JP2001046996A - Treatment of waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste treating method capable of inexpensively and efficiently separating lead and copper in wastes and capable of reusing the treated wastes as a cement starting material. SOLUTION: In the treating method, the wastes containing metal are subjected to acid leaching, and a solid component in the acid leached slurry is subjected to alkali treatment and used as the cement starting material. On the other hand, zinc, etc., are added to the separated filtrate solution to precipitate the copper component in the liq. and the copper component is recovered by solid-liq. separation. The zinc, etc., are separated and recovered by solvent extraction, or copper is extracted by adding solvent in the filtrate of the acid leached slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste treatment method for separating and removing lead, copper, etc. in waste, and more particularly to a waste treatment for removing lead and copper from waste so that the waste can be used as a cement raw material. The present invention relates to a method of processing an object.

[0002]

[Prior art and its problems] General industrial waste, domestic waste, and incinerated fly ash have been mostly landfilled, but it is becoming increasingly difficult to set up a disposal site. Effective 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 purity of valuable metals such as copper is reduced. Further, since lead is converted into lead sulfate and remains in the residue during the sulfuric acid treatment, even a residue containing a large amount of calcium is not suitable for a cement raw material due to its 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 has been made to solve the above-mentioned problems in the conventional waste treatment, and easily and efficiently separates and removes lead, copper and the like in the waste, and effectively treats the treated waste as a raw material for cement. It provides an available processing method.

[0005]

According to a first aspect of the present invention, there is provided:
The present invention relates to a method for removing metals in waste and relates to a treatment method having the following configuration. (1) A step of leaching metals in waste by acid treatment of waste, a step of solid-liquid separation of the acid leached slurry, and a metal (substituted metal) which is less base than a metal leached by acid treatment (leached metal). ) Is added to the filtrate of the acid leaching slurry to precipitate leached metal (substitution precipitation step), and a step of solid-liquid separation of the deposited precipitate is provided. (2) In the treatment method of the above (1), after the solid-liquid separation step following the substitution precipitation step, a step of adding an extraction solvent to the separated filtrate to extract a substitution metal and a step of back-extracting the extracted substitution metal are included. Waste disposal method.

[0006] The treatment method of the present invention has the following second aspect for separation and removal of metals in waste. (3) acid-treating the waste to leach metals in the waste, solid-liquid separation of the acid-leached slurry, extracting the leachable metal by adding an extraction solvent to the separated filtrate,
The step of back-extracting the extracted leached metal, having a step of adding a metal lower than the leached metal (substituted metal) to the liquid containing the back-extracted leached metal to precipitate and precipitate the leached metal (substitution precipitation step). Characteristic waste treatment method.

[0007] The waste treatment method of the present invention is specifically a waste treatment method in which copper is leached by acid treatment of waste and zinc is used as a replacement metal.

[0008] A third aspect of the present invention relates to the conversion of waste into a raw material for cement, and is a processing method having the following steps accompanying the above-mentioned processing steps. (5) In any one of the treatment methods (1) to (4), after solid-liquid separation of the acid leaching slurry, the separated solid is treated with alkali to leach out the lead in the solid and simultaneously remove the calcium. A method for treating waste, comprising the steps of converting calcium hydroxide to a solid content and leaving the solid content containing calcium hydroxide in a solid-liquid separation. (6) The method for treating waste as described in (5) above, wherein the solid content containing calcium hydroxide is separated and then recovered and used as a cement raw material. (7) The method for treating waste as described in (5) or (6) above, wherein the solid content containing calcium hydroxide is separated, the lead content in the filtrate is precipitated, and the precipitate is solid-liquid separated and recovered.

