JP4044068B2 - Method for treating substances containing heavy metals - Google Patents

Description

  The present invention relates to a treatment method for removing heavy metals such as zinc from a substance containing heavy metals such as zinc such as fly ash generated in garbage incineration facilities.

Incineration products such as fly ash generated in garbage incineration facilities contain harmful heavy metals such as zinc and lead in addition to water-soluble components such as sodium, potassium and chlorine. The treatment to prevent the elution of the species and the detoxification treatment.
As an example of a method for detoxifying incineration products such as fly ash, incineration products such as fly ash are washed with water to remove water-soluble components such as sodium, potassium and chlorine, and then inorganic acids and alkalis. There is known a method of eluting heavy metals using a chemical such as an agent and solidifying the eluted heavy metals with various chemicals.

For example, a process of obtaining a desalted cake that is a solid content by separating the solid waste into waste water such as dust discharged from a garbage incineration facility by rinsing with water and eluting chlorine into the wash water ( In the water washing step), sulfuric acid is added to the obtained desalted cake to obtain an acid leaching slurry containing copper and zinc in the liquid, and then the acid leaching slurry is subjected to solid-liquid separation. After adding the zinc powder to the liquid of the acid leaching slurry and precipitating copper with a smaller ionization tendency than zinc, solid-liquid separation is performed, and then the resulting filtrate is sulfided. A zinc sulfide is formed by adding an agent, and a strong alkaline solution (around pH 13) obtained in the lead recovery step described later is added to the filtrate to adjust the pH to 8 or more, and a precipitate containing zinc sulfide and zinc hydroxide is added. Obtaining step (copper and zinc recovery step) and said acid leaching slurry A step of adding a caustic soda or the like to the solid content of the slurry to elute the lead content into the liquid, followed by solid-liquid separation to obtain a solid content mainly composed of calcium hydroxide and a filtrate containing the lead content (alkali A leaching step), and a step of adding a sulfiding agent to the filtrate containing this lead content, followed by solid-liquid separation to obtain lead sulfide as a solid content and a strong alkaline solution (around pH 13) as a filtrate (lead recovery step) ) Has been proposed (Patent Document 1).
Japanese Patent Laid-Open No. 2002-126693

In the technique described in Patent Document 1, in the copper and zinc recovery step, a sulfide such as sodium hydrosulfide is added to the filtrate after removing copper to generate zinc sulfide, and the lead recovery step is further performed in this filtrate. The strong alkaline solution (about pH 13) obtained in (1) was added to adjust the pH to 8 or more to obtain a precipitate containing zinc sulfide and zinc hydroxide.
Here, the reason why zinc sulfide is generated is that the solid-liquid separability (filterability) of the precipitate consisting only of zinc hydroxide is inferior, so that zinc sulfide coexists to improve the solid-liquid separability.

However, the generation of two kinds of zinc compounds in this way leads to complicated processing steps and the like. In addition, if the proportion of zinc sulfide is increased in order to shorten the time required for solid-liquid separation, the particle size of zinc sulfide is extremely small. Increases and the recovery rate of the zinc compound decreases. Further, even if zinc sulfide is present together, the property itself of the gel-like zinc hydroxide having a large water content is not improved, so there is a limit to the improvement of the solid-liquid separation property. Furthermore, since the amount of water contained in the gel-like zinc hydroxide is large, there is a problem that the load on transportation when the gel-like zinc hydroxide is transported to the Yamamoto reduction factory is large.
Therefore, the present invention obtains a solid content containing zinc or the like while exhibiting good solid-liquid separation properties when recovering zinc or the like as a solid content from a substance such as fly ash containing heavy metals containing zinc or the like. Another object of the present invention is to provide a treatment method capable of significantly reducing the water content in the solid content containing zinc and the like.

  As a result of intensive studies to solve the above problems, the present inventor, in the above-described treatment method described in Patent Document 1, in the filtrate containing zinc sulfide in the “copper and zinc recovery step”, a strong alkali If the filtrate containing zinc sulfide is gradually added to the strong alkaline liquid instead of adding the liquid, it has good solid-liquid separability and after solid-liquid separation. The inventors have found that a precipitate containing zinc having a low moisture content can be produced, and the present invention has been completed.

