JP2000212654A - Recovery of heavy metal from substance containing heavy metal and chlorine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering heavy metal contents from a substance containing copper, lead, zinc and other heavy metal contents, and chlorine in which the heavy metal is directly separated and recovered from chlorine in an initial stage of processing the heavy metal, by reducing chlorine to a degree that the heavy metal can be introduced in a refining process as it is. SOLUTION: After a substance containing the heavy metal such as fly ash and chlorine is changed into a slurry with water, the pH value is regulated to be 12 or over to separate the solid from the liquid, and a sediment containing the heavy metal in which chlorine is remarkably reduced is recovered. The substance containing the heavy metal such as fly ash and chlorine is changed into a slurry, and its pH value is regulated to be 5 or under, and again regulated to be at least 12 with an alkaline agent to separate the solid from the liquid, and the sediment containing the heavy metal with less chlorine is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is applicable to all treatments of substances containing heavy metal components and chlorine, and in particular, treats incinerators, melting furnaces, or sludge in municipal waste incineration facilities, industrial waste incineration plants, and the like. The present invention relates to a treatment method suitable for recovering heavy metals from heavy metal-containing fly ash generated from a cement kiln or the like.

[0002]

2. Description of the Related Art Garbage (called "municipal waste" or "general waste") discharged from general offices and households is collected and incinerated at municipal waste incineration facilities and industrial waste incineration plants. The incineration ash and fly ash generated from the incinerator at that time are deposited at the final disposal site after being subjected to chemical treatment or intermediate treatment such as melting furnace and cement kiln treatment.

However, in the above-mentioned intermediate treatment in a melting furnace or a cement kiln, heavy metals such as lead, zinc and cadmium having a high vapor pressure volatilize in the furnace and enter the exhaust gas. It was condensed in the processing equipment and became fly ash again. That is, in the fly ash again, lead, copper, zinc, in addition to useful heavy metals such as cadmium as described above, contains a large amount of chlorine, and recovers useful heavy metals from these fly ash A way was sought.

[0004] Such fly ash is disclosed in
No. 9533 discloses that fly ash is suspended in water in a tank, and the suspension is subjected to pH adjustment to an appropriate value in an alkaline region by adding an acid or alkali to precipitate heavy metals in the fly ash as hydroxide. And a method for recovering the precipitate is disclosed. The present applicant has also previously filed a method for coping with the wet processing method (Japanese Unexamined Patent Application Publication No. H8-1177).
No. 24 and Japanese Unexamined Patent Publication No. Hei 8-141539), such a wet treatment method allows useful heavy metals such as copper contained in fly ash to be separated in a stable form and to be effectively recovered as heavy metal resources. Was.

[0005] That is, JP-A-8-117724 discloses that fly ash is slurried with water, adjusted for pH, and leached.
A first step of solid-liquid separation, a second step of repulping the residue from the first step, leaching and dissolving with a mineral acid, and then performing a solid-liquid separation to obtain a lead product; the first step and the second step; A neutralizing agent or further sodium bisulfide is added to the acidic filtrate from the two steps, and a product containing zinc and copper is separated by filtration.
A method comprising steps is disclosed.
Japanese Patent No. 141539 discloses a first step in which fly ash is neutralized with water and a neutralizing agent to perform solid-liquid separation, and the precipitate from the first step is repulped, leached and dissolved with sulfuric acid, and then solid-liquid separated. A second step of separating to obtain a lead product, a third step of adding a neutralizing agent to the filtrate from the second step to filter out a product containing zinc and copper, and filtering the filtered water of the third step. Repeated as a neutralization solution in the first step,
A method is disclosed in which a sulphating agent is added to the filtrate from the first step for drainage treatment.

