Purification agent for aqueous nickel-containing solution and method for purifying aqueous nickel-containing solution

Abstract

The present invention relates to a purifying agent for a nickel-containing aqueous solution and a method for purifying a nickel-containing aqueous solution. The present invention provides a method for purifying a nickel-containing aqueous solution, which reduces the nickel concentration of an aqueous solution containing a compound having a capability of complexing with nickel and nickel. In an aqueous solution containing a compound having a capability of complexing with nickel and nickel, a salt of dithiocarbamic acid, a polyamine having 3 to 8 nitrogen atoms, an alkaline earth metal compound are added, followed by adding an inorganic flocculant in an amount of not less than the amount of the compound having a capability of complexing with nickel, and then removing the solid.

Description

[0001] This application is a divisional application of the application filed on October 8, 2018, with application number 201811167866.6, entitled "Purifying Agent for Nickel-Containing Aqueous Solution and Purification Method for Nickel-Containing Aqueous Solution". Technical Field

[0002] The present invention relates to a purification method capable of removing nickel from an aqueous solution containing a compound having the ability to complex with nickel. Background Technology

[0003] It is known that aqueous solutions containing nickel are treated by methods such as transporting them to wastewater treatment equipment, for example, adding iron ions to make the solution alkaline, causing nickel ions and other contained ions to precipitate together with iron ions and other contained ions in the form of hydroxides, and then separating them from the aqueous solution before discharging them.

[0004] Nickel is a harmful heavy metal and is designated as a Category 1 chemical substance under the Chemical Substances Control and Management Promotion Law. It has been set as an important monitoring item in environmental benchmarks related to water pollution, increasing the importance of wastewater treatment.

[0005] However, there are increasing instances where wastewater from plating plants, electronic / mechanical component manufacturing plants, automobile factories, thermal power plants, and waste incineration plants contains organic acids such as citric acid and gluconic acid, compounds such as ethylenediaminetetraacetic acid (EDTA), cyanide, amines, ammonia, and polyphosphoric acid that have the ability to complex with nickel, and these cannot be treated using the aforementioned hydroxide method.

[0006] In contrast, methods are known to render nickel insoluble by chemically treating compounds capable of complexing with nickel. However, the current situation is that even with chemical treatments such as oxidation using chlorine-based reagents, electrolytic oxidation, hydrogen peroxide-ferrous salt method, ozone oxidation, and wet oxidation, sufficient purification cannot be achieved due to problems such as hindrance to the oxidation reaction caused by coexisting heavy metal elements and the formation of oxide scale.

[0007] As a technology for removing various heavy metal elements contained in wastewater, various methods have been proposed, such as aggregation and separation removal by adding inorganic or organic flocculants, removal by electrolysis, adsorption removal using activated carbon, inorganic adsorbents or organic polymer materials, drying and solidification method by heating and evaporating wastewater, reverse osmosis using membranes, electrodialysis or ultrafiltration, etc.

[0008] Even with the above methods employed, several problems remain, requiring corresponding improvements to any single method. For example:

[0009] (1) Aggregation and separation removal method: cannot fully remove nickel.

[0010] (2) Adsorption removal methods, etc.: For example, even if nickel can be adsorbed, a large amount of solid components will still be generated after treatment.

[0011] (3) Reverse osmosis, electrodialysis, or ultrafiltration: These methods are difficult to remove organic matter from wastewater, and their treatment costs are high.

[0012] (4) Drying method using heating and evaporation: This method is complicated and has high processing costs.

[0013] Therefore, methods for using dithiocarbamic acid salts as heavy metal treatment agents in wastewater have been proposed (for example, see Patent Documents 1-4). However, the methods described in these patent documents are insufficient in purifying heavy metals from nickel-containing wastewater containing compounds that have the ability to complex with heavy metals.

[0014] In addition, heavy metal treatment agents comprising dithiocarboxylate salts of polyamines and amines having three or more amino groups within the molecule have been proposed (for example, see Patent Document 5). However, the method disclosed in Patent Document 5 is not sufficiently effective in purifying nickel.

