JP2001058170A - Waste treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste treatment method capable of efficiently separating lead or cooper remaining in waste at a low cost to utilize the treated waste as a cement raw material. SOLUTION: In a waste treatment method, waste is treated with an acid to leach a copper component and this acid leached slurry is subjected to solid- liquid separation treatment and a separated solid is treated with alkali and subsequently subjected to solid-liquid separation treatment to be recovered as a cement raw material. Zinc or iron is added to the filtrate of the acid leached slurry to precipitate copper in the slurry and this copper precipitate is subjected to solid-liquid separation treatment and the separated filtrate is neutralized or sulfurized to precipitate zinc or iron which is, in turn, recovered by solid-liquid separation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating waste which separates and removes lead, copper and the like remaining in the waste.
In particular, the present invention relates to a waste treatment method for removing lead and copper from the waste so that the waste can be used as a cement raw material.

[0002]

2. Description of the Related Art Conventional industrial waste, household waste and incinerated ash have been mostly landfilled, but it has become increasingly difficult to set up a disposal site. Treatment measures are required. In addition, these wastes contain several percent of metals such as lead and copper. If these wastes are landfilled, heavy metals such as lead will flow out and cause environmental pollution. It is necessary to separate and remove metals as much as possible.

Conventionally, there has been proposed a treatment method in which heavy metals such as copper are leached by treating such wastes with sulfuric acid, and are converted into sulfides to be precipitated and recovered. Since many metals contained in the solution precipitate together, there is a problem that the quality of valuable metals such as copper is lowered. Further, since lead is converted into lead sulfate in the residue during sulfuric acid treatment and remains in the residue, even a residue having a high calcium content is not suitable as a cement raw material due to a high lead content. Furthermore, since calcium is also included as gypsum by sulfuric acid treatment, if this is used as a cement raw material, an excessive amount of sulfate is brought into the cement, which makes it difficult to convert the cement raw material.

The present invention solves the above-mentioned problems in the conventional waste treatment, and easily and efficiently separates and removes lead, copper, and the like remaining in the waste, and uses the treated waste as a cement raw material. It is intended to provide a processing method that can be used for:

[0005]

According to a first aspect of the present invention, there is provided:
The present invention relates to a method for removing metals remaining in waste, and relates to a processing method having the following configuration. (1) A step of leaching wastes by acid treatment of wastes, a step of solid-liquid separation of the acid leached slurry, and a step of removing a metal (substituted metal) which is more base than the metal leached by the acid treatment (leached metal). A step of adding leachate to the filtrate of the acid leaching slurry to precipitate leached metal (substitution precipitation step), a step of solid-liquid separation of the precipitate, and a step of neutralizing or sulfurizing the separated filtrate to precipitate the substitution metal. A method for treating waste, comprising a step and a step of solid-liquid separation thereof. (2) In the acid leaching step of the above (1), p
A waste treatment method in which H is adjusted to 2 to 4 to leach metals in the waste. (3) In the substitution precipitation step of the above (1), zinc or iron is used as a substitution metal with respect to copper in the acid-leached liquid, and zinc or iron is used in a concentration of 0.8 to 1.1 of copper ion in the liquid. A method for treating waste in which double equivalents are added to precipitate copper. (4) In the above neutralization treatment step (1), a method of treating a waste in which the filtrate obtained by separating the substituted precipitate is adjusted to pH 8 or more by adding alkali to precipitate iron or zinc in the liquid. .

A second aspect of the present invention relates to the conversion of waste into a raw material for cement, and relates to a treatment method having the following configuration. (5) acid treatment of waste to leaching residual metals, solid-liquid separation of the acid leached slurry, alkali treatment of the separated solids to leach lead solids and calcium A process of converting calcium hydroxide to calcium hydroxide to remain as a solid content, and a process of solid-liquid separation of the solid content. (6) In the treatment method of the above (5), a method for treating a waste material which is used after separating and collecting a solid content containing calcium hydroxide and using it as a cement raw material. (7) The method for treating waste according to the treatment method of (5) above, wherein a solid content containing calcium hydroxide is separated, a lead content in the filtrate is precipitated, and the precipitate is solid-liquid separated and recovered.