[0006]

However, in the smelting process of heavy metals, chlorine in the raw material becomes an obstacle. Therefore, in each of the above methods, fly ash slurried is subjected to acid leaching, alkali neutralization and solidification. Although the operation of dissolution / separation treatment consisting of liquid separation is repeated to obtain individual metal residues such as lead residues and zinc deposits with low chlorine, it can be said that this is not necessarily an efficient means of treating fly ash. There were no aspects.
That is, complex heavy metal deposits obtained directly from slurry fly ash by only a single dissolution / separation treatment contain a large amount of chlorine and are difficult to introduce into the smelting process as it is. The problem that was left.

[0007] In view of such circumstances, the present invention separates chlorine directly from substances such as fly ash containing chlorine together with useful heavy metals in the initial stage, and reduces the chlorine in a form that can be reused in the smelting process. An object of the present invention is to provide a method for recovering heavy metals from a substance containing heavy metals and chlorine, which can recover heavy metal deposits.

[0008]

In order to achieve the above object, the present invention firstly recovers a heavy metal component from a substance containing at least one heavy metal component of zinc, copper and lead and chlorine. The method is characterized in that water is added to the substance to form a slurry, the pH is adjusted to 12 or more using an alkaline agent, and then the heavy metal-containing precipitate is separated from the chlorine-containing filtrate by solid-liquid separation and collected. A method for recovering heavy metals from a substance containing chlorine and heavy metal components of at least one of zinc, copper and lead; and A chlorine dissolving step of dissolving chlorine by adjusting the pH to 5 or less by adding a mineral acid to the substance, and adding an alkaline agent to the slurry in the chlorine dissolving step to adjust the pH to 12
After the above adjustment, by performing solid-liquid separation, the heavy metal-containing precipitate is separated from the chlorine-containing filtrate and collected. And a method for recovering heavy metals.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the process diagram of FIG. 1 by taking as an example a method of treating fly ash from an incinerator for industrial waste. First, fly ash is mixed with water to form a slurry, and while the slurry is being stirred, an alkaline agent such as sodium hydroxide is added to adjust the pH to 12 or more, and then the heavy metal-containing precipitate and chloride are added. And a filtrate containing chlorine. As described above, by setting the pH of the slurry from a chlorine-containing substance such as fly ash to 12 or more, separation of heavy metal-containing precipitates and chlorine becomes extremely good,
The chlorine in the heavy metal-containing precipitate can be reduced to less than half of the chlorine value at pH 11.

Further, as shown in the treatment process diagram of FIG. 2, fly ash is mixed with water to form a slurry, and while the slurry is being stirred, the pH is adjusted to 5 or less using a mineral acid such as hydrochloric acid or sulfuric acid.
Preferably, the pH is adjusted to 4 or less to dissolve chlorine in the liquid in the form of chlorides of sodium and calcium (chlorine dissolving step). Then, the heavy metal is converted into a precipitate by adding an alkali neutralizing agent such as sodium hydroxide to adjust the pH to 12 or more. Therefore, the heavy metal-containing precipitate is subjected to solid-liquid separation, and a salt such as chlorine, sodium, calcium or the like is removed. (Heavy metal-containing residue collection step). Since the pH of the slurry varies depending on the composition of the fly ash, the amount of the mineral acid added in the chlorine dissolving step is adjusted according to the fly ash. Therefore,
If the pH of the slurry is already at the optimum pH,
There is no need to add mineral acids.

As described above, after the chloride chlorine in the chlorine-containing substance such as fly ash is sufficiently eluted in the acidic region in the chlorine dissolving step, the acidic eluate is strongly concentrated in the heavy metal-containing precipitate recovery step. By adjusting to an alkaline range, the chlorine content of the heavy metal-containing precipitate can be further significantly reduced. The heavy metal-containing deposit having a low chlorine content can be directly used as a raw material in a smelting process.

When it is desired to further reduce the chlorine content, a mineral acid such as hydrochloric acid or sulfuric acid is further added to the low-chlorine heavy metal-containing precipitate obtained in the above-mentioned heavy metal-containing precipitate recovery step, and the pH is reduced again. Is adjusted to 5 or less, and by adding an alkali agent such as sodium hydroxide to adjust the pH to 6 or more, a heavy metal-containing precipitate with extremely reduced chlorine content can be obtained.