[0015] Existing technical documents

[0016] Patent documents

[0017] Patent Document 1: Japanese Patent Application Publication No. 2009-249399

[0018] Patent Document 2: Japanese Patent Application Publication No. 2011-074350

[0019] Patent Document 3: Japanese Patent Application Publication No. 2014-088477

[0020] Patent Document 4: Japanese Patent Application Publication No. 2002-177902

[0021] Patent Document 5: Japanese Patent No. 5272306 Summary of the Invention

[0022] The problem the invention aims to solve

[0023] The present invention was made in view of the above-mentioned background technology, and its object is to provide: a purifying agent for reducing the nickel concentration of an aqueous solution containing a compound having the ability to complex with nickel; and a purification method for a nickel-containing aqueous solution using the purifying agent.

[0024] Solution for solving the problem

[0025] In order to solve the above-mentioned problems, the inventors conducted repeated and in-depth research and found that by using the novel purification method for nickel-containing aqueous solutions disclosed in this invention, the nickel concentration of aqueous solutions containing compounds that have the ability to complex with nickel can be reduced in a simple way, thus completing this invention.

[0026] That is, the present invention has the following main points.

[0027] [1] A purifying agent for nickel-containing aqueous solutions, characterized in that it comprises, relative to 100 parts by weight of a salt of dithiocarbamic acid, 20 parts by weight or more of a polyamine having 3 to 8 nitrogen atoms and an alkaline earth metal compound.

[0028] [2] A purifying agent for nickel-containing aqueous solutions, characterized in that, relative to 100 parts by weight of a salt of dithiocarbamic acid, it comprises 20 or more parts by weight of a polyamine having 3 to 8 nitrogen atoms, an alkaline earth metal compound, and an inorganic sulfide.

[0029] [3] The purifying agent for nickel-containing aqueous solution described in [2] above is characterized in that the inorganic sulfide is sodium hydrogen sulfide.

[0030] [4] The purifying agent for nickel-containing aqueous solutions described in [1] or [2] above is characterized in that the salt of dithiocarbamic acid is the reaction product of an amine compound having at least one amino group selected from the group consisting of primary and secondary amino groups and carbon disulfide and an alkali metal hydroxide.

[0031] [5] The purifying agent for nickel-containing aqueous solutions described in [1] or [2] above is characterized in that the salt of dithiocarbamic acid is a reaction product of an amine compound having two or more amino groups selected from the group consisting of primary and secondary amino groups and carbon disulfide and alkali metal hydroxide.

[0032] [6] The purifying agent for nickel-containing aqueous solutions described in [1] or [2] above is characterized in that the salt of dithiocarbamic acid is a reaction product of piperazine or tetraethylenepentamine with carbon disulfide and alkali metal hydroxide.

[0033] [7] A method for purifying a nickel-containing aqueous solution, characterized in that, in the nickel-containing aqueous solution, the purifying agent for the nickel-containing aqueous solution described in any one of [1] to [6] is added, and then the generated solids are removed.

[0034] [8] The method for purifying a nickel-containing aqueous solution according to [7] above is characterized in that the nickel-containing aqueous solution further contains a compound having the ability to complex with nickel.

[0035] [9] The method for purifying nickel-containing aqueous solutions according to [8] above is characterized in that the compound having the ability to complex with nickel is a compound having a functional group selected from the group consisting of carboxyl and amino groups within its molecule.

[0036]

[10] The method for purifying nickel-containing aqueous solutions according to any one of [7] to [9] above is characterized in that an inorganic flocculant is added before removing solids.

[0037]

[11] The method for purifying nickel-containing aqueous solutions according to any one of [7] to [9] above is characterized in that an inorganic flocculant and a polymeric flocculant are added before removing solids.

[0038]

[12] The method for purifying nickel-containing aqueous solutions according to

[10] or

[11] above is characterized in that the inorganic flocculant is a substance selected from the group consisting of iron compounds and aluminum compounds.

