JP6969076B2 - Purifying agent for heavy metal-containing aqueous solution, and method for purifying heavy metal-containing aqueous solution - Google Patents

Description

The present invention relates to a purifying agent that makes it possible to remove the heavy metal from an aqueous solution containing a heavy metal such as zinc and cadmium, and a method for purifying the heavy metal-containing aqueous solution using the same.

An aqueous solution containing heavy metals such as zinc and cadmium is sent to a wastewater treatment facility, for example, iron ions are added to make it alkaline, and zinc ions, cadmium ions and the like are precipitated as hydroxides together with iron ions and other contained ions. A method has been used in which a treatment such as cadmium is performed, the solution is separated from the aqueous solution, and then the solution is discharged.

The effluent standard for zinc content was previously set at 5 mg / L, but the effluent standard has been strengthened from the viewpoint of aquatic organism conservation, and was changed to 2 mg / L in 2006. However, 5 mg / L has been applied as a provisional effluent standard to specific business establishments belonging to 10 industries in which it is extremely difficult to comply with the uniform effluent standard. In recent years, the zinc effluent standard of 2 mg / L has been required.

In addition, since cadmium is a very harmful heavy metal, in recent years, 0.03 mg / L or less has been required as a wastewater standard, and the importance of wastewater treatment is increasing.

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, sulfuric acid, polyphosphate and other heavy metals such as zinc and cadmium and compounds having complex formation ability are included, and there are many cases where purification treatment cannot be performed by the above-mentioned hydroxide method.

On the other hand, there is known a method of chemically treating a compound having a complex formation ability with a heavy metal such as zinc and cadmium, and then insolubilizing these heavy metals. However, even if chemical treatments such as an oxidation method using a chlorine-based chemical, 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 due to the coexisting heavy metal elements can be carried out. Due to problems such as inhibition and 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 method, 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 of them needed improvement. for example,
(1) Zinc cannot be sufficiently treated by the coagulation separation and removal method.
(2) In the adsorption removal method, even if zinc can be adsorbed, a large amount of solid components are generated after the treatment.
(3) In the reverse osmosis method, electrodialysis, ultrafiltration method, etc., it is difficult to remove organic substances if they are contained in the wastewater, and the treatment cost is high.
(4) In the dry solidification method by heating and evaporation, the treatment method is complicated and the treatment cost is high.
And so on.

By the way, a method of using a salt of dithiocarbamic acid as a heavy metal treating agent in wastewater has been proposed (see, for example, Patent Documents 1 to 4). However, the methods described in these patent documents do not have a sufficient effect of purifying the heavy metal from the heavy metal-containing wastewater containing a compound having a complex formation ability with the heavy metal.

Further, a heavy metal treatment agent containing a polyamine having three or more amino groups in the molecule and a carbodithioate salt of the amine has been proposed (see, for example, Patent Document 5). However, the method disclosed in Patent Document 5 is insufficient in the purifying effect of heavy metals such as zinc and cadmium.

JP-A-2009-249399A Japanese Unexamined Patent Publication No. 2011-074350 Japanese Unexamined Patent Publication No. 2014-08477 JP-A-2002-177902. Japanese Unexamined Patent Publication No. 2008-273995

The present invention has been made in view of the above problems, and an object thereof is to provide a purifying agent for an aqueous solution containing heavy metals such as zinc and cadmium, and to purify a heavy metal-containing aqueous solution using the same. To provide.

As a result of diligent studies to solve the above problems, the present inventors have found a purifying agent for a heavy metal-containing aqueous solution of the present invention and a method for purifying a heavy metal-containing aqueous solution using the same, and complete the present invention. It came to.

That is, the present invention has the following gist.

[1] A purifying agent for a heavy metal-containing aqueous solution containing 2 to 50 parts by weight of a polyamine having a weight average molecular weight of 300 or more with respect to 100 parts by weight of a salt of dithiocarbamic acid.

[2] A reaction product of an amine compound in which a salt of dithiocarbamic acid has at least one amino group selected from the group consisting of a primary amino group and a secondary amino group, carbon disulfide, and an alkali metal hydroxide. The purifying agent according to the above [1], which is characterized by the above.

[3] A reaction product of an amine compound in which a salt of dithiocarbamic acid has two or more amino groups selected from the group consisting of a primary amino group and a secondary amino group, carbon disulfide, and an alkali metal hydroxide. The purifying agent according to the above [1], which is characterized by the above.

[4] The purifying agent according to the above [1], wherein the salt of dithiocarbamic acid is a reaction product of piperazine or tetraethylenepentamine, carbon disulfide, and an alkali metal hydroxide.

[5] The purifying agent according to any one of the above [1] to [4], wherein the polyamine having a weight average molecular weight of 300 or more is polyethyleneimine having a weight average molecular weight of 300 or more.

[6] The purifying agent according to any one of the above [1] to [4], wherein the polyamine having a weight average molecular weight of 300 or more is polyethyleneimine having a weight average molecular weight of 1800 to 2 million.

[7] Generated after adding a purifying agent for a heavy metal-containing aqueous solution according to any one of [1] to [6] above to a heavy metal-containing aqueous solution containing at least one heavy metal selected from the group consisting of zinc and cadmium. A method for purifying a zinc-containing aqueous solution, which comprises removing solid substances.

[8] The purification method according to the above [7], wherein the heavy metal-containing aqueous solution further contains a compound having a complex formation ability with zinc or cadmium.

[9] The purification method according to the above [8], wherein the compound having a complexing ability with zinc or cadmium is a compound having a functional group selected from the group consisting of a carboxyl group and an amino group in the molecule. ..

[10] The purification method according to any one of the above [7] to [9], wherein an inorganic flocculant is added before the solid matter is removed.

[11] The purification method according to any one of the above [7] to [9], wherein an inorganic flocculant and a polymer flocculant are added before the solid matter is removed.

[12] The purification method according to the above [10] or [11], wherein the inorganic flocculant is selected from the group consisting of an iron compound and an aluminum compound.

The purifying agent for a heavy metal aqueous solution of the present invention has a zinc concentration of 2 mg / L even if it is a zinc-containing aqueous solution (for example, a compound having a zinc complexing ability and an aqueous solution containing zinc), which is difficult to purify zinc. It can be reduced to the following, and its removal speed is also fast.

The purifying agent for a heavy metal aqueous solution of the present invention has a cadmium concentration of 0.03 mg even if it is a cadmium-containing aqueous solution (for example, a compound having a cadmium and complex formation ability and an aqueous solution containing cadmium) in which it is difficult to purify cadmium. It can be reduced to / L or less, and its removal speed is fast.

The purifying agent for heavy metal aqueous solution of the present invention has a zinc concentration of 2 mg even in an aqueous solution containing heavy metals such as lead, mercury and palladium (for example, desulfurized wastewater from a coal-fired power plant) in addition to zinc and cadmium. It can be reduced to / L or less, the cadmium concentration can be reduced to 0.03 mg / L or less, and the concentration of heavy metals such as lead, mercury, and palladium can be significantly reduced.

The purifying agent for a heavy metal aqueous solution of the present invention is economical because the amount of a drug including dithiocarbamate can be reduced by containing a predetermined amount of a polyamine having a weight average molecular weight of 300 or more.

Hereinafter, the present invention will be described in detail.

The purifying agent for a heavy metal-containing aqueous solution of the present invention is characterized by containing 2 to 50 parts by weight of a polyamine having a weight average molecular weight of 300 or more with respect to 100 parts by weight of a salt of dithiocarbamic acid.

The salt of dithiocarbamic acid is not particularly limited as long as it is a compound having a dithiocarbamyl group in the molecule. For example, an amine compound having at least one amino group selected from the group consisting of a primary amino group and a secondary amino group, and a compound obtained by reacting carbon disulfide with an alkali metal hydroxide can be mentioned. A compound obtained by reacting an amine compound having two or more amino groups selected from the group consisting of a primary amino group and a secondary amino group with carbon disulfide and an alkali metal hydroxide is more preferable.

Specific examples of the amine compound having at least one amino group selected from the group consisting of a primary amino group and a secondary amino group include diethylamine, piperazine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. , Heptaethyleneoctamine and the like are exemplified.

Of these, a compound obtained by reacting piperazine or tetraethylenepentamine with carbon disulfide and an alkali metal hydroxide is preferable in terms of the treatment performance of zinc and cadmium and the stability as a compound. However, the salt of dithiocarbamate of tetraethylenepentamine is an analog body [see formulas (2) to (4) below) in addition to the linear body [see formula (1) below] whose main component is tetraethylenepentamine, which is the raw material. ] Is industrially produced, so that the obtained salt of dithiocarbamic acid is also a composition, which has a drawback of complicated quality control. On the other hand, the salt of piperazine dithiocarbamic acid is particularly preferable because it does not have such a drawback.

As the alkali metal hydroxide, sodium hydroxide and potassium hydroxide are particularly preferable because they are easily available.

Examples of polyamines having a weight average molecular weight of 300 or more include polyethyleneimines having a weight average molecular weight of 300 or more and polyetheramines having a weight average molecular weight of 300 or more (polypropylene glycol, polyethylene glycol and other compounds obtained by converting terminal hydroxyl groups into primary amino groups). ) Etc. can be mentioned. Of these, polyethyleneimines having a weight average molecular weight of 300 or more are preferable in terms of processing performance of heavy metals such as zinc and cadmium.

The weight average molecular weight of the polyamine is preferably 1800 or more in terms of improving the processing capacity of zinc and cadmium. By setting the weight average molecular weight to 1800 or more, the amount of the drug including dithiocarbamate may be reduced. Of these, polyethyleneimines having a weight average molecular weight of 1800 or more are more preferable in terms of processing performance of heavy metals such as zinc and cadmium.

The amount of the polyamine having a weight average molecular weight of 300 or more is 2 to 50 parts by weight, preferably 8 to 25 parts by weight, based on 100 parts by weight of the salt of dithiocarbamic acid. Sufficient zinc processing capacity can be obtained by adding 2 parts by weight or more, but if it is added in excess of 50 parts by weight, the treatment effect of zinc and cadmium is lowered.

The purifying agent of the present invention is particularly useful for purifying a heavy metal-containing aqueous solution containing at least one heavy metal selected from the group consisting of zinc and cadmium.

The method for purifying a heavy metal-containing aqueous solution of the present invention removes the solid matter produced after adding the above-mentioned purifying agent of the present invention to a heavy metal-containing aqueous solution containing at least one heavy metal selected from the group consisting of zinc and cadmium. It is characterized by that. Here, the produced solid contains heavy metals immobilized by the purifying agent of the present invention.

The purification method of the present invention comprises a zinc-containing aqueous solution that is difficult to treat with zinc (for example, a compound having a zinc complexing ability and an aqueous solution containing zinc), and a cadmium-containing aqueous solution that is difficult to treat cadmium (for example, cadmium and complex formation). It is particularly effective against compounds having the ability and aqueous solutions containing cadmium.

The compound having a complex forming ability with zinc or cadmium is not particularly limited as long as it is a compound forming a complex with zinc or cadmium. For example, a compound having a functional group selected from the group consisting of a carboxyl 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 zinc and cadmium.

The zinc concentration in the heavy metal-containing aqueous solution is not particularly limited, but it is preferable to contain zinc having a concentration higher than the wastewater standard of 2 mg / L.

The zinc concentration in the heavy metal-containing aqueous solution is not particularly limited, but it is preferable to contain cadmium having a concentration higher than the wastewater standard of 0.03 mg / L.

When the salt of dithiocarbamic acid and the polyamine having a weight average molecular weight of 300 or more are separately added to the heavy metal-containing aqueous solution, the order of addition is not particularly limited. For example, a method of first adding a salt of dithiocarbamic acid and then a polyamine having a weight average molecular weight of 300 or more, a method of first adding a polyamine having a weight average molecular weight of 300 or more, and then a method of adding a salt of dithiocarbamic acid, etc. Can be mentioned.

In order to quickly remove the solid matter, it is preferable to add a flocculant before removing the solid matter. Examples of the flocculant include an inorganic flocculant and a polymer flocculant, 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 a complex-forming ability with zinc or cadmium, the amount of the inorganic flocculant added shall be equal to or greater than the content of the compound having a complex-forming ability with zinc or cadmium contained in the heavy metal-containing aqueous solution. Is preferable. By increasing the amount of the inorganic flocculant added to be equal to or greater than the content of zinc or a compound having the ability to form a complex with cadmium, the cohesiveness can be increased and the zinc concentration and cadmium concentration of the treated aqueous solution can be reduced below the wastewater standard. It will be easier.

The content of the compound having the ability to form a complex with zinc or cadmium in the heavy metal-containing aqueous solution is the concentration of the compound having the ability to form a complex with zinc or cadmium in the heavy metal-containing aqueous solution, for example, HPLC, gas chromatography, titration. It can be calculated by performing an analysis such as.

As the polymer flocculant, a commercially available polymer flocculant can be used, and the polymer flocculant 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 limited to these examples.

(Analysis method)
The heavy metal ion concentration (for example, zinc ion concentration, cadmium ion concentration, etc.) in the aqueous solution was measured by an ICP emission spectrophotometer (OPTISMA3300DV, manufactured by Perkin Elmaer).

As an index of the removal rate of heavy metals (for example, zinc, cadmium, etc.) in the aqueous solution, the transmittance of the supernatant liquid of the aqueous solution after the purification treatment was measured. That is, it is shown that the larger the transmittance in a predetermined time, the faster the solid matter generated by the addition of the chemical is settled, and the higher the removal rate of heavy metals in the aqueous solution is. For the measurement, a transmissive digital laser sensor (LX2-02, manufactured by KEYENCE CORPORATION) was used, and the transmittance was measured from the following formula.

Transmittance = light receiving amount (mV) of the supernatant liquid of the aqueous solution after purification treatment ÷ light receiving amount of pure water (mV) × 100 (%).

Preparation example.
The salt of dithiocarbamic acid used in Examples and Comparative Examples was prepared according to the following method.

(Preparation of salt A of dithiocarbamic acid)
After mixing 112 g of piperazine (manufactured by Tosoh) and 386 g of pure water, 306 g of 48 wt% potassium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 196 g of carbon disulfide (manufactured by Kishida Chemical Co., Ltd.) while stirring in a nitrogen stream at 25 ° C. ) Was divided into 4 portions and dropped alternately. The mixture was stirred for 1 hour to obtain an aqueous solution containing 40% by weight of the compound represented by the chemical formula (5).

(Preparation of salt B of dithiocarbamic acid)
After mixing 159 g of tetraethylenepentamine (manufactured by Tosoh) and 331 g of pure water, 281 g of 48 wt% sodium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 230 g of carbon disulfide (Kishida) while stirring in a nitrogen stream at 25 ° C. (Manufactured by Kagaku Co., Ltd.) was divided into 4 portions and dropped alternately. The mixture was stirred for 1 hour to obtain an aqueous solution containing 40% by weight of the compound represented by the chemical formula (6).

(Polyamine)
As polyamines, the following polyethyleneimines manufactured by Nippon Catalyst (weight average molecular weight 1,800 to 70,000), polyethyleneimines manufactured by BASF (weight average molecular weight 750,000 to 2 million), polyetheramine manufactured by Huntsman, and triethylene manufactured by Tosoh Co., Ltd. Tetramine was used.

A product having a weight average molecular weight of 1800 polyethyleneimine (hereinafter abbreviated as PEI (1800)).

Polyethyleneimine has a weight average molecular weight of 10,000 (hereinafter abbreviated as PEI (10,000)).

Polyethyleneimine has a weight average molecular weight of 70,000 (hereinafter abbreviated as PEI (70,000)).

Weight average molecular weight of polyethyleneimine 750,000 products (hereinafter abbreviated as PEI (750,000)).

Weight average molecular weight of polyethyleneimine 2 million products (hereinafter abbreviated as PEI (2 million)).

400 products with a weight average molecular weight of polyetheramine (grade name, Jeffamine D-400, hereinafter abbreviated as D-400).

A product having a weight average molecular weight of 3000 (grade name, Jeffamine T-3000, hereinafter abbreviated as T-3000).

Triethylenetetramine (weight average molecular weight 146) (hereinafter abbreviated as EA (146)).

Heptaethylene octamine (weight average molecular weight 320) (hereinafter abbreviated as EA (320)).

(Inorganic flocculant)
As the inorganic flocculant, a 38 wt% ferric chloride aqueous solution (manufactured by Kishida Chemical Co., Ltd.), a 27 wt% aluminum sulfate aqueous solution (manufactured by Kishida Chemical Co., Ltd.), and a 30 wt% polyaluminum chloride aqueous solution (manufactured by Kishida Chemical Co., Ltd.) were used. ..

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

Example 1.
A Jar Tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of zinc ions and 260 mg / L of EDTA was added. Then, while stirring at 150 rpm, 640 mg / L of salt A of dithiocarbamic acid and 20 mg / L of PEI (1800) as a polyamine were 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 using 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 zinc concentration of the treated aqueous solution was measured. The results are shown in Table 1.

Examples 2-19.
The zinc 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 Tables 1 to 3. These results are also shown in Tables 1 to 3.

In Examples 1 to 5, the zinc concentration of the aqueous solution after the treatment was 2 mg / L or less, which was lower than the wastewater standard of 2 mg / L, and the zinc treatment was sufficient.

Examples 6 to 19 are examples of treatment in which the weight part of polyamine with respect to 100 parts by weight of the salt of dithiocarbamic acid is changed within the range of the present invention. The zinc concentration of the aqueous solution after the treatment was 2 mg / L or less, which was lower than the wastewater standard of 2 mg / L, and the zinc treatment was sufficient. Further, there is an optimum range in the weight part of the polyamine with respect to 100 parts by weight of the salt of dithiocarbamic acid, and if the weight part of the polyamine is increased, the zinc concentration of the aqueous solution after the treatment may not be reduced accordingly. I understand.

Comparative example 1.
Zinc in the aqueous solution after treatment was prepared in the same manner as in Example 1 except that the agent to be added was changed to the agent shown in Table 4 and the pH of the aqueous solution was always adjusted to pH 10 with a small amount of hydrochloric acid and sodium hydroxide. The concentration was measured. These results are also shown in Table 4.

Comparative Examples 2-8.
The zinc concentration of the treated aqueous solution 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. These results are also shown in Table 4.

Comparative Example 1 is an example of a conventional treatment method in which iron ions are added to neutralize and zinc ions are precipitated as a hydroxide together with iron ions. The zinc concentration of the aqueous solution after the treatment was 4.3 mg / L, which exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient.

Comparative Examples 2 and 3 are examples in which the amount of the salt A of dithiocarbamic acid added was reduced without adding the polyamine. The zinc concentration of the aqueous solution after the treatment was 4.1 mg / L or more, which exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient.

Comparative Example 4 is an example in which a polyamine having a weight average molecular weight of 146, which is outside the scope of the present invention, and a salt A of dithiocarbamic acid are used in combination, but the zinc concentration of the treated aqueous solution is 5 mg / L or more, based on the wastewater standard. It was above a certain 2 mg / L and the zinc treatment was inadequate.

Comparative Example 5 is an example in which only PEI (1800) was added as a polyamine without adding the salt A of dithiocarbamic acid, and then an inorganic flocculant was added and treated at pH 7. The zinc concentration of the aqueous solution after the treatment was 6 mg / L or more, which exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient.

Comparative Example 6 is an example in which only the salt A of dithiocarbamic acid is added in a large amount without adding the polyamine. In order to reduce the zinc concentration of the aqueous solution after treatment to 2 mg / L or less, which is the wastewater standard, 1300 mg / L of expensive dithiocarbamic acid salt A is added, which is not economical.

Comparative Example 7 is an example in which salt A of dithiocarbamic acid and PEI (1800) in an amount below the range of the present invention were added. There was no effect of reducing the amount of the salt A of dithiocarbamic acid added as compared with Comparative Example 6.

Comparative Example 8 is an example in which salt A of dithiocarbamic acid and PEI (1800) in an amount exceeding the range of the present invention are added. The zinc concentration of the aqueous solution after the treatment was 6.0 mg / L, and the zinc treatment performance was significantly deteriorated.

From Comparative Examples 6 to 8, it can be seen that the amount of polyamine used in combination with the salt of dithiocarbamic acid has a suitable range in which zinc can be treated. Further, it can be seen that the purifying agent of the present invention can significantly reduce the amount of the expensive dithiocarbamic acid salt A added.

Example 20.
The zinc concentration of the aqueous solution after the treatment was measured in the same manner as in Example 1 except that the compound having the ability to form a complex with zinc and the agent to be added were changed to the compounds and agents shown in Table 5. These results are also shown in Table 5.

Comparative Examples 9 to 10.
Except for changing the compounds having the ability to form complex with zinc and the chemicals to be added to the compounds and chemicals shown in Table 5, and adjusting the pH of the aqueous solution to always be 10 with a small amount of hydrochloric acid and sodium hydroxide. The zinc concentration of the treated aqueous solution was measured in the same manner as in Example 1. These results are also shown in Table 5.

Example 20 is an example of treatment with a drug within the scope of the present invention, but the zinc concentration could be sufficiently reduced.

Comparative Examples 9 to 10 are examples of a conventional treatment method in which iron ions are added to neutralize and zinc ions are precipitated as a hydroxide together with iron ions. The zinc concentration of the aqueous solution after the treatment was 10 mg / L, which exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient.

Example 21.
A Jar Tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of zinc ions and 260 mg / L of EDTA was added. Then, while stirring at 150 rpm, 400 mg / L of salt A of dithiocarbamic acid and 12 mg / L of PEI (1800) as a polyamine were 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. The pH of the aqueous solution was adjusted to always be pH 7 using a small amount of hydrochloric acid and sodium hydroxide. After the stirring was completed, the treated aqueous solution was transferred to a 500 mL measuring cylinder, allowed to stand for 10 minutes, and then 100 mL of the supernatant was separated and the transmittance of the treated aqueous solution was measured. Further, after the stirring was completed, the treated aqueous solution that had been allowed to stand for 10 minutes was filtered off with a filter paper of 5A manufactured by Advantech, and the zinc concentration was measured. The results are shown in Table 6.

Examples 22-40.
The transmittance and zinc concentration of the aqueous solution after the treatment were measured in the same manner as in Example 21 except that the chemicals to be added were changed to the chemicals shown in Tables 6 and 7. These results are also shown in Tables 6 and 7.

As is clear from Tables 6 and 7, in Examples 21 to 40, the zinc concentration of the treated aqueous solution was lower than the wastewater standard of 2.0 mg / L, and the zinc treatment was sufficient. In addition, the transmittance of the aqueous solution after the treatment was 70% or more, and the zinc removal rate was sufficiently high.

Examples 21 to 27 are examples in which the type of polyamine is changed. Regardless of the type of polyamine, the zinc concentration of the treated aqueous solution was 2 mg / L or less, which is the wastewater standard, and the zinc treatment was sufficient. In addition, the transmittance of the aqueous solution after the treatment was 70% or more, and the zinc removal rate was sufficiently high.

Examples 21 and 28 to 33 are examples in which 100 parts by weight of a salt of dithiocarbamic acid is treated by changing the weight of polyamine (PEI (1800)) within the range of the present invention. Regardless of the amount of polyamine added, the zinc concentration of the treated aqueous solution was 2 mg / L or less, which is the wastewater standard, and the zinc treatment was sufficient. In addition, the transmittance of the treated aqueous solution was 70% or more, and the zinc removal rate was sufficiently high.

Examples 34 to 35 are examples in which the amount of ferric chloride added is increased. Regardless of the amount of ferric chloride added, the zinc concentration of the aqueous solution after the treatment was 2 mg / L or less, which is the wastewater standard, and the zinc treatment was sufficient. In addition, the transmittance of the treated aqueous solution was 70% or more, and the zinc removal rate was sufficiently high.

Examples 36 to 39 are examples in which an aluminum sulfate aqueous solution and a polyaluminum chloride aqueous solution are used as the inorganic flocculant. Regardless of the type of the inorganic flocculant, the zinc concentration of the aqueous solution after the treatment was 2 mg / L or less, which is the wastewater standard, and the zinc treatment was sufficient. In addition, the transmittance of the aqueous solution after the treatment was 78% or more, and the zinc removal rate was sufficiently high.