[0013]

[Example 1] (Test No. 1) First, 6 g of pure water was placed in a 10-liter beaker and stirred, and 600 g of fly ash from the A treatment plant was added as a raw material to form a slurry and stirred for 10 minutes. Meanwhile, the pH was adjusted to 13 with a 200 g / liter sodium hydroxide solution as an alkaline agent, and the mixture was maintained for 30 minutes. Then, the heavy metal-containing precipitate and the filtrate were separated by a filtration operation. After the whole amount of the obtained heavy metal-containing precipitate was washed with 2 liters of water for 5 minutes by repulping, a heavy metal precipitate was obtained by a filtration operation. The Cl, Cu, Pb, and Zn contents in the heavy metal-containing precipitate were measured, and the results are shown in Table 1 along with the composition of the raw material fly ash as Test No. 1.

[Example 2] (Test No. 2) As in Example 1, 6 liters of pure water was placed in a 10 liter beaker and stirred, and the fly ash 60 of the A treatment plant was stirred.
0 g was added to form a slurry, and while stirring for 10 minutes, 36% hydrochloric acid was added as a mineral acid to adjust and maintain the pH at 4, and a dissolution treatment was performed for 30 minutes (chlorine dissolution step), followed by alkali neutralization. After adding 200 g / l of sodium hydroxide solution as an agent to adjust the pH to 13 and maintaining it for 30 minutes, it was separated by filtration into a heavy metal-containing precipitate and a filtrate mainly containing chlorine (recovery of heavy metal-containing precipitate). Process). After the entire amount of the obtained heavy metal-containing precipitate was repulped and washed with 2 liters of water for 5 minutes, a heavy metal-containing precipitate was obtained by a filtration operation. Cl, Cu, P in this heavy metal-containing precipitate
The b and Zn contents were measured, and the results are shown in Table 1 as Test No. 2.

Example 3 (Test No. 3) In the dissolution treatment of the slurry, 98 wt% as mineral acid
A recovery treatment was performed in the same manner as in Example 2 except that a sulfuric acid solution obtained by diluting sulfuric acid with the same amount of water was used. Table 1 shows the measurement results of the contents of Cl, Cu, Pb, and Zn in the obtained heavy metal-containing precipitate as Test No. 3.

Example 4 (Test No. 4) The same operation as in Example 3 was carried out, and the obtained low-chlorine heavy metal-containing precipitate was further repulped with 2 liters of water, and 98 wt% sulfuric acid was again used in the same amount with 98 wt% sulfuric acid. PH 4 with sulfuric acid diluted with water
After adjusting the pH to 9 and performing a dissolution treatment for 10 minutes, adding a 200 g / L sodium hydroxide solution as an alkali neutralizer to adjust the pH to 9 and maintaining the mixture for 30 minutes, the heavy metals are filtered out. And a filtrate mainly containing heavy metal and a filtrate mainly containing chlorine. After the entire amount of the obtained heavy metal-containing precipitate was repulped and washed with 2 liters of water for 5 minutes, a heavy metal-containing precipitate was obtained by a filtration operation. The contents of Cl, Cu, Pb, and Zn in the heavy metal-containing precipitate were measured, and the results are shown in Table 1 as Test No. 4.

[0017]

[Table 1]

As can be seen from Table 1, according to the present invention,
By adjusting and maintaining the fly ash slurry to pH 13,
It is understood that heavy metals such as copper and lead are concentrated and recovered in the precipitate, and chlorine in the precipitate is significantly reduced. In particular, it can be seen that, by dissolving the slurry in acid and maintaining it in an alkaline region of pH 13, it is significantly reduced. As a mineral acid, sulfuric acid is more effective in reducing chlorine than hydrochloric acid. Furthermore, chlorine was drastically reduced by repeating the dissolution of acid and the maintenance of the alkaline region again for the treated heavy metal-containing precipitate.

