 A

Patent Document 1 described above is an excellent method for obtaining an arsenic raw material source for producing crystalline iron arsenate from non-ferrous smelting ash. However, according to the study by the present inventors from the viewpoint of constructing a high-load operation system for arsenic, the following problems have been clarified.
1. A sulfiding agent is required to convert arsenic contained in non-ferrous smelting ash into arsenic sulfide. Moreover, the cost which leaches out the produced | generated arsenic sulfide generate | occur | produces, Furthermore, it is necessary to supply the iron source required for crystalline iron arsenate manufacture from the outside. That is, the drug cost may increase.
2. A step of recovering arsenic contained in non-ferrous smelting ash as arsenic sulfide and a step of leaching arsenic sulfide to produce an arsenic solution again are required. Further, the arsenic sulfide produced is mostly trivalent arsenic. For this reason, a step of oxidizing the trivalent arsenic to pentavalent arsenic is also required. As a result, the entire process from charging of non-ferrous smelting ash to recovery of a liquid arsenic-containing solution suitable as a raw material liquid for producing crystalline iron arsenate is lengthened.
3. I want to lower the copper concentration of the arsenic solution to be recovered. This is to recover the copper contained in the smoke ash at an early stage and lower the copper concentration of the arsenic solution.

  Based on the above problems, the problem to be solved by the present invention is that arsenic can be recovered as a pentavalent arsenic solution from non-ferrous smelting ash without using a sulfurizing agent, and copper is mixed into the pentavalent arsenic solution. The present invention provides a method for recovering arsenic from non-ferrous smelting smoke ash.

  In order to solve the above-mentioned problems, the present inventors conducted research. Then, the smoke ash is slurried, and the slurry is leached with an acid to obtain a leachate containing trivalent and pentavalent arsenic, copper, iron and the like. Then, when the leachate is neutralized and oxidized to trivalent arsenic and pentavalent arsenic under appropriate conditions, 99% by mass or more of the arsenic is oxidized to pentavalent arsenic, and becomes a solid layer. It was found that it was introduced and deposited from the leachate. Further, the precipitate is an intermediate product in which arsenic is concentrated as pentavalent arsenic (hereinafter sometimes referred to as “oxidized precipitate” in the present invention), and the knowledge that copper is hardly contained is obtained. The present invention has been completed.

That is, the first invention for solving the above-described problem is
A method for recovering arsenic from non-ferrous smelting ash containing arsenic, copper and iron,
A step of slurrying the non-ferrous smelting ash;
A primary leaching step of adding an acid to the slurry and leaching the slurry with a pH value of 0.1 or more and 0.5 or less;
The slurry after completion of the primary leaching step is subjected to solid-liquid separation, and a neutralizing step of obtaining a post-neutralization solution by adding a neutralizing agent to the obtained primary leaching solution;
An oxidizing step of adding a neutralizing agent to the post-neutralized solution to adjust the pH value to 1.5 or more and 3 or less, and further adding an oxidizing agent, followed by solid-liquid separation to obtain an oxidized residue,
A method of recovering arsenic from non-ferrous smelting ash, comprising: leaching the oxidized product secondarily to obtain an arsenic solution of crystalline iron arsenate production raw material as a second leaching solution.

The second invention is
The secondary leaching is a step in which the oxidized precipitate is used as a slurry, and an acid is added to the slurry and leached.
Separating the slurry after completion of the leaching into a secondary leaching solution and a secondary leaching residue, and obtaining a pentavalent arsenic solution of a crystalline iron arsenate production raw material as the secondary leaching solution. It is a collection | recovery method of arsenic from the nonferrous smelting ash as described in 1st invention.

The third invention is
The non-ferrous smelting method according to the first or second invention, wherein the oxidizing agent used in the oxidation step is hydrogen peroxide and / or a mixed gas of an oxidizing gas and sulfur dioxide (SO ₂ ). This is a method for recovering arsenic from smoke ash.

The fourth invention is:
The oxidizing gas is any one selected from oxygen (O ₂ ), air, and a mixed gas of oxygen and air, and the arsenic from non-ferrous smelting ash according to the third invention It is a collection method.