The above-mentioned processing method of the present invention preferably includes the following aspects. (8) In the acid leaching step, the pH of the leached slurry is adjusted to 2 to
The above (1) to (7), which adjust to 4 and leach copper in waste
A method for treating waste as described in any one of the above. (9) In any one of the above (1) to (8), in the substitution precipitation step, zinc is used as a substitution metal, and zinc is added in an amount of 0.8 to 3 equivalents of the copper ion concentration in the solution to precipitate copper. The waste disposal method to be described. (10) The method for treating waste as described in any one of (1) to (9) above, wherein a solid containing lead separated from waste is used as a raw material for smelting lead, and a solid containing copper is used as a raw material for smelting copper.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. The processing method of the present invention is schematically shown in FIGS. As shown, the processing method of the present invention comprises:
The first step includes a step of acid leaching waste and a step of solid-liquid separating solids containing lead from the leached slurry. The processing method shown in FIG. 1 is a method having a processing step of substituting and depositing leached metal after the first-stage processing step. On the other hand, the processing method shown in FIG. 2 is a method having a processing step of extracting a leached metal by solvent extraction after the first-stage processing step. Each processing step will be specifically described below. In the present invention, copper and / or a copper compound and lead and / or a lead compound are referred to as copper and lead, respectively, for convenience.

(A) Acid Leaching Process (A-1) Waste The waste to be treated by 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 waste so as to have an appropriate solid-liquid ratio to form an aqueous slurry. 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 in the waste are leached into the slurry (the metal which has been acid-leached is abbreviated as a leached metal). The acid used here may be any acid that insolubilizes the lead in the waste while leaching copper or zinc into the slurry. Specifically, sulfuric acid is preferred. The slurry should have a solid-liquid ratio of 100 g / l or less, and a pH of 2
~ 4 acidic slurries 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. On the other hand, when the pH is less than 2, the load of the alkali treatment in the next step increases, which is not preferable.

[0014] By this acid leaching treatment, copper, zinc and the like in the waste are leached into the slurry. On the other hand, the lead contained in the waste leach into the liquid at first, but immediately forms an insoluble lead compound such as lead sulfate and remains as a solid. Further, calcium contained in the waste is converted into gypsum (calcium sulfate) and solidified, and remains in the solid content.

(A-II) Solid-liquid separation The 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 base than the leachable metal, ie, a metal that has a higher ionization tendency than the leachable metal, to the filtrate that has been subjected to solid-liquid separation 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.

In general, 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, high-grade copper can be recovered because calcium and the like having a higher ionization tendency than the substitution metals such as zinc and iron do not precipitate. 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 the displacement 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. In addition, the substituted metal is advantageous in that the powdered metal enhances reactivity and solubility. 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) Solvent Extraction of Substituted Metal A solvent (organic phase) for extracting the substituted metal is added to the liquid phase (aqueous phase) subjected to the solid-liquid separation in the substitution precipitation step, and the substituted metal is added to the organic solvent. Transfer and extract. When zinc is used as the substitution metal, a chelating agent (di-2-ethylhexyl phosphoric acid) diluted to 15 vol% with kerosene can be used as an extraction solvent. In this case, the liquid volume ratio of the aqueous phase to the organic phase is preferably about 1: 1 and the liquid property is preferably around pH 4.
In addition, you may use the solvent generally used as a zinc extraction solvent. In this solvent extraction, chlorine in the liquid remains in the aqueous phase without being extracted, so that a dechlorination effect is obtained.

(B-III) Back-extraction step A back-extraction solution (aqueous phase) is added to an extracted organic solvent containing a substituted metal (zinc, etc.) ion and mixed, and the substituted metal (zinc, etc.) is back-extracted into an aqueous phase. I do. Sulfuric acid can be used as the back extract. In this case, the liquid amount ratio of sulfuric acid to the organic extract is suitably about 1: 4 sulfuric acid (aqueous phase): extract (organic phase), and the pH of the liquid is preferably about 0.5. By this back-extraction, a substituted metal (such as zinc) can be recovered. The concentration of zinc or the like can be increased by repeating back extraction.
The zinc sulfate solution obtained by the back extraction can be used as a zinc smelting raw material. On the other hand, the organic solvent separated from the aqueous phase can be recycled and reused in the solvent extraction step.

