JP5848584B2 - Arsenic leaching recovery method from non-ferrous smelting ash - Google Patents

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 ash and water, adding an alkaline agent to the slurry, controlling it within a predetermined pH value range, and leaching the leaching solution containing copper and arsenic by leaching reaction. It is a method of obtaining the leaching residue containing. Then, the leaching residue containing arsenic is re-leached with acid to obtain an arsenic solution. The arsenic solution is sulfided to recover arsenic as arsenic sulfide, and the arsenic sulfide is used as an arsenic raw material source for producing crystalline iron arsenate.

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.
3. I want to lower the copper concentration of the arsenic solution to be recovered. This is because copper loss in the subsequent operations of the present invention can be prevented as much as possible by recovering copper contained in the smoke ash early and lowering the copper concentration of the arsenic solution.

  Based on the above problems, the problem to be solved by the present invention is that when recovering arsenic from non-ferrous smelting ash, most arsenic can be recovered as a pentavalent arsenic solution without using a sulfiding agent. An object of the present invention is to provide a method for leaching arsenic from non-ferrous smelting ash that can suppress copper contamination in an arsenic solution.

As a result of researches, the inventors have arrived at the following configuration and completed the present invention.
As primary leaching, the ash slurry is leached at a pH value of 3-4. Then, copper, sodium, and potassium are leached into the primary leachate. On the other hand, since arsenic enters the solid side, it is mainly contained in the primary leaching residue.
Next, as secondary leaching, acid is added to the primary leaching residue containing arsenic to leach arsenic. Then, since arsenic is leached to the liquid side, it is mainly contained in the secondary leaching solution.
The secondary leachate is neutralized by adding an alkali to lower the acidity. Then, since arsenic is leached to the liquid side, it is contained in the liquid after neutralization.
Next, an oxidant is added to the post-neutralization solution, and trivalent arsenic dissolved in the post-neutralization solution (slurry state) is oxidized to pentavalent arsenic. Then, since arsenic is oxidized almost completely (99% or more) to form pentavalent arsenic and enter the oxide, it is contained in the oxide.
Next, a raw material liquid of crystalline iron arsenate can be produced by a tertiary leaching step of leaching pentavalent arsenic contained in the oxide.

That is, the first invention for solving the above-described problem is
A process of making non-ferrous smelting ash into a slurry;
A primary leaching step of adding an alkali to the slurry, primary leaching at a pH value of the slurry of 3 to 4 and obtaining a primary leaching residue by solid-liquid separation of the slurry after completion of the primary leaching;
An acid is added to the primary leaching residue to form a primary leaching slurry, the secondary leaching is performed at a pH value of 0.1 to 0.5 and the slurry after the secondary leaching is solidified. A secondary leaching step for obtaining a secondary leaching solution by liquid separation;
A neutralization step of adding an alkali to the secondary leachate to bring the pH value into a range of 0.8 to 1.2, and obtaining a solution after neutralization;
An oxidation step of adding an alkali to the post-neutralized solution to adjust the pH value to 1.5 or more and 3.0 or less, and further adding an oxidizing agent, followed by solid-liquid separation to obtain an oxidized residue;
Leaching of arsenic from non-ferrous smelting ash characterized by adding and leaching an acid to the oxidized residue to obtain a raw arsenic solution for producing crystalline iron arsenate as a leaching solution Is the method.

The second invention is
The tertiary leaching is a step in which the oxidized precipitate is made into a slurry, and an acid is added to the slurry and leached.
Solid-liquid separation of the slurry after completion of the leaching to obtain a tertiary leaching solution and a tertiary leaching residue, and obtaining a raw material arsenic solution for producing crystalline iron arsenate as the tertiary leaching solution. The leaching method of arsenic from the non-ferrous smelting ash as described in the first invention.

The third invention is
The method of leaching arsenic from non-ferrous smelting ash according to the first or second invention, wherein the primary leaching residue is added as the alkali to the secondary leaching solution in the neutralization step. .

