JP4690881B2 - Method for treating lead-containing sludge and method for treating lead-containing wastewater - Google Patents

Description

  The present invention relates to a method for treating lead-containing sludge and a method for treating lead-containing wastewater. In particular, the amount of flocculant used as a wastewater treatment agent can be reduced, high-purity lead can be efficiently recovered, and a simple treatment method for lead-containing wastewater that does not produce new waste and treatment of lead-containing sludge Regarding the method.

  As a treatment method of waste water containing lead and / or a salt thereof (referred to as “lead-containing waste water” in the present invention), a flocculant such as ferric chloride, ferric sulfate or aluminum hydroxide is added to the waste water. To adjust the liquidity to alkaline, convert compounds such as iron, aluminum and lead into metal hydroxides, and separate lead from wastewater together with iron and aluminum using the coprecipitation phenomenon of these hydroxides (Hydroxide precipitation method, neutralization aggregation precipitation method) are known (see Non-Patent Document 1).

However, in this method, in order to meet the lead drainage standard (0.1 mg / L defined in Article 3, Paragraph 1 and Article 12 of the Water Pollution Control Law), the lead content contained in the wastewater must be reduced. On the other hand, it is necessary to use a flocculant several to dozens of times, and at least 5 to 6 times (in terms of mass), and sludge settled by the coprecipitation phenomenon (also referred to as sludge) becomes very large in the sludge. The content of lead hydroxide is also small (about 10% by mass).
Therefore, it is difficult to efficiently recover lead from a large amount and low content of lead-containing sludge by a simple process (operation), and there is a problem that energy consumption is large and not economical. Further, when a large amount of lead-containing sludge is discarded, there is a problem that enormous costs are required and it is against the social trend of waste reduction.

  On the other hand, as a method for treating fly ash, acid is added to fly ash containing heavy metals such as lead discharged from an incinerator or melting furnace, and then heavy metals other than lead are extracted, followed by solid-liquid separation. Next, the lead-containing residue obtained by solid-liquid separation is added with a solubilizing agent to extract lead, followed by solid-liquid separation, and further, an insolubilizing agent is added to the filtrate obtained by solid-liquid separation to lead A method for recovering lead in fly ash is known (see Patent Document 1). However, in general, the fly ash has a very low lead content (about several mass%), and it is not economical when treating the above lead-containing wastewater or sludge having a content of several to dozens of times. . In addition, secondary waste is generated, which is not a preferable industrial treatment method for environmental measures in recent years.

  As another processing method, there is known a method for recycling fly ash discharged from a waste incineration facility or melting facility characterized by comprising five steps (see Patent Document 2). . This method consists of five steps, and the operation of each step is complicated, and is not suitable for an industrial scale.

JP-A-10-204552 JP 2001-47001 A “Pollution Prevention Technology and Regulations (Water Quality)”, Industrial Environment Management Association, 5th edition (supplement), issued June 30, 1994, p. 140-141

The present invention aims to solve at least one of the above problems.
Specifically, an object of the present invention is to provide a treatment method for lead-containing wastewater or lead-containing sludge that can efficiently recover lead from a large amount of low-content lead-containing wastewater or lead-containing sludge with high purity. To do.
It is another object of the present invention to provide a simple (economic) lead-containing wastewater suitable for an industrial scale that does not generate new waste and a method for treating lead-containing sludge.
Furthermore, the present invention provides a method for treating lead-containing wastewater that can reduce the amount of flocculant used as a wastewater treatment agent, reduce the sludge generated from lead-containing wastewater, and increase the lead content of the sludge. With the goal.

As a result of intensive investigations on the treatment method of lead-containing wastewater and lead-containing sludge, the present inventors added solid sulfuric acid to lead-containing sludge obtained from the lead-containing wastewater by the hydroxide precipitation method, etc. In addition, it was found that lead can be easily and efficiently purified as lead sulfate, and the filtrate can be reused as a flocculant for wastewater treatment.
In addition, the amount of sludge produced by the above method is small compared to the amount of lead-containing sludge produced by a hydroxide coprecipitation method such as lead and iron, and the volume of sludge can be reduced. It has been found that the amount of the flocculant used can be reduced by reusing as a flocculant for wastewater treatment, and continuous treatment is possible without generating new waste.
The present inventors have completed the present invention based on the above findings.

  That is, the present invention provides the following (1) to (5).

(1) A method for treating lead-containing sludge, comprising the step (b) of adding sulfuric acid to lead-containing sludge to adjust the pH to 1.3 or lower and solid-liquid separation using a precipitate containing lead sulfate as a solid phase.
By this method, lead can be efficiently recovered from a large amount of low-content lead-containing wastewater with high purity and can be simply (economically) treated without generating new waste. Moreover, since it has the said characteristic, this method is suitable as an industrial processing method.

