Purification method for nickel-containing aqueous solution

Abstract

To provide a purification method capable of rapidly reducing nickel concentration in an aqueous solution containing nickel and compounds capable of forming complexes with nickel.SOLUTION: An alkaline earth metal compound is added to an aqueous solution containing a compound capable of complexing with nickel and nickel, and the pH of the aqueous solution is adjusted to a range exceeding 11.5 and less than 13.5, and subsequently, a salt of dithiocarbamic acid and a polyamine having 3 to 5 nitrogen atoms are added to the aqueous solution, and subsequently, the solids formed are removed from the aqueous solution.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for purifying an aqueous solution containing nickel. [Background technology]

[0002] As a method for purifying an aqueous solution containing heavy metals, for example, a method using a salt of dithiocarbamic acid as an agent for treating heavy metals in wastewater has been proposed (see, for example, Patent Documents 1 to 4). However, the methods described in these Patent Documents do not provide a sufficient effect for purifying heavy metals from nickel-containing wastewater that contains compounds capable of forming complexes with the heavy metals.

[0003] Also, a method for purifying a nickel-containing aqueous solution using a polyamine having 3 to 8 nitrogen atoms, an alkaline earth metal compound, and a salt of dithiocarbamic acid has been proposed (see, for example, Patent Document 5). However, in the method of Patent Document 5, in order to remove nickel, it is necessary to add the polyamine, the alkaline earth metal compound, and the salt of dithiocarbamic acid to the nickel-containing aqueous solution, and then stir the nickel-containing aqueous solution for one hour. In order to ensure one hour of stirring time, the treatment equipment for treating the nickel-containing aqueous solution must be large, and there is a problem in that the amount of aqueous solution that can be treated per hour is limited. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-249399 A [Patent Document 2] JP2011-074350A [Patent Document 3] JP2014-088477A [Patent Document 4] JP 2002-177902 A [Patent Document 5] Patent Publication No. 2023-060143 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above-mentioned background art, and an object of the present invention is to provide a purification method for quickly reducing the nickel concentration in an aqueous solution containing nickel and a compound capable of forming a complex with nickel. [Means for solving the problem]

[0006] As a result of intensive research aimed at solving the above problems, the present inventors have found that by using the novel method for purifying a nickel-containing aqueous solution shown in the present disclosure, the nickel concentration can be reduced in a simple manner from an aqueous solution containing nickel and a compound capable of forming a complex with nickel, and have completed the present invention.

[0007] That is, the present disclosure includes the following embodiments.

[0008] [1] The method includes the following steps 1 to 3: (Step 1) adding an alkaline earth metal compound to an aqueous solution containing nickel and a compound capable of forming a complex with nickel, and adjusting the pH of the aqueous solution to a range of more than 11.5 and less than 13.5; (Step 2) adding a salt of dithiocarbamic acid and a polyamine having 3 to 5 nitrogen atoms to the aqueous solution obtained in Step 1; (Step 3) removing the solid matter produced from the aqueous solution obtained in Step 2; the amount of the alkaline earth metal added in step 1 is more than 25 parts by weight and not more than 500 parts by weight per part by weight of the amount of the salt of dithiocarbamic acid added in step 2; the amount of the polyamine having 3 to 5 nitrogen atoms added in step 2 is 1 part by weight or more per 1 part by weight of the salt of dithiocarbamic acid added in step 2; A method for purifying an aqueous solution containing nickel.

[0009] [2] The method for purifying a nickel-containing aqueous solution according to the above [1], wherein the nickel concentration in the aqueous solution containing nickel and a compound capable of forming a complex with nickel is less than 5 mg / L.

[0010] [3] The method for purifying a nickel-containing aqueous solution according to the above [1] or [2], wherein the alkaline earth metal compound is at least one selected from the group consisting of calcium chloride, calcium hydroxide, magnesium chloride, and magnesium hydroxide.

[0011] [4] The method for purifying a nickel-containing aqueous solution according to any one of [1] to [3] above, wherein the salt of dithiocarbamic acid is dipotassium piperazine-1,4-bis(carbodithioate), disodium piperazine-1,4-bis(carbodithioate), sodium N,N-diethyldithiocarbamate, or a reaction product of tetraethylenepentamine, carbon disulfide, and an alkali metal hydroxide.

[0012] [5] The method for purifying a nickel-containing aqueous solution according to any one of the above [1] to [4], wherein the polyamine having 3 to 5 nitrogen atoms is at least one selected from the group consisting of triamine, triethylenetetramine, and tetraethylenepentamine.