A third aspect of the present invention is a processing method for continuously removing metals remaining in waste and converting it into a cement raw material, and relates to a processing method having the following configuration. (8) After the waste is subjected to acid treatment to leach copper and lead, the acid leached slurry is subjected to solid-liquid separation, and the separated solid is subjected to alkali treatment and then collected by solid-liquid separation to be used as a cement raw material. On the other hand, zinc or iron is added to the filtrate of the acid leaching slurry to precipitate copper in the solution, and this copper precipitate is separated into a solid and a liquid,
A method for treating waste, comprising subjecting a separated filtrate to a neutralization treatment or a sulfuration treatment to precipitate zinc or iron, and separating and collecting the solid or liquid.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. FIG. 1 schematically shows a processing method according to the present invention.
Shown in As shown in the drawing, the treatment method of the present invention comprises, as a first step, a treatment step A comprising a step of leaching acid waste and a step of solid-liquid separation of the acid leached slurry, and separating a metal component from a filtrate of the acid leached slurry. There is a processing step B for removing and a processing step C for converting the separated solid content into a cement raw material.
Each processing step will be specifically described below. In the present invention, copper and / or a copper compound, lead and / or
Alternatively, the lead compound is referred to as copper and lead for convenience.

(A) Acid Leaching Treatment Step (A-1) Waste The waste to be treated in the treatment method of the present invention is general industrial waste, domestic waste, and waste discharged in the manufacturing processes of various mining industries. Waste, or incineration ash or molten slag fly ash. As mentioned earlier, these wastes contain some percent of lead and copper for some time.

Prior to the acid leaching treatment, if necessary, water may be added to the above-mentioned waste so as to have an appropriate solid-liquid ratio, and solid-liquid separation may be performed. Thereby, the water-soluble chlorine compound contained in the waste is eluted and the solid content is desalted. In addition, some of the water-soluble alkali metal compounds and lead compounds elute with chlorine.

(A-II) Acid Leaching An acid is added to the above-mentioned waste to form a slurry, and metals remaining in the waste are leached into a liquid (the acid-leached metal is abbreviated as a leached metal). The acid used here may be any acid that insolubilizes the lead remaining in the waste while leaching copper, zinc or the like into the slurry. Specifically, sulfuric acid is preferred.
This slurry has a solid-liquid ratio of preferably 500 g / l or less,
Acidic slurries of pH 2-4 are preferred. Although depending on the acid concentration, the leaching time is suitably 20 minutes or more, and may be about 30 minutes. If the pH of the slurry exceeds 4, the leaching efficiency of copper may decrease, which is not preferable. PH 2
If it is less than the above, the load of the alkali treatment in the next step increases, which is not preferable.

[0012] Copper and zinc remaining in the waste by the acid leaching process leach into the liquid. On the other hand, the lead content contained in the waste is leached into the liquid at first, but immediately forms an insoluble lead compound such as lead sulfate, solidifies, and remains in the leach residue. Further, calcium contained in the waste is converted into gypsum (calcium sulfate) and solidified, and remains in the leaching residue.

(A-II) Solid-Liquid Separation The above-mentioned acid leached slurry is filtered to separate a solid content. This solid content contains a large amount of calcium, and can be used as a cement raw material through an alkali treatment step described below. On the other hand, the separated filtrate is sent to the following copper separation step.

(B) Leaching Metal Treatment Step (BI) Substitution Precipitation Addition of a metal that is more noble than the leachable metal, ie, a metal that has a higher ionization tendency than the leachable metal, to the filtrate separated by solid-liquid in the acid leaching step Of leached metal is precipitated. As the added metal with high ionization tendency dissolves in the liquid,
Thus, a leached metal having a low ionization tendency is deposited instead. In the present invention, for convenience, a metal having a higher ionization tendency than a leached metal is abbreviated as a substitution metal, and this precipitation is abbreviated as a substitution precipitation. The replacement metal has only to have a higher ionization tendency than the leached metal. Specifically, when the leached metal is copper, zinc powder or iron powder can be used as the replacement metal. If zinc is used, a zinc sulfate solution is finally obtained by a series of processing steps of the present invention, and this can be used as a zinc smelting raw material to recover zinc by zinc electrolysis or the like. On the other hand, iron powder is economically advantageous.