(2) Step (a) for solid-liquid separation after adding flocculant and alkali agent to lead-containing wastewater to adjust to alkalinity;
A step (b) of solid-liquid separation using a precipitate containing lead sulfate as a solid phase by adding sulfuric acid to the lead-containing sludge obtained by the solid-liquid separation in the step (a) to adjust the pH to 1.3 or less; A method for treating lead-containing wastewater.

  (3) The method for treating lead-containing wastewater according to (2) above, wherein the filtrate obtained by solid-liquid separation in the step (b) or a concentrate thereof is used as the flocculant in the step (a).

By the methods (2) and (3) above, lead can be efficiently recovered from a large amount of low-content lead-containing wastewater with high purity and can be simply (economically) treated without generating new waste. Furthermore, the amount of flocculant used as a wastewater treatment agent can be reduced, and sludge obtained from lead-containing wastewater can be reduced.
Moreover, since it has the said characteristic, this method is suitable as an industrial processing method.
In the present invention, the filtrate refers to a liquid portion obtained by solid-liquid separation or the like. For example, in addition to the filtrate obtained by solid-liquid separation, the supernatant obtained by decantation (gradient method). Including liquids.

(4) A method for treating lead-containing wastewater,
A step (c) of adding a flocculant and an alkali agent to lead-containing wastewater to adjust it to alkalinity, followed by solid-liquid separation, and discharging the obtained filtrate;
The lead-containing sludge obtained by the solid-liquid separation in the step (c) is added with sulfuric acid to adjust the pH to 1.3 or less, and the precipitate containing lead sulfate is solid-liquid separated as a solid phase to recover lead sulfate. Step (d);
The filtrate obtained by the solid-liquid separation in the step (d) or the concentrate thereof is added to another lead-containing wastewater as a flocculant, further adjusted to be alkaline by adding an alkali agent, and then subjected to solid-liquid separation to obtain a filtrate. A step (e) of discharging the liquid;
The lead-containing wastewater cycle treatment method is characterized in that the steps (d) and (e) are repeated alternately in order.

With this method, lead can be efficiently recovered with high purity from a large amount of low-content lead-containing wastewater, and it can be easily (economically) treated without generating new waste, and used as a wastewater treatment agent. The amount of flocculant used can be reduced, and sludge obtained from lead-containing wastewater can be reduced. In particular, lead can be continuously processed without being discharged out of the processing system, and automatic control or the like is also possible.
Since it has such characteristics, the method is particularly suitable as an industrial treatment method.

In the present invention, when discharging each filtrate, etc., it is preferable to measure pH, metal content, etc. to confirm that the drainage standard is satisfied.
In the method, it is preferable to perform solid-liquid separation in the step (d).

(5) A flocculant for wastewater treatment containing a filtrate obtained by solid-liquid separation in the step (b) or the step (d) or a concentrate thereof.
Another object of the present invention is to provide a flocculant for wastewater treatment that is preferably used in the above-described treatment method, and the flocculant can easily (economically) treat lead-containing wastewater without generating new waste. In addition, the amount of flocculant used as a wastewater treatment agent can be reduced, and sludge obtained from lead-containing wastewater can be reduced.
Due to the above characteristics, the flocculant for treating wastewater is suitable as a flocculant for treating industrial wastewater, particularly lead-containing wastewater.

ADVANTAGE OF THE INVENTION By this invention, the processing method of the lead containing waste water or the lead containing sludge which can collect | recover lead with high purity efficiently from a large quantity and low content lead-containing waste water or lead containing sludge can be provided.
Moreover, according to the present invention, it is possible to provide a simple (economic) lead-containing wastewater and a method for treating lead-containing sludge suitable for an industrial scale that does not generate new waste.
Furthermore, according to the present invention, it is possible to provide a method for treating lead-containing wastewater that can reduce the amount of flocculant used as a wastewater treatment agent, reduce the sludge generated from the lead-containing wastewater, and increase the lead content of the sludge.

Hereinafter, the present invention will be described in detail.
First, the lead-containing wastewater and lead-containing sludge used in the present invention will be described.

[Lead-containing wastewater]
Lead contained in the wastewater containing lead used in the present invention is inorganic lead such as metallic lead, its ions, salts thereof (for example, lead hydroxide, lead sulfate, lead chloride, etc.) and compounds thereof.

The lead-containing wastewater is not particularly limited as long as it contains lead as described above. For example, a factory that discharges lead-containing wastewater, specifically, a lead-containing wastewater that is discharged from a lead chemical factory, a lead smelter, a battery factory, or the like.
Moreover, the lead content contained in the wastewater is not particularly limited.
Further, the heavy metal other than lead contained in the wastewater is not particularly limited, but a metal insoluble in sulfuric acid, for example, tin or the like remains in the sludge (lead sulfate) in the step (b) to be described later. A metal that is soluble in sulfuric acid is preferred because it reduces the purity.
The heavy metal is more preferably a heavy metal that can be separated from lead in the step (b) described later, and examples thereof include iron, aluminum, zinc, copper, and cadmium.

