JP6862659B2 - How to purify nickel-containing aqueous solution - Google Patents

Description

The present invention relates to a compound having the ability to form a complex with nickel, and a purification method capable of removing nickel from an aqueous solution containing nickel.

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

The nickel content wastewater standard 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 wastewater treatment. Is becoming more important.

By the way, organic acids such as citric acid and gluconic acid, ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA), cyanide, amine, ammonia and polyphosphorus are used for wastewater from plating factories, electronic parts / mechanical parts manufacturing factories, automobile factories, etc. It contains compounds such as acids that have the ability to form complex with nickel, and there are many cases where it cannot be treated by the hydroxide method as described above.

On the other hand, there is a method of insolubilizing nickel after treating a compound having a complex forming ability with nickel by a chemical treatment with a compound having a complex forming ability with nickel. However, even in chemical treatments such as oxidation method with chlorine-based chemicals, electrolytic oxidation method, hydrogen peroxide-ferrous iron salt method, ozone oxidation method, wet oxidation method, etc., inhibition of oxidation reaction by coexisting heavy metal elements, There are problems such as scale generation.

Techniques for removing various heavy metal elements contained in such wastewater include, for example, a coagulation separation removal method by adding an inorganic or organic coagulant, a removal method by electrodialysis, activated carbon, an inorganic adsorbent or an organic polymer material. Adsorption removal methods, dry solidification methods that heat and evaporate wastewater, reverse osmosis methods using membranes, electrodialysis, ultrafiltration methods, and the like have been proposed.

When the above methods were used, there were many problems such as the following, and there was a need for improvement in each method. For example, (1) the coagulation separation and removal method cannot sufficiently treat nickel, (2) the adsorption and removal method and the like generate a large amount of solid components after the treatment even if nickel can be adsorbed, and (3) the reverse osmosis method. , Electrodialysis or ultrafiltration is difficult to remove if organic matter is contained in the wastewater, and the treatment cost is high. (4) The dry-drying method by heat evaporation is complicated and the treatment cost is high. 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 (see, for example, Patent Documents 1 to 4) has been proposed. However, no example is given regarding the treatment of nickel-containing wastewater containing nickel and a compound having a complexing ability.

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

An object of the present invention is to provide a compound having an ability to form a complex with nickel, and a method for purifying a nickel-containing aqueous solution that reduces the nickel concentration of the nickel-containing aqueous solution.

As a result of diligent studies to solve the above problems, the present inventors, etc., by using the novel method for purifying a nickel-containing aqueous solution shown in the present invention, contain nickel, a compound having an ability to form a complex, and nickel. We have found that the nickel concentration can be reduced by a simple method, and have completed the present invention.

That is, the present invention has the following gist.
[1] After adding a salt of dithiocarbamic acid and an inorganic flocculant having a content of nickel and a compound having a complex forming ability or more to an aqueous solution containing nickel and a compound having a complex forming ability, a solid substance is added. A method for purifying a nickel-containing aqueous solution, which comprises removing it.
[2] The compound having an ability to form a complex with nickel is a compound having at least one substituent selected from a carboxyl group, an amino group and a phosphoric acid group in the molecule [1]. The method for purifying a nickel-containing aqueous solution according to.
[3] The salt of dithiocarbamic acid is obtained by reacting an amine compound having a primary amino group / or a secondary amino group with carbon disulfide and an alkali metal hydroxide. The method for purifying a nickel-containing aqueous solution according to the above [1] or [2].
[4] The nickel-containing agent according to any one of [1] to [3] above, wherein the inorganic flocculant is at least one selected from ferric chloride, aluminum sulfate and polyaluminum chloride. Aqueous solution purification method.

Hereinafter, the present invention will be described in detail.

The method for purifying a nickel-containing aqueous solution of the present invention is characterized by adding a salt of dithiocarbamic acid and an inorganic flocculant to a compound having a ability to form a complex with nickel and an aqueous solution containing nickel, and then removing solid substances. To do.

The compound having a complex forming ability with nickel is not particularly limited as long as it is a compound forming a complex with nickel, but for example, at least one or more substituents selected from a carboxyl group, an amino group and a phosphoric acid group are contained in the molecule. Examples include compounds having. In particular, EDTA, citric acid, and pyrophosphoric acid are examples of compounds that form a strong complex with nickel.

The salt of dithiocarbamic acid is not particularly limited as long as it is a compound having a dithiocarbamyl group in the molecule, but for example, diethylamine, piperazine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and heptaethyleneoctamine. Examples thereof include a compound obtained by reacting an amine compound having a primary amino group / or a secondary amino group with carbon disulfide and an alkali metal hydroxide.

Of these, a compound obtained by reacting piperazine or tetraethylenepentamine with carbon disulfide and an alkali metal hydroxide is preferable in terms of nickel treatment performance and compound stability. However, the salt of tetraethylenepentamine dithiocarbamic acid has a composition in which the raw material tetraethylenepentamine contains analogs [chemical formulas (2) to (4)] in addition to the linear body [chemical formula (1)] as the main component. Since only the product is manufactured industrially, 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 does not have such a drawback and is particularly preferable.

アルカリ金属水酸化物としては、入手が容易な点で、水酸化ナトリウムや水酸化カリウムが特に好ましい。

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

Inorganic flocculants need to be added to expedite the removal of solids. Further, it is preferable to use an inorganic compound and a polymer compound in combination as the flocculant. As the inorganic compound, a commercially available inorganic flocculant can be used, and examples thereof include ferric chloride, aluminum sulfate, and polyaluminum chloride.

As the inorganic flocculant, it is preferable to add the content of nickel and a compound having a complexing ability or more. If the amount of the inorganic cohesive agent added is smaller than the content of the compound having the ability to form a complex with nickel, the cohesiveness may be insufficient and the nickel concentration may not be reduced.

The content of the compound having the ability to form a complex with nickel can be calculated by analyzing the concentration of the compound having the ability to form a complex with nickel in the nickel-containing aqueous solution by HPLC, gas chromatography, titration or the like.

As the polymer compound, a commercially available polymer flocculant can be used, and examples thereof include an acrylic acid polymer, an acrylamide polymer, and a dimethylaminoethyl methacrylate polymer. A weak anionic acrylic acid polymer is preferable in terms of aggregation performance.

The order in which the salt of dithiocarbamic acid and the inorganic flocculant are added is not particularly limited, but for example, a method of first adding the salt of dithiocarbamic acid and then adding the inorganic flocculant, or adding the inorganic flocculant first. Then, a method of adding a salt of dithiocarbamic acid can be mentioned. In the method of adding the inorganic aggregating agent first, it may be necessary to add the inorganic aggregating agent again after adding the salt of dithiocarbamic acid. Therefore, the salt of dithiocarbamic acid is added first, and then the inorganic aggregating agent is added. Is preferred.

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.

According to the present invention, the nickel concentration can be reduced even in an aqueous solution containing nickel and a compound having a ability to form a complex with nickel, which is difficult to treat with nickel.

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 (ICP-9820, manufactured by Shimadzu Corporation).

Reference example 1
The chelating agent A (salt of dithiocarbamic acid) used in Examples 1 to 18 was prepared according to the following method.

(Preparation of chelating agent A)
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 parts 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).

（無機凝集剤）
キシダ化学社製３８重量％塩化第二鉄水溶液を無機凝集剤として使用した。

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

An aqueous solution (30 wt% aluminum sulfate aqueous solution) made by adding 30 g of aluminum sulfate manufactured by Kanto Chemical Co., Inc. to water to make a total of 100 g was used as an inorganic flocculant.

30 g of polyaluminum chloride manufactured by Kishida Chemical Co., Ltd. was added to water to make a total of 100 g, and an aqueous solution (30 wt% polyaluminum chloride aqueous solution) was used as an inorganic flocculant.

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

As an example of a method for quantifying a compound having an ability to form a complex with nickel, a method for quantifying EDTA in an aqueous solution containing nickel is shown.