[0013] [6] The method for purifying a nickel-containing aqueous solution according to any one of the above [1] to [4], wherein the polyamine having 3 to 5 nitrogen atoms is diethylenetriamine or triethylenetetramine.

[0014] [7] A method for purifying a nickel-containing aqueous solution according to any one of [1] to [6] above, wherein an inorganic coagulant is added to the aqueous solution before removing the solid matter.

[0015] [8] A method for purifying a nickel-containing aqueous solution according to any one of [1] to [6] above, wherein an inorganic flocculant and a polymer flocculant are added to the aqueous solution before removing the solid matter.

[0016] [9] The method for purifying a nickel-containing aqueous solution according to the above [7] or [8], wherein the inorganic flocculant is at least one selected from the group consisting of iron compounds and aluminum compounds. Effect of the Invention

[0017] INDUSTRIAL APPLICABILITY The method for purifying a nickel-containing aqueous solution disclosed herein is extremely useful industrially because it can rapidly reduce the nickel concentration even in an aqueous solution containing nickel and a compound capable of forming a complex with nickel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The method of the present disclosure includes the following steps 1 to 3.

[0019] (Process 1) An alkaline earth metal compound is added to an aqueous solution containing nickel and a compound capable of forming a complex with nickel, and the pH of the aqueous solution is adjusted to a range of more than 11.5 and less than 13.5.

[0020] (Process 2) To the aqueous solution obtained in step 1, a salt of dithiocarbamic acid and a polyamine having 3 to 5 nitrogen atoms are added.

[0021] (Step 3) The solid matter formed is removed from the aqueous solution obtained in step 2.

[0022] The amount of the polyamine having 3 to 5 nitrogen atoms added in step 2 is 1 part by weight or more per part by weight of the salt of dithiocarbamic acid added in step 2, and the amount of the alkaline earth metal added in step 1 is more than 25 parts by weight and 500 parts by weight or less per part by weight of the salt of dithiocarbamic acid added in step 2.

[0023] The nickel concentration in an aqueous solution containing nickel and a compound capable of forming a complex with nickel (hereinafter simply referred to as a "nickel-containing aqueous solution") is preferably less than 5 mg / L, more preferably 2 mg / L or less, and even more preferably 1 mg / L or less, in terms of excellent treatment efficiency of the nickel-containing aqueous solution.

[0024] The compound capable of forming a complex with nickel is not particularly limited as long as it is a compound that forms a complex with nickel. 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. Specifically, EDTA, polyphosphoric acid, etc. are exemplified, and EDTA is particularly effective.

[0025] Examples of the 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 hydrogen carbonate, calcium nitrate, calcium sulfate, calcium sulfide, calcium phosphate, calcium acetate, calcium oxalate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium hydrogen carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, calcium iodide, calcium iodide, calcium oxide, calcium hydroxide, calcium sulfate, calcium sulfide, calcium phosphate, calcium acetate, calcium oxalate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium carbonate, magnesium nitrate, calcium iodide, calcium oxide, calcium hydroxide, calcium sulfate, calcium sulfide, calcium phosphate, calcium acetate, calcium oxalate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium oxide, magnesium hydroxide ... Examples of suitable calcium chloride include calcium 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, calcium hydroxide, and magnesium chloride are particularly preferred in terms of easy availability.

[0026] In step 1, examples of the method for adding an alkaline earth metal compound to the nickel-containing aqueous solution include a method for adding a solid alkaline earth metal compound to the nickel-containing aqueous solution, or a method for adding an aqueous solution of the compound. From the viewpoint of excellent operability, the method of adding an aqueous solution is preferred.

[0027] The alkaline earth metal compound can obtain nickel treatment capacity when added at 0.01 g / L or more, and relatively speaking, it is sufficient to add more than 25 parts by weight per 1 part by weight of the salt of dithiocarbamic acid added in step 2. Even if the alkaline earth metal compound is added in excess of 500 parts by weight, the nickel treatment capacity remains constant, so adding an excessive amount of the alkaline earth metal compound increases the cost of nickel wastewater treatment and is not economical.

[0028] After adding an alkaline earth metal to the nickel-containing aqueous solution, the pH of the nickel-containing aqueous solution is adjusted to a strong alkaline range (a pH range of more than 11.5 and less than 13.5). In this case, a pH of 12 to 13 is preferred from the viewpoint of excellent treatment efficiency of the nickel-containing aqueous solution.