[Lead-containing sludge]
In the present invention, sludge includes sludge waste made of hydroxide such as lead that has already been discarded, in addition to waste water generated from the above-mentioned factories and the like and sludge generated in the treatment process.
The lead-containing sludge used in the present invention refers to a sludge containing at least lead hydroxide or lead sulfate, and preferably containing a metal hydroxide such as iron or aluminum that forms a hydroxide coprecipitate with it. Examples of the metal hydroxide include hydroxides such as zinc, copper, and cadmium, as well as iron and aluminum hydroxides, and metals that do not adversely affect the coprecipitation phenomenon.
The sludge is not particularly limited as long as it contains at least lead hydroxide or lead sulfate, and preferably contains other metal hydroxides.
Examples thereof include lead-containing sludge discharged from factories that discharge the lead-containing wastewater, or lead-containing sludge that has been processed from lead-containing wastewater discharged from these factories.
Moreover, the lead content contained in the sludge is not particularly limited.

[Treatment method of lead-containing sludge]
The first aspect of the present invention is a lead-containing sludge comprising a step (b) of adding solid acid to lead-containing sludge to adjust the pH to 1.3 or less and solidifying a precipitate containing lead sulfate as a solid phase. It is a processing method.

A specific processing method according to the first aspect of the present invention will be described.
Lead-containing sludge is put into an appropriate amount of water, and while stirring, concentrated sulfuric acid is added to adjust the liquidity to pH 1.3 or less. Here, the “appropriate amount” is an amount in a state where a stirring operation can be performed, and the amount of water is not particularly limited as long as stirring can be performed. Further, when the lead-containing sludge is in a slurry state, water may not be required.
After the pH adjustment, the mixture is stirred at room temperature for 1 hour, and insoluble components such as lead sulfate are solid-liquid separated. If necessary, the insoluble components are washed with water to recover sludge (lead sulfate).

This method is simple and economical because it mainly separates insoluble components as described above, and can efficiently recover lead from a large amount of low-content lead-containing sludge, which is industrially suitable.
Moreover, the filtrate obtained by the separation operation of the insoluble component contains sulfates of heavy metals (for example, iron, aluminum, etc.), and lead described later as the filtrate as it is or as the filtrate is concentrated. Since it can be reused as a coagulant for the treatment of contained wastewater, the method of the present invention is in line with recent environmental measures without generating new waste, and is a social reduction of waste by recycling. It matches the trend.

In step (b) of the present invention, sulfuric acid is added to the lead-containing sludge to adjust the liquidity to pH 1.3 or less.
Preferably, sulfuric acid is added to the above-mentioned lead-containing sludge with stirring to adjust the liquidity to pH 1.3 or less, followed by further stirring. By stirring, the inside of the system can be made uniform and the pH can be adjusted accurately. When stirring is difficult, an appropriate amount of a solvent such as water can be added as appropriate.

The amount of sulfuric acid used is not particularly limited as long as the liquidity in the system after the addition of sulfuric acid is pH 1.3 or less, preferably 1.2 or less, the amount of lead-containing sludge treated, the amount of lead contained in it It can be arbitrarily adjusted depending on the content. By adjusting the pH to 1.3 or less, sulfates and lead sulfates of heavy metals (for example, iron, aluminum, etc.) other than lead contained in the sludge can be reliably separated. When the pH is 1.5 or more, the dissolution of heavy metals other than lead becomes insufficient and the separation from lead may be poor.
In the case of stirring after pH adjustment, the stirring time is preferably 0.2 hours or more, and more preferably 1 to 2 hours. Within this range, the formation of lead sulfate and the dissolution of sulfates of heavy metals other than lead are reliably performed, and the separation ability of these metals is excellent.
Although processing (stirring) temperature is not specifically limited, About normal temperature-about 50 degreeC are preferable.

  The sulfuric acid is not particularly limited, and concentrated sulfuric acid, dilute sulfuric acid and the like can be used. The sulfuric acid having a concentration of 10 to 50% by mass is preferable because of high reactivity such as formation of lead sulfate. As long as they do not affect the above-mentioned metal separation ability, industrial sulfuric acid, sulfuric acid recovered in various steps, and the like can be used.

A method for solid-liquid separation of insoluble components is not particularly limited, and a commonly performed method, for example, gravity sedimentation methods such as various filtrations and dehydration, specific gravity separation methods, and the like can be used.
In addition, if the 1st aspect of this invention is a method containing the said process (b), other processes, for example, a water washing process, another impurity removal process, etc. may be included.