Reference example 2
200 mL of an aqueous solution containing 10 mg / L of nickel ions and 25 mg / L of EDTA was prepared in a beaker, and trans-1,2-diaminocyclohexane-N, N, N', N'-tetraacetic acid (Dojin Kagaku) was prepared as an internal standard substance (surrogate). After adding 25 μL of the solution (manufactured by the laboratory) (40 mg / L), the mixture was heated on a hot plate and concentrated by evaporation until the residual liquid became about 2 mL. The residual liquid was transferred to a centrifugal settling tube with a 10 mL screw cap, and a small amount of washing liquid was combined. 200 μL of formic acid was added to this concentrated solution and mixed, and nitrogen gas was sprayed on a heat block while heating at about 70 ° C. to completely evaporate and dry. Boron trifluoride-methanol (1 mL) was added to the residue in the centrifugal settling tube, sealed, and heated to 80 ° C. on a heat block to carry out a derivatization reaction for 1 hour. After cooling, 3 mL of phosphate buffer and 2 mL of dichloromethane were added, and the mixture was vigorously shaken for 10 minutes and then centrifuged at 3500 rpm for 15 minutes. The dichloromethane layer was removed, filtered using filter paper, and the filtrate was analyzed with a gas chromatograph-mass spectrometer.

As a result of the analysis, it was confirmed by quantitative analysis that the EDTA concentration was 25 mg / L, which was the same as the charged concentration.

Examples 1-6
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 25 mg / L of EDTA was added. While stirring at 150 rpm, add a predetermined amount of chelating agent A, stir at 150 rpm for 10 minutes, then add a predetermined amount of 38 wt% ferric chloride aqueous solution, 30 wt% aluminum sulfate or 30 wt% polyaluminum chloride, 150 rpm. Then, a predetermined amount of 0.1 wt% OA-23 aqueous solution was added, 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 nickel concentration of the aqueous solution after the treatment was measured.

The results are shown in Table 1 below.

実施例１〜３のＥＤＴＡ含有排水では、無機凝集剤に塩化第二鉄を使用した例であり、ニッケル濃度を５ｍｇ／Ｌ以下に低減することができた。

In the EDTA-containing wastewater of Examples 1 to 3, ferric chloride was used as the inorganic flocculant, and the nickel concentration could be reduced to 5 mg / L or less.

Further, in Example 4, the polymer flocculant (OA-23) was not added after the addition of ferric chloride, but the nickel concentration of the aqueous solution after the treatment was the case where the polymer flocculant was added. The value was almost the same as that of the above, and the result was that the nickel concentration could be reduced without adding a polymer flocculant.

Instead of ferric chloride, which is an inorganic flocculant, aluminum sulfate is used in Example 5, and polyaluminum chloride is used in Example 6, but the nickel concentration of the treated aqueous solution is the case where ferric chloride is used. The nickel concentration could be reduced regardless of the type of inorganic flocculant.

Comparative Examples 1 to 4
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 25 mg / L of EDTA was added. While stirring at 150 rpm, add a predetermined amount of 38 wt% ferric chloride aqueous solution, 30 wt% aluminum sulfate or 30 wt% polyaluminum chloride, stir at 150 rpm for 5 minutes, and then 0.1 wt% OA-23 aqueous solution. Was added in a predetermined amount, and the mixture was stirred at 50 rpm for 5 minutes. The pH of the aqueous solution was adjusted to always be a predetermined pH value 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 nickel concentration of the aqueous solution after the treatment was measured.

Comparative Example 5
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 25 mg / L of EDTA was added. While stirring at 150 rpm, a predetermined amount of chelating agent A was added, and the mixture was stirred at 150 rpm for 10 minutes, then a predetermined amount of 0.1 wt% OA-23 aqueous solution was added, 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 nickel concentration of the aqueous solution after the treatment was measured.

The results are shown in Table 2 below.

比較例１，２は、ＥＤＴＡ含有排水に鉄イオンを添加して中和し、ニッケルイオンを鉄イオンと共に水酸化物として沈殿させる従来の凝集沈殿法の例であるが、処理後水溶液のニッケル濃度は７ｍｇ／Ｌ以上であり、ニッケルの処理が不十分であった。

Comparative Examples 1 and 2 are examples of the conventional coagulation-precipitation method in which iron ions are added to the EDTA-containing wastewater to neutralize the nickel ions and the nickel ions are precipitated as a hydroxide together with the iron ions. Was 7 mg / L or more, and the treatment with nickel was insufficient.

Comparative Examples 3 and 4 are examples of a conventional coagulation-precipitation method in which aluminum ions are added to EDTA-containing wastewater to neutralize them and nickel ions are precipitated as hydroxides together with aluminum ions. Was 7 mg / L or more, and the treatment with nickel was insufficient.

Comparative Example 5 is an example in which the inorganic flocculant is not added, but the nickel concentration of the aqueous solution after the treatment is 7.4 mg / L, and the nickel treatment is insufficient as compared with the case where the inorganic flocculant is added. It was.

Examples 7-12
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 320 mg / L of citric acid was added. While stirring at 150 rpm, add a predetermined amount of chelating agent A, stir at 150 rpm for 10 minutes, then add a predetermined amount of 38 wt% ferric chloride aqueous solution, 30 wt% aluminum sulfate or 30 wt% polyaluminum chloride, 150 rpm. Then, a predetermined amount of 0.1 wt% OA-23 aqueous solution was added, 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 nickel concentration of the aqueous solution after the treatment was measured.

The results are shown in Table 3 below.

実施例７〜９のクエン酸含有排水では、無機凝集剤に塩化第二鉄を使用した例であり、ニッケル濃度を１ｍｇ／Ｌ以下に低減し、ニッケルを十分処理することができた。

In the citric acid-containing wastewater of Examples 7 to 9, ferric chloride was used as the inorganic flocculant, and the nickel concentration was reduced to 1 mg / L or less, and nickel could be sufficiently treated.

Further, Example 10 is an example in which the polymer flocculant was not added after the addition of ferric chloride, but the nickel concentration of the aqueous solution after the treatment was substantially the same as that when the polymer flocculant was added. The result was that the nickel concentration could be reduced without adding a polymer flocculant.

Instead of ferric chloride, which is an inorganic flocculant, aluminum sulfate is used in Example 11 and polyaluminum chloride is used in Example 12, but the nickel concentration of the treated aqueous solution is the case where ferric chloride is used. The nickel concentration could be reduced regardless of the type of inorganic flocculant.

Comparative Examples 6-9
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 320 mg / L of citric acid was added. While stirring at 150 rpm, add a predetermined amount of 38 wt% ferric chloride aqueous solution, 30 wt% aluminum sulfate or 30 wt% polyaluminum chloride, stir at 150 rpm for 5 minutes, and then 0.1 wt% OA-23 aqueous solution. Was added in a predetermined amount, and the mixture was stirred at 50 rpm for 5 minutes. The pH of the aqueous solution was adjusted to always be a predetermined pH value 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 nickel concentration of the aqueous solution after the treatment was measured.

Comparative Example 10
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ions and 320 mg / L of citric acid was added. While stirring at 150 rpm, a predetermined amount of chelating agent A was added, and the mixture was stirred at 150 rpm for 10 minutes, then a predetermined amount of 0.1 wt% OA-23 aqueous solution was added, 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 nickel concentration of the aqueous solution after the treatment was measured.

The results are shown in Table 4 below.

比較例６，７は、クエン酸含有排水に鉄イオンを添加して中和する凝集沈殿法の例であるが、処理後水溶液のニッケル濃度は１０ｍｇ／Ｌであり、ニッケルを全く処理できない結果となった。

Comparative Examples 6 and 7 are examples of the coagulation-precipitation method in which iron ions are added to the citric acid-containing wastewater to neutralize the waste, but the nickel concentration of the aqueous solution after the treatment is 10 mg / L, and the result is that nickel cannot be treated at all. became.

Comparative Examples 8 and 9 are examples of a coagulation-precipitation method in which aluminum ions are added to the citric acid-containing wastewater to neutralize the wastewater, but the nickel concentration of the aqueous solution after the treatment is 10 mg / L, and the result is that nickel cannot be treated at all. became.

Comparative Example 10 is an example in which the inorganic flocculant is not added, but the nickel concentration of the aqueous solution after the treatment is 2.0 mg / L of the citric acid-containing wastewater, and the nickel treatment is compared with the case where the inorganic flocculant is added. Was inadequate.

Examples 13-18
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ion and 303 mg / L of pyrophosphate was added. While stirring at 150 rpm, add a predetermined amount of chelating agent A, stir at 150 rpm for 10 minutes, then add a predetermined amount of 38 wt% ferric chloride aqueous solution, 30 wt% aluminum sulfate or 30 wt% polyaluminum chloride, 150 rpm. Then, a predetermined amount of 0.1 wt% OA-23 aqueous solution was added, 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 nickel concentration of the aqueous solution after the treatment was measured.