That is, in the method for treating a substance containing heavy metals of the present invention, (A) a substance containing heavy metals including zinc and a sulfuric acid solution are mixed to obtain an acidic slurry, and then the acidic slurry is separated into solid and liquid. Then, an acid leaching step for obtaining a solid content, an acidic aqueous solution containing zinc, (B) the solid content obtained in the step (A), an alkalizing agent (for example, sodium hydroxide), and water. After mixing to obtain an alkaline slurry, the alkaline slurry is subjected to solid-liquid separation to obtain a solid content and an alkaline leaching step to obtain an alkaline aqueous solution, and (C) the alkaline aqueous solution obtained in the step (B) above. The acidic aqueous solution containing zinc obtained in the step (A) is gradually added at an addition time of 20 minutes or more to obtain an alkaline slurry, and then the alkaline slurry is solid-liquid separated to contain zinc. Obtain solids and liquids Characterized in that it comprises a metal recovery process.

As an example of a preferred embodiment of the treatment method of the present invention, (A) a substance containing heavy metals including zinc and lead and a sulfuric acid solution are mixed to obtain an acidic slurry, and then the acidic slurry is solid-liquid. Separately, solid content containing lead (specifically lead sulfate), acid leaching step to obtain an acidic aqueous solution containing zinc, (B) solid content containing lead obtained in the step (A), An alkali leaching step of mixing an alkalinizing agent (for example, sodium hydroxide) and water to obtain an alkaline slurry, and then solid-liquid separating the alkaline slurry to obtain an alkaline aqueous solution containing solids and lead. (C) The acidic aqueous solution containing zinc obtained in the step (A) is gradually added to the alkaline aqueous solution containing lead obtained in the step (B) at an addition time of 20 minutes or more. After obtaining an alkaline slurry, the alkaline And solid-liquid separation of slurry, and solids containing zinc and lead, include those containing a heavy metal recovery process of obtaining a liquid component (claim 2).

As another example of a preferred embodiment of the treatment method of the present invention, (A) a substance containing heavy metals including zinc and lead and a sulfuric acid solution are mixed to obtain an acidic slurry. Solid-liquid separation, solid content containing lead (specifically lead sulfate), acid leaching step to obtain an acidic aqueous solution containing zinc, (B) solid content containing lead obtained in the step (A) And alkaline agent (for example, sodium hydroxide) and water are mixed to obtain an alkaline slurry, and then the alkaline slurry is solid-liquid separated to obtain an alkaline aqueous solution containing solids and lead. And (C) an alkaline aqueous solution containing lead obtained in the above step (B) and a sulfurizing agent (for example, sodium hydrosulfide) to obtain a slurry, and then the slurry is solid-liquid separated. Obtain solids and liquids containing lead (specifically lead sulfide) Both the liquid component, an acidic aqueous solution containing zinc obtained in the above step (A), was added slowly with the addition of more than 20 minutes time, after obtaining the alkaline slurry, solid-liquid separating the alkaline slurry Then, what contains the solid content containing zinc and the heavy metal collection | recovery process of obtaining a liquid component is mentioned (Claim 3).

In the step (C) of the treatment method of the present invention, the time required for adding the acidic aqueous solution obtained in the step (A) to the alkaline aqueous solution obtained in the step (B) is the same as that in the step (C). It is preferable to determine the moisture content of the solid content to be 75% by mass or less (claim 4).
In the step (C) of the treatment method of the present invention, the liquid temperature of the mixed solution produced by adding the acidic aqueous solution obtained in the step (A) to the alkaline aqueous solution obtained in the step (B) is 30 ° C. It is preferable to adjust to the above (claim 5).
In the step (C) of the treatment method of the present invention, the pH of the alkaline slurry is preferably adjusted to 8.5 to 13. (Claim 6)

According to the treatment method of the present invention, since the property of the precipitate containing zinc in the alkaline slurry in the step (C) is different from the property of the conventional precipitate, solid-liquid separation can be performed efficiently, Moreover, the water content in the solid content after solid-liquid separation can be greatly reduced. Therefore, it is possible to reduce the size of the solid-liquid separation device, reduce the load of transport of zinc or the like to the Yamamoto reduction destination, and the like.
Further, according to the treatment method of the present invention, it is necessary to coexist two types of zinc sulfide and zinc hydroxide as in the conventional case as the zinc compound constituting the precipitate containing zinc in the alkaline slurry in the step (C). Therefore, simplification of the process and reduction of drug costs can be achieved.

Hereinafter, the processing method of the substance containing the heavy metals of this invention is demonstrated in detail, referring drawings. FIG. 1 is a flowchart showing an example of an embodiment of the processing method of the present invention, and FIG. 2 is a flowchart showing another example of the embodiment of the processing method of the present invention.
[Pretreatment process]
In the present invention, as shown in FIG. 1 and FIG. 2, usually, as a pretreatment step, a substance containing heavy metals including zinc, which is the object to be treated of the present invention (hereinafter also referred to as “heavy metal-containing substance”). ) Is washed with water, followed by a step of solid-liquid separation.
In this step, first, a heavy metal-containing substance and water are mixed to form a slurry, and water-soluble components (K, Na, Cl, etc.) in the heavy metal-containing substance are eluted into the liquid.
Here, examples of the heavy metal-containing material include soot dust and incineration ash remaining as an incineration residue on the bottom of the incinerator.
In addition, as dust, for example, fly ash generated from an incinerator (incineration fly ash), fly ash generated from a melting furnace such as incineration ash (molten fly ash), or extracted from a cement manufacturing process and collected. And powder collected on a bag filter obtained during the production of ecocement.

An example of the component composition of the powder collected in the bag filter obtained at the time of eco-cement production is the mass ratio in terms of oxide, 2% calcium, 13% potassium, 32% sodium, 2% lead, 1% zinc, copper 2% and chlorine 38%.
Although the heavy metal-containing material to be treated in the present invention has a difference in the content ratio for each element, the elements (Ca, K, Na, Pb, Zn) contained in the powder collected by the bag filter are generally. , Cu, Cl). Hereinafter, description will be made assuming that the heavy metal-containing substance contains these elements.
In this step, the pH of the slurry is preferably adjusted to the range of 8.5 to 13, more preferably 9 to 12, and particularly preferably 9 to 11.
When the pH is less than 8.5, the amount of elution of lead, zinc, and copper gradually increases as the pH decreases. When the pH is 9 to 12, none of lead, zinc and copper is eluted. When pH exceeds 12, the amount of elution of lead increases. When pH exceeds 13, the elution amount of zinc increases.
As a pH adjusting agent for adjusting the pH within the above numerical range, an inorganic acid such as hydrochloric acid or an alkalizing agent such as sodium hydroxide is used.

The solid-liquid ratio of the slurry (the mass of fly ash in 1 liter of solution) is preferably 100 to 600 g / liter, more preferably 150 to 400 g / liter. When the solid-liquid ratio is less than 100 g / liter, the processing efficiency decreases, for example, the time required for solid-liquid separation of the slurry increases. If the solid-liquid ratio exceeds 600 g / liter, the chlorine content may not be sufficiently eluted.
The slurry is usually stirred for a predetermined time (for example, about 10 to 40 minutes).
The slurry after stirring is separated into a solid content from which chlorine and the like have been removed and a liquid content using solid-liquid separation means such as a filter press.
Among these, the liquid component is discharged out of the system after passing through a step of recovering salts such as sodium chloride and potassium chloride by a crystallization method.
The solid content (desalted cake) contains zinc, lead, calcium and the like, and is crushed and then processed in step (A).

[(A) Acid leaching step]
In this step, a heavy metal-containing substance (specifically, a solid crushed material obtained in the pretreatment step) and a sulfuric acid solution are mixed to obtain an acidic slurry, and then the acidic slurry is subjected to solid-liquid separation. In this step, a solid content containing lead (specifically lead sulfate) and calcium (specifically calcium sulfate) and an acidic aqueous solution containing zinc and copper are obtained.

The acidic slurry is separated into a solid content containing lead sulfate, calcium sulfate (gypsum) and the like and a liquid content containing zinc, copper and the like using solid-liquid separation means such as a filter press.
Among these, about the liquid component containing zinc, copper, etc., the process for collect | recovering copper is performed. Specifically, a powder such as zinc or iron having a higher ionization tendency than copper is added to the liquid to precipitate the copper in the liquid as a solid. Among them, zinc is preferably used because it has a higher ionization tendency than iron and can be recovered later together with zinc dissolved in the liquid.

[(B) Alkali leaching step]
In this step, the solid content (containing lead sulfate and calcium sulfate) obtained in step (A), an alkalizing agent, and water are mixed to obtain an alkaline slurry, and then the alkaline slurry is solid-liquid. This is a step of separating and obtaining an alkaline aqueous solution containing solids containing calcium hydroxide and lead (alkali leachable heavy metal).
Here, as the alkalizing agent, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are used.

Solid-liquid separation of the alkaline slurry is performed using solid-liquid separation means such as a filter press. The solid content after the solid-liquid separation contains calcium hydroxide and can be used as a cement raw material. On the other hand, the liquid component after solid-liquid separation (alkaline aqueous solution containing lead) may be immediately treated in step (C) as shown in FIG. 1 as the first embodiment, or as shown in FIG. As shown as the second embodiment, after the lead removal process, the process may be performed in the step (C).
Among these, in 1st embodiment shown in FIG. 1, it is not necessary to use a sulfiding agent in the processing method of this invention, and it can aim at simplification of a process and reduction of chemical | medical agent cost. On the other hand, in the second embodiment shown in FIG. 2, lead and zinc can be separated and recovered.
In the second embodiment shown in FIG. 2, as a method for removing lead, for example, sodium hydrosulfide (NaHS) or sodium sulfide (sodium sulfide) may be used as a liquid after solid-liquid separation (an alkaline aqueous solution containing lead). After adding a sulfurizing agent such as Na ₂ S) to produce lead sulfide (PbS), solid-liquid separation is performed with a filter press or the like to obtain a solid content composed of lead sulfide and an alkaline aqueous solution containing no lead. A method is mentioned. In this case, the addition amount of the sulfiding agent is preferably 1 to 1.5 times equivalent to the amount of lead in the liquid. The obtained lead sulfide can be used as a refining raw material.

[(C) Heavy metal recovery process]
In this step, the acidic aqueous solution containing zinc obtained in step (A) is gradually added to the alkaline aqueous solution obtained in step (B), and a pH adjusting agent is added as necessary. After obtaining the alkaline slurry, the alkaline slurry is subjected to solid-liquid separation to obtain a solid content containing zinc and a liquid content.
Here, as the alkaline aqueous solution, as described above, either one containing lead (see FIG. 1) or one from which lead has been removed (see FIG. 2) may be used.
In the present invention, it is essential to gradually add the acidic aqueous solution containing zinc obtained in the step (A) to the alkaline aqueous solution obtained in the step (B). By adding in this procedure, the precipitate in the obtained mixed liquid (alkaline slurry) has good solid-liquid separation (filterability), and the water content in the solid content after solid-liquid separation is, for example, It has a unique property of being 70% by mass or less.

When the alkaline aqueous solution obtained in the step (B) is gradually added to the reverse procedure, that is, the acidic aqueous solution containing zinc obtained in the step (A), the resulting mixed solution ( The property of the precipitate in the alkaline slurry) becomes a gel that is difficult to separate into solid and liquid, and the water content in the solid content obtained by solid-liquid separation of this mixed solution is 80% by mass or more. The same applies when these two aqueous solutions are mixed at one time.
In the present specification, “water content in solid content (mass%)” means [(mass of solid content before drying) − (mass of solid content after drying)] ÷ (mass before drying). The mass calculated by (mass of solid content) × 100.