Generally, the amount of the substituted metal is slightly excessive with respect to the leached metal in the liquid, for example, 1 to 3 times the concentration of the leached metal.
Double equivalents are appropriate. Almost all of the leached metal in the liquid can be precipitated by adding the substitution metal in a slightly excessive amount. On the other hand, in order to recover the leached metal with high quality, the amount of the replacement metal added is 0.8 to 1.1 with respect to the concentration of the leached metal.
An equivalent amount is appropriate. For example, when recovering copper by adding zinc powder or iron powder to copper leached into the liquid, if the amount of zinc added is too high than the copper concentration in the liquid, undissolved zinc or iron will be added to the liquid. This is mixed with the copper precipitate and reduces the quality of the recovered copper. On the other hand, when the liquid from which zinc powder or the like has been removed after copper recovery is reused as a sulfuric acid leaching solution, there is no problem even if a small amount of copper is present in the liquid. Therefore, the addition amount of these is preferably about 0.8 to 1.1 equivalents to the copper concentration in the liquid.

In this substitution precipitation, calcium and the like, which have a higher ionization tendency than substituted metals such as zinc and iron, do not precipitate, so that high-grade copper can be recovered. Incidentally, in the conventional method of recovering copper by sulfurating a sulfuric acid leaching solution, zinc and iron mixed in the solution co-precipitate as sulfide with copper, so that the quality of recovered copper is low. On the other hand, in this treatment method, high-grade copper of 90% or more can be recovered.

In this substitution precipitation, it is preferable to adjust the pH of the solution to 2 or more. If the pH is less than 2, electrons emitted from the substituted metal are consumed not only by copper ions but also by hydrogen ions, so that it is necessary to considerably increase the amount of the substituted metal added. Since the precipitate generated by the substitutional precipitation contains high-grade copper, it can be recovered by solid-liquid separation and used as a raw material for copper smelting.

(B-II) Recovery of Substituted Metal After the precipitate of the leached metal generated by the above-mentioned substitutional precipitation is separated, the filtrate (acid leached solution) is neutralized or sulfurized, and the added zinc or iron is removed. The substituted metal is precipitated and separated and recovered. That is, an alkaline solution such as caustic soda is added to the sulfuric acid leachate to adjust the pH of the leachate to 8 or more, preferably 9 to 12, to convert zinc or iron to hydroxide and precipitate it. The filtrate from which zinc or iron has been separated may be recycled to the acid leaching step and reused.

A sulfurizing treatment may be performed instead of the neutralizing treatment. That is, a sulfurizing agent such as sodium hydrosulfide is added to the sulfuric acid leachate to precipitate zinc or iron sulfide.
The addition amount of the sulfurizing agent is 1 to the zinc and iron contents in the liquid.
Two equivalents are preferred. In this sulfidation treatment, the pH of the liquid from which zinc or iron is separated is almost neutral, so that by adding a small amount of new sulfuric acid, it can be recycled to sulfuric acid leaching and reused. The recovered zinc or iron hydroxide or sulfide can be used as a raw material for smelting. In particular, sulfide is preferable as a smelting raw material because the sulfur content is a heat source.

(C) Cement Raw Material Making Step (CI) Alkali Treatment The residue obtained by the solid-liquid separation after the above acid leaching step is added with alkali to leach out the lead content (mainly lead sulfate) contained in the solid content. Let it. Caustic soda is preferred as the alkali. The concentration of caustic soda is suitably 1 N or more, preferably 2 N or more, and the solid-liquid ratio is suitably 75 g / l or less, preferably 50 g / l or less. The pH of the solution is preferably 12-14. Most of the lead sulfide contained in the residue is eluted into the liquid by this alkali treatment. On the other hand, calcium (mainly gypsum) in the residue is converted into calcium hydroxide and remains in the residue. The alkali-treated slurry is subjected to solid-liquid separation to recover a solid content, and the liquid content is sent to the next recovery step.