[0029] When adjusting the pH of the nickel-containing aqueous solution to a desired range, a pH adjuster may be used. The pH adjuster is not particularly limited, but examples thereof include inorganic salts such as hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid and their aqueous solutions when adjusting to acidity, and inorganic bases such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and potassium carbonate and their aqueous solutions when adjusting to alkalinity.

[0030] In step 2, examples of the method for adding a dithiocarbamic acid salt to the nickel-containing aqueous solution include a method for adding a solid dithiocarbamic acid salt to the nickel-containing aqueous solution, or a method for adding an aqueous solution of the salt. From the viewpoint of excellent operability, the method of adding an aqueous solution is preferred.

[0031] When the salt of dithiocarbamic acid and the polyamine having 3 to 5 nitrogen atoms are added to the nickel-containing aqueous solution, they may be added separately, or they may be mixed together in advance and then added. When they are added separately, the order of addition is not limited.

[0032] 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, a compound obtained by reacting an amine compound having at least one amino group selected from the group consisting of a primary amino group and a secondary amino group with carbon disulfide and an alkali metal hydroxide can be mentioned. In the present disclosure, 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 preferred.

[0033] Examples of the amine compound having at least one amino group selected from the group consisting of primary amino groups and secondary amino groups include diethylamine, piperazine, diethylenetriamine, N-(2-aminoethyl)piperazine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and heptaethyleneoctamine.

[0034] Among these, in terms of nickel treatment performance and stability as a compound, a compound obtained by reacting piperazine or tetraethylenepentamine with carbon disulfide and an alkali metal hydroxide is preferred.

[0035] However, the salts of dithiocarbamic acid of tetraethylenepentamine are only produced industrially as compositions in which the raw material tetraethylenepentamine contains analogues [see formulas (2) to (4) below] in addition to the linear form [see formula (1) below] which is the main component. Therefore, the resulting salts of dithiocarbamic acid are also compositions, which has the disadvantage that quality control becomes complicated.

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] On the other hand, a salt of piperazine with dithiocarbamic acid is particularly preferably used in step 2 since it does not have such a drawback.

[0041] As the alkali metal hydroxide, sodium hydroxide and potassium hydroxide are particularly preferred because of their ready availability.

[0042] Examples of polyamines having 3 to 5 nitrogen atoms include diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0043] The amount of polyamine having 3 to 5 nitrogen atoms added per part by weight of the salt of dithiocarbamic acid is preferably 1 part by weight or more. By adding 7.5 parts by weight or more, a more sufficient nickel treatment ability can be obtained.

[0044] In order to quickly remove the solid matter in step 3, it is preferable to add a flocculant before removing the solid matter. Examples of the flocculant include inorganic flocculants and polymer flocculants, and it is more preferable to use an inorganic flocculant and a polymer flocculant in combination.

[0045] When the coagulant is added to the nickel-containing aqueous solution, the pH of the nickel-containing aqueous solution is preferably in the neutral to alkaline range (pH 6.5 to 9). From the viewpoint of the pH at which the aqueous solution after nickel removal can be discharged, the pH of 6.5 to 8 is more preferable.

[0046] The inorganic flocculant may be any commercially available inorganic flocculant, and is not particularly limited. Examples of the inorganic flocculant include iron compounds such as ferric chloride, aluminum sulfate, and aluminum compounds such as polyaluminum chloride.

[0047] The amount of inorganic flocculant added is preferably equal to or greater than the content of the compound capable of forming a nickel complex contained in the nickel-containing aqueous solution, since this increases the flocculation properties and makes it easier to reduce the nickel concentration in the aqueous solution after treatment to below the effluent standard.

[0048] The content of the compound capable of forming a complex with nickel in the nickel-containing aqueous solution can be calculated by analyzing the concentration of the compound capable of forming a nickel complex in the nickel-containing aqueous solution, for example, by HPLC, gas chromatography, titration, or the like.

[0049] The polymer flocculant can be a commercially available polymer flocculant, and is not particularly limited. For example, acrylic acid polymer, acrylamide polymer, dimethylaminoethyl methacrylate polymer, etc. are listed. In terms of flocculation performance, weakly anionic acrylic acid polymer is preferred. By adding a polymer flocculant before removing solid matter, handling of the solid matter to be removed may be made easier.

[0050] When an inorganic flocculant and a 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 add the polymer flocculant.