The fourth invention is:
The method for leaching arsenic from non-ferrous smelting ash according to the third invention, wherein the neutralized precipitate in the neutralization step is repeated in the secondary leaching step.

The fifth invention is:
The method for leaching arsenic from non-ferrous smelting ash according to any one of the first to fourth aspects, wherein the tertiary leaching solution is repeated in the tertiary leaching step.

The sixth invention is:
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 ), according to any one of the first to fifth inventions, This is a method of leaching arsenic from non-ferrous smelting ash.

The seventh invention
The oxidizing gas is any one selected from oxygen (O ₂ ), air, and a mixed gas of oxygen and air, wherein arsenic from non-ferrous smelting ash according to the sixth aspect of the invention The leaching method.

The eighth invention
The iron source is previously removed from the primary leaching step so that the molar ratio of iron and arsenic dissolved in the tertiary leaching solution obtained in the tertiary leaching step is Fe / As = 1 to 1.5. The arsenic leaching method from non-ferrous smelting ash according to any one of the first to seventh inventions, wherein the arsenic ash is added in any step up to the oxidation step.

  According to the method of leaching arsenic from non-ferrous smelting ash according to the present invention, it is possible to efficiently separate copper and arsenic from smoke ash containing arsenic, copper, iron, etc., and almost all trivalent arsenic is obtained. A pentavalent arsenic solution not containing can be obtained. Furthermore, iron coexists in the pentavalent arsenic solution and can be effectively used as an iron source for producing crystalline iron arsenate.

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

  While referring to FIG. 1 for the mode for carrying out the present invention, smoke ash, primary leaching, secondary leaching, neutralization process, alkali in neutralization process, oxidation, examination of operating conditions in oxidation process, examination of iron addition The third leaching and the crystallization process will be described in this order.

<Smoke ashes>
Any material containing arsenic, copper, and iron can be applied to various types of smoke ash generated from the non-ferrous smelting process. In addition to arsenic, the smoke ash contains expensive elements such as copper and zinc and various elements derived from ore. Especially, this invention can be effectively applied to the copper smelting ash generated from the dry smelting process etc. in copper smelting.

<Primary leaching>
In the primary leaching process according to the present invention, a liquid such as water or process water is added to the above-described smoke ash and stirred to obtain a slurry of smoke ash having a concentration of 300 g / L to 800 g / L. By adding a pH adjusting agent such as alkali to the slurry and suppressing the acid concentration of the slurry, arsenic contained in the smoke ash is put into the primary leaching residue, and copper is leached as much as possible into the primary leaching solution. It is a stage.

  In the leaching operation, a pH adjusting agent such as alkali is added to the smoke ash slurry, and the pH of the slurry is adjusted between 2.0 and 4.0, preferably between 3.0 and 4.0. Is what you do. As a result, most of copper, sodium, and potassium can be leached into the slurry, and arsenic can be left as a residue.

During leaching, there is no need for heating, and leaching is possible even at room temperature. Since the slurry after the leaching becomes a leaching solution and an undissolved residue, solid-liquid separation is performed.
The recovered primary leaching residue is provided as a raw material for the secondary leaching process.
Since the primary leaching solution contains copper at a high concentration, copper can be easily recovered by a general-purpose method.

As the alkali that is a pH adjuster used in the primary leaching step, an alkali containing an alkaline earth metal can be preferably used. Among these, Ca (OH) ₂ , CaCO _3, Mg (OH) _{2, and the} like are preferable because they are available for general use.

<Secondary leaching>
In the secondary leaching step according to the present invention, the pH value of the slurry is adjusted to 0.1 or more and 0.5 or less by addition of an acid, and further heated to perform leaching under the condition that the temperature of the slurry is 50 ° C. or more. 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.
The optimum leaching pH value and temperature should be determined in detail for each ash generated at each smelter. However, in the tests by the present researchers, the leaching rate of arsenic and copper contained in the primary leaching residue is about 80 to 90% of arsenic and copper to be leached if the pH value is 0.5. It has been found that if leaching is performed and the pH value is 0.2 to 0.3, leaching is almost completed.
Regarding the temperature, the finding that the leaching rate is remarkably improved as the temperature increases between room temperature (25 ° C.) and 50 ° C., and the degree of the leaching rate improvement gradually decreases at 50 ° C. or higher. It has gained. Therefore, the leaching temperature is preferably 50 ° C. or higher, and is preferably 100 ° C. or lower, most preferably 80 to 90 ° C. in consideration of equipment specifications during actual operation.
The leaching reaction time in the secondary leaching is required to be 30 minutes or more from the time when the leaching condition is satisfied, and the target leaching is almost achieved in one hour.
From the slurry after the secondary leaching, a secondary leaching solution and a secondary leaching residue are obtained by solid-liquid separation. The solid-liquid separation in the present invention can be carried out using a general filtration device such as a filter press. What is necessary is just to use what is marketed.

<Neutralization process>
The neutralization step according to the present invention is a step of reducing the acid content of the secondary leaching solution.
Specifically, this is a step of neutralizing the secondary leachate by adding an alkali to a pH value of 0.8 to 1.2.
The secondary leaching solution contains a large amount of copper. For this reason, for example, when calcium carbonate is used as the alkali, the copper in the secondary leachate is likely to be engulfed as copper carbonate in the gypsum that is neutralized when the pH value is 1.2 or more. Further, if a high alkali such as calcium hydroxide is used as the alkali, for example, copper is easily caught as copper hydroxide.
Moreover, it is preferable from a viewpoint of the quantity balance of the flow which concerns on this invention as pH value is 0.8 or more.

<Alkali in neutralization process>
As described above, alkali is added to adjust the pH value in the neutralization step. As the _{alkali, CaCO 3, Ca (OH)} 2, alkali containing calcium etc., one or more selected from alkali containing magnesium ₂ such Mg _(OH), can be used for general purposes.

  The temperature during the neutralization step is not particularly limited, but is preferably 40 ° C. or higher in order to obtain gypsum with good filterability.

(Regarding the configuration in which the primary leaching residue is directly fed into the neutralization process)
If the neutralization process mentioned above starts operation, it can take the structure which inputs a primary leaching residue to the said neutralization process directly, aiming at the material balance of each process.
That is, in the primary, secondary leaching process, and neutralization process, the flow of the generated residue and neutralized precipitate can be varied. In the present invention, in the initial stage of the start of each process, the primary leaching process, the secondary leaching process, and then the neutralization process are sequentially performed. In each process, the reactants can be stored. If so, the flow of the leachate, the primary leach residue, and the neutralized precipitate can be varied.
Specifically, the primary leaching residue can be input to the neutralization step (a flow indicated by a dotted line (A) in FIG. 1). When this primary leaching residue is introduced into the neutralization step, the neutralized precipitate from the neutralization step can be introduced into the secondary leaching step (the flow indicated by the dotted line (B) in FIG. 1).
Thus, it is possible to reduce the amount used for the alkali agent for neutralization by changing the flow destination of the primary leaching residue and the neutralized precipitate, which is a more preferable configuration.
In addition, according to the research by the present inventors, the knowledge that 80% by mass or more of the alkali used in the neutralization step can be reduced by using the primary leaching residue as a neutralizing agent for the secondary leaching solution. It has gained.

<Oxidation>
The oxidation step according to the present invention is an oxidation stage that oxidizes trivalent arsenic contained in the post-neutralization solution obtained in the neutralization step described above to pentavalent arsenic.
Specifically, an alkali (neutralizing agent) is added to the neutralized solution obtained in the neutralization step to reduce the acidity, and the pH value of the neutralized solution is 3 or less, preferably a pH value of 1.5. -3, most preferably a step of adding an oxidizing agent to obtain an oxidized slurry when the pH value reaches around 2.
By this operation, the state in which copper is dissolved in the solution after the neutralization can be maintained, so that the copper can be avoided from being taken into the residue, contributing to the separation of arsenic and copper Become.

For adjusting the pH value, an alkali or the like is added as a neutralizing agent. As the alkali or the like, one or more selected from alkalis including calcium such as CaCO ₃ and Ca (OH) ₂ and alkalis including magnesium such as Mg (OH) ₂ can be used for general purposes.

As the oxidizing agent, hydrogen peroxide, ozone, a mixed gas of oxidizing gas and sulfur dioxide (SO ₂ ), or the like can be used, but hydrogen peroxide and / or oxidizing gas and sulfur dioxide (SO ₂ ) can be used. A mixed gas is preferred. Here, the oxidizing gas is oxygen (O ₂ ), air, or a mixed gas thereof, and the mixing ratio of sulfur dioxide (SO ₂ ) in the mixed gas is preferably 1 to 10% by volume. 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 by adjusting the pH value of the post-neutralization solution obtained in the neutralization step. After adding quantitatively, hold for about 10 minutes. If the liquid potential at this time point is 550 mV or more, preferably 600 mV or more, based on the Ag / AgCl electrode reference, 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 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 slurry. In addition, it is preferable that it is 100 degrees C or less from a viewpoint of process control.
The oxidized slurry after the oxidation step is subjected to solid-liquid separation to obtain a post-oxidation solution and an oxidized precipitate.

  In this oxide deposit, arsenic is highly concentrated as pentavalent arsenic. Most of the copper is transferred to the solution after oxidation and contained. As a result, the copper contained in the oxidized precipitate is the copper content of the post-oxidation solution contained as adhering water. 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 deposit to the tertiary leaching step of the next step, a tertiary leaching solution containing almost no copper is obtained.

  The oxidative leachate hardly contains arsenic at 1 g / L or less, while copper has a concentration of several g / L to 10 g / L. Therefore, the post-oxidation solution can be sent to the copper recovery step, but can also be used as water for slurry preparation for primary leaching and secondary leaching.

<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 slurry produced from the above-mentioned non-ferrous smelting ash, in addition to arsenic, various heavy metal elements derived from ore, such as bismuth, lead, antimony, tin, molybdenum, etc., light metal elements such as sodium, potassium, etc. Contains ions.
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%). As mentioned above, it has been found that it is difficult to oxidize pentavalent arsenic.

Therefore, before oxidizing trivalent arsenic contained in the slurry 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.

1.1 Primary leaching Pure water was added to the copper smelting smelting furnace ash and stirred to prepare a slurry having a concentration of 400 g / L. A 200 g / L Ca (OH) ₂ aqueous solution (milk) was added to the slurry, and primary leaching was performed for 30 minutes while maintaining the pH value of the slurry at 3.5. After the primary leaching, the slurry was subjected to solid-liquid separation to obtain a primary leaching solution and a primary leaching residue. Further, the primary leaching residue was washed with water in a filter using the same amount of pure water as that used for slurrying and recovered as a washed primary leaching residue.
2.2 Secondary leaching Next, the above-described primary cleaning leaching residue was made into a slurry having a concentration of 400 dry · g / L, and 95% by mass sulfuric acid was added to the slurry to adjust the pH value to 0.2. And secondary leaching was performed for 1 hour. After the secondary leaching, the slurry was subjected to solid-liquid separation to obtain a secondary leaching solution and a secondary leaching residue. Furthermore, the secondary leaching residue was washed with water in a filter using substantially the same amount of pure water as the secondary leaching solution. By this operation, a secondary leaching solution, water-washed washing water, and a washed secondary leaching residue were obtained.
3. Neutralization Mix the obtained secondary leachate and water washing solution, add Ca (OH) ₂ aqueous solution (milk) with a concentration of 200 g / L while heating to 45 ° C., and adjust the pH value to 1.0. It was summed up. The mixture was further stirred for 15 minutes while maintaining the pH value, then subjected to solid-liquid separation, and the neutralized solution was collected as a filtrate. Here, a small amount of the neutralized solution was sampled.
Subsequently, a Ca (OH) ₂ aqueous solution (milk) having a concentration of 200 g / L is added to the post-neutralization solution, and the predetermined pH values are 1.5, 1.75, 2.0, 2.5. The sample was neutralized in stages up to 3.0, and sampling was performed each time. Sampling was performed 10 minutes after reaching the predetermined pH value.
Each sample was filtered through an MCE filter having a pore size of 0.2 μm, and the obtained filtrate was used for analysis. The analysis values are shown in Table 1.

  As is apparent from Table 1, each ion coexisting with arsenic in the slurry gradually decreases by reducing the acidity of the slurry. For example, at a pH of 1.5, bismuth is 50% or more, and antimony. , Tin decreased to below the lower limit of analytical determination (<5 mg / L). Furthermore, when the pH was 2.0, bismuth decreased by 80% or more, lead decreased to less than half, and molybdenum decreased to the lower limit of analytical 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 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. Become. Therefore, the oxidation of trivalent arsenic to pentavalent arsenic in the oxidation step can be performed almost completely 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.
Further, when the pH value of the slurry is increased to 4 or more, most of the copper is deposited, making it difficult to separate arsenic and copper, and a tertiary leaching solution (crystalline hydride obtained in the tertiary leaching step described later). The copper concentration of the raw material liquid for producing iron oxide will increase. Therefore, the copper concentration of the tertiary leachate can be suppressed by setting the pH value of the slurry to 3 or less.

<Examination of iron addition>
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 any step from the primary leaching step to the oxidation step is a preferred 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 secondary 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.

<3rd leaching>
The tertiary leaching step according to the present invention is a step in which the oxidized precipitate is dissolved with an acid such as sulfuric acid and then solid-liquid separated to obtain a tertiary leaching solution containing iron and pentavalent arsenic and a tertiary leaching residue. is there.
The pH value at the time of the third leaching does not require leaching at a 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 tertiary leaching can be room temperature, but it may be heated to around 50 ° C. The tertiary leaching time can be completed in about 30 minutes because arsenic contained in the oxidative leaching residue is easily soluble.
The leaching slurry after the tertiary leaching step is subjected to solid-liquid separation to obtain a tertiary leaching solution and a tertiary leaching residue.

  Since the tertiary leaching residue contains a copper component that has not been dissolved by the tertiary leaching, it can also be used as a raw material for smelting.

  The tertiary leachate has a low dissolved copper concentration and becomes a high concentration pentavalent arsenic solution. In addition, since iron necessary for the production of crystalline iron arsenate is also included, it is optimal as a raw material arsenic solution for producing crystalline iron arsenate.

  In addition, by repeating the tertiary leaching solution to the tertiary leaching step, arsenic in the tertiary leaching solution can be concentrated, which is a preferable configuration.

<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)
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 was used as the acid, and an CaCO ₃ aqueous solution (milk) having a concentration of 200 g / L and an Ca (OH) ₂ aqueous solution (milk) having a concentration of 200 g / L were prepared as the alkali.
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, primary leaching was continued for another 20 minutes while maintaining the pH value. Filtration was performed after the stirring was completed to obtain a primary leaching solution and a primary leaching residue.

The obtained primary leaching solution was 918 ml, from which a small amount was sampled and used for analysis. Table 2 shows the composition of the obtained primary leachate.
After collecting the primary leachate, the primary leach residue in the filter was 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 collected 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.

  From the balance between the composition of the primary leachate shown in Table 2 and the amount of liquid, about 80% of the copper in the smoke ash is transferred to the primary leachate, and about 97% of arsenic is put into the primary leach residue. It has been found.

(Secondary leaching process)
The entire amount of the washed primary leaching residue obtained in the primary leaching step was made into a slurry having a concentration of 400 dry · g / L and subjected to secondary leaching.
Specifically, 487 wet · g of the primary leaching residue washed with water in a 1 L beaker was charged. Considering the amount of water contained in the primary cleaning residue, 398 mL of pure water was added thereto to prepare a slurry having a concentration of 400 dry · g / L.
Next, 95% by mass 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, followed by filtration.

First, the leaching-finished slurry was filtered to collect the secondary leaching solution, and then a small amount was sampled (analysis results of the sample are shown in comparative examples described later). Subsequently, the residue in the filter was washed with water in the filter using 200 mL of pure water. The water washing operation was performed twice, and a mixed solution of the secondary leachate and water washing water and the washed secondary leach residue were collected.
The secondary leaching mixed solution was 1020 mL, and from this, a small amount of sampling was performed and used for analysis. The composition of the secondary leaching mixed solution is shown in Table 3.
Further, the recovered cleaning secondary leaching residue was 231 wet · g, and the water content was 30.2% by mass.
The pentavalent arsenic concentration is obtained by subtracting the value of trivalent arsenic concentration from the total arsenic concentration. Therefore, the pentavalent arsenic concentration in Table 3 is 12.0 g / L. The same applies to the following tables.

(Neutralization process)
Next, the total amount of the secondary leaching mixed solution was transferred to a 2 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 to 1.0. After maintaining the said pH value for 20 minutes, the said neutralization operation was complete | finished and it used for filtration, and obtained the liquid after neutralization and the neutralization deposit.

First, the neutralized slurry was filtered to recover the neutralized solution. Subsequently, the neutralized precipitate (gypsum) in the filter was washed with water in the filter using 250 mL of pure water. The water washing operation was performed twice, and the mixed solution after neutralization and water washing water was collected.
The mixed solution in the neutralization step was 1640 mL. A small amount of sampling was performed for analysis. The composition of the mixed solution in the neutralization step is shown in Table 4.
In addition, the collect | recovered washing | cleaning neutralization deposit (gypsum) was 192 wet * g, and the water | moisture content was 55.0 mass%.

(Oxidation process)
Next, the entire mixed solution in the neutralization step obtained in the neutralization step was charged into a 3 L beaker. Then, while maintaining the temperature at 75 ° C., a Ca (OH) ₂ aqueous solution (milk) having a concentration of 200 g / L was added and neutralized to pH 2.0, and then hydrogen peroxide solution 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 6 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. Thereafter, stirring was continued for 20 minutes, and then the reaction was terminated and subjected to filtration to obtain a post-oxidation solution and an oxidized residue.
The obtained post-oxidation solution was 1818 mL. A small sample was taken from here and used for analysis. The composition of the post-oxidation solution is shown in Table 5.
The hydrogen peroxide consumed for the oxidation was 16.4 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 1,000 mL of pure water.
The recovered washed oxide was 192 wet · g. From this, 5 wet · g was sampled and subjected to moisture measurement. As a result, it was found that the moisture content was 32.1% by mass.

(3rd leaching)
Secondary leaching was performed on the total amount of the cleaned oxide obtained in the oxidation step as a slurry having a concentration of 400 dry · g / L.
Specifically, a 1L beaker was charged with 187 wet · g of cleaning oxide, and the amount of water contained in the cleaning oxide was taken into account, 257 mL of pure water was added thereto, and the concentration was 400 dry · g / L. A slurry was prepared.

Subsequently, 95 mass% sulfuric acid was added to the slurry, and leaching was performed for 60 minutes at a constant temperature of 40 ° C. while maintaining the pH value at 0.3.
The slurry obtained by the leaching was subjected to filtration, and 320 mL of the tertiary leaching solution and 96 wet · g of the tertiary leaching residue were recovered. The adhering liquid content of the tertiary leaching residue was found to be 23.3% by mass as a result of measurement.
Table 6 shows the composition of the obtained tertiary leachate.

  The tertiary leaching solution is a concentrated solution having a low copper concentration, a total arsenic concentration of 40 g / L or more, and a trivalent arsenic amount based on the total arsenic amount is 1% by mass or less, and is used for producing crystalline scorodite. The composition was suitable as a raw material arsenic solution.

  In addition, when the primary leaching residue and the intermediate sample of the cleaning oxide deposit are also used for the third leaching and the third leaching liquid adhering to the third leaching residue is taken into consideration, the third leaching step is performed. It was also understood that about 77% by mass of arsenic contained in the non-ferrous smelting ash A sample was leached.

(Comparative Example 1)
The processing operation of the smoke ash in the comparative example 1 is comprised from the primary leaching process and secondary leaching process in Example 1 mentioned above. The obtained arsenic solution corresponds to the secondary leaching solution in the secondary leaching step of Example 1.
Table 7 shows the composition of the obtained secondary leachate in Example 1 described above.

  The arsenic solution according to Comparative Example 1 (secondary leachate according to Example 1) contains 12.7 g / L of copper, and the total arsenic concentration is 21.3 g / L. The concentration was less than half of the solution. 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.

Claims (8)

A process of making non-ferrous smelting ash into a slurry;
A primary leaching step of adding an alkali to the slurry, primary leaching at a pH value of the slurry of 3 to 4 and obtaining a primary leaching residue by solid-liquid separation of the slurry after completion of the primary leaching;
An acid is added to the primary leaching residue to form a primary leaching slurry, and the pH of the primary leaching slurry
Secondary leaching with a value of 0.1 or more and 0.5 or less, and obtaining a secondary leaching liquid by solid-liquid separation of the slurry after completion of the secondary leaching;
A neutralization step of adding an alkali to the secondary leachate to bring the pH value into a range of 0.8 to 1.2, and obtaining a solution after neutralization;
An oxidation step of adding an alkali to the post-neutralized solution to adjust the pH value to 1.5 or more and 3.0 or less, and further adding an oxidizing agent, followed by solid-liquid separation to obtain an oxidized residue;
Leaching of arsenic from non-ferrous smelting ash characterized by adding and leaching an acid to the oxidized residue to obtain a raw arsenic solution for producing crystalline iron arsenate as a leaching solution Method. The tertiary leaching is a step in which the oxidized precipitate is made into a slurry, and an acid is added to the slurry and leached.
Solid-liquid separation of the slurry after completion of the leaching to obtain a tertiary leaching solution and a tertiary leaching residue, and obtaining a raw material arsenic solution for producing crystalline iron arsenate as the tertiary leaching solution. A method for leaching arsenic from non-ferrous smelting ash according to claim 1. The method for leaching arsenic from non-ferrous smelting ash according to claim 1 or 2, wherein the primary leaching residue is added as the alkali to the secondary leaching solution in the neutralization step. The method for leaching arsenic from nonferrous smelting ash according to claim 3, wherein the neutralized precipitate in the neutralization step is repeated in the secondary leaching step. The method of leaching arsenic from non-ferrous smelting ash according to any one of claims 1 to 4, wherein the tertiary leaching solution is repeated in the tertiary leaching step. The non-ferrous product according to any one of claims 1 to 5, 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 leaching method from smelting ash. 7. The arsenic leaching from non-ferrous smelting ash according to claim 6, wherein the oxidizing gas is any one selected from oxygen (O ₂ ), air, and a mixed gas of oxygen and air. Method. The molar ratio of iron and arsenic dissolved in the tertiary leaching solution obtained in the tertiary leaching step is Fe / A.
The iron source is added in advance in any step from the primary leaching step to the oxidation step so that s = 1 to 1.5. The leaching method of arsenic from non-ferrous smelting ash described in 1.

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