[Comparative Example 1] (Test No. 5) 6 g of pure water was placed in a 10 liter beaker and stirred, and 600 g of fly ash from the A treatment plant as in the embodiment was added as a raw material to form a slurry. The pH was adjusted to 7 with a 200 g / liter sodium hydroxide solution as an alkaline agent while stirring for 30 minutes, and after maintaining for 30 minutes,
The heavy metal-containing precipitate and the filtrate were separated by a filtration operation.
(The treatment in Comparative Example 1 was the same as in Example 1 except that the pH adjusted with an alkaline agent was adjusted to 7.) The Cl content in the obtained heavy metal-containing precipitate was measured, and the results were used as test numbers. 5 is shown in Table 2.

[Comparative Example 2] (Test No. 6)
The same operation as in Comparative Example 1 was performed except that H was set to 9. The Cl content in the obtained heavy metal-containing precipitate was measured, and the results are shown in Table 2 as Test No. 6.

[Comparative Example 3] (Test No. 7)
The same operation as in Comparative Example 1 was performed except that H was set to 11. The Cl content in the obtained heavy metal-containing precipitate was measured, and the results are shown in Table 2 as Test No. 7.

[0022]

[Table 2]

In the case of the comparative example in which the fly ash was treated by the same operation as in Example 1 except that the pH of the fly ash slurry was adjusted to be outside the range of the present invention, the numerical value of Test No. 1 in Table 1 was used. As is apparent from comparison with the above, in the heavy metal-containing precipitate,
It can be seen that a large amount of chlorine remains.

[0024]

According to the present invention, a slurry of a substance containing a heavy metal and chlorine such as fly ash is adjusted to pH 12 or more to separate heavy metal deposits. According to the present invention, the slurry is included in a substance containing a heavy metal such as fly ash and chlorine. Heavy metals such as copper, lead, zinc, etc. directly in the initial stage of treatment, in a stable and concentrated manner, and with a reduced chlorine content to such an extent that it can be directly introduced into the smelting process. An effect is provided that a method for recovering heavy metals from substances containing chlorine and heavy metals such as fly ash that can be recovered can be provided. According to the present invention, in which the slurry is adjusted to a pH of 12 or more through a mineral acid dissolving step, a method for recovering heavy metals from substances containing chlorine and heavy metals such as fly ash, which can further remarkably reduce chlorine in heavy metal deposits, is provided. It has the effect of being able to.

[Brief description of the drawings]

FIG. 1 is a process chart showing an embodiment of a heavy metal recovery method of the present invention.

FIG. 2 is a process chart showing another embodiment of the heavy metal recovery method of the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22B 13/00 C22B 3/00 Q 15/00 13/04 19/20 15/12 (72) Inventor Tokumitsu Shunsho 1-8-2 Marunouchi, Chiyoda-ku, Tokyo F-term in Dowa Mining Co., Ltd. (reference) 4D004 AA37 AB06 AC04 BA05 CA13 CA34 CA35 CC12 DA03 DA20 4K001 AA09 AA20 AA30 BA08 BA14 CA02 DB02 DB07 DB23

Claims (2)

[Claims] 1. A method for recovering a heavy metal component from a substance containing at least one heavy metal component of zinc, copper and lead and chlorine, wherein said substance is slurried by adding water, and the pH is adjusted using an alkaline agent. After adjusting to 12 or more,
A method for recovering heavy metals from substances containing heavy metals and chlorine, wherein the heavy metal-containing precipitates are separated from the chlorine-containing filtrate by solid-liquid separation and recovered. 2. A method for recovering a heavy metal component from a substance containing at least one heavy metal component of zinc, copper and lead and chlorine, wherein said substance is slurried by adding a mineral acid to adjust the pH to 5 or less. A chlorine dissolving step of adjusting and dissolving chlorine, and after adding an alkali agent to the slurry in the chlorine dissolving step to adjust the pH to 12 or more, separating heavy metal-containing precipitates from the chlorine-containing filtrate by solid-liquid separation. And recovering the heavy metal from the substance containing heavy metal and chlorine.