  Moreover, metal salts, such as iron sulfate and aluminum sulfate contained in the filtrate at the time of solid-liquid separation, remain in the sludge (lead sulfate) obtained in the step (b). If it is not desirable to contain these metal salts in the recovered sludge (lead sulfate), the sludge (lead sulfate) can be recovered with higher purity and efficiency by changing the conditions of the separation method in step (b). You can also Examples of such methods include, but are not limited to, a method of washing lead sulfate with a large amount of water after separation of insoluble components, a method of using a filtration device having a strong drainage power, and the like. .

The filtrate in step (b) contains a metal sulfate used as a coagulant for lead-containing wastewater, for example, ferric sulfate, aluminum sulfate, etc. In a concentrated state, it can be reused as a wastewater treatment agent.
Thereby, the filtrate of the said process (b) shows the effect as a waste-water-treatment agent.
Moreover, even if lead is contained in the filtrate of the step (b), if the filtrate is reused as a wastewater treatment agent as described above, lead in the filtrate may be discharged out of the system. In addition, since it is not necessary to remove lead in the filtrate, it is useful as a simple (economic) treatment method without generating new waste.

[Treatment method of lead-containing wastewater]
The second aspect of the present invention includes a step (a) of solid-liquid separation after adding a flocculant and an alkali agent to lead-containing wastewater to adjust the alkalinity, and
A lead-containing wastewater comprising the step (b) of solid-liquid separation using a precipitate containing lead sulfate as a solid phase by adding sulfuric acid to the lead-containing sludge obtained by the solid-liquid separation to adjust the pH to 1.3 or less. It is a processing method.

A specific processing method according to the second aspect of the present invention will be described with reference to FIG.
Here, FIG. 1 is a schematic flowchart showing an example of the processing method of the second aspect of the present invention.
First, an appropriate amount of a flocculant (preferably the flocculant recovered in step (b)) and an alkali agent are added to lead-containing wastewater to adjust the liquidity to about pH 7 or more. Then, it stirs at normal temperature for 1 hour, solid-liquid-separates a deposit, and a lead containing sludge is obtained (process (a)). In addition, the lead content in the filtrate is less than the above-mentioned drainage standard value.
Next, the lead-containing sludge is put into an appropriate amount of water, and while stirring, concentrated sulfuric acid is added to adjust the liquidity to pH 1.3 or less. Then, it stirs at normal temperature for 1 hour, solid-liquid-separates an insoluble component, and if necessary, this insoluble component is wash | cleaned with water, and sludge (lead sulfate) is collect | recovered (process (b)).

Preferably, the filtrate obtained in step (b) is reused as described above. As a result, the treatment method according to the second aspect of the present invention does not discharge lead in the filtrate out of the system and does not require removal of lead in the filtrate. This is a simple (economic) treatment method without causing any problems.
The method of recycling the filtrate is the same as that described in the first embodiment.

This method is simple and economical because it mainly uses solid-liquid separation, and it is industrially suitable because lead can be efficiently recovered with high purity from a large amount and low content of lead-containing wastewater.
Moreover, the filtrate obtained by the solid-liquid separation in the step (a) satisfies the lead wastewater standard and can be discharged (discarded) as it is. In discharging, it is preferable to measure pH, metal content and the like to confirm that the drainage standard is satisfied.
Furthermore, the amount of flocculant used as a wastewater treatment agent can be reduced, and sludge obtained from lead-containing wastewater can be reduced.
Furthermore, the method is in line with the recent environmental measures without generating new waste, and also meets the social trend of waste reduction by recycling.

The step (a) of the second aspect is a step of solid-liquid separation after adjusting the alkali by adding a flocculant and an alkali agent to the lead-containing wastewater.
Preferably, the flocculant and the alkali agent are added to the lead-containing wastewater with stirring, and then the liquid property is adjusted to about pH 7 or more and further stirred. By stirring, the inside of the system can be made uniform and the pH can be adjusted accurately.

The flocculant is not particularly limited, and examples thereof include ferric chloride, ferric sulfate, aluminum sulfate, and basic aluminum chloride.
A commercially available polymer flocculant can also be used as the flocculant.
These flocculants may be used alone or in combination of two or more. Among these, ferric chloride, ferric sulfate, aluminum sulfate, and basic aluminum chloride are preferable because they can be easily separated from lead in the step (b) described later.

The alkali agent is not particularly limited as long as it is an alkali compound other than calcium, barium or the like, or a solution thereof, which is combined with sulfate ions to become a solid.
The alkaline compound is not particularly limited as long as it is a compound that forms lead hydroxide, and examples thereof include hydroxides such as sodium hydroxide, potassium hydroxide, and magnesium hydroxide. An aqueous solution may be mentioned. An alkaline agent may be used independently and may be used in combination of 2 or more types.
As these alkali agents, industrial ones and those recovered in various steps can be used as long as they do not affect the metal separation ability.

The amount of the alkali agent used is not particularly limited as long as the liquidity in the system after addition of the alkali agent is about pH 7 or more, preferably about 9 or more. The capacity of lead-containing wastewater to be treated and the lead contained therein It can be arbitrarily adjusted depending on the content of. By adjusting the pH to about 7 or more, the flocculant and lead hydroxide of the wastewater can be reliably separated from the wastewater. If the pH is less than about 7, the production of lead hydroxide, which is an insolubilized product, tends to be insufficient, and the amount of lead recovered tends to decrease, and the solid-liquid separated filtrate cannot be discharged. The pH need not be strictly adjusted, and may be neutral, preferably alkaline.
In the case of stirring after pH adjustment, the stirring time is preferably 0.5 hours or more, and more preferably 1 to 1.5 hours.
Although processing (stirring) temperature is not specifically limited, About normal temperature-about 50 degreeC are preferable.

The method for solid-liquid separation is not particularly limited, and a commonly performed method, for example, various types of filtration separation, gravity sedimentation method such as dehydration, specific gravity separation method and the like can be used.
In addition, although the state of the lead containing sludge obtained by solid-liquid separation is a slurry form or a dehydrated sludge form normally, it is not limited to these.

  In addition, as long as the 2nd aspect of this invention is a method containing the said process (a) and (b), another process, for example, a water washing process, another impurity removal process, etc. may be included.

Step (b) is basically the same as described in the first embodiment.
Further, as described above, the filtrate obtained by solid-liquid separation in the step (b) can be reused as a flocculant for treatment of lead-containing wastewater. That is, it is preferable to use the filtrate obtained by the solid-liquid separation in the step (b) as the flocculant in the step (a).

A third aspect of the present invention is a method for treating lead-containing wastewater, which comprises adding a flocculant and an alkali agent to the lead-containing wastewater to adjust it to alkalinity, followed by solid-liquid separation, and discharging the resulting filtrate ( c) and the lead-containing sludge obtained by solid-liquid separation, sulfuric acid is added to adjust the pH to 1.3 or lower, and the precipitate containing lead sulfate is solid-liquid separated as a solid phase to recover lead sulfate. The step (d) and the filtrate obtained by solid-liquid separation in the step (d) or a concentrate thereof are added to another lead-containing wastewater as a flocculant and adjusted to be alkaline, and then obtained by solid-liquid separation. This is a cycle treatment method for lead-containing wastewater, characterized in that the step (e) for discharging the filtrate is sequentially performed, and then the step (d) and the step (e) are alternately repeated.
In discharging, it is preferable to measure pH, metal content and the like to confirm that the drainage standard is satisfied.

  In the present invention, the metal sulfate contained in the filtrate obtained by the above steps (b) and (d) can be reused as a flocculant. In this case, the ease of operation of each step, the separation ability of lead, and the third It was made by finding that it can be continuously processed without affecting the characteristics of the embodiment.

A particularly preferred treatment method of the third aspect of the present invention will be specifically described with reference to FIG.
Here, FIG. 2 is a schematic flowchart showing a preferred example of the processing method of the third aspect of the present invention.
First, an appropriate amount of an aggregating agent and an alkali agent are added to lead-containing wastewater to adjust the liquidity to about pH 7 or more. Then, it stirs at normal temperature for 1 hour, solid-liquid separation lead containing sludge is obtained, and a filtrate is discharged (discarded) (process (c)).
Next, the lead-containing sludge is put into an appropriate amount of water, and while stirring, concentrated sulfuric acid is added to adjust the liquidity to pH 1.3 or less. Then, it stirs at normal temperature for 1 hour, solid-liquid-separates an insoluble component, this is wash | cleaned with water, and sludge (lead sulfate) is obtained (process (d), 1st round completion).

Further, the filtrate is put into another new lead-containing wastewater, and an alkali agent is added to adjust the liquid property to about pH 7 or more. The lead-containing sludge is obtained in the same manner as in step (c), and the filtrate is discharged (discarded) (step (e)). Subsequently, step (d) is performed using the sludge to obtain lead sulfate (end of the second round).
Further, the step (e) and the step (d) are alternately repeated, and the processing cycle is performed until the n-th round.

The filtrate obtained by the separation in the step (d) can be reused as a flocculant for treatment of lead-containing wastewater described later.
Moreover, the filtrate obtained by the solid-liquid separation in the above steps (c) and (e) satisfies the lead wastewater standard and can be discharged (discarded) as it is. In discharging, it is preferable to measure pH, metal content and the like to confirm that the drainage standard is satisfied.

This method is simple and economical because it mainly uses solid-liquid separation, and it is industrially suitable because lead can be efficiently recovered with high purity from a large amount and low content of lead-containing wastewater.
Furthermore, the amount of flocculant used as a wastewater treatment agent can be reduced, and sludge obtained from lead-containing wastewater can be reduced.
Furthermore, the method is in line with the recent environmental measures without generating new waste, and also meets the social trend of waste reduction by recycling.
In particular, the method is particularly suitable as an industrial processing method because it can be continuously processed and automatic control is easy.