The results are shown in Table 5 below.

実施例１３〜１５のピロリン酸含有排水では、無機凝集剤に塩化第二鉄を使用した例であり、ニッケル濃度を１ｍｇ／Ｌ以下に低減し、ニッケルを十分処理することができた。

In the pyrophosphoric acid-containing wastewater of Examples 13 to 15, ferric chloride was used as the inorganic flocculant, and the nickel concentration was reduced to 1 mg / L or less, and nickel could be sufficiently treated.

Further, Example 16 is an example in which the polymer flocculant was not added after the addition of ferric chloride, but the nickel concentration of the aqueous solution after the treatment was substantially the same as that in the case where the polymer flocculant was added. The result was that the nickel concentration could be reduced without adding a polymer flocculant.

Instead of ferric chloride, which is an inorganic flocculant, aluminum sulfate is used in Example 17, and polyaluminum chloride is used in Example 18, but the nickel concentration of the treated aqueous solution is the case where ferric chloride is used. The nickel concentration could be reduced regardless of the type of inorganic flocculant.

Comparative Examples 11-14
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ion and 303 mg / L of pyrophosphate was added. While stirring at 150 rpm, add a predetermined amount of 38 wt% ferric chloride aqueous solution, 30 wt% aluminum sulfate or 30 wt% polyaluminum chloride, stir at 150 rpm for 5 minutes, and then 0.1 wt% OA-23 aqueous solution. Was added in a predetermined amount, and the mixture was stirred at 50 rpm for 5 minutes. The pH of the aqueous solution was adjusted to always be a predetermined pH value 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 nickel concentration of the aqueous solution after the treatment was measured.

Comparative Example 15
A jar tester was placed in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L of nickel ion and 303 mg / L of pyrophosphate was added. While stirring at 150 rpm, a predetermined amount of chelating agent A was added, and the mixture was stirred at 150 rpm for 10 minutes, then a predetermined amount of 0.1 wt% OA-23 aqueous solution was added, 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 nickel concentration of the aqueous solution after the treatment was measured.

The results are shown in Table 6 below.

比較例１１，１２は、ピロリン酸含有排水に鉄イオンを添加して中和する凝集沈殿法の例であるが、処理後水溶液のニッケル濃度は５ｍｇ／Ｌ以上であり、ニッケルの処理が不十分であった。

Comparative Examples 11 and 12 are examples of a coagulation-precipitation method in which iron ions are added to the pyrophosphate-containing wastewater to neutralize the wastewater, but the nickel concentration of the aqueous solution after the treatment is 5 mg / L or more, and the nickel treatment is insufficient. Met.

Comparative Examples 13 and 14 are examples of a coagulation-precipitation method in which aluminum ions are added to the pyrophosphate-containing wastewater to neutralize the wastewater, but the nickel concentration of the aqueous solution after the treatment is 5 mg / L or more, and the nickel treatment is insufficient. Met.

Comparative Example 15 is an example in which the inorganic flocculant is not added, but the nickel concentration of the aqueous solution after the treatment is 2.0 mg / L, and the nickel treatment is insufficient as compared with the case where the inorganic flocculant is added. there were.

According to the method for purifying a nickel-containing aqueous solution of the present invention, the nickel concentration can be reduced even in a compound containing nickel and a compound having an ability to form a complex with nickel, which is difficult to treat with nickel, and thus a novel nickel-containing aqueous solution is contained. As a method for purifying an aqueous solution, it has the potential to be used as a method for treating nickel-containing wastewater from plating factories, electronic parts / mechanical parts manufacturing factories, automobile factories, and the like.

Claims (1)

A salt of dithiocarbamic acid obtained by reacting piperazine, carbon disulfide and an alkali metal hydroxide in an aqueous solution containing ethylenediaminetetraacetic acid and nickel, ferric chloride, aluminum sulfate and aluminum sulfate having a content equal to or higher than that of ethylenediaminetetraacetic acid. A method for purifying a nickel-containing aqueous solution, which comprises adding at least one inorganic flocculant selected from polyaluminum chloride and then removing solid matter.