The fifth invention is:
The iron source is previously changed from the primary leaching step to the oxidation step so that the molar amount of iron and arsenic dissolved in the secondary leaching solution obtained in the secondary leaching step is Fe / As = 1 to 1.5. The method for recovering arsenic from non-ferrous smelting ash according to any one of the first to fourth inventions, wherein the arsenic is added in any of the steps up to here.

The sixth invention is:
The secondary leachate obtained in the secondary leaching step is repeated as water for use in the secondary leaching step, and arsenic in the secondary leaching solution is concentrated. It is a recovery method of arsenic from the non-ferrous smelting ash described.

The seventh invention
From the non-ferrous smelting ash according to any one of the first to sixth inventions, wherein the neutralizing agent is at least one selected from an alkaline agent containing calcium and an alkaline agent containing magnesium. This is a method for recovering arsenic.

  According to the method for recovering arsenic from non-ferrous smelting ash according to the present invention, it was possible to efficiently separate arsenic from ash containing arsenic, copper, iron and the like without adding a sulfurizing agent. Furthermore, the mixing of copper was suppressed, and a pentavalent arsenic solution containing almost no trivalent arsenic could be obtained.

It is a process flow figure showing the recovery method of arsenic from nonferrous smelting smoke ash concerning the present invention.

  The form for implementing this invention is demonstrated in order of each process of smoke ash, primary leaching, neutralization, oxidation, secondary leaching, and a crystallization process, referring FIG.

<Smoke ash>
Smoke ash is generated from each process of dry smelting in non-ferrous smelting, especially copper smelting. In addition to arsenic, the smoke ash often contains valuable copper and zinc, and further elements such as iron, bismuth, tin, antimony and lead.
The present invention is applicable to these various types of smoke ash.

<Primary leaching>
In the first leaching process according to the present invention, liquids such as water, process water, and acid are added to smoke ash and stirred to form a slurry, and arsenic, copper, iron, and the like contained in the smoke ash are leached as much as possible. It is a process.
Specifically, the pH value of the slurry is set to 0.1 or more and 0.5 or less, and the slurry is further heated so that the slurry temperature is 50 ° C. or more and leaching is performed. In addition, as an acid used for pH adjustment, it is preferable to use sulfuric acid produced in a non-ferrous smelting process and used for general purposes.

  Of course, the optimum leaching pH value and temperature should be determined in detail for each smoke ash generated at each smelter. However, according to the study by the present inventors, the leaching rate of arsenic and copper in the ash is about 80 to 90% by mass of arsenic and copper to be leached when the pH value of the slurry is 0.5 or less. It has been found that when the slurry has a pH value of 0.2 to 0.3, the slurry is almost completely leached. If the pH value is 0.1 or more, the drug cost is suppressed.

  Regarding the slurry temperature, it has been found that the leaching rate is remarkably improved between room temperature (25 ° C.) and 50 ° C., and the degree of the leaching rate improvement gradually decreases when the temperature exceeds 50 ° C. Therefore, the slurry temperature at the time of leaching is preferably 50 ° C. or higher, and is preferably 100 ° C. or lower, considering the equipment specifications at the time of actual operation, etc., and is considered to be optimal at 80 to 90 ° C.

  The leaching time in the primary leaching step is 30 minutes or more from the time when the leaching condition is satisfied, and the target leaching is almost achieved in one hour.

  A primary leaching solution and a primary leaching residue are obtained by solid-liquid separation of the leaching slurry that has been processed in the primary leaching step. The primary leachate is sent to the neutralization step of the next step. On the other hand, since the primary leaching residue contains unleached copper, it can be used as a smelting raw material.

<Neutralization>
The neutralization process which concerns on this invention is a process of reducing the acid content of the primary leaching liquid produced | generated at the primary leaching process. Specifically, it is a step of adding an alkali agent to the primary leachate and neutralizing it to obtain a neutralized slurry.
As the alkali agent, an alkali agent containing calcium and an alkali agent containing magnesium can be preferably used. Among these, calcium carbonate (CaCO ₃ ) is preferable because it is inexpensive.

The pH value after neutralization of the primary leachate is preferably 0.8 to 1.2. This is because the primary leachate contains a large amount of copper. For example, when the pH value exceeds 1.2 using calcium carbonate, the copper is converted into copper carbonate in the gypsum produced by the neutralization. It is because it becomes easy to get involved. Further, for example, when the pH value exceeds 1.2 using a high alkali such as calcium hydroxide, the copper is easily caught as copper hydroxide.
On the other hand, the pH value after neutralization of the primary leachate is 0.8 or more from the viewpoint of considering the balance of the quantity of the entire process flow showing the arsenic recovery method according to the present invention, and from the viewpoint of facilitating reuse of the neutralized precipitate. It is preferable that

In addition, it is a preferable structure to add in advance the gypsum produced in the previous lot to the primary leachate during the neutralization. After the addition of the gypsum, a neutralizing step is performed to obtain gypsum with good filterability. The amount of gypsum added in advance is preferably 2 to 4 times the amount of newly generated gypsum.
The temperature of the primary leachate in the neutralization step is not particularly limited, but is preferably 40 ° C. or higher in order to obtain gypsum with good filterability.

The generated neutralized slurry is subjected to solid-liquid separation, and the neutralized precipitate and the neutralized liquid are separated and recovered.
As described above, when an alkaline agent containing calcium is used as the neutralizing agent, a neutralized precipitate mainly composed of gypsum and a post-neutralized solution are obtained. On the other hand, when an alkali agent containing magnesium is used, the neutralized precipitate hardly precipitates.
The post-neutralization solution is sent to the next oxidation step. Here, even if it passes through a neutralization process, when neutralization completion slurry hardly deposits a neutralization deposit, it can also send to the next process, without carrying out solid-liquid separation of neutralization completion slurry.

<Oxidation>
The oxidation step according to the present invention is a step of obtaining an oxidized slurry by oxidizing trivalent arsenic present in a post-neutralization solution or neutralized slurry containing almost no neutralized precipitate to pentavalent arsenic. Specifically, the neutralization agent is added to the post-neutralization solution to reduce the acidity, the pH value is adjusted to 1.5 to 3, preferably around 2, and then the oxidizing agent is added to obtain an oxidized slurry. It is.

As the neutralizing agent, the alkaline agent used in the neutralization step described above may be used. CaCO ₃ , Ca (OH) ₂ or the like as the alkaline agent containing calcium, or Mg (OH) ₂ as the alkaline agent containing magnesium. Etc. can be preferably used.

Examples of the oxidizing agent include hydrogen peroxide, ozone, and a mixed gas of oxidizing gas and sulfur dioxide (SO ₂ ). The oxidizing gas includes oxygen (O ₂ ), air, or a mixed gas thereof. The mixing ratio of sulfur dioxide (SO ₂ ) in the mixed gas is preferably 1 to 10%. As the mixed gas, a smelting furnace SO ₂ exhaust gas mixed with oxygen gas or air can also be used.

  For example, in the case of using hydrogen peroxide which can be used for general purposes, the oxidizing agent is added for a period of about 10 minutes after a predetermined amount of the oxidizing agent is added to the neutralized solution. If the liquid potential at the time point shows 550 mV or more and around 600 mV with respect to the Ag / AgCl electrode, it is judged that the oxidation is completed. The standard of the predetermined amount of the oxidizing agent is about 2 to 3 times the stoichiometric amount required for oxidation of trivalent arsenic and divalent iron eluted by acid leaching of the smoke ash.

  The reaction temperature in the oxidation step is preferably 50 ° C. or higher, more preferably 70 ° C. or higher, from the reaction efficiency and the behavior of various elements contained in the oxidation step slurry.

The oxidized slurry generated after the oxidation step is subjected to solid-liquid separation to obtain a post-oxidation solution and an oxidized product.
The obtained oxide deposit is sent to the secondary leaching step which is the next step.
In the oxide, the arsenic is concentrated as pentavalent arsenic. On the other hand, most of the copper has moved to the post-oxidation solution. As a result, the copper contained in the oxide is the copper content of the post-oxidation solution contained as adhering moisture. Therefore, by thoroughly washing the oxidized precipitate with water, a washed oxidized precipitate from which the attached copper content is removed can be obtained. By subjecting the washed oxide residue to the secondary leaching step of the next step, a secondary leaching solution containing almost no copper is obtained.

  The post-oxidation solution contains almost no arsenic at 1 g / L or less, while copper has a high concentration of 20 g / L to 30 g / L, so it can be efficiently recovered by sending it to the copper recovery process. I can do it.

<Examination of operating conditions in oxidation process>
In order to set the operating conditions in the above-described oxidation step, the present inventors conducted the following studies.
First, in the liquid after neutralization described above, in addition to arsenic, various heavy metal elements derived from ores, such as bismuth, lead, antimony, tin, molybdenum, etc., light metal elements, such as ions of sodium, potassium, etc. It is included.
According to the study by the present inventors, when trying to oxidize trivalent arsenic in the presence of these various ions, not only the oxidation efficiency is very bad, but the trivalent arsenic is completely (99 mass%). It has been found that it is difficult to oxidize even to pentavalent arsenic.

Therefore, before the trivalent arsenic contained in the solution after neutralization is oxidized to pentavalent arsenic, it is necessary to reduce the concentration of these various ions.
The inventors of the present invention have made various studies on the method. As a result, the inventors have found a unique phenomenon in which the concentration of the various ions described above can be rapidly decreased by an operation with predetermined conditions. This knowledge will be described.

First, the inventors examined the influence of the pH value in the solution after neutralization on arsenic and other metal elements. Specific test conditions and results will be described.
1. Pure water was added to the copper smelting furnace ash and stirred to prepare a slurry having a pulp concentration of 500 g / L.
2. Sulfuric acid was added to the slurry and leached for 1 hour while maintaining a pH value of 0.25 and a temperature of 75 ° C. Next, the slurry was diluted with the same amount of pure water as used in the slurry preparation described above, heated again to 75 ° C., stirred for 10 minutes, and leaching was completed. The leaching slurry was subjected to filtration to obtain a leaching solution.
3. Next, an aqueous solution of Mg (OH) ₂ having a concentration of 200 g / L was added to the leachate to adjust the pH value to 1.0. A small amount of the slurry was sampled here.
4). Next, an aqueous Ca (OH) ₂ solution having a concentration of 200 g / L is added to the slurry to reach a predetermined pH value of 3.0, 1.25, 1.5, 1.75, 2.0, 2.5, 3 The sample was neutralized step by step and sampling was performed each time. The sampling was performed 10 minutes after the slurry reached a predetermined pH value.
5. Each sample was filtered through an MCE filter having a pore size of 0.2 μm, and the obtained filtrate was subjected to analysis. The analysis results are shown in Table 1.
In the present invention, the total arsenic is the amount of arsenic that is a total of trivalent arsenic and pentavalent arsenic.

  As is apparent from Table 1, the concentration of each ion coexisting with arsenic in the slurry gradually decreases as the acidity of the slurry is reduced. For example, at a pH value of 1.5, antimony and tin decreased to below the lower limit of analytical determination (<5 mg / L). Furthermore, at pH 2.0, bismuth decreased by 85% or more, lead decreased by 50% or more, and molybdenum decreased to a lower limit of quantification (<10 mg / L).

  That is, it has been found that, by reducing the acidity of the slurry, most of the ions such as bismuth, lead, antimony, tin, and molybdenum coexisting with arsenic in the slurry can be precipitated and removed from the liquid layer portion of the neutralized slurry.

On the other hand, when the pH value is 1.5 to 3, pentavalent arsenic shows the behavior of precipitation as an arsenic compound, and most of the arsenic ions dissolved in the slurry are trivalent arsenic.
From the above, in the liquid layer portion of the slurry in the region where the pH value is around 2, miscellaneous ions acting as an oxidation inhibitor do not coexist and trivalent arsenic to be oxidized exists. Therefore, the oxidation of trivalent arsenic to pentavalent arsenic in the oxidation step can be performed almost completely and efficiently.

  Further, when the pH value of the slurry is 3 or more, trivalent arsenic also takes a behavior of precipitating from the liquid layer portion of the slurry, so that trivalent arsenic can be oxidized but efficiency tends to decrease. When the pH value of the slurry is further increased, the pH value of the slurry does not increase easily even when a neutralizing agent is added over a pH value of 3.4 to 3.5, and copper is rapidly deposited. . As a result, it becomes difficult to separate copper and arsenic, and the copper concentration of the secondary leaching solution (raw material solution for producing crystalline iron arsenate) obtained in the secondary leaching step described later increases. Therefore, the copper concentration of the secondary leaching solution can be suppressed by setting the pH value of the slurry to 1.5 to 3.

<Examination of iron addition>
The addition of iron is to promote the leaching of arsenic from the smoke ash and is performed as necessary.
Specifically, iron can be added at any stage as long as it is between the primary leaching process and the crystallization process. This is because the added iron is finally converted as an iron source of scorodite crystals in the crystallization step.
However, the addition of iron in the primary leaching step or the oxidation step is a preferable configuration because the coexistence of the iron promotes the formation of pentavalent arsenic in the oxidation step. What is necessary is just to set the addition amount of iron according to the amount of dissolved arsenic, and it is preferable that it is 1-1.5 in the molar ratio of Fe / As. This range is also preferable from the viewpoint of suppressing production costs.

The iron source to be added may be a salt such as iron sulfate, but iron deposits generated during the treatment of wastewater containing arsenic are also suitable. This is because the iron temple contains more iron than arsenic. Furthermore, since the iron temple is easily leached in the primary leaching process, not only replenishment of the iron source but also arsenic in the iron temple can be finally stabilized as crystalline iron arsenate. Because you can.
If the Fe / As molar ratio in the liquid after neutralization obtained in the neutralization step is already 1 or more due to the properties of smoke ash, the addition of iron is unnecessary.

<Secondary leaching process>
In the secondary leaching step according to the present invention, the oxidized precipitate obtained in the above-described oxidation step is dissolved with an acid such as sulfuric acid, and then subjected to solid-liquid separation to contain a secondary leaching solution containing pentavalent arsenic and iron; This is a step of obtaining a next leaching residue.
The pH value at the time of the secondary leaching does not require leaching at a particularly low pH value because the oxidized residue is easily soluble. Specifically, the pH value may be 0.3 to 0.9.

The temperature of the secondary leaching can be room temperature, but it may be heated to around 50 ° C.
The secondary leaching time can be completed in about 30 minutes because arsenic contained in the oxide is easily soluble.
The leaching slurry after the secondary leaching step is subjected to solid-liquid separation to obtain a secondary leaching solution and a secondary leaching residue.

Since the secondary leaching residue contains a copper content not dissolved by the secondary leaching, it can be used as a smelting raw material.
The secondary leachate is a pentavalent arsenic solution with a low concentration of dissolved copper. In addition, since iron necessary for the production of crystalline iron arsenate is also included, it is optimal as a raw material liquid for producing crystalline iron arsenate.
In addition, by repeating the secondary leaching solution to the secondary leaching step, arsenic in the secondary leaching solution can be concentrated, which is a preferable configuration.

According to the arsenic leaching method from the smoke ash according to the present invention, a complicated process is not required, a special apparatus is not required, and a high-cost chemical such as a sulfiding agent is unnecessary, and a general-purpose and inexpensive chemical. Is significant in industrial costs.
And the pentavalent arsenic solution which does not contain sodium and potassium, and is suitable for the production method of crystalline scorodite can be easily leached from the oxide that has transferred arsenic.
Furthermore, in the pentavalent arsenic solution used for the production of crystalline scorodite, the copper elution amount can be reduced to 1/3 or less of the conventional method (the copper concentration is 5 g / L or less), and the copper contained in the smoke ash can be reduced. By being able to collect early, copper loss can be prevented as much as possible.

<Crystalling process>
Since the obtained raw material arsenic solution for producing crystalline iron arsenate contains iron and pentavalent arsenic, a known crystallization process can be performed to produce crystalline iron arsenate (scorodite). For example, known methods such as a method of adding alkali to a raw arsenic solution to crystallize trivalent iron and pentavalent arsenic, a method of reducing iron to divalent and adding an oxidizing agent to crystallize are applied. it can.

Example 1
<Smoke ash>
A non-ferrous smelting furnace ash A sample containing 5.2% by mass of arsenic and 17.4% by mass of copper was prepared at 400 dry · g. The component analysis was performed by ICP (component analysis was also performed by ICP in the following examples and comparative examples).
The smoke ash A sample 400dry · g was charged into a 2 liter beaker container, 1000 mL of pure water was added, and the mixture was stirred for 10 minutes using a two-stage turbine stirring blade equipped with four baffle plates to prepare a slurry.

<Primary leaching>
As an acid, a 95% by mass sulfuric acid reagent was prepared.
While heating the prepared slurry, 95% by mass sulfuric acid was added, and the pH value was adjusted to 0.2 while maintaining the temperature at 75 ° C. Stirring was continued for an additional 60 minutes from that point to complete the primary leaching, and the solution was subjected to filtration.
Filtration first filtered the leaching finished slurry using a filter to obtain a primary leachate. Subsequently, the primary leaching residue in the filter was washed with water through the filter using 150 mL of pure water. The water washing operation was performed twice to obtain a mixed primary leachate of the primary leachate and the two water wash water.
The mixed primary leachate was 1326 mL. 10 mL of the mixed primary leachate was sampled for analysis. The analysis values of the mixed primary leachate are shown in Table 2.
On the other hand, the washed primary leaching residue was 137 wet · g, and the water content was 29.6%.

<Neutralization>
Next, the total amount of the mixed solution was transferred to a 3 L beaker, and a CaCO ₃ aqueous solution having a concentration of 200 g / L was added while maintaining the temperature at 60 ° C. to adjust the pH value to 1.0. After maintaining the pH value for 20 minutes, the neutralization operation was completed to obtain a neutralized slurry. The neutralized slurry was subjected to filtration using a filter to obtain a neutralized solution. Subsequently, the neutralized precipitate (gypsum) in the filter was washed with water in the filter using 300 mL of pure water. The water-washing operation was performed twice to obtain a mixed neutralized solution after neutralization and twice water-washed water.
The mixed neutralized solution was 2123 mL. From the mixed neutralized solution, 10 mL was sampled and used for analysis. Table 3 shows the analytical values of the mixed neutralized solution.
On the other hand, the washed neutralized precipitate (gypsum) was 289 wet · g, and the water content was 55.0%.

<Oxidation>
The total amount of the mixed neutralized solution obtained in the neutralization step was transferred to a 3 L beaker, and while maintaining the temperature at 75 ° C., a 200 g / L Ca (OH) ₂ aqueous solution was added to adjust the pH value to 2.0. Summed into a slurry. Thereafter, hydrogen peroxide water was added to the slurry.

  As the added hydrogen peroxide solution, 30% by mass of hydrogen peroxide solution diluted with pure water 5 times was used. The hydrogen peroxide solution was added little by little into the slurry, and after about 5 minutes from the start of addition, it was confirmed that the liquid potential of the slurry exceeded 600 mV (Ag / AgCl electrode standard), and the addition was completed. Then, after continuing stirring for 20 minutes, the said oxidation reaction was complete | finished and the obtained oxidation completion | finish slurry was used for filtration. The obtained post-oxidation solution (filtrate) was 2296 mL. 10 mL of the sample after the oxidation was sampled and used for analysis. Table 4 shows analysis values of the mixed post-oxidation solution.

The hydrogen peroxide consumed for the oxidation was 18.3 g as 30% by mass hydrogen peroxide.
On the other hand, the oxidized product in the filter was recovered as a washed oxidized product after washing with water in the filter using 1000 mL of pure water.
The recovered washed oxide was 230 wet · g. As a result of sampling 10 wet · g from the washed oxide and subjecting it to moisture measurement, it was found that the moisture content was 32.0% by mass.

<Secondary leaching>
Secondary leaching was performed on the total amount of the washed oxide obtained in the oxidation step as a slurry having a concentration of 400 dry · g / L.
Specifically, 220 wt · g of the washed oxide residue is transferred to a 1 L liter beaker, and 303 mL of pure water is added and stirred in consideration of the amount of water contained in the washed oxide precipitate, and the slurry has a concentration of 400 dry · g / L. Was prepared.

Next, 95% by mass sulfuric acid was added to the slurry, and leaching was performed for 60 minutes while maintaining the pH value of the slurry at 0.3 and the temperature at 40 ° C.
The slurry obtained by the leaching was subjected to filtration using a filter, and 370 mL of the secondary leaching solution and 113 watt · g of the secondary leaching residue were collected. The adhering liquid content of the secondary leaching residue was found to be 23.8% by mass as a result of measurement.
Table 5 shows the composition of the obtained secondary leachate.

The obtained secondary leaching solution is a concentrated solution having a low copper concentration and a total arsenic concentration of 30 g / L or more, and trivalent arsenic is 1% or less based on the total arsenic, and is used for producing crystalline scorodite. The composition was suitable as a raw material liquid.
Moreover, as a result of taking into account the amount of secondary leaching liquid adhering to the secondary leaching residue, the intermediate sample 10 wet · g of the above-described cleaning oxide deposit is also subjected to the secondary leaching. It was also found that about 78% by mass of arsenic contained in the raw smoke ash A sample was leached.

(Comparative Example 1)
(Smoke ashes)
400 dry · g of a non-ferrous smelting ash A sample containing 5.2% by mass of arsenic and 17.4% by mass of copper was prepared. The components were analyzed by ICP.
A 95 mass% sulfuric acid as an acid and a Ca (OH) ₂ aqueous solution (milk) having a concentration of 200 g / L as an alkali were prepared.
In addition, a two-stage turbine stirring blade provided with four baffle plates was prepared for the stirring device.

(Primary leaching process)
To a 2-liter beaker, 1000 mL of pure water and a smoke ash A sample of 400 dry · g were added, and stirred for 10 minutes to prepare a smoke ash slurry. The pH value of the slurry at this time was 1.32 (40 ° C.).

Next, a Ca (OH) ₂ aqueous solution (milk) having a concentration of 200 g / L was added to the prepared smoke ash slurry, and the pH value of the slurry was neutralized to 3.5. After reaching the pH value, leaching was continued while maintaining the pH for another 20 minutes, and then stirring was terminated and filtration was performed to obtain a primary leaching solution and a primary leaching residue.

The obtained primary leachate was 918 ml. A small sample was taken from here and used for analysis. Table 6 shows the composition of the obtained primary leachate.
After recovering the primary leachate, the primary leach residue in the filter was subsequently washed with water in the filter using 400 mL of pure water. The water washing operation was performed twice, and the cleaning primary leaching residue was collected. The recovered washing primary leaching residue was 497 wet · g. As a result of sampling 10 wet · g from here and measuring the water content, the water content was 48.1% by mass.
Based on the balance of the filtrate composition shown in Table 6 and the amount of leachate, about 80% of the copper in the smoke ash is transferred to the primary leachate, and about 97% of arsenic is contained in the primary leach residue. found.

(Secondary leaching process)
The total amount of the washed primary leaching residue obtained in the primary leaching step was subjected to secondary leaching as a slurry having a concentration of 400 dry · g / L.
Specifically, a primary leaching residue 487 wet · g is loaded into a 1 liter beaker, and the amount of water contained in the primary cleaning residue is taken into account, 398 mL of pure water is added thereto, and 400 gry · g / L is added. A slurry was prepared.
Next, 95% sulfuric acid was added to the slurry, and leaching was performed for 60 minutes at a constant temperature of 75 ° C. while maintaining the pH value at 0.2. Then, filtration was performed, and the secondary leaching solution and the secondary leaching residue were removed. Obtained.
The obtained secondary leachate was 620 mL. A small amount of sampling was performed for analysis. The composition of the secondary leachate is shown in Table 7.

  The obtained secondary leachate contained 12.7 g / L of copper. Furthermore, the most feared trivalent arsenic was contained in an amount of 20% by mass or more based on the total amount of arsenic, and it was a composition that could not be used directly as a raw material liquid for producing crystalline scorodite.

(Summary)
The method for recovering arsenic from non-ferrous smelting ash according to the present invention exerted the following effects.
1. Copper / arsenic separation was improved by adding an iron source to the smoke ash containing copper and arsenic and neutralizing and leaching. Specifically, it was 1/3 or less of the copper elution amount in the conventional method, and the copper concentration was 5 g / L or less.
2. Separation of copper and arsenic became possible even with smoke ash, which is difficult to separate copper and arsenic.
3. In any smoke ash containing sodium, potassium, etc., copper, sodium, potassium were transferred to the leachate in the primary leaching, and arsenic could be put into the residue. As a result, copper and arsenic could be efficiently solid-liquid separated and an arsenic solution containing almost no sodium potassium could be obtained.
4). Since there are no complicated processes, the added drug can be a general-purpose drug, and no special equipment is required, the pentavalent arsenic solution can be recovered at low cost.
5. The secondary leaching solution containing arsenic became suitable for the production of crystalline scorodite and enabled stable storage of arsenic.

Claims (7)

A method for recovering arsenic from non-ferrous smelting ash containing arsenic, copper and iron,
A step of slurrying the non-ferrous smelting ash;
A primary leaching step of adding an acid to the slurry and leaching the slurry with a pH value of 0.1 or more and 0.5 or less;
The slurry after completion of the primary leaching step is subjected to solid-liquid separation, and a neutralizing step of obtaining a post-neutralization solution by adding a neutralizing agent to the obtained primary leaching solution;
An oxidizing step of adding a neutralizing agent to the post-neutralized solution to adjust the pH value to 1.5 or more and 3 or less, and further adding an oxidizing agent, followed by solid-liquid separation to obtain an oxidized residue,
A method of recovering arsenic from non-ferrous smelting ash, comprising: second leaching the oxide residue and obtaining a arsenic solution of crystalline iron arsenate raw material as a second leaching solution. The secondary leaching is a step in which the oxidized precipitate is used as a slurry, and an acid is added to the slurry and leached.
Separating the slurry after completion of the leaching into a secondary leaching solution and a secondary leaching residue, and obtaining a pentavalent arsenic solution of a crystalline iron arsenate production raw material as the secondary leaching solution. A method for recovering arsenic from the non-ferrous smelting ash according to claim 1. The non-ferrous smelting ash according to claim 1 or 2, wherein the oxidizing agent used in the oxidation step is hydrogen peroxide and / or a mixed gas of an oxidizing gas and sulfur dioxide (SO ₂ ). Arsenic recovery method. The recovery of arsenic from non-ferrous smelting ash according to claim 3, wherein the oxidizing gas is selected from oxygen (O ₂ ), air, and a mixed gas of oxygen and air. Method.   The iron source is previously changed from the primary leaching step to the oxidation step so that the molar amount of iron and arsenic dissolved in the secondary leaching solution obtained in the secondary leaching step is Fe / As = 1 to 1.5. The method for recovering arsenic from non-ferrous smelting ash according to any one of claims 1 to 4, wherein the arsenic is added in any one of steps up to.   The secondary leaching solution obtained in the secondary leaching step is repeated as water for use in the secondary leaching step to concentrate arsenic in the secondary leaching solution. A method for recovering arsenic from non-ferrous smelting ash.   7. The arsenic from non-ferrous smelting ash according to claim 1, wherein the neutralizing agent is at least one selected from an alkali agent containing calcium and an alkali agent containing magnesium. Collection method.

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