Step (c) is basically the same as step (a) above.
As described above, the lead content in the filtrate of the step (a) is less than the above-mentioned drainage standard value and can be discharged.

  Step (d) is basically the same as step (b) above, but the lead-containing sludge used is obtained in step (c) (first round) and step (e). Is different (after the second round).

The step (e) is basically the same as the step (a), but is different from the lead-containing wastewater used in the step (a) (already treated at the step (e)). The difference is that a lead-containing wastewater is used, and the filtrate obtained by the step (d) or the concentrate thereof is used as a flocculant.
The content of the flocculant in the filtrate obtained by solid-liquid separation in step (d) is because the flocculant adheres to the lead-containing sludge or is discharged as a filtrate, and the content decreases. When the amount of other new lead-containing wastewater is not sufficient, usually, a slight amount of the flocculant described in the step (a) can be added.

In this method, by repeating step (d) and step (e) alternately, it is possible to treat lead-containing wastewater continuously, and automatic control is also possible, which is industrially suitable.
By this method, a closed system capable of continuous processing is constructed without fear of discharging lead from the processing system.

  In addition, if the 3rd aspect of this invention is a method containing the said process (c)-(e), it may also include another process.

In addition, the apparatus used with the processing method of the 1st-3rd aspect of this invention is not specifically limited, A general apparatus can be used.
For example, for pH adjustment and the like, various reaction tanks, mixing tanks, stirring devices and the like can be mentioned, and for solid-liquid separation, various membrane separation devices used for gravity sedimentation method, specific gravity separation method and the like can be mentioned. It is done.

  The method for treating lead-containing wastewater and lead-containing sludge according to the present invention is suitable for a factory that discharges lead-containing wastewater and lead-containing sludge, such as a lead chemical factory, a lead smelter, a battery factory, and a waste battery treatment factory. Available.

[Flocculant for wastewater treatment]
A fourth aspect of the present invention is a flocculant for wastewater treatment containing a filtrate obtained by solid-liquid separation in the above step (b) or step (d) or a concentrate thereof.
The form of the filtrate and concentrate is not particularly limited, and may be, for example, liquid, dry solid, or dry powder.
The use of the filtrate or the concentrate thereof is not particularly limited, and is suitable as a flocculant for treating industrial wastewater, particularly lead-containing wastewater.

  The flocculant for wastewater treatment is inexpensive and can be suitably used industrially, and when used in the method for treating lead-containing wastewater or sludge according to the present invention, the amount of the flocculant used and the volume of sludge can be reduced. Continuous processing is possible without generating new waste.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

The lead-containing wastewater was treated using the above-described method for treating lead-containing wastewater of the present invention.
The operation process performed in the Example of this invention is shown in FIG.

<Example 1>
Lead-containing wastewater containing 30 mg / L of metallic lead is added to the mixing tank 1, and an appropriate amount of flocculant (ferric chloride 150 mg / L, aluminum sulfate 10 mg / L) and 20% sodium hydroxide aqueous solution as an alkali agent are added. The liquidity was adjusted to about pH 8. Thereafter, the mixture was stirred at room temperature for about 0.5 hours, and solid-liquid separation was performed with thickener 1 to obtain lead-containing sludge I (solid content 40 g / L) (step (a)).
Next, the lead-containing sludge I was put into the mixing tank 2, and 50% sulfuric acid was added with stirring to adjust the liquidity to pH 1.0. Thereafter, the mixture was stirred at room temperature for 1 hour, and the insoluble components were separated into solid and liquid by thickener 2, and dehydrated sludge sludge (lead sulfate) I (water content 60%) and sulfuric acid-dissolved filtrate I were obtained (process). (B)).

  Since the sulfuric acid solution I contains iron sulfate and aluminum sulfate, it was recovered as a flocculant for wastewater treatment.

  As a separate step, water was added to slurry-like lead sulfate I in an amount 6 times the volume of the slurry, and after stirring, allowed to stand for natural sedimentation to remove the supernatant. When this precipitate was filtered, washed lead sulfate I (water content 60%) having a lead sulfate content of 51% could be recovered as sludge.

  Moreover, the sulfuric acid solution filtrate I and sodium hydroxide which were obtained in the mixing tank 3 were thrown in, and it adjusted to pH8.5. Then, it stirred at normal temperature for 0.5 hour, the crystal component which precipitated was filtered with the filter, and the filtrate IV and the neutralization deposit IV were obtained.