(C) Solvent treatment of leached metals (CI) Solvent extraction Among the metals contained in the waste, those having a low metal content other than copper and lead are subjected to the acid leaching step of the first stage and the solid-liquid separation After the step, as shown in FIG. 2, instead of a method of replacing and recovering a leachable metal such as copper by substitution precipitation, the leachable metal may be separated by solvent extraction. Specifically, as shown in the figure, for example, a copper extraction solvent (such as an organic solvent obtained by diluting 2-Hydroxy-5-Nonylacetophenone Oxime to 10 vol% with kerosene) is mixed with the filtrate obtained by solid-liquid separation of the leach slurry, Copper ions are extracted into the organic solvent. The liquid ratio of the aqueous phase to the organic phase is appropriately about 1: 1 and the liquid property is preferably around pH 6.

(C-II) Back extraction Next, a back extraction solution such as dilute sulfuric acid is added to an organic solvent containing copper ions, and the copper ions are transferred to the dilute sulfuric acid for back extraction. A replacement metal (zinc or the like) is added to the copper sulfate solution to precipitate and precipitate copper, and the precipitate can be separated and recovered by solid-liquid separation. The separated and recovered copper-containing solid can be used as a copper smelting raw material.

(D) Cement Raw Material Treatment The solid content obtained by the solid-liquid separation after the acid leaching step is added with an alkali to leach out the lead content (mainly lead sulfide) contained in the solid content. 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 solid content is eluted into the liquid by the alkali treatment. On the other hand, calcium in solids
(Mainly gypsum) turns into calcium hydroxide and remains in the solids. 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 raw material for cement because the gypsum containing sulfate is converted to calcium hydroxide to remove the sulfate, and there is a possibility that excessive sulfate is brought into the cement. Absent. Further, by using it as a cement raw material, there is an advantage that even if dioxins contained in the waste remain in this solid content, they can be easily decomposed and detoxified by high-temperature sintering at the time of cement production.

On the other hand, after the alkali treatment, a sulfurizing agent such as sodium hydrogen sulfide is added to the filtrate separated into solid and liquid to convert lead and the like in the solution to sulfide and 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. Further, since the filtrate from which lead sulfide or the like has been separated is a strong alkali solution, it can be recycled to the alkali leaching step and reused. In addition, instead of the method using a sulfurizing agent,
Lead may be precipitated and recovered by means such as electrolysis.

[0027]

EXAMPLES The present invention will be specifically described below by way of examples. Example 1 To 120 g of molten slag fly ash (Cu: 1.3 wt%, Zn: 6.5 wt%)
Add 1000 ml of water and sulfuric acid to adjust the pH to pH 3,
The metal contained in the fly ash was leached by stirring for 30 minutes, followed by solid-liquid separation. 1.8 g of zinc powder was added to 1000 ml of the separated filtrate and stirred for 30 minutes to form a precipitate, which was then filtered to recover 1.5 g of copper (recovery rate: about 96%). Although the surface of the recovered copper was partially oxidized, the copper quality was about 90% by weight.

Subsequently, the filtrate 300 from which the copper precipitate was separated was removed.
20 vol% of di-2ethylhexyl phosphoric acid with kerosene per ml
The mixture was mixed for 20 minutes while adjusting the pH of the solution to pH 4 by adding NaOH, and then allowed to stand for 1 minute to separate the organic phase. The organic phase was recovered. Further, 150 ml of dilute sulfuric acid having a pH of 0.5 was added to this organic solution, mixed for 5 minutes, and allowed to stand for 1 minute, and then the organic and aqueous phases were added.
(Zinc sulfate solution), and the organic phase and the aqueous phase were collected. The zinc concentration in the zinc sulfate solution obtained by this back extraction was 18 g / l, and no lead or copper was detected.

Example 2 Fly slag fly ash (Cu: 1.3 wt%, Zn: 6.5 wt%, Pb: 2.5 wt%
(%, Ca: 3.1 wt%), 120 ml of water and 1000 ml of sulfuric acid were added to adjust the liquid property to pH 3, and the mixture was stirred for 30 minutes to leach out the metal contained in the fly ash, followed by solid-liquid separation. To 50 g of the separated solid was added 1000 ml of 1.5N caustic soda and mixed for 30 minutes to carry out solid-liquid separation. When this solid was analyzed with a powder X-ray diffractometer to analyze the components contained, no peak other than the calcium hydroxide peak was detected. From this, it was confirmed that substantially all of the calcium converted to gypsum in the sulfuric acid leaching treatment was converted to calcium hydroxide and remained in the solid content by the alkali treatment using caustic soda.