Calcium contained in the solid content is suitable as a cement raw material since the gypsum containing sulfate is converted into calcium hydroxide to remove the sulfate, and there is no possibility that excessive sulfate is introduced into the cement. . Further, when used as a cement raw material, there is an advantage that even if an organic chlorine compound such as dioxin is contained in the waste, it can be easily decomposed and detoxified by high-temperature firing during the production of cement.

(C-II) Sulfurization Treatment On the other hand, after alkali treatment, a sulfide agent such as sodium hydrogen sulfide is added to the filtrate which has been subjected to solid-liquid separation to convert lead and the like in the liquid to sulfide to precipitate. The amount of the sulfurizing agent to be added is suitably 1 to 2 equivalents to the lead content in the liquid. This is filtered to recover lead sulfide and the like. It is preferable to use the recovered lead sulfide or the like as a raw material for lead smelting because the sulfur content becomes a heat source. Also,
Since the filtrate from which lead sulfide or the like has been separated is a strong alkaline solution, it can be recycled and reused in the alkaline leaching step. Note that lead may be precipitated and recovered by a method such as electrolysis instead of the method using a sulfide agent.

[0023]

EXAMPLES The present invention will be specifically described below by way of examples.

Example 1 Molten slag fly ash (Cu: 1.2 wt%, Pb: 2.5 wt%, Zn: 10 wt%
%, Ca: 3 wt%), and 300 ml of water was added to 1000 ml of water to form an aqueous slurry, which was subjected to solid-liquid separation. The filtrate had a chlorine concentration of 4.8% by weight. 1080 ml of water and 120 ml of 4N sulfuric acid were added to the separated solid to obtain a sulfuric acid leached slurry having a pH of 3, which was subjected to solid-liquid separation. The concentrations of copper and zinc in the filtrate were 3000 ppm and 25500 ppm, respectively, and most of the copper and zinc contained in the fly ash were leached. On the other hand, 1800 ml of 2N caustic soda was added to 90 g of the residue.
Was added and mixed for 30 minutes to obtain a pH 13 alkaline leaching slurry, which was subjected to solid-liquid separation. When the separated solid was analyzed by powder X-ray diffraction, a gypsum peak was not found and a calcium hydroxide peak was found. Subsequently, 1.8 g of sodium hydrogen sulfide was added to the filtrate from which the solid content was separated.
To form a precipitate, which is separated into a solid and a liquid by precipitation.
6 g were recovered. It was confirmed by powder X-ray diffraction that the recovered material was lead sulfide.

Example 2 Regarding the solid content of sulfuric acid leached from the molten slag fly ash of Example 1,
Caustic soda having a concentration (0.5N, 1.0N, 2.0N) shown in Table 1 was added to obtain an alkaline leached slurry having a solid-liquid ratio of 50 g / l, which was subjected to solid-liquid separation. The heavy metal concentration of this filtrate is shown in Table 1 together with the concentration of caustic soda. As shown, when the concentration of caustic soda is 2N, the amount of lead leached is the largest and the amount of calcium leached is the smallest. The caustic soda concentration is 0.5
In N, the amount of lead leached decreases and the amount of calcium leached increases. From these results, the concentration of caustic soda is suitably 1N or more, and preferably 2N or more.

[0026]

[Table 1]

Example 3 The sulfuric acid leached solid content of the molten slag fly ash of Example 1 was
1N caustic soda was added to obtain an alkali leached slurry adjusted to a solid-liquid ratio shown in Table 2, and this was subjected to solid-liquid separation. Table 2 shows the heavy metal concentration in the leachate for each solid-liquid ratio. As shown, when the solid-liquid ratio is 100 g / l, the leaching rate of calcium is high and the leaching rate of lead is low. Solid-liquid ratio 50g /
In the case of l, the lead leaching rate is greatly increased, so that the intermediate solid-liquid ratio of 75 g / l or less is appropriate and 50 g / l or less is good.

[0028]

[Table 2]

Example 4 1000 ml of water was added to 150 g of molten slag fly ash (Cu: 2.1 wt%), and sulfuric acid was added thereto to form a slurry having a pH of about 3, which was subjected to solid-liquid separation. Iron powder is added to 1000 ml of the separated filtrate.
6 g was added and mixed, and after 30 minutes, the resulting precipitate was subjected to solid-liquid separation to recover 3.5 g of copper. Although the surface of the recovered copper was partially oxidized, the copper quality was about 90%. On the other hand, 16 g of sodium bisulfide was added to 1000 ml of the filtrate from which copper was recovered, and the resulting precipitate was subjected to solid-liquid separation to recover 27 g of a mixture of iron sulfide and zinc sulfide.

Example 5 To 150 g of molten slag fly ash (Cu: 2.1 wt%), 1000 ml of water was added, and sulfuric acid was added thereto to form a slurry having a pH of about 3, which was separated into a solid and a liquid. Zinc powder 3 in 1000 ml of separated filtrate
g was added and mixed, and after 30 minutes, the resulting precipitate was solid-liquid separated to recover 3.4 g of copper. Although the surface of the recovered copper was partially oxidized, the copper quality was about 93%. On the other hand, 16 g of sodium hydrogen sulfide was added to 1000 ml of the filtrate from which copper was recovered, and the resulting precipitate was subjected to solid-liquid separation to recover 27 g of zinc sulfide.

Example 6 Water (1000 ml) was added to 150 g of molten slag fly ash (Cu: 2.1 wt%), and sulfuric acid was added thereto to form a slurry having a pH of about 3, which was subjected to solid-liquid separation. Iron powder is added to 1000 ml of the separated filtrate.
6 g was added and mixed, and after 30 minutes, the resulting precipitate was subjected to solid-liquid separation to recover 3.5 g of copper. Although the surface of the recovered copper was partially oxidized, the copper quality was about 93%. On the other hand, caustic soda was added to 1000 ml of the filtrate after copper was recovered to adjust the pH to 9%.
The resulting precipitate was subjected to solid-liquid separation, and 27 g of a mixture of iron hydroxide and zinc hydroxide was recovered.

Example 7 To 150 g of molten slag fly ash (Cu: 2.1 wt%) was added 1000 ml of water, and sulfuric acid was added thereto to form a slurry having a pH of about 3, which was subjected to solid-liquid separation. Zinc powder 3 in 1000 ml of separated filtrate
g was added and mixed, and after the elapse of 30 powders, the resulting precipitate was subjected to solid-liquid separation to recover 3.4 g of copper. Although the surface of the recovered copper was partially oxidized, the copper quality was about 93%. On the other hand, caustic soda was added to 1000 ml of the filtrate after copper was recovered to adjust the pH to 9, and the resulting precipitate was subjected to solid-liquid separation to recover 27 g of a mixture of iron hydroxide and zinc hydroxide.

Example 8 Fly ash from molten slag (Cu: 2.2 wt%, Pb: 6.1 wt%, Zn: 4.5 wt%
%, Ca: 10.2 wt%) to 300 g of water to obtain an aqueous slurry, which was subjected to solid-liquid separation. To the separated solid content, 200 ml of water and 400 ml of 4N sulfuric acid were added to adjust the pH to 3 to obtain a sulfuric acid leached slurry, which was subjected to solid-liquid separation.
The filtrate had a copper concentration of 11,000 ppm and a zinc concentration of 2 ppm.
2500 ppm, and most of the copper and zinc contained in the fly ash were leached. 600 ml of 2N caustic soda was added to 30 g of this solid content and mixed for 30 minutes to obtain a pH 13 alkaline leaching slurry, which was subjected to solid-liquid separation. When the separated solid was analyzed by powder X-ray diffraction, a gypsum peak was not found and a calcium hydroxide peak was found. Subsequently, 5.2 g of sodium hydrosulfide was added to the filtrate obtained by solid-liquid separation of the alkaline leaching slurry to form a precipitate,
This was subjected to solid-liquid separation to recover 148 g of a solid content. Powder X
The recovered material was confirmed to be lead sulfide by X-ray diffraction. On the other hand, iron powder 4.
9 g was added and mixed, and after 30 minutes, the resulting precipitate was subjected to solid-liquid separation to recover 6.1 g of copper. Although the surface of the recovered copper was partially oxidized, the copper quality was about 90%. further,
17.4 g of sodium hydrogen sulfide was added to 500 ml of the filtrate from which copper was recovered, and the resulting precipitate was subjected to solid-liquid separation to recover 24 g of a mixture of iron sulfide and zinc sulfide.

Example 9 Copper 5.9 g was prepared in the same manner as in Example 1 except that 5.7 g of zinc was added instead of iron powder to 500 ml of the filtrate of the sulfuric acid leaching slurry.
Was recovered. Although the surface of the recovered copper was partially oxidized, the copper quality was about 93%. The amount of the mixture of iron sulfide and zinc sulfide recovered from the filtrate after the recovery of copper was 24.5.
g.

[0035]

According to the treatment method of the present invention, it is possible to efficiently separate and recover copper, lead, zinc and the like contained in various kinds of wastes, and furthermore, to treat wastes having a high calcium content in the treated solids. There is an advantage that a portion can be used as a cement raw material. That is, in the conventional treatment method, most of the calcium contained in the waste remains in the solid content as gypsum, which is a sulfate compound, and thus is not suitable for a cement raw material. Since it remains in the solid content as a substance, it is preferable that even if this is used as a cement raw material, there is no risk of excessive sulfate groups being introduced into the cement component.
Further, the treatment method of the present invention has high quality of copper and lead recovered from waste. In addition, since it is recovered as metallic copper powder, it is easy to use.

[Brief description of the drawings]

FIG. 1 is a process chart showing a processing method of the present invention.

Claims (9)

[Claims] 1. A step of subjecting waste to acid treatment to leach out residual metals, a step of solid-liquid separation of the acid leached slurry, and a metal (substituted metal) that is less basic than the metal leached by the acid treatment (leached metal). ) Is added to the filtrate of the acid leaching slurry to precipitate leached metal (substitution precipitation step), a step of solid-liquid separation of the deposited precipitate, and a neutralization treatment or a sulfuration treatment of the separated filtrate to remove the substituted metal. A method for treating waste, comprising a step of precipitating and a step of solid-liquid separation. 2. The method for treating waste according to claim 1, wherein in the acid leaching step, the pH of the leached slurry is adjusted to 2 to 4 to leaches metals in the waste. 3. The substitution precipitation step of claim 1, wherein zinc or iron is used as a substitution metal with respect to copper in the acid-leached liquid, and zinc or iron has a copper ion concentration of 0.8 to 1.0.
A method for treating waste which adds one equivalent to precipitate copper. 4. In the neutralization treatment step of claim 1, an alkali is added to the filtrate from which the substituted precipitate has been separated to adjust the liquid property to p.
A method for treating waste which is adjusted to H8 or more to precipitate iron or zinc in a liquid. 5. A step of leaching wastes by acid treatment of wastes, a step of solid-liquid separation of the acid leached slurry, and a step of alkali-treating the separated solids to leaching lead of solids. A method for treating waste, comprising: a step of converting calcium into calcium hydroxide to remain in solids; and a step of solid-liquid separation of the solids. 6. The method for treating waste according to claim 5, wherein solids containing calcium hydroxide are separated, recovered, and used as a cement raw material. 7. The method for treating waste according to claim 5, wherein a solid content containing calcium hydroxide is separated, a lead content in the filtrate is precipitated, and solid content is separated and recovered. 8. After the waste is acid-treated to leach copper and lead, the acid-leached slurry is solid-liquid separated, and the separated solid is alkali-treated and then solid-liquid separated and collected to obtain a cement raw material. On the other hand, zinc or iron is added to the filtrate of the acid leaching slurry to precipitate copper in the solution, the copper precipitate is separated into solid and liquid, and the separated filtrate is neutralized or sulfurized to obtain zinc or iron. A method for treating waste, comprising precipitating and collecting solids and liquids. 9. The waste according to claim 1, wherein a lead-containing precipitate separated from the waste is recovered and used as a lead smelting raw material, and a copper-containing precipitate is recovered and used as a copper smelting raw material. How to handle things.