JP6891653B2 - Wastewater purification agent for heavy metal-containing aqueous solution - Google Patents

Description

The present invention relates to a wastewater purifying agent for a heavy metal-containing aqueous solution composed of a compound having a ability to form a complex with a heavy metal and a polyamine compound suitable for removing heavy metals from an aqueous solution containing the heavy metal.

The aqueous solution containing heavy metals is sent to a wastewater treatment facility, for example, iron ions are added to make it alkaline, and heavy metal ions and the like are precipitated as hydroxides together with iron ions and other contained ions. Methods such as discharging after separation have been carried out.

By the way, organic acids such as citric acid and gluconic acid and ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA) are used for wastewater from plating factories, electronic parts / mechanical parts manufacturing factories, automobile factories, thermal power plants, waste incineration plants, etc. , Cyan, amine, ammonia, polyphosphoric acid, and other compounds that have the ability to form complex with heavy metals are included, and there are many cases where they cannot be treated by the hydroxide method as described above.

On the other hand, there is known a method of insolubilizing a heavy metal after chemically treating a compound having a complex forming ability with a heavy metal. However, even if chemical treatments such as an oxidation method using a chlorine-based agent, an electrolytic oxidation method, a hydrogen peroxide-ferrous iron salt method, an ozone oxidation method, and a wet oxidation method are used, the oxidation reaction is inhibited by coexisting substances. Due to problems such as scale generation, sufficient purification treatment cannot be performed.

Techniques for removing various heavy metal elements contained in wastewater include, for example, a coagulation separation removal method by adding an inorganic coagulant or an organic coagulant, a removal method by electrodialysis, adsorption by activated carbon, an inorganic adsorbent or an organic polymer material. A removal method, a dry solidification method in which wastewater is heated and evaporated, a reverse osmosis method using a membrane, an electrodialysis or an ultrafiltration method and the like have been proposed.

Even when the above-mentioned methods were used, there were many problems such as the following, and all the methods needed improvement. For example
(1) Heavy metals cannot be sufficiently treated by the coagulation separation and removal method.
(2) In the adsorption removal method, even if heavy metals can be adsorbed, a large amount of solid components are generated after the treatment.
(3) The reverse osmosis method, electrodialysis, ultrafiltration method, etc. are difficult to remove if organic substances are contained in the wastewater, and the treatment cost is high.
(4) The dry-drying method by heating and evaporation is complicated and expensive.
And so on.

By the way, nickel is a harmful heavy metal designated as a Class 1 designated chemical substance in the Chemical Substance Emission Control Promotion Law, and is set as a monitoring item in the environmental standard for water pollution, and the importance of wastewater treatment is important. It is increasing.
A method of using a salt of dithiocarbamic acid as a heavy metal treatment agent for an aqueous solution containing a heavy metal has been proposed (see, for example, Patent Documents 1 and 2). However, the methods described in these patent documents do not have a sufficient effect of purifying the heavy metal from nickel-containing wastewater containing a compound having a complex formation ability with nickel.

Japanese Patent No. 3271621 Patent No. 6044160

The present invention has been made in view of the above background technology, and an object of the present invention is a compound having a ability to form a complex with a heavy metal, a purifying agent for reducing the heavy metal concentration of an aqueous solution containing a heavy metal, and a heavy metal using the same. The present invention is to provide a method for purifying a contained aqueous solution.

As a result of diligent studies to solve the above problems, the present inventors have made it easy to determine the heavy metal concentration of a polyamine compound having a specific structure, a compound having a ability to form a complex with a heavy metal, and an aqueous solution containing a heavy metal. We have found that it can be reduced, and have completed the present invention.

That is, the present invention has the following gist.

[1] A wastewater purification agent for a heavy metal-containing aqueous solution composed of a polyamine compound containing a structural unit represented by the following formulas (I), (II), and (III).

[In the formula, X represents hydrogen, alkali metal, or alkaline earth metal, and R represents a hydrocarbon group. ],

[However, the total of the structural units (I) and (II) is 40 to 70 mol% with respect to the total of the structural units (I), (II), and (III), and the total is with respect to the structural unit (I). , The molar ratio of the structural unit (II) is 2-9. ]
[2] A method for purifying a heavy metal-containing aqueous solution, which comprises adding the wastewater purification agent according to the above [1] to the heavy metal-containing aqueous solution and then removing the produced solid matter.

[3] The purification method according to the above [2], wherein the heavy metal-containing aqueous solution contains a compound having an ability to form a complex with a heavy metal.

[4] The purification method according to the above [3], wherein the compound having an ability to form a complex with a heavy metal is a compound having a functional group selected from the group consisting of a carboxy group and an amino group in the molecule.

[5] The purification method according to any one of the above [2] to [4], which comprises adding an inorganic flocculant before removing the produced solid matter.

[6] The purification method according to any one of the above [2] to [5], wherein an inorganic flocculant and a polymer flocculant are added before removing the produced solid matter.

[7] The purification method according to the above [5] or [6], wherein the inorganic flocculant is selected from the group consisting of an iron compound and an aluminum compound.

The wastewater purifying agent for a heavy metal-containing aqueous solution of the present invention reduces the heavy metal concentration even in a heavy metal-containing aqueous solution (for example, a compound having a ability to form a complex with a heavy metal and an aqueous solution containing a heavy metal) in which it is difficult to purify the heavy metal. It is extremely useful industrially because it can be used.

Hereinafter, the present invention will be described in detail.

The wastewater purification agent for a heavy metal-containing aqueous solution of the present invention comprises a polyamine compound containing structural units represented by the above formulas (I), (II), and (III). However, the total of the structural units (I) and (II) is 40 to 70 mol% with respect to the total of the structural units (I), (II), and (III), and the total of the structural units (I) is. The molar ratio of structural unit (II) is 2-9.

The quantitative relationship can be calculated, for example, by elemental analysis of oxygen atoms, sulfur atoms, and nitrogen atoms in the polyamine compound.

In the present invention, the method for synthesizing the polyamine compound is not particularly limited, and for example, a method in which a polyamine is reacted with a halogenated carboxylic acid and carbon disulfide to introduce the structural units (I) and (II) into the polyamine. Can be mentioned.

The polyamine is not particularly limited, and examples thereof include polyethyleneimines and polypropyleneimines. The weight average molecular weight of the polyamine is preferably 1800 or more in terms of improving the processing capacity of heavy metals. By setting the weight average molecular weight to 1800 or more, the amount of the drug used may be reduced.

The halogenated carboxylic acid is not particularly limited, and is, for example, chloroacetic acid, bromoacetic acid, dichloroacetic acid, dibromoacetic acid, 3-chloropropionic acid, 3-bromopropionic acid, 4-chlorobutyric acid, 4-bromobutyric acid, 5-. Examples include chloroacetic acid and 5-bromovaleric acid. Of these, chloroacetic acid and bromoacetic acid are particularly preferable in terms of heavy metal processing performance and water solubility.

The wastewater purification agent for a heavy metal-containing aqueous solution of the present invention is useful for purifying a heavy metal-containing aqueous solution.

The method for purifying a heavy metal-containing aqueous solution of the present invention is characterized by adding the above-mentioned wastewater purification agent for a heavy metal-containing aqueous solution of the present invention to a heavy metal-containing aqueous solution, and then removing the produced solid matter. Here, the produced solid contains a heavy metal immobilized by the purifying agent of the present invention.

The purification method of the present invention is particularly effective for a heavy metal-containing aqueous solution in which it is difficult to treat a heavy metal (for example, a compound having an ability to form a complex with a heavy metal, and an aqueous solution containing a heavy metal.

The compound having the ability to form a complex with a heavy metal is not particularly limited as long as it is a compound forming a complex with a heavy metal. For example, a compound having a functional group selected from the group consisting of a carboxy group and an amino group in the molecule can be mentioned. Specific examples thereof include EDTA and polyphosphoric acid, and EDTA is particularly mentioned as a compound forming a strong complex with a heavy metal.

In order to remove the solid matter quickly, it is preferable to add a flocculant before removing the solid matter. Examples of the flocculant include an inorganic flocculant, a polymer flocculant, and the like, and it is more preferable to use the inorganic flocculant and the polymer flocculant in combination.

As the inorganic flocculant, a commercially available inorganic flocculant can be used and is not particularly limited. For example, iron compounds such as ferric chloride, aluminum compounds such as aluminum sulfate and polyaluminum chloride, and the like can be mentioned.

When the heavy metal-containing aqueous solution contains a compound having the ability to form a complex with a heavy metal, the amount of the inorganic flocculant added is preferably equal to or greater than the content of the compound having the ability to form a heavy metal complex contained in the heavy metal-containing aqueous solution. By setting the addition amount of the inorganic cohesive agent to be equal to or greater than the content of the compound having the ability to form complex with heavy metals, the cohesiveness is increased and it becomes easy to sufficiently reduce the heavy metal concentration of the aqueous solution after the treatment.

For the content of the compound having the ability to form a complex with a heavy metal in the heavy metal-containing aqueous solution, the concentration of the compound having the ability to form a heavy metal complex in the heavy metal-containing aqueous solution is analyzed by, for example, HPLC, gas chromatography, titration or the like. It can be calculated by

As the polymer flocculant, a commercially available polymer flocculant can be used and is not particularly limited. For example, acrylic acid polymer, acrylamide polymer, dimethylaminoethyl methacrylate polymer and the like can be mentioned. A weak anionic acrylic acid polymer is preferable in terms of aggregation performance. By adding the polymer flocculant before removing the solid matter, the handling of the solid matter to be removed may be facilitated.

When the inorganic flocculant and the polymer flocculant are used in combination, the order in which these flocculants are added is not particularly limited, but it is preferable to add the inorganic flocculant and then the polymer flocculant.

The method for removing the solid matter is not particularly limited, and examples thereof include filtration, centrifugation, and a method in which the solid matter is settled and then separated from the supernatant liquid.

Hereinafter, the present invention will be specifically described, but the present invention is not construed as being limited to these examples.

(Analysis method)
The nickel ion concentration in the aqueous solution was measured by an ICP emission spectrophotometer (OPTIMA3300DV, manufactured by Perkin Elmer).

Preparation example 1.
The polyamine compounds used in Examples and Comparative Examples were prepared according to the following methods.

(Preparation of polyamine compound)
9.0 g of polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd.) having a weight average molecular weight of 10,000 and 73 g of pure water were mixed and stirred at 25 ° C. for 1 hour. Next, 1.5 g of bromoacetic acid (manufactured by Kanto Chemical Co., Inc.) and 13 g of 1 mol / L sodium hydroxide (manufactured by Kishida Chemical Co., Ltd.) were added, and the mixture was stirred at 60 ° C. for 6 hours and then cooled to 25 ° C. Next, 5.3 g of 48 wt% potassium hydroxide (manufactured by Kanto Chemical Co., Inc.) was mixed, stirred at 25 ° C. for 15 minutes, and then 4.4 mL of carbon disulfide (manufactured by Kishida Chemical Co., Ltd.) was added dropwise over 1 hour. The mixture was stirred for 120 minutes. Next, 3.5 g of 48% by weight potassium hydroxide was added and the mixture was stirred for 120 minutes, and then 50 g of water was added to obtain an aqueous solution containing 10% by weight of the polyamine compound.
This polyamine compound has a structural unit derived from bromoacetic acid (structural unit (I)) of 5 mol%, a structural unit derived from carbon disulfide (structural unit (II)) of 35 mol%, and a structural unit derived from unsubstituted amine (structural unit (II)). It has 60 mol% of structural unit (III)). The ratio of the total of the structural units (I) and (II) to the total of the structural units (I), (II), and (III) (hereinafter referred to as (I + II) / (I + II + III)) is 40 mol%. The molar ratio of the structural unit (II) to the structural unit (I) (hereinafter referred to as II / I) is 7.

In addition, polyamine compounds in which the mole fraction of each structural unit was changed were synthesized by increasing or decreasing the amount of bromoacetic acid and carbon disulfide added.

(Inorganic flocculant)
A 38 wt% ferric chloride aqueous solution (manufactured by Kishida Chemical Co., Ltd.) was used as the inorganic flocculant.

(Polymer flocculant)
OA-23 (weak anion polymer) manufactured by Organo Corporation was used as the polymer flocculant.

Example 1.
A 500 mL beaker was placed in a Jar Tester, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 25 mg / L of EDTA was added. Then, while stirring at 150 rpm, 2000 mg / L of the 10 wt% polyamine compound prepared in Preparation Example 1 was added, and the mixture was stirred at 150 rpm for 10 minutes. Then, 800 mg / L of a 38 wt% ferric chloride aqueous solution was added, and the mixture was stirred at 150 rpm for 5 minutes. Next, 2000 mg / L of a 0.1 wt% OA-23 aqueous solution was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. The pH of the aqueous solution was adjusted to always be pH 7 with a small amount of hydrochloric acid and sodium hydroxide. After the stirring was completed, the mixture was allowed to stand for 10 minutes, the aqueous solution was filtered off with a 5A filter paper manufactured by Advantech, and the nickel concentration of the treated aqueous solution was measured. The results are shown in Table 1.
Examples 2-5.
The nickel concentration of the aqueous solution after the treatment was measured in the same manner as in Example 1 except that the chemicals to be added were changed to the chemicals shown in Table 1. The results are shown in Table 1.

In Examples 1 to 5, the total of the structural units (I) and (II) is 40 mol% to 70 mol% with respect to the total of the structural units (I), (II), and (III), and This is an example of treatment with a polyamine compound synthesized so that the molar ratio of the structural unit (II) to the structural unit (I) is 2-9. As shown in Table 1, the nickel concentration of the aqueous solution after the treatment of the EDTA-containing wastewater was about 4 mg / L, and the nickel could be sufficiently reduced.

Comparative example 1.
A 500 mL beaker was placed in a Jar Tester, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 25 mg / L of EDTA was added. Then, 800 mg / L of a 38 wt% ferric chloride aqueous solution was added, and the mixture was stirred at 150 rpm for 15 minutes. Next, 2000 mg / L of a 0.1 wt% OA-23 aqueous solution was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. The pH of the aqueous solution was adjusted to always be pH 7 with a small amount of hydrochloric acid and sodium hydroxide. After the stirring was completed, the mixture was allowed to stand for 10 minutes, the aqueous solution was filtered off with a 5A filter paper manufactured by Advantech, and the nickel concentration of the treated aqueous solution was measured. The results are shown in Table 3.

Comparative example 2.
The nickel concentration of the aqueous solution after the treatment was measured in the same manner as in Example 1 except that the chemicals to be added were changed to the chemicals shown in Table 2. The salt A of dithiocarbamic acid is a drug having the structure of the chemical formula (IV) and is considered to be useful in heavy metal treatment. The results are shown in Table 2.

Comparative Example 1 is an example of a treatment method in which iron ions are added to neutralize and nickel ions are precipitated as a hydroxide together with iron ions. The nickel concentration of the aqueous solution after the treatment was 7 mg / L or more, and nickel could not be sufficiently reduced.

Comparative Example 2 is an example in which a salt A of dithiocarbamic acid, which is a known heavy metal treatment agent, is added instead of the polyamine compound. The nickel concentration of the aqueous solution after the treatment was 7 mg / L or more, and nickel could not be sufficiently reduced.

Comparative Examples 3 to 5.
The nickel concentration of the aqueous solution after the treatment was measured in the same manner as in Example 1 except that the chemicals to be added were changed to the chemicals shown in Table 3. The results are shown in Table 3 below.

Comparative example 6.
A 500 mL beaker was placed in a Jar Tester, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 25 mg / L of EDTA was added. Then, while stirring at 150 rpm, two kinds of 10 wt% polyamine compounds shown in Table 4 were added at 1000 mg / L without delay, and the mixture was stirred at 150 rpm for 10 minutes. Then, 800 mg / L of a 38 wt% ferric chloride aqueous solution was added, and the mixture was stirred at 150 rpm for 5 minutes. Next, 2000 mg / L of a 0.1 wt% OA-23 aqueous solution was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. The pH of the aqueous solution was adjusted to always be pH 7 with a small amount of hydrochloric acid and sodium hydroxide. After the stirring was completed, the mixture was allowed to stand for 10 minutes, the aqueous solution was filtered off with a 5A filter paper manufactured by Advantech, and the nickel concentration of the treated aqueous solution was measured. The results are shown in Table 3.

Comparative Example 3 is an example of treatment with a polyamine compound containing no structural unit derived from bromoacetic acid (structural unit (I)) and structural unit derived from carbon disulfide (structural unit (II)). There was no change in nickel concentration before and after the treatment, and the treatment was not completed.

Comparative Example 4 is an example of treatment with a polyamine compound containing no structural unit (structural unit (II)) derived from carbon disulfide. There is no change in nickel concentration before and after the treatment, indicating that the structural unit (II) is indispensable in the nickel treatment.

Comparative Example 5 is an example of treatment with a polyamine compound containing no structural unit (structural unit (I)) derived from bromoacetic acid. The nickel concentration after the treatment is as low as 6.3 mg / L, and it can be seen that the structural unit (I) contributes to the improvement of the treatment ability.

Comparative Example 6 is an example in which the polyamine compounds of Comparative Examples 4 and 5 were mixed and treated. The nickel concentration after the treatment was 6.9 mg / L, and the nickel could not be sufficiently reduced.

Comparative Examples 7-9.
The nickel concentration of the aqueous solution after the treatment was measured in the same manner as in Example 1 except that the chemicals to be added were changed to the chemicals shown in Table 4. The results are shown in Table 4.

Comparative Example 7 is an example of treatment with a polyamine compound in which the molar ratio of the structural unit (II) to the structural unit (I) is smaller than 2. The nickel concentration of the aqueous solution after the treatment of the EDTA-containing wastewater was 4.7 mg / L.

Comparative Example 8 is an example of treatment with a polyamine compound in which the molar ratio of the structural unit (II) to the structural unit (I) is larger than 9. The nickel concentration of the aqueous solution after the treatment of the EDTA-containing wastewater was 4.9 mg / L.

Comparative Example 9 is an example in which the total of the structural units (I) and (II) is treated with a polyamine compound in which the total of the structural units (I), (II), and (III) is 80 mol% with respect to the total of the structural units (I), (II), and (III). The nickel concentration of the aqueous solution after the treatment of the EDTA-containing wastewater was 5.2 mg / L.

According to the purifying agent for a heavy metal-containing aqueous solution containing a reactant of the present invention and the purification method using the purifying agent, the heavy metal is difficult to treat, the compound having a heavy metal complexing ability, and the aqueous solution containing the heavy metal. However, since the concentration of heavy metals can be reduced, it has the potential to be used as a new method for purifying heavy metal-containing aqueous solutions, as a method for treating heavy metal-containing wastewater from plating factories, electronic parts / mechanical parts manufacturing factories, automobile factories, etc. ing.

Claims (7)

A wastewater purification agent for a heavy metal-containing aqueous solution composed of a polyamine compound containing a structural unit represented by the following formulas (I), (II), and (III).

[In the formula, X represents hydrogen, alkali metal, or alkaline earth metal, and R represents a hydrocarbon group. ],

[However, the total of the structural units (I) and (II) is 40 to 70 mol% with respect to the total of the structural units (I), (II), and (III), and the total is with respect to the structural unit (I). , The molar ratio of the structural unit (II) is 2-9. ] A method for purifying a heavy metal-containing aqueous solution, which comprises adding the wastewater purification agent according to claim 1 to the heavy metal-containing aqueous solution and then removing the produced solid matter. The purification method according to claim 2, wherein the heavy metal-containing aqueous solution contains a compound having an ability to form a complex with a heavy metal. The purification method according to claim 3, wherein the compound having an ability to form a complex with a heavy metal is a compound having a functional group selected from the group consisting of a carboxy group and an amino group in the molecule. The purification method according to any one of claims 2 to 4, wherein an inorganic flocculant is added before removing the produced solid matter. The purification method according to any one of claims 2 to 5, wherein an inorganic flocculant and a polymer flocculant are added before removing the produced solid matter. The purification method according to claim 5 or 6, wherein the inorganic flocculant is selected from the group consisting of an iron compound and an aluminum compound.