Example 40 is an example using the salt B of dithiocarbamic acid, but the zinc concentration of the aqueous solution after the treatment was 2.0 mg / L or less, which is the wastewater standard, and the zinc treatment was sufficient. Further, the transmittance of the aqueous solution after the treatment was 80%, and the zinc removal rate was sufficiently high.

Comparative Example 11.
The chemicals to be added are changed to the chemicals shown in Table 8, and the pH of the aqueous solution is adjusted to always be 10 by using a small amount of hydrochloric acid and sodium hydroxide, but the permeation of the aqueous solution after the treatment is carried out in the same manner as in Example 21. The rate and zinc concentration were measured. These results are also shown in Table 8.

Comparative Examples 12-18.
The transmittance and zinc concentration of the treated aqueous solution were measured in the same manner as in Example 21 except that the chemicals to be added were changed to the chemicals shown in Table 8. These results are also shown in Table 8.

Comparative Example 11 is an example of a conventional treatment method in which iron ions are added to neutralize and zinc ions are precipitated as a hydroxide together with iron ions. The transmittance of the aqueous solution after the treatment was 99%, but the zinc concentration was 4.3 mg / L, which exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient.

Comparative Examples 12 to 14 are examples in which the salt A of dithiocarbamic acid was added without adding the polyamine. The zinc concentration of the aqueous solution after the treatment regardless of the amount added exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient. In addition, the transmittance was 63% or less, which was lower than that of Examples 21 to 40 to which polyamine was added, and the zinc removal rate was insufficient.

Comparative Example 15 is an example in which only PEI (1800) was added without adding the salt A of dithiocarbamic acid, and then an inorganic flocculant was added and treated at pH 7. The transmittance of the aqueous solution after the treatment was 84%, but the zinc concentration was 6.2 mg / L. That is, it exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient.

Comparative Example 16 is an example in which a polyamine (EA (146)) having a weight average molecular weight of 146, which is outside the scope of the present invention, and a salt A of dithiocarbamic acid are used in combination. The transmittance of the aqueous solution after the treatment was 62% and the zinc concentration was 5.5 mg / L, and no significant improvement effect was observed in the zinc treatment and the transmittance as compared with Comparative Example 15 to which EA (146) was not added. rice field.

Comparative Example 17 is an example in which salt A of dithiocarbamic acid and PEI (1800) in an amount below the range of the present invention are added. The zinc concentration of the aqueous solution after the treatment exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient. In addition, the transmittance of the aqueous solution after the treatment was 52%, and the zinc removal rate was insufficient.

Comparative Example 18 is an example in which salt A of dithiocarbamic acid and PEI (1800) in an amount exceeding the range of the present invention are added. The zinc concentration of the aqueous solution after the treatment was 6.0 mg / L, and the zinc treatment performance was significantly deteriorated. In addition, the transmittance of the aqueous solution after the treatment was 49%, and the zinc removal rate was insufficient.

From Comparative Example 17 and Comparative Example 18, it can be seen that the amount of polyamine used in combination with the salt of dithiocarbamic acid has a suitable range in which zinc can be treated.

Example 41.
A Jar Tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of zinc ions and 260 mg / L of EDTA was added. Then, while stirring at 150 rpm, 400 mg / L of salt A of dithiocarbamic acid and 12 mg / L of PEI (1800) as a polyamine were 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 using a small amount of hydrochloric acid and sodium hydroxide. After the stirring was completed, the treated aqueous solution was transferred to a 500 mL measuring cylinder, allowed to stand for 10 minutes, and then 100 mL of the supernatant was separated and the transmittance of the treated aqueous solution was measured. Further, after the stirring was completed, the treated aqueous solution that had been allowed to stand for 10 minutes was filtered off with a filter paper of 5A manufactured by Advantech, and the zinc concentration was measured. The results are shown in Table 9.

Example 42, Comparative Examples 20-21.
The transmittance and zinc concentration of the treated aqueous solution were measured in the same manner as in Example 41 except that the chemicals to be added were changed to the chemicals shown in Table 9. These results are also shown in Table 9.

Comparative Example 19.
Permeation of the aqueous solution after treatment is carried out in the same manner as in Example 42, except that the agent to be added is changed to the agent shown in Table 9 and the pH of the aqueous solution is always adjusted to pH 10 with a small amount of hydrochloric acid and sodium hydroxide. The rate and zinc concentration were measured. These results are also shown in Table 9.

Examples 41 to 42 are examples in which a polymer flocculant (OA-23) is added to Examples 21 to 22. The zinc concentration after the treatment was the same as that in the case where the polymer flocculant was not added, but the transmittance was 90% or more. When OA-23 was added, the sedimentation property of the solid matter was improved.

Comparative Example 19 is an example in which a polymer flocculant (OA-23) is added to Comparative Example 13. The zinc concentration of the aqueous solution after the treatment was the same as that in the case where OA-23 was not added. That is, it exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient.

Comparative Example 20 is an example in which a large amount of the polymer flocculant (OA-23) is added to Comparative Example 14. The zinc concentration of the aqueous solution after the treatment was 4.0 mg / L and the transmittance was 65%, and no significant improvement effect was observed as compared with Comparative Example 14 to which OA-23 was not added.

Comparative Example 21 is an example in which a polymer flocculant (OA-23) is added to Comparative Example 15. The transmittance of the aqueous solution after the treatment was improved to 90%, but the zinc concentration was the same as that in the case where OA-23 was not added. That is, it exceeded the wastewater standard of 2 mg / L, and the zinc treatment was insufficient.

From Comparative Examples 19 to 21, it can be seen that, as an additive to be combined with a salt of dithiocarbamic acid, a general polymer flocculant does not show much improvement in the treatment effect, and a specific polyamine is required.

Example 43.
A Jar Tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of cadmium ion and 260 mg / L of EDTA was added. Then, while stirring at 150 rpm, 400 mg / L of dithiocarbamic acid salt A and 12 mg / L of EA (320) as a polyamine were 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 10 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 using 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 cadmium concentration of the treated aqueous solution was measured. The results are shown in Table 10.

Examples 44-55.
The cadmium concentration of the aqueous solution after the treatment was measured in the same manner as in Example 44 except that the chemicals to be added were changed to the chemicals shown in Tables 10 and 11. These results are also shown in Tables 10 and 11.

As is clear from Tables 10 and 11, in Examples 43 to 55, the cadmium concentration of the aqueous solution after the treatment was 0.03 mg / L or less. That is, it was below the wastewater standard of 0.03 mg / L, and the treatment of cadmium was sufficient.

Examples 43 to 46 and 52 to 55 are examples in which the type of polyamine is changed. The cadmium concentration of the aqueous solution after the treatment is 0.03 mg / L or less, and it can be seen that the cadmium treatment effect can be obtained regardless of the type of polyamine.

Further, from Examples 43 to 46, polyethyleneimine having a weight average molecular weight of 1800 or more can reduce the amount of the drug including dithiocarbamate added as compared with polyamine (EA (320)) having a weight average molecular weight of 320. I know I can do it.

Examples 44, 47 to 50 are examples in which the weight portion of the polyamine [PEI (1800)] is changed within the range of the present invention with respect to 100 parts by weight of the salt of dithiocarbamic acid, but the amount of the polyamine added is increased. As a result, the amount of dithiocarbamic acid salt added could be reduced.

Example 51 is an example using the salt B of dithiocarbamic acid, but the cadmium concentration of the treated aqueous solution was 0.03 mg / L or less, and the cadmium treatment was sufficient.

Comparative Example 22.
The cadmium in the aqueous solution after treatment is the same as in Example 43, except that the agent to be added is changed to the agent shown in Table 12 and the pH of the aqueous solution is always adjusted to pH 9 with a small amount of hydrochloric acid and sodium hydroxide. The concentration was measured. The results are shown in Table 12.

Comparative Examples 23 to 29.
The cadmium concentration of the treated aqueous solution was measured in the same manner as in Example 43 except that the chemicals to be added were changed to the chemicals shown in Table 12. These results are also shown in Table 12.

Comparative Example 22 is an example of a conventional treatment method in which iron ions are added to make it alkaline and cadmium ions are precipitated as a hydroxide together with iron ions. The cadmium concentration of the aqueous solution after the treatment was 4 mg / L or more, which exceeded the wastewater standard of 0.03 mg / L, and the cadmium treatment was insufficient.

Comparative Examples 23 to 24 are examples in which only PEI (1800) was added without adding the salt A of dithiocarbamic acid. The cadmium concentration of the aqueous solution after the treatment was 2.9 mg / L, which exceeded the wastewater standard of 0.03 mg / L, and the cadmium treatment was insufficient.

Comparative Example 25 is an example in which only the salt A of dithiocarbamic acid was added at 320 mg / L without adding the polyamine. The cadmium concentration of the aqueous solution after the treatment was 0.10 mg / L, which exceeded the wastewater standard of 0.03 mg / L, and the cadmium treatment was insufficient.

Comparative Example 26 is an example in which salt A of dithiocarbamic acid and EA (146), which is outside the scope of the present invention, are added. The cadmium concentration of the aqueous solution after the treatment was 0.10 mg / L, and no improvement effect was observed in the cadmium treatment as compared with Comparative Example 4 in which EA (146) was not added.

Comparative Example 27 is an example in which salt A of dithiocarbamic acid and PEI (1800) in an amount exceeding the range of the present invention are added. The cadmium concentration of the aqueous solution after the treatment was 0.81 mg / L, and the cadmium treatment performance was significantly deteriorated.

Comparative Example 28 is an example in which a large amount of dithiocarbamic acid salt A is added without adding polyamine. In order to reduce the cadmium concentration of the aqueous solution after treatment to 0.03 mg / L or less, which is the wastewater standard, 480 mg / L of expensive dithiocarbamic acid salt A is added, which is not economical.

Comparative Example 29 is an example in which salt A of dithiocarbamic acid and PEI (1800) in an amount below the range of the present invention are added. The amount of dithiocarbamate salt A added to reduce the cadmium concentration to 0.03 mg / L or less was 480 mg / L, and there was no effect of reducing the amount of dithiocarbamate salt A added as compared with Comparative Example 28.

From Comparative Examples 27 to 29, it can be seen that the amount of polyamine used in combination with the salt of dithiocarbamic acid has a suitable range in which cadmium can be treated. Further, it can be seen that the purifying agent of the present invention can significantly reduce the amount of the expensive dithiocarbamic acid salt A added.

Example 56.
The cadmium concentration of the aqueous solution after the treatment was measured in the same manner as in Example 43, except that the compound having the ability to form a complex with cadmium and the agent to be added were changed to the compound shown in Table 13 and the agent. The results are shown in Table 13.

Comparative Examples 30 to 31.
Except for changing the compounds having cadmium and complex formation ability and the chemicals to be added to the compounds and chemicals shown in Table 13, and adjusting the pH of the aqueous solution to always pH 9 with a small amount of hydrochloric acid and sodium hydroxide. The cadmium concentration of the treated aqueous solution was measured in the same manner as in Example 43. The results are also shown in Table 13.

As is clear from Table 13, in Example 56, the cadmium concentration of the aqueous solution after the treatment was 0.03 mg / L or less. That is, it was below the wastewater standard of 0.03 mg / L, and the treatment of cadmium was sufficient.

Comparative Examples 30 to 31 are examples of conventional treatment methods in which iron ions are added to make them alkaline and cadmium ions are precipitated as a hydroxide together with iron ions. The cadmium concentration of the aqueous solution after the treatment was 1.5 mg / L or more, which exceeded the wastewater standard of 0.03 mg / L, and the cadmium treatment was insufficient.

Examples 57-59.
The cadmium concentration of the treated aqueous solution was measured in the same manner as in Example 43 except that the agent to be added was changed to the agent shown in Table 14. These results are also shown in Table 14.