The time required for the addition of the acidic aqueous solution of step (A) to the alkaline aqueous solution of step (B) is the water content in the solid content after the liquid mixture (alkaline slurry) of these two aqueous solutions has been subjected to solid-liquid separation. It can be appropriately determined so as to be a certain value or less (for example, 75% by mass or less).
Although specific addition time changes also with conditions, such as the liquid quantity and liquid temperature of two aqueous solution, Preferably it is 20 minutes or more, More preferably, it is 30 minutes or more. When the addition time is about 10 minutes, the water content in the solid content is about 75% by mass, and the effects of the present invention cannot be sufficiently obtained. In addition, when addition time exceeds 60 minutes, the fall of the water content rate in the said solid content may become a peak tendency.
The liquid temperature of the mixed solution (alkaline slurry) when the acidic aqueous solution of step (A) is added to the alkaline aqueous solution of step (B) is preferably 30 ° C. or higher, more preferably 35 ° C. or higher, particularly preferably. Is 40 ° C. or higher. The higher the liquid temperature, the lower the water content in the solid content after solid-liquid separation of the mixed liquid (alkaline slurry). However, if the liquid temperature exceeds 60 ° C., the decrease in the water content in the solid content tends to reach a peak, and in this case, the liquid temperature is set to 60 to reduce the energy required for heating. It is desirable to keep it below ℃.

The pH of the mixed solution (alkaline slurry) is preferably adjusted to 8.5 to 13, more preferably 8.5 to 12, and particularly preferably 9 to 11. By adjusting the pH within this numerical range, the recovery rate of zinc and lead can be increased. When the pH is less than 8.5, the amount of zinc and lead eluted in the liquid increases. When the pH exceeds 13, the amount of lead eluted in the liquid increases.
Examples of the pH adjusting agent include inorganic acids such as sulfuric acid and alkalizing agents such as sodium hydroxide.

The mixed solution (alkaline slurry) is desirably left for a while before solid-liquid separation. By leaving it for a predetermined time, the properties of the precipitate in the alkaline slurry are improved, and the effects of the present invention (such as solid-liquid separation) can be further improved.
The standing time is not particularly limited, but is preferably 10 minutes or more, more preferably 20 minutes or more.
The water content in the solid content after the solid-liquid separation is preferably 65% by mass or less, more preferably 55% by mass or less, and particularly preferably 45% by appropriately determining the conditions such as the addition time and the liquid temperature. % Or less.
The alkaline slurry is separated into a solid content containing zinc (and lead) and a liquid content using solid-liquid separation means such as a filter press.
Heavy metals such as zinc contained in the solid content are reduced to the mountain and recycled.

[Example 1]
Fly ash generated in a cement production facility (component composition: Ca: 3 mass%, K: 17 mass%, Na: 21 mass%, Cl: 40 mass%, Cu: 1 mass%, Pb: 2 mass%, Zn: 1 After 30 kg (mass%) was put into a water tank storing 100 liters of water, acid or alkali was added to adjust the pH of the slurry to 10.5, and the mixture was stirred and mixed.
This slurry was subjected to solid-liquid separation with a filter press to obtain a solid content of 6.0 kg. After this solid content was crushed, it was mixed with 24 liters of water while adding 2 mol / liter sulfuric acid and stirred to obtain a slurry of pH 3.2. This slurry was subjected to solid-liquid separation with a filter press to obtain 3.9 kg of a solid content containing lead sulfate, gypsum (calcium sulfate) and the like, and 20.7 liter of a filtrate containing zinc, copper and the like.
Among these, about the filtrate containing zinc, copper, etc., after adding 0.352 kg of zinc powder, it solid-liquid-separates with a filter press, 0.336 kg of solid content containing the copper which precipitated, and the filtrate 19.6 containing zinc I got a liter. The filtrate was heated to 35 ° C.

On the other hand, about solid content containing lead sulfate, gypsum, etc., it mixed with 39 liters of water, adding sodium hydroxide, and stirred, and the slurry of pH 13.8 was obtained. This slurry was subjected to solid-liquid separation with a filter press to obtain 2.5 kg of a solid content containing calcium hydroxide and 35 liters of a filtrate containing lead. The filtrate was heated to 35 ° C.
The lead-containing filtrate (liquid temperature: 35 ° C.) was stirred and mixed while gradually adding the above-described zinc-containing filtrate (liquid temperature: 35 ° C.) over a period of 40 minutes. Sulfuric acid was appropriately added to maintain the pH of the mixed solution within the range of 9-11. Finally, a slurry with a pH of 10.5 was obtained and left for 20 minutes. Thereafter, the slurry was subjected to solid-liquid separation with a filter press to obtain 0.42 kg of a solid content containing zinc and lead and a filtrate.
Among these, solid content had the component composition of Zn: 45 mass%, Pb: 29 mass%, and Ca: 1 mass% after drying. Moreover, the moisture content of solid content was 45 mass%.

[Example 2]
30 kg of fly ash similar to that in Example 1 was put into a water tank storing 100 liters of water, and then acid or alkali was added to adjust the pH of the slurry to 10.5, followed by stirring and mixing.
This slurry was subjected to solid-liquid separation with a filter press to obtain a solid content of 6.0 kg. After this solid content was crushed, it was mixed with 24 liters of water while adding 2 mol / liter sulfuric acid, and stirred to obtain a slurry of pH 3.2. This slurry was subjected to solid-liquid separation with a filter press to obtain 20.7 liters of a filtrate containing 3.9 kg of solids containing lead sulfate, gypsum (calcium sulfate), etc., and zinc, copper and the like.
Among these, about the filtrate containing zinc, copper, etc., after adding zinc powder 0.352kg, it solid-liquid-separates with a filter press, solid content 0.336kg containing the deposited copper, and the filtrate 19.6 containing zinc Liter was obtained. The filtrate was heated to 35 ° C.

On the other hand, about solid content containing lead sulfate, gypsum, etc., it mixed with 39 liters of water, adding sodium hydroxide, and stirred, and the slurry of pH 13.8 was obtained. This slurry was subjected to solid-liquid separation with a filter press to obtain 2.5 kg of a solid content containing calcium hydroxide and 35 liters of a filtrate containing lead.
After adding 0.200 kg of sodium hydrosulfide to this filtrate, solid-liquid separation was performed with a filter press to obtain 0.497 kg of solid content composed of lead sulfide and 34 liters of filtrate from which lead was removed. The filtrate was heated to 35 ° C.
In the filtrate from which lead has been removed (liquid temperature: 35 ° C.), the above-described filtrate containing zinc (liquid temperature: 35 ° C.) is stirred and mixed while gradually added over 45 minutes, and 2 mol / liter. Was appropriately added to maintain the pH of the mixed solution in the range of 9-11. Finally, a slurry with a pH of 10.2 was obtained and left for 20 minutes. Thereafter, this slurry was subjected to solid-liquid separation with a filter press to obtain a solid content of 0.49 kg containing zinc and a filtrate.
Among these, solid content had the component composition of Zn: 58 mass% and Ca: 1 mass% after drying. The moisture content of the solid content was 52% by mass.

[Comparative Example 1]
A solid containing lead and lead and a filtrate were obtained in the same manner as in Example 1 except that the filtrate containing lead was gradually added to the filtrate containing zinc over 30 minutes.
Among these, solid content had the component composition of Zn: 45 mass%, Pb: 29 mass%, and Ca: 1 mass% after drying. The moisture content of the solid content was 82% by mass.
[Comparative Example 2]
A solid containing lead and lead and a filtrate were obtained in the same manner as in Example 1 except that the filtrate containing zinc and the filtrate containing lead were rapidly mixed (about 10 seconds).
Among these, solid content had the component composition of Zn: 45 mass%, Pb: 29 mass%, and Ca: 1 mass% after drying. The water content of the solid content was 83% by mass.