[0039] The effects of the invention

[0040] The purifying agent for nickel-containing aqueous solutions of the present invention can reduce the nickel concentration even in nickel-containing aqueous solutions (e.g., containing compounds that have the ability to complex with nickel and nickel aqueous solutions) where nickel purification is difficult, and is therefore extremely useful in industry. Detailed Implementation

[0041] The present invention will now be described in detail.

[0042] The purifying agent for nickel-containing aqueous solutions of the present invention is characterized in that, relative to 100 parts by weight of a dithiocarbamic acid salt, it comprises 20 or more parts by weight of a polyamine having 3 to 8 nitrogen atoms and an alkaline earth metal compound.

[0043] As a salt of dithiocarbamic acid, there is no particular limitation as long as the compound has a dithiocarbamoyl group in its molecule. Examples include compounds obtained by reacting an amine compound having at least one amino group selected from the group consisting of primary and secondary amino groups with carbon disulfide and an alkali metal hydroxide. More preferably, compounds obtained by reacting an amine compound having two or more amino groups selected from the group consisting of primary and secondary amino groups with carbon disulfide and an alkali metal hydroxide.

[0044] Examples of amine compounds having at least one amino group selected from the group consisting of primary and secondary amino groups include: diethylamine, piperazine, diethylenetriamine, N-(2-aminoethyl)piperazine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, heptaethyleneoctamine, etc.

[0045] Among these, considering both nickel processing performance and the stability of the compound, compounds obtained by reacting piperazine or tetraethylenepentamine with carbon disulfide and alkali metal hydroxides are preferred. However, for dithiocarbamate salts of tetraethylenepentamine, only compositions of tetraethylenepentamine as a raw material containing analogues [refer to formulas (2) to (4)) in addition to the linear form of the main component [refer to formula (1) below] are industrially manufactured. Therefore, the resulting dithiocarbamate salt is also a composition, which has the disadvantage of complicating quality control. In contrast, dithiocarbamate salts of piperazine do not have this disadvantage and are particularly preferred.

[0046]

[0047] Sodium hydroxide and potassium hydroxide are particularly preferred as alkali metal hydroxides, considering their easy availability.

[0048] Examples of polyamines having 3 to 8 nitrogen atoms include: diethylenetriamine, N-(2-aminoethyl)piperazine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, heptaethyleneoctamine, and polyethyleneimines with a weight-average molecular weight of 300.

[0049] The amount of polyamine having 3 to 8 nitrogen atoms added relative to 100 parts by weight of dithiocarbamic acid salt is preferably 20 parts by weight or more. By adding 20 parts by weight or more, sufficient nickel treatment capability can be obtained.

[0050] Examples of alkaline earth metal compounds include: beryllium fluoride, beryllium chloride, beryllium bromide, beryllium iodide, beryllium oxide, beryllium hydroxide, beryllium carbonate, beryllium nitrate, beryllium sulfate, beryllium sulfide, calcium fluoride, calcium chloride, calcium bromide, calcium iodide, calcium oxide, calcium hydroxide, calcium carbonate, calcium bicarbonate, calcium nitrate, calcium sulfate, calcium sulfide, calcium phosphate, calcium acetate, calcium oxalate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium oxide, and magnesium hydroxide. Magnesium carbonate, magnesium bicarbonate, magnesium nitrate, magnesium sulfate, magnesium sulfide, magnesium phosphate, magnesium acetate, strontium fluoride, strontium chloride, strontium bromide, strontium iodide, strontium oxide, strontium hydroxide, strontium carbonate, strontium nitrate, strontium sulfate, strontium sulfide, strontium phosphate, strontium acetate, barium chloride, barium bromide, barium iodide, barium oxide, barium hydroxide, barium carbonate, barium nitrate, barium sulfide, barium sulfate, barium sulfide, barium phosphate, barium acetate, radium chloride, radium bromide, etc. Among these, calcium chloride and calcium hydroxide are particularly preferred due to their ease of availability.

[0051] For alkaline earth metal compounds, nickel treatment capacity can be obtained when added at a concentration of 0.01 g / L or higher. Relatively speaking, it is advisable to add more than 5 parts by weight relative to 100 parts by weight of thiocarbamate salt. Even if more than 250,000 parts by weight are added, the nickel treatment capacity is still fixed. Therefore, excessive addition of alkaline earth metal compounds will increase the cost of nickel wastewater treatment and is not economical.