Comparative Examples 32 to 35.
The agent to be added is changed to the agent shown in Table 14, and the pH of the aqueous solution is adjusted to always be pH 9 with a small amount of hydrochloric acid and sodium hydroxide in the same manner as in Example 43, except that the cadmium in the aqueous solution after treatment is used. The concentration was measured. These results are also shown in Table 14.

As is clear from Table 14, in Examples 57 to 59, the cadmium concentration of the aqueous solution after the treatment was 0.03 mg / L or less. That is, it was below the wastewater standard of 0.03 mg / L, and the treatment of cadmium was sufficient.

Comparative Examples 32 to 35 are examples of conventional treatment methods in which aluminum ions are added to make them alkaline and cadmium ions are precipitated as hydroxides together with aluminum ions. The cadmium concentration of the treated aqueous solution was 5.8 mg / L or more, which exceeded the wastewater standard of 0.03 mg / L, and the cadmium treatment was insufficient.

Example 60.
A Jar Tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of cadmium ion and 260 mg / L of EDTA was added. Then, while stirring at 150 rpm, 400 mg / L of dithiocarbamic acid salt A and 12 mg / L of EA (320) as a polyamine were 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 10 minutes. The pH of the aqueous solution was adjusted to always be pH 7 using a small amount of hydrochloric acid and sodium hydroxide. After the stirring was completed, the treated aqueous solution was transferred to a 500 mL measuring cylinder, allowed to stand for 10 minutes, and then 100 mL of the supernatant was separated and the transmittance of the treated aqueous solution was measured. Further, after the stirring was completed, the treated aqueous solution that had been allowed to stand for 10 minutes was filtered off with a filter paper of 5A manufactured by Advantech, and the cadmium concentration was measured. The results are shown in Table 15.

Examples 61-74.
The transmittance and cadmium concentration of the treated aqueous solution were measured in the same manner as in Example 60 except that the chemicals to be added were changed to the chemicals shown in Tables 15 and 16. These results are also shown in Tables 15 and 16.

These results are also shown in Tables 15 and 16.

As is clear from Tables 15 and 16, in Examples 60 to 74, the cadmium concentration of the aqueous solution after the treatment was both below the wastewater standard of 0.03 mg / L, and the cadmium treatment was sufficient. .. In addition, the transmittance of the treated aqueous solution was 80% or more, and the cadmium removal rate was sufficiently high.

Examples 60 to 67 are examples in which the type of polyamine is changed. The cadmium concentration of the aqueous solution after the treatment was 0.03 mg / L or less regardless of the type of polyamine, and the cadmium treatment was sufficient. In addition, the transmittance of the aqueous solution after the treatment was 80% or more, and the cadmium removal rate was sufficiently high.

Examples 63, 68 to 71 are examples in which the weight of polyamine (PEI (1800)) is changed within the range of the present invention with respect to 100 parts by weight of the salt A of dithiocarbamic acid. The cadmium concentration of the aqueous solution after the treatment was 0.03 mg / L or less, which is the wastewater standard, regardless of the amount of polyamine added, and the cadmium treatment was sufficient. The transmittance of the aqueous solution after the treatment was 81%, and the cadmium removal rate was sufficiently high.

Example 72 is an example using the salt B of dithiocarbamic acid. The cadmium concentration of the aqueous solution after the treatment was 0.03 mg / L or less, and the cadmium treatment was sufficient. The transmittance of the aqueous solution after the treatment was 93%, and the cadmium removal rate was sufficiently high.

Examples 73 and 74 are examples in which an aluminum sulfate aqueous solution and a polyaluminum chloride aqueous solution are used as the inorganic flocculants. The cadmium concentration of the aqueous solution after the treatment was 0.03 mg / L or less regardless of the type of the inorganic flocculant, and the cadmium treatment was sufficient. The transmittance of the aqueous solution after the treatment was 89% and 90%, and the cadmium removal rate was sufficiently high.

Comparative Examples 36 to 38.
Permeation of the aqueous solution after treatment is carried out in the same manner as in Example 60, except that the agent to be added is changed to the agent shown in Table 17 and the pH of the aqueous solution is always adjusted to pH 9 with a small amount of hydrochloric acid and sodium hydroxide. The rate and cadmium concentration were measured. These results are also shown in Table 17.

Comparative Examples 39 to 44.
The transmittance and cadmium concentration of the treated aqueous solution were measured in the same manner as in Example 60 except that the chemicals to be added were changed to the chemicals shown in Table 17. These results are also shown in Table 17.

Comparative Examples 36 to 38 are examples of a conventional treatment method in which iron ions or aluminum ions are added to make them alkaline, and cadmium ions are precipitated as a hydroxide together with iron ions or aluminum ions. The transmittance of the aqueous solution after the treatment was 90% or more, but the cadmium concentration was 4 mg / L or more. That is, it exceeded the wastewater standard of 0.03 mg / L, and the treatment of cadmium was insufficient.

Comparative Example 39 is an example in which only the salt A of dithiocarbamic acid was added at 320 mg / L without adding the polyamine. The cadmium concentration of the aqueous solution after the treatment was 0.10 mg / L, which exceeded the wastewater standard of 0.03 mg / L, and the cadmium treatment was insufficient. In addition, the transmittance of the aqueous solution after the treatment was 68%, and the removal rate of cadmium was insufficient as compared with Examples 61 to 75 to which polyamine was added.

Comparative Examples 40 to 41 are examples in which only PEI (1800) was added without adding the salt A of dithiocarbamic acid, and then an inorganic flocculant was added and treated at pH 7. The transmittance of the aqueous solution after the treatment was 80% or more, but the cadmium concentration of the aqueous solution after the treatment was 2.9 mg / L. That is, it exceeded the wastewater standard of 0.03 mg / L, and the treatment of cadmium was insufficient.

Comparative Example 42 is an example in which a polyamine having a weight average molecular weight of 146, which is outside the scope of the present invention, and a salt A of dithiocarbamic acid are used in combination. The cadmium concentration of the aqueous solution after the treatment was 0.10 mg / L, and no improvement effect was observed in the cadmium treatment amount and the transmittance (that is, the cadmium removal rate) as compared with Comparative Example 39 to which no polyamine was added. rice field.

Comparative Example 43 is an example in which the salt A of dithiocarbamic acid and the polyamine in an amount below the range of the present invention are added. The cadmium concentration of the aqueous solution after the treatment exceeded the wastewater standard of 0.03 mg / L, and the cadmium treatment was insufficient. Further, the transmittance of the aqueous solution after the treatment was 68%, and the removal rate of cadmium was insufficient as compared with Examples 61 to 75 in which the polyamine was added in an amount within the range of the present invention.

Comparative Example 44 is an example in which salt A of dithiocarbamic acid and a polyamine in an amount exceeding the range of the present invention are added. The cadmium concentration of the aqueous solution after the treatment exceeded the wastewater standard of 0.03 mg / L, and the cadmium treatment was insufficient. Further, the transmittance of the aqueous solution after the treatment was 45%, and the sedimentation property of the solid matter was significantly deteriorated as compared with Examples 61 to 75 in which the polyamine was added in an amount within the range of the present invention.

From Comparative Example 43 and Comparative Example 44, it can be seen that the amount of polyamine used in combination with the salt of dithiocarbamic acid has a suitable range in which cadmium can be treated.

Example 75.
A Jar Tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of cadmium ion and 260 mg / L of EDTA was added. While stirring at 150 rpm, 320 mg / L of salt A of dithiocarbamic acid and 10 mg / L of PEI (1800) as a polyamine were 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 10 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 using a small amount of hydrochloric acid and sodium hydroxide. After the stirring was completed, the treated aqueous solution was transferred to a 500 mL measuring cylinder, allowed to stand for 10 minutes, and then 100 mL of the supernatant was separated and the transmittance of the treated aqueous solution was measured. Further, after the stirring was completed, the treated aqueous solution that had been allowed to stand for 10 minutes was filtered off with a filter paper of 5A manufactured by Advantech, and the cadmium concentration was measured. The results are shown in Table 18.

Examples 76-77.
The transmittance and cadmium concentration of the treated aqueous solution were measured in the same manner as in Example 75, except that the chemicals to be added were changed to the chemicals shown in Table 18. These results are also shown in Table 18.

Comparative Examples 45 to 47.
Permeation of the aqueous solution after treatment is carried out in the same manner as in Example 75, except that the agent to be added is changed to the agent shown in Table 18 and the pH of the aqueous solution is always adjusted to pH 9 with a small amount of hydrochloric acid and sodium hydroxide. The rate and cadmium concentration were measured. These results are also shown in Table 18.

Example 75 is an example in which a polymer flocculant (OA-23) is further added to Example 63. The cadmium concentration of the aqueous solution after the treatment was the same as that in the case where the polymer flocculant was not added, but the transmittance was improved to 90%.

Example 76 is an example in which the amount of the dithiocarbamate salt A and PEI (1800) added in Example 75 is reduced. The cadmium concentration and transmittance of the aqueous solution after the treatment were the same as those of Example 75.

Example 77 is an example in which a polymer flocculant is further added to Example 73. The cadmium concentration of the aqueous solution after the treatment was the same as that in the case where the polymer flocculant was not added, but the transmittance was improved to 93%.

Comparative Examples 45 to 47 are examples in which a polymer flocculant is further added to Comparative Examples 36 to 38. The cadmium concentration of the aqueous solution after the treatment was 4 mg / L or more, which was the same value as when the polymer flocculant was not added. That is, it exceeded the wastewater standard of 0.03 mg / L, and the treatment of cadmium was insufficient.

Example 78.
A Jar Tester was installed in a 500 mL beaker, and 500 mL of desulfurized wastewater from a coal-fired power plant was added. Then, while stirring at 150 rpm, 9.7 mg / L of salt A of dithiocarbamic acid and 0.3 mg / L of PEI (10,000) as a polyamine were added, and the mixture was stirred at 150 rpm for 10 minutes. Then, 1000 mg / L of a 30 wt% polyaluminum 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 using 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 heavy metal concentration of the treated aqueous solution was measured. The results are shown in Table 19.

Example 79.
The heavy metal concentration of the treated aqueous solution was measured in the same manner as in Example 78, except that the desulfurized wastewater from the coal-fired power plant was changed to the desulfurized wastewater shown in Table 19. The results are also shown in Table 19.

Examples 78 and 79 are examples in which a chemical is added to the desulfurized wastewater of a coal-fired power plant within the scope of the present invention for treatment. The zinc concentration of the aqueous solution after the treatment was less than 0.1 mg / L, the cadmium concentration was less than 0.03 mg / L, and other heavy metals could be treated below the wastewater standard. That is, it was confirmed that the purifying agent of the present invention is effective in purifying actual wastewater containing heavy metals.

The wastewater standards for each heavy metal are lead <0.1 mg / L and mercury <0.005 mg / L.

Claims (6)

A heavy metal containing 5 to 50 parts by weight of polyethyleneimine having a weight average molecular weight of 1800 to 2 million with respect to 100 parts by weight of a salt of dithiocarbamic acid obtained by reacting piperazine or tetraethylenepentamine with carbon disulfide and an alkali metal hydroxide. Purifying agent for contained aqueous solution. Zinc containing 8 to 10 parts by weight of polyethyleneimine having a weight average molecular weight of 1800 to 10,000 with respect to 100 parts by weight of a salt of dithiocarbamic acid obtained by reacting piperazine or tetraethylenepentamine with carbon disulfide and an alkali metal hydroxide. Purifying agent for contained aqueous solution. A solid substance produced after adding a purifying agent for a heavy metal-containing aqueous solution according to claim 1 to a heavy metal-containing aqueous solution containing at least one heavy metal selected from the group consisting of zinc and cadmium and ethylenediaminetetraacetic acid or polyphosphoric acid. A method for purifying a heavy metal-containing aqueous solution, which comprises removing it. The method for purifying a heavy metal-containing aqueous solution according to claim 3 , wherein an inorganic flocculant is added before the solid matter is removed. The method for purifying a heavy metal-containing aqueous solution according to claim 3 , wherein an inorganic flocculant and a polymer flocculant are added before the solid matter is removed. The method for purifying a heavy metal-containing aqueous solution according to claim 4 or 5, wherein the inorganic flocculant is selected from the group consisting of an iron compound and an aluminum compound.