For each of the lead-containing sludge I, sludge (lead sulfate) I, sulfuric acid-dissolved filtrate I and washed lead sulfate I obtained by the above wastewater treatment method, the content of lead, iron, and aluminum (content in the total volume) The mass (g / L or mg / L) or the content (% by mass in the total solid content) was measured. Moreover, about filtrate IV, content of lead, iron, and aluminum (content in total capacity, mg / L) was measured.
The results are shown in Table 1. In Table 1, “-” indicates that the content of the corresponding metal could not be detected.

As shown in Table 1, the lead-containing sludge I contains a large amount of iron and aluminum. However, according to the method of the present invention, lead sulfate can be efficiently recovered as sludge having a high lead sulfate content and high purity with a simple process (sludge (lead sulfate) I).
Further, since iron and aluminum in the sludge (lead sulfate) I remain as sulfate in the water remaining in the sludge (lead sulfate) I, the separation method in step (b) is changed. It was possible to recover lead sulfate with higher purity and efficiency (washed lead sulfate I).
In addition, sludge (lead sulfate), washed lead sulfate, and dewatered sludge (cake) in Tables 1 to 4 indicate dry weight%. The other is the concentration display in slurry (moisture). The lead concentration of the dehydrated sludge (cake) II obtained by dehydrating the lead-containing sludge I is 12% (dry basis), and the lead concentration of the washed lead sulfate I treated by the step (b) of the present invention is 51% (dry basis). The amount of sludge generated was reduced to about 1/4.
Further, by neutralizing the sulfuric acid-dissolved filtrate, the lead content contained in the filtrate IV is set to the wastewater standard value 0. 0 defined in Article 3 paragraph 1 and Article 12 of the Water Pollution Control Law. It could be 1 mg / L or less. In addition, the solubility of lead sulfate is 40 mg / L at normal temperature and neutral conditions.

<Example 2>
Using the dehydrated sludge II obtained by further dehydrating the lead-containing sludge I and an appropriate amount of water, the pH of the step (b) is adjusted to 1.3, and the treatment is performed in the same manner as in Example 1 to obtain sludge (lead sulfate). II and sulfuric acid dissolved filtrate II were obtained.

About each of dehydrated sludge II, lead sulfate II, and sulfuric acid dissolution filtrate II obtained by the above wastewater treatment method, the content of lead, iron, and aluminum (content mass g / L or mg / L in the total volume) ) Or content (% by mass in the total solid content).
The results are shown in Table 2.

  Even when the pH of step (b) of the present invention was adjusted to 1.3, the same effect as in Example 1 was achieved by the method of the present invention.

<Example 3>
To lead-containing wastewater containing 25 mg / L of metallic lead, an appropriate amount of a flocculant (ferric chloride, a polymer flocculant (anionic acrylamide flocculant)) and an alkali agent are added, and the step (a) of Example 1 is performed. In the same manner, lead-containing sludge III was obtained.
Next, the lead-containing sludge III was put into an appropriate amount of water, and 50% sulfuric acid was added with stirring to adjust the liquidity to pH 1.2. Then, it carried out similarly to the process (b) of Example 1, and obtained the cake-form sludge (lead sulfate) III and the sulfuric acid dissolution filtrate III (process (b)).

For each of the lead-containing sludge III, the sludge (lead sulfate) III, and the sulfuric acid-dissolved filtrate III obtained by the above wastewater treatment method, the lead and iron contents (content mass g / L or mg / L in the total volume) L) or content (mass% in the total solid content) was measured.
The results are shown in Table 3.

  Even when the polymer flocculant was used, the same effect as in Example 1 was achieved by the method of the present invention.

<Example 4>
An appropriate amount of flocculant (ferric sulfate, aluminum sulfate) and 20% aqueous caustic soda solution as an alkaline agent were added to lead-containing wastewater V containing 30 mg / L of metallic lead to adjust the liquidity to about pH 8 or more. Then, it stirred at normal temperature for about 0.5 hour, solid-liquid-separated with the thickener, the lead containing sludge V was obtained, and the filtrate was discharged | emitted (discarded) (process (c)). During discharge, the pH was adjusted to neutral, the metal content was measured, and it was confirmed that the drainage standards were satisfied.
Next, the lead-containing sludge V was put into an appropriate amount of water, and while stirring, 50% sulfuric acid was added to adjust the liquidity to pH 1.0. Thereafter, the mixture was stirred at room temperature for 1 hour, and the insoluble components were separated into solid and liquid by a thickener to obtain dry dewatered sludge-like sludge (lead sulfate) V (step (d), completion of the first round).

  To another lead-containing wastewater VI containing 30 mg / L of metallic lead, the filtrate V obtained above and a deficient flocculant (ferric sulfate, aluminum sulfate) are added, and an alkali agent is further added to make the solution liquid. Was adjusted to about pH 8 or higher. Then, it stirred at normal temperature for about 0.5 hour, solid-liquid-separated with the thickener, the lead containing sludge VI was obtained, and the filtrate was discharged | emitted (discarded) (process (e)). In addition, at the time of discharge, the pH was similarly adjusted to neutral, and the metal content was measured to confirm that the drainage standards were satisfied.