It is a flowchart which shows an example of embodiment of the processing method of the substance containing the heavy metals of this invention. It is a flowchart which shows the other example of embodiment of the processing method of the substance containing the heavy metals of this invention.

Claims (6)

(A) After an acidic slurry is obtained by mixing a substance containing heavy metals containing zinc and a sulfuric acid solution, the acidic slurry is solid-liquid separated to obtain an acidic aqueous solution containing a solid content and zinc. Process,
(B) The solid content obtained in the step (A), the alkalizing agent, and water are mixed to obtain an alkaline slurry, and then the alkaline slurry is subjected to solid-liquid separation to obtain a solid content and an alkaline aqueous solution. An alkali leaching step to obtain,
(C) In the alkaline aqueous solution obtained in the step (B), the acidic aqueous solution containing zinc obtained in the step (A) is gradually added with an addition time of 20 minutes or more, and the alkaline slurry is added. After obtaining, the alkaline slurry is subjected to solid-liquid separation, a solid content containing zinc, and a heavy metal recovery step for obtaining a liquid content,
A method for treating a substance containing heavy metals, comprising: (A) After a substance containing heavy metals including zinc and lead and a sulfuric acid solution are mixed to obtain an acidic slurry, the acidic slurry is subjected to solid-liquid separation, and solids containing lead and acidic containing zinc An acid leaching step to obtain an aqueous solution;
(B) After mixing solid content containing the lead obtained by the said process (A), an alkalizing agent, and water to obtain an alkaline slurry, the alkaline slurry is subjected to solid-liquid separation to obtain a solid content. An alkaline leaching step to obtain an alkaline aqueous solution containing lead;
(C) In the alkaline aqueous solution containing lead obtained in the step (B), the acidic aqueous solution containing zinc obtained in the step (A) is gradually added with an addition time of 20 minutes or more , After obtaining the alkaline slurry, the alkaline slurry is subjected to solid-liquid separation, a solid content containing zinc and lead, and a heavy metal recovery step for obtaining a liquid content,
A method for treating a substance containing heavy metals, comprising: (A) After a substance containing heavy metals including zinc and lead and a sulfuric acid solution are mixed to obtain an acidic slurry, the acidic slurry is subjected to solid-liquid separation, and solids containing lead and acidic containing zinc An acid leaching step to obtain an aqueous solution;
(B) After mixing solid content containing the lead obtained by the said process (A), an alkalizing agent, and water to obtain an alkaline slurry, the alkaline slurry is subjected to solid-liquid separation to obtain a solid content. An alkaline leaching step to obtain an alkaline aqueous solution containing lead;
(C) The alkaline aqueous solution containing lead obtained in the above step (B) and a sulfiding agent are mixed to obtain a slurry, and then the slurry is solid-liquid separated to obtain a solid content and a liquid content containing lead. At the same time, the acidic aqueous solution containing zinc obtained in the step (A) is gradually added to the liquid in an addition time of 20 minutes or more to obtain an alkaline slurry, and then the alkaline slurry is subjected to solid-liquid separation. And a solid content containing zinc, and a heavy metal recovery step for obtaining a liquid content,
A method for treating a substance containing heavy metals, comprising:   In the step (C), the time required for the addition of the acidic aqueous solution obtained in the step (A) to the alkaline aqueous solution obtained in the step (B) is the water content of the solid content obtained in the step (C). The processing method of the substance containing the heavy metals of any one of Claims 1-3 defined so that a content rate may be 75 mass% or less.   In said process (C), the liquid temperature of the liquid mixture which arises by addition of the acidic aqueous solution obtained at the said process (A) to the alkaline aqueous solution obtained at the said process (B) is adjusted to 30 degreeC or more. The processing method of the substance containing heavy metals of any one of 1-4.   The processing method of the substance containing the heavy metals of any one of Claims 1-5 which adjusts the pH of the said alkaline slurry to 8.5-13 in the said process (C).

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