[0052] Examples of inorganic sulfides include sodium sulfide, sodium hydrogen sulfide, potassium sulfide, potassium hydrogen sulfide, calcium sulfide, calcium hydrogen sulfide, magnesium hydrogen sulfide, and ammonium sulfide. Among these, sodium hydrogen sulfide is preferred from an economic perspective.

[0053] The amount of inorganic sulfide added relative to 100 parts by weight of dithiocarbamate salt is preferably 250 parts by weight or more. By adding 250 parts by weight or more, sufficient nickel treatment capability can be obtained.

[0054] The purifying agent of the present invention is particularly useful for the purification treatment of nickel-containing aqueous solutions.

[0055] The purification method for nickel-containing aqueous solutions of the present invention is characterized by adding the purification agent of the present invention described above to the nickel-containing aqueous solution, and then removing the generated solids. Here, the generated solids contain nickel immobilized using the purification agent of the present invention.

[0056] The purification method of the present invention is particularly effective for nickel-containing aqueous solutions (e.g., compounds with the ability to complex with nickel) and nickel-containing aqueous solutions, which are particularly difficult to treat.

[0057] As for compounds capable of complexing with nickel, there are no particular limitations as long as they form complexes with nickel. Examples include compounds with functional groups selected from the group consisting of carboxyl and amino groups within their molecules. Specifically, examples include EDTA and polyphosphates, with EDTA being a particularly notable example of a compound that forms a strong complex with nickel.

[0058] There is no particular order in which dithiocarbamic acid salts, polyamines with 3 to 8 nitrogen atoms, and alkaline earth metal compounds are added to nickel-containing aqueous solutions.

[0059] To rapidly remove solids, it is preferable to add a flocculant before removing the solids. Examples of flocculants include inorganic flocculants and polymeric flocculants, and more preferably, a combination of inorganic and polymeric flocculants.

[0060] As an inorganic flocculant, commercially available inorganic flocculants can be used without particular limitations. Examples include: iron compounds such as ferric chloride, aluminum compounds such as aluminum sulfate and polyaluminum chloride, etc.

[0061] When the nickel-containing aqueous solution contains compounds capable of complexing with nickel, the amount of inorganic flocculant added is preferably set to be higher than or equal to the content of the compounds capable of complexing with nickel contained in the nickel-containing aqueous solution. By setting the amount of inorganic flocculant added to be higher than or equal to the content of the compounds capable of complexing with nickel, aggregation is increased, and it is easier to reduce the nickel concentration of the treated aqueous solution to below the discharge standard.

[0062] The concentration of compounds capable of complexing with nickel in nickel-containing aqueous solutions can be calculated by analysis methods such as HPLC, gas chromatography, and titration.

[0063] Commercially available polymeric flocculants can be used, with no particular limitation. Examples include acrylic polymers, acrylamide polymers, and dimethylaminoethyl methacrylate polymers. From the perspective of aggregation performance, weakly anionic acrylic polymers are preferred. Adding a polymeric flocculant before removing solids can sometimes facilitate the treatment of the removed solids.

[0064] When using inorganic flocculants and polymeric flocculants in combination, there is no particular limitation on the order in which these flocculants are added, but it is preferable to add the inorganic flocculant first, followed by the polymeric flocculant.

[0065] There are no particular limitations on the methods for removing solids. Examples include methods such as filtration, centrifugation, and separation of solids from the supernatant after sedimentation.

[0066] Example

[0067] The present invention will be described in detail below, but the present invention is not limited to these embodiments.

[0068] (Analysis Methods)

[0069] The concentration of nickel ions in the aqueous solution was determined using an ICP emission spectrometer (ICPE-9800, manufactured by Shimadzu Corporation).

[0070] Preparation Example 1

[0071] The dithiocarbamic acid salts used in the examples and comparative examples were prepared according to the following method.

[0072] (Preparation of dithiocarbamic acid salt A)

[0073] 112 g of piperazine (manufactured by Tosoh Corporation) and 386 g of pure water were mixed. Then, under a nitrogen atmosphere at 25°C, 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.) were added dropwise in four portions, alternatingly. After stirring for 1 hour, an aqueous solution containing 40 wt% of the compound represented by chemical formula (5) was obtained.

[0074]

[0075] (Preparation of dithiocarbamic acid salt B)

[0076] 159 g of tetraethylenepentamine (manufactured by Tosoh Corporation) and 331 g of pure water were mixed. Then, under a nitrogen atmosphere at 25°C, 281 g of sodium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 230 g of carbon disulfide (manufactured by Kishida Chemical Co., Ltd.) were added dropwise in four portions, one by one, while stirring. After stirring for 1 hour, an aqueous solution containing 40% by weight of the compound shown in formula (6) was obtained.

[0077]

[0078] (C, a salt of dithiocarbamic acid)

[0079] As salt C of dithiocarbamate, a 40% by weight aqueous solution is formed by adding water to the compound N,N-diethyldithiocarbamate sodium trihydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation) as shown in chemical formula (7).

[0080]

[0081] (Polyamines)

[0082] As polyamines, the following are used: ethyleneimine produced by Tosoh Corporation and polyethyleneimine produced by Nippon Shokubai Co., Ltd.

[0083] Ethylene diamine (hereinafter referred to as EA(2)).

[0084] Diethylenetriamine (hereinafter referred to as EA(3)).

[0085] Triethylenetetramine (hereinafter referred to as EA(4)).

[0086] Tetraethylenepentamine (hereinafter referred to as EA(5)).

[0087] Pentylenehexamine (hereinafter referred to as EA(6)).

[0088] Heptaethylene octamine (hereinafter referred to as EA(8)).

[0089] The product of poly(ethylene imide) with a weight average molecular weight of 300 (hereinafter referred to as PEI(300)).

[0090] The product of poly(ethylene imide) with a weight average molecular weight of 1800 (hereinafter referred to as PEI(1800)).

[0091] (Alkali earth metal compounds)

[0092] The following compounds, prepared by Kishida Chemical Co., Ltd., are used as alkaline earth metal compounds.

[0093] Magnesium chloride, calcium chloride, calcium hydroxide, strontium chloride, barium nitrate, barium hydrochloride.

[0094] (Inorganic flocculant)

[0095] The following aqueous solution is used as an inorganic flocculant.

[0096] Add 30g of polyaluminum chloride prepared by Kishida Chemical Co., Ltd. to water to form a total of 100g of aqueous solution (30% by weight polyaluminum chloride aqueous solution).

[0097] Kishida Chemical Co., Ltd. prepared a 38% by weight aqueous solution of ferric chloride.

[0098] (Polymer flocculant)

[0099] OA-23 (a weakly anionic polymer) manufactured by Organo Corporation was used as a polymeric flocculant.

[0100] Example 1

[0101] A 500 mL beaker was set up with a Jar Tester and 500 mL of an aqueous solution containing 10 mg / L nickel ions and 25 mg / L EDTA was added. Then, while stirring at 150 rpm, 500 mg / L of dithiocarbamate salt A, 400 mg / L of diethylenetriamine [EA(3)], and 1 g / L of calcium chloride were added to adjust the pH to 11, and the mixture was stirred at 150 rpm for 1 hour. Next, 1000 mg / L of a 30% by weight polyaluminum chloride (hereinafter referred to as PAC) aqueous solution was added to adjust the pH to 7, and the mixture was stirred at 150 rpm for 5 minutes. The pH of the aqueous solution was always adjusted to the specified pH using trace amounts of hydrochloric acid and sodium hydroxide. After stirring, the mixture was allowed to stand for 10 minutes, and the aqueous solution was filtered using 5A filter paper made by Advantech Co., Ltd. The nickel concentration of the treated aqueous solution was measured. The results are shown in Table 1.

[0102] Examples 2-11

[0103] The added reagents were changed to those shown in Tables 1 and 2, and the nickel concentration of the treated aqueous solution was measured in the same manner as in Example 1. These results are presented together in Tables 1 and 2.

[0104] [Table 1]

[0105]

[0106] [Table 2]

[0107]

[0108] As shown in Examples 1-8, the nickel concentration in the treated aqueous solution of EDTA-containing wastewater can be reduced to below 0.8 mg / L.

[0109] Comparative Example 1

[0110] A Jar Tester was set up in a 500 mL beaker, and 500 mL of an aqueous solution containing 10 mg / L nickel ions and 25 mg / L EDTA was added. The pH was then adjusted to 11, and the mixture was stirred at 150 rpm for 1 hour. Next, 1000 mg / L of a 30% (w / w) PAC aqueous solution was added, the pH was adjusted to 7, and the mixture was stirred at 150 rpm for 5 minutes. The pH of the aqueous solution was always adjusted to the specified pH using trace amounts of hydrochloric acid and sodium hydroxide. After stirring, the mixture was allowed to stand for 10 minutes, and the aqueous solution was filtered through 5A filter paper made by Advantech Co., Ltd. The nickel concentration of the treated aqueous solution was determined. The results are shown in Table 3.

[0111] Comparative Examples 2-13

[0112] The added reagents were changed to those shown in Tables 3 and 4, and the nickel concentration of the treated aqueous solution was measured in the same manner as in Example 1. These results are presented together in Tables 3 and 4.

[0113] Reference Example 1

[0114] A 500 mL beaker was set up with a Jar Tester for coagulation testing. 500 mL of an aqueous solution containing 10 mg / L nickel ions and 25 mg / L EDTA was added. Then, while stirring at 150 rpm, 500 mg / L of dithiocarbamate salt A and 400 mg / L of pentaethylenehexamine were added to adjust the pH to 11. The mixture was stirred at 150 rpm for 14 hours. Next, 1000 mg / L of a 30% (w / w) PAC aqueous solution was added to adjust the pH to 7, and the mixture was stirred at 150 rpm for 5 minutes. The pH of the aqueous solution was always adjusted to the specified pH using trace amounts of hydrochloric acid and sodium hydroxide. After stirring, the mixture was allowed to stand for 10 minutes, and the aqueous solution was filtered through 5A filter paper manufactured by Advantech Co., Ltd. The nickel concentration of the treated aqueous solution was measured. The results are shown in Table 4.

[0115] [Table 3]

[0116]

[0117] [Table 4]

[0118]

[0119] Comparative Example 1 is an example of a treatment method that involves adding aluminum ions for neutralization, causing nickel ions to precipitate together with the aluminum ions as a hydroxide. The nickel concentration in the treated aqueous solution was 7.0 mg / L, and the nickel content could not be reduced.

[0120] Comparative Examples 2 and 3 are examples where only calcium chloride was added for treatment. The nickel concentration in the treated aqueous solution was 4.7–5.3 mg / L, which could not be reduced.

[0121] Comparative Examples 4-6 are examples where only dithiocarbamic acid salts were added. The nickel concentration in the treated aqueous solutions was 4.9-5.5 mg / L, and the nickel content could not be reduced.

[0122] Comparative Example 7 is an example where only dithiocarbamic acid salt A and sodium hydrogen sulfide were added. The nickel concentration in the treated aqueous solution was 5.2 mg / L, and the nickel content could not be reduced.

[0123] Comparative Example 8 is an example of salt A containing dithiocarbamic acid and calcium chloride. The nickel concentration in the treated aqueous solution was 4.3 mg / L, which was insufficient to adequately reduce the nickel content.

[0124] Comparative Example 9 is an example where only polyamine was added. The nickel concentration in the treated aqueous solution was the same as before the addition of the reagent, at 10 mg / L, and the nickel concentration could not be reduced.

[0125] Comparative Example 10 is an example where polyamines and calcium chloride were added. The nickel concentration in the treated aqueous solution was the same as before the addition of the reagents, at 10 mg / L, and the nickel concentration could not be reduced.

[0126] Comparative Example 11 is an example of adding dithiocarbamic acid salt A and a polyamine. The nickel concentration in the treated aqueous solution was 3.0 mg / L, which was insufficient to adequately reduce the nickel content.

[0127] Comparative Example 12 is an example in which dithiocarbamic acid salt A and EA (2) (outside the scope of the present invention) and calcium chloride were added. The nickel concentration of the treated aqueous solution was not improved compared with that of Comparative Example 8 (without EA (2)).

[0128] Comparative Example 13 is an example in which dithiocarbamic acid salt A and PEI (1800) and calcium chloride (which are outside the scope of this invention) were added. The nickel concentration of the treated aqueous solution was 3.5 mg / L, which was insufficient to reduce nickel.

[0129] Reference Example 1 is an example where the same amount of reagent was added as in Comparative Example 11, but the stirring time after adding the reagent was changed from 1 hour to 14 hours. The nickel concentration of the treated aqueous solution was almost the same as that in Example 4 where calcium chloride was added, but it took a long time to reduce the nickel concentration.

[0130] Examples 12-16, Comparative Example 14

[0131] The added reagents were changed to those shown in Table 5, and the nickel concentration of the treated aqueous solution was measured in the same manner as in Example 1. These results are shown in Table 5.

[0132] [Table 5]

[0133]

[0134] Examples 12-16 are examples of treatments in which the weight percentage of the polyamine is varied within the scope of the present invention. Regardless of the weight percentage of the polyamine, the nickel concentration can be reduced to below 1.6 mg / L.

[0135] Comparative Example 14 is an example of adding salt A of dithiocarbamic acid and a polyamine in amounts below the scope of the present invention. The nickel concentration of the treated aqueous solution was 4.1 mg / L, which could not reduce the nickel content.

[0136] Examples 17-21

[0137] The added reagents were changed to those shown in Table 6, and the nickel concentration of the treated aqueous solution was measured in the same manner as in Example 1. These results are shown in Table 6.

[0138] [Table 6]

[0139]

[0140] Examples 17-21 are examples of treatments in which the type of alkaline earth metal is changed within the scope of the present invention. Regardless of the type of alkaline earth metal, the concentration of nickel can be reduced to below 1.0 mg / L.

[0141] Examples 22-25, Comparative Example 15

[0142] The added reagents were changed to those shown in Table 7, and the nickel concentration of the treated aqueous solution was measured in the same manner as in Example 1. These results are shown in Table 7.

[0143] [Table 7]

[0144]

[0145] Examples 22-25 are examples of treatments where the amount of calcium chloride, an alkaline earth metal, added was changed. By adding 0.01 g / L or more of calcium chloride, the concentration of nickel was reduced to below 0.2 mg / L.

[0146] Comparative Example 15 is an example in which calcium chloride, as an alkaline earth metal, is added at an amount of 0.001 g / L. As shown in Comparative Example 15, it can be seen that when the amount of alkaline earth metal used in combination with the salt of dithiocarbamic acid and the polyamine is small, the reduction effect on nickel is low.

[0147] Examples 26-27

[0148] The added reagents were changed to those shown in Table 8, and the nickel concentration of the treated aqueous solution was measured in the same manner as in Example 1. These results are presented together in Table 8.

[0149] [Table 8]

[0150]

[0151] Examples 26 and 27 are examples of treatments involving changes in the amount of inorganic sulfide added. Both examples reduced the nickel concentration to below 1.2 mg / L.

[0152] Example 28

[0153] A 500 mL beaker was set up with a Jar Tester and 500 mL of an aqueous solution containing 10 mg / L nickel ions and 25 mg / L EDTA was added. Then, while stirring at 150 rpm, 500 mg / L of dithiocarbamate salt A, 400 mg / L of diethylenetriamine [EA(3)], and 1 g / L of calcium chloride were added to adjust the pH to 11, and the mixture was stirred at 150 rpm for 1 hour. Next, 1000 mg / L of a 30 wt% PAC aqueous solution was added, and the pH was adjusted to 7, and the mixture was stirred at 150 rpm for 5 minutes. Then, 2000 mg / L of a 0.1 wt% OA-23 aqueous solution was added as a polymeric flocculant, and the pH was adjusted to 7, and the mixture was stirred at 50 rpm for 5 minutes. The pH of the aqueous solution was always adjusted to the specified pH using trace amounts of hydrochloric acid and sodium hydroxide. After stirring, the solution was allowed to stand for 10 minutes, then filtered through 5A filter paper made by Advantech Co., Ltd., and the nickel concentration of the treated solution was measured. The results are shown in Table 9.

[0154] Example 29

[0155] The 30% by weight PAC aqueous solution was replaced with a 38% by weight ferric chloride aqueous solution, and the nickel concentration of the treated aqueous solution was measured in the same manner as in Example 28. The results are shown in Table 9.

[0156] [Table 9]

[0157]

[0158] Example 28 is an example of adding a polymeric flocculant in Example 1. The nickel concentration in the treated aqueous solution was the same as that without the addition of the polymeric flocculant, indicating that the nickel treatment was sufficient.

[0159] Example 29 is an example of using an aqueous solution of ferric chloride as an inorganic flocculant. The nickel concentration in the treated aqueous solution was 0.2 mg / L, and the nickel treatment was sufficient regardless of the type of inorganic flocculant.

[0160] Industrial availability

[0161] According to the purification method of the nickel-containing aqueous solution of the present invention, even in nickel-containing aqueous solutions containing compounds capable of complexing with nickel, which are difficult to process, the nickel concentration can be reduced. Therefore, as a novel purification method for nickel-containing aqueous solutions, it has the potential to treat nickel-containing wastewater from plating plants, electronic component / mechanical component manufacturing plants, automobile plants, etc.

Claims

1. A method for purifying an aqueous solution containing ethylenediaminetetraacetic acid and nickel, characterized in that, In an aqueous solution containing ethylenediaminetetraacetic acid and nickel, a salt of dithiocarbamic acid (a product of the reaction of piperazine or tetraethylenepentamine with carbon disulfide and alkali metal hydroxide), at least one selected from diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine, and calcium hydroxide are added. The resulting solids are then removed from the aqueous solution. The amount of the added dithiocarbamic acid salt is 100 parts by weight, the amount of the added at least one selected from diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine is 20 parts by weight or more, and the amount of the added calcium hydroxide is 5 parts by weight or more and 250,000 parts by weight or less, relative to 100 parts by weight of the added dithiocarbamic acid salt.

2. The purification method for an aqueous solution containing ethylenediaminetetraacetic acid and nickel according to claim 1, characterized in that, The salt of dithiocarbamate, which is the product of the reaction of piperazine or tetraethylenepentamine with carbon disulfide and alkali metal hydroxide, is a sodium or potassium salt of dithiocarbamate, wherein the sodium or potassium salt of dithiocarbamate is the product of the reaction of piperazine or tetraethylenepentamine with carbon disulfide and sodium or potassium hydroxide.

3. The purification method for an aqueous solution containing ethylenediaminetetraacetic acid and nickel according to claim 1, characterized in that, The amount of calcium hydroxide added is set to be 0.01 g / L or more relative to the aqueous solution containing ethylenediaminetetraacetic acid and nickel.

4. The purification method for an aqueous solution containing ethylenediaminetetraacetic acid and nickel according to claim 1, characterized in that, Inorganic flocculants are added before the solids are removed.

5. The purification method for an aqueous solution containing ethylenediaminetetraacetic acid and nickel according to claim 1, characterized in that, Inorganic flocculants and polymeric flocculants are added before the solids are removed.

6. The purification method for an aqueous solution containing ethylenediaminetetraacetic acid and nickel according to claim 4 or 5, characterized in that, Inorganic flocculants are substances selected from the group consisting of iron compounds and aluminum compounds.

7. The purification method for an aqueous solution containing ethylenediaminetetraacetic acid and nickel according to any one of claims 1 to 5, characterized in that, The amount of calcium hydroxide added is 500 parts by weight or more and 250,000 parts by weight or less, relative to 100 parts by weight of the salt of the dithiocarbamic acid.

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