  Subsequently, the lead-containing sludge VI was put into an appropriate amount of water, and while stirring, 50% sulfuric acid was added to adjust the liquidity to pH 1.0. Thereafter, the mixture was stirred at room temperature for 1 hour, and insoluble components were solid-liquid separated by a thickener to obtain dry dewatered sludge-like sludge (lead sulfate) VI (step (d), completion of the second round).

For each of lead-containing sludges V and VI, sulfuric acid-dissolved filtrates V and VI, and lead sulfate V and lead sulfate VI obtained by the above method, the content of lead and iron (mass content g / L or mg / L) or content (mass% in total solids) was measured.
The results are shown in Table 4.

本発明のサイクル処理方法においても、実施例１と同様の結果が得られた。

In the cycle processing method of the present invention, the same result as in Example 1 was obtained.

In other words, this method enables efficient recovery of lead with high purity and high purity in a simple process, and further reduces the amount of flocculant used as a wastewater treatment agent without generating new waste. The volume of sludge obtained from lead-containing wastewater can be reduced.
In particular, a closed system that can be continuously processed, can be automatically controlled, and is suitable as an industrial processing method has been constructed.
Moreover, the same effect was demonstrated also in the 2nd round using the filtrate obtained by the process (d), and this filtrate was suitable as a flocculant for a process of industrial wastewater, especially lead-containing wastewater.

The following effects were obtained by the method for treating lead-containing wastewater and lead-containing sludge of the present invention.
1) The total amount of sludge produced by the above method is small compared to the amount of sludge produced by the hydroxide coprecipitation method of lead, iron, etc. The volume of sludge is reduced (specifically, the volume ratio is 1 / 3 to 1/10).
2) Lead sulfate can be recovered with a high content. The content of lead sulfate in the treated sludge (lead sulfate) is 30 to 50% by mass.
3) In addition to the waste generated by the hydroxide coprecipitation method, no new waste is generated.
4) The sulfuric acid dissolved filtrate can be reused as a wastewater treatment agent for ferric sulfate.
5) Since the method of the present invention has the above-mentioned effects, it is suitable for an industrial scale.

<Measurement of metal content in lead-containing sludge, lead sulfate V, and various filtrates>
The analysis method of each metal was performed by the JIS K0102 factory wastewater test method.

<Purity measurement of lead sulfate>
FIG. 4 shows the result of analyzing the components of sludge (lead sulfate) I obtained in Example 1 by X-ray analysis (continuous scanning method (2θ / θ method)).
As is clear from FIG. 4, in the sludge (lead sulfate), aluminum hydroxide, lead hydroxide, aluminum sulfate and iron sulfate were not detected, and the main constituent was lead sulfate.
The measurement conditions are shown below.
Measurement range (2θ): 5 to 80 deg, tube voltage: 40 kV,
Tube current: 150 mA, radiation source: Cu, sampling width: 0.02 deg,
Scanning speed: 4.0 deg / min, DS, SS: 1.0 deg,
RS = 0.15mm, using counter monochromator

FIG. 1 is a schematic flowchart showing an example of the processing method according to the second aspect of the present invention. FIG. 2 is a schematic flowchart showing a preferred example of the processing method according to the third aspect of the present invention. It is a figure showing the operation process performed in the Example of this invention. It is a figure which shows the analysis result by the X-ray analysis of lead sulfate.

Claims (2)

A step (a) for solid-liquid separation after adding a flocculant and an alkali agent to lead-containing wastewater to adjust to alkalinity;
A step (b) of solid-liquid separation using a precipitate containing lead sulfate as a solid phase by adding sulfuric acid to the lead-containing sludge obtained by the solid-liquid separation in the step (a) to adjust the pH to 1.3 or less; Including
A method for treating lead-containing wastewater, wherein a filtrate obtained by solid-liquid separation in the step (b) or a concentrate thereof is used as a flocculant in the step (a). A method for treating lead-containing wastewater,
A step (c) of adding a flocculant and an alkali agent to lead-containing wastewater to adjust it to alkalinity, followed by solid-liquid separation, and discharging the obtained filtrate;
The lead-containing sludge obtained by the solid-liquid separation in the step (c) is added with sulfuric acid to adjust the pH to 1.3 or less, and the precipitate containing lead sulfate is solid-liquid separated as a solid phase to recover lead sulfate. Step (d);
The filtrate obtained by the solid-liquid separation in the step (d) or the concentrate thereof is added to another lead-containing wastewater as a flocculant, further adjusted to be alkaline by adding an alkali agent, and then subjected to solid-liquid separation to obtain a filtrate. A step (e) of discharging the liquid;
The lead-containing wastewater cycle treatment method is characterized in that the steps (d) and (e) are repeated alternately in order.

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