[0051] The method for removing solid matter is not particularly limited, and examples thereof include filtration, centrifugation, and a method in which solid matter is allowed to settle and then separated from the supernatant liquid. EXAMPLES

[0052] The present invention will be described in detail below, but the present invention should not be construed as being limited to these examples.

[0053] (Nickel concentration analysis method) The nickel concentration in the aqueous solution was measured using an ICP emission spectrometer (ICPE-9800, manufactured by Shimadzu Corporation).

[0054] Preparation Example The salts of dithiocarbamic acid used in the examples and comparative examples were prepared according to the following method.

[0055] (Preparation of dithiocarbamic acid salt A) After mixing 112 g of piperazine (manufactured by Tosoh Corporation) 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.) were alternately dropped in four portions at 25° C. under stirring in a nitrogen stream. After stirring for one hour, an aqueous solution containing 40 wt% of the compound (dipotassium=piperazine-1,4-bis(carbodithioate)) represented by the following formula (5) was obtained.

[0056] [ka]

[0057] (Preparation of dithiocarbamic acid salt B) After mixing 159 g of tetraethylenepentamine (manufactured by Tosoh Corporation) 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 (manufactured by Kishida Chemical Co., Ltd.) were alternately dropped in four portions at 25° C. under stirring in a nitrogen stream. After stirring for one hour, an aqueous solution containing 40 wt % of the compound shown in the following formula (6) was obtained.

[0058] [ka]

[0059] (Preparation of dithiocarbamic acid salt C) Pure water was added to 52.6 g of sodium N,N-diethyldithiocarbamate trihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) until the total amount reached 100 g, to obtain an aqueous solution containing 40% by weight of sodium N,N-diethyldithiocarbamate.

[0060] [ka]

[0061] (Polyamine) As polyamines, the following ethyleneamines manufactured by Tosoh Corporation were used: Ethylenediamine (hereinafter referred to as EA(2)), Diethylenetriamine (hereinafter referred to as EA(3)), Triethylenetetramine [hereinafter abbreviated as EA(4)], Tetraethylenepentamine [hereinafter abbreviated as EA(5)], Pentaethylenehexamine [hereinafter abbreviated as EA(6)].

[0062] (Alkaline earth metal compounds) As alkaline earth metals, the following compounds manufactured by Kishida Chemical Co., Ltd. were used: Magnesium chloride, calcium chloride, calcium hydroxide.

[0063] As alkaline earth metals, the following compounds manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. were used: Magnesium hydroxide.

[0064] (Inorganic flocculant) As inorganic flocculants the following aqueous solutions were used: An aqueous solution (30% by weight polyaluminum chloride aqueous solution) was prepared by adding 30 g of polyaluminum chloride (Kishida Chemical Co., Ltd.) to water to make a total of 100 g.

[0065] (Polymer flocculant) The polymer flocculant used was OA-23 (weak anionic polymer) manufactured by Organo Corporation.

[0066] Example 1 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, while stirring at 150 rpm, 350 mg of calcium hydroxide (concentration: 700 mg / L) was added to adjust the nickel-containing aqueous solution to pH 12.5.

[0067] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg of dithiocarbamic acid salt A, concentration 12 mg / L), and 45 mg / L of diethylenetriamine [EA(3)] was added (concentration 90 mg / L), and the mixture was stirred at 150 rpm for 10 minutes. The required stirring time from after the addition of the dithiocarbamic acid salt and polyamine to before the addition of polyaluminum chloride is defined as the reaction time.

[0068] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and further hydrochloric acid was added to adjust the pH to 7, and the solution was stirred at 150 rpm for 5 minutes (hereinafter, "polyaluminum chloride" may be abbreviated as "PAC"). Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the solution was stirred at 50 rpm for 5 minutes. After the stirring was completed, the solution was left to stand for 5 minutes, and the aqueous solution was filtered with Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 1.

[0069] [Table 1]

[0070] Examples 2 to 5 The nickel concentration in the aqueous solution after treatment was measured in the same manner as in Example 1, except that the chemicals added were changed to those shown in Table 1. The results are shown in Table 1.

[0071] Examples 1 to 5 are examples in which the type of dithiocarbamic acid salt or polyamine was changed within the range of the present invention. Regardless of the type of dithiocarbamic acid salt or polyamine, the reaction time required to reduce the nickel concentration of the treated aqueous solution of EDTA-containing wastewater to 0.1 mg / L or less was 10 minutes or less.

[0072] Example 6 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, 500 mg of calcium chloride (concentration: 1000 mg / L) was added while stirring at 150 rpm, and the nickel-containing aqueous solution was adjusted to pH 12.5 using sodium hydroxide.