Example 3 To 120 g of molten slag fly ash (Cu: 1.3 wt%, Zn: 6.5 wt%)
Add 1000 ml of water and sulfuric acid to adjust the pH to pH 3,
The metal contained in the fly ash was leached by stirring for 30 minutes, followed by solid-liquid separation. Copper extraction solvent (2
-Hydroxy-5-Nonylacetophenone Oxime with kerosene 10
300 ml of a solution (vol.% diluted) was added, and the mixture was mixed for 15 minutes while adjusting the pH to 6 by adding NaOH, and then allowed to stand for 1 minute to separate the organic phase, and the organic phase was recovered. Further, 150 m of dilute sulfuric acid having a pH of 0.5 was added to the organic solution.
was added and mixed for 10 minutes, and then allowed to stand for 1 minute to separate an organic phase and an aqueous phase (zinc sulfate solution), and the organic phase and the aqueous phase were collected. 0.6 g of zinc powder was added to this aqueous phase (zinc sulfate solution) and stirred for 30 minutes to form a precipitate. Then, the precipitate was filtered to recover 0.45 g of copper (recovery rate: about 97%) and a zinc sulfate solution.

[0031]

According to the treatment method of the present invention, metals such as lead and copper in waste can be efficiently separated and removed at low cost, and the treated waste can be used as a cement raw material. .

[Brief description of the drawings]

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

FIG. 2 is another process chart showing the processing method of the present invention.

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Claims (10)

[Claims] 1. A step of leaching metals in waste by acid treatment of waste, a step of solid-liquid separation of the acid leached slurry, and a metal (leached metal) which is less leached by the acid treatment (leached metal). A process for adding leachable metal to the filtrate of the acid leach slurry to precipitate leachable metal (replacement deposition process), and a process for solid-liquid separation of the deposited precipitate. 2. The processing method according to claim 1, wherein after the solid-liquid separation step following the substitution precipitation step, a step of adding an extraction solvent to the separated filtrate to extract a substitution metal, and a step of back-extracting the extracted substitution metal. Waste treatment method having the following. 3. a step of acid-treating the waste to leach metals in the waste, a step of solid-liquid separating the acid-leached slurry, a step of adding an extraction solvent to the separated filtrate to extract the leachable metal, The step of back-extracting the extracted leached metal, having a step of adding a metal lower than the leached metal (substituted metal) to the liquid containing the back-extracted leached metal to precipitate and precipitate the leached metal (substitution precipitation step). Characteristic waste treatment method. 4. The method for treating waste according to claim 1, 2 or 3, wherein copper is leached by acid treatment of the waste and zinc is used as a replacement metal. 5. The treatment method according to claim 1, wherein after solid-liquid separation of the acid leaching slurry, the separated solid is treated with alkali to leach lead in the solid and to remove calcium from water. A method for treating waste, comprising a step of converting calcium oxide to remain in solids and a step of solid-liquid separating the solids containing calcium hydroxide. 6. The waste treatment method according to claim 5, wherein a solid content containing calcium hydroxide is separated and recovered and used as a cement raw material. 7. The method for treating waste according to claim 5, wherein after separating a solid content containing calcium hydroxide, a lead content in the filtrate is precipitated and the solid content is separated and recovered. 8. In the acid leaching step, p of the leached slurry is
The method for treating waste according to any one of claims 1 to 7, wherein H is adjusted to 2 to 4 so that copper in the waste is leached. 9. The method according to claim 1, wherein in the substitution precipitation step, zinc is used as a substitution metal, and zinc is added in an amount of 0.8 to 3 times equivalent of a copper ion concentration in the liquid to precipitate copper. Waste disposal method. 10. The method for treating waste according to claim 1, wherein the solid containing lead separated from the waste is used as a raw material for smelting lead, and the solid containing copper is used as a raw material for smelting copper.