[0073] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg of dithiocarbamic acid salt A, concentration: 12 mg / L), and 45 mg / L of triethylenetetramine [EA(4)] was added (concentration: 90 mg / L), and the mixture was stirred at 150 rpm for 20 minutes.

[0074] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 2.

[0075] [Table 2]

[0076] Examples 7 to 8 The nickel concentration in the aqueous solution after treatment was measured in the same manner as in Example 6, except that the alkaline earth metal to be added was changed to the agent shown in Table 2. The results are shown in Table 2.

[0077] Examples 7 and 8 are examples in which the type of alkaline earth metal was changed within the range of the present invention. Regardless of the type of alkaline earth metal, the required reaction time for reducing the nickel concentration in the treated aqueous solution of EDTA-containing wastewater to 0.1 mg / L or less was 20 minutes or less.

[0078] Example 9 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, while stirring at 150 rpm, 250 mg of calcium hydroxide (concentration: 500 mg / L) was added, and the nickel-containing aqueous solution was adjusted to pH 12.5 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0079] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg of dithiocarbamic acid salt A, concentration: 12 mg / L), and 45 mg / L of diethylenetriamine [EA(3)] was added (concentration: 90 mg / L), and the mixture was stirred at 150 rpm for 20 minutes.

[0080] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 3.

[0081] [Table 3]

[0082] Example 10 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, 750 mg of calcium hydroxide (concentration: 1500 mg / L) was added while stirring at 150 rpm, and the nickel-containing aqueous solution was adjusted to pH 13 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0083] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg of dithiocarbamic acid salt A, concentration: 12 mg / L), and 45 mg / L of diethylenetriamine [EA(3)] was added (concentration: 90 mg / L), and the mixture was stirred at 150 rpm for 10 minutes.

[0084] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 3.

[0085] Example 11 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, while stirring at 150 rpm, 350 mg of calcium hydroxide (concentration: 700 mg / L) was added, and the nickel-containing aqueous solution was adjusted to pH 12 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0086] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg of dithiocarbamic acid salt A, concentration: 12 mg / L), and 45 mg / L of diethylenetriamine [EA(3)] was added (concentration: 90 mg / L), and the mixture was stirred at 150 rpm for 10 minutes.

[0087] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 3.

[0088] Examples 9 to 11 are examples in which the amount of alkaline earth metal added or the pH of the aqueous solution was changed within the range of the present invention. By adjusting the amount of alkaline earth metal added and the pH of the aqueous solution within the range of the present invention, the reaction time required to reduce the nickel concentration of the aqueous solution after treatment of the EDAT-containing wastewater to 0.1 mg / L or less was reduced to 20 minutes or less.

[0089] Example 12 500 mg / L of an aqueous solution containing 3 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, 750 mg of calcium hydroxide (concentration: 1500 mg / L) was added while stirring at 150 rpm, and the nickel-containing aqueous solution was adjusted to pH 13 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0090] Next, 45 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (18 mg of dithiocarbamic acid salt A, concentration 36 mg / L), and 45 mg / L of diethylenetriamine [EA(3)] was added (concentration 90 mg / L), and the mixture was stirred at 150 rpm for 10 minutes.

[0091] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 3.

[0092] Example 12 is an example in which the nickel concentration of the nickel-containing aqueous solution was changed within the range of the present invention. The reaction time required to reduce the nickel concentration of the aqueous solution after treatment of the EDAT-containing wastewater to 0.1 mg / L or less was 10 minutes or less.

[0093] Comparative Example 1 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, while stirring at 150 rpm, the nickel-containing aqueous solution was adjusted to pH 12.5 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0094] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg as dithiocarbamic acid salt A, concentration 12 mg / L), and 45 mg / L of diethylenetriamine [EA(3)] was added (concentration 90 mg / L), and the mixture was stirred at 150 rpm for 60 minutes. Next, 500 mg of a 30% by weight aqueous solution of polyaluminum chloride was added (150 mg as polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, and the mixture was stirred at 150 rpm for 5 minutes.

[0095] Next, 500 mg of OA-23 (concentration: 1000 mg / L) was added as a polymer flocculant and stirred at 50 rpm for 5 minutes. After stirring, the solution was left to stand for 5 minutes, filtered with Advantec 5A filter paper, and the nickel concentration of the treated solution was measured. The results are shown in Table 4.

[0096] Comparative Example 1 is an example in which only dithiocarbamic acid salt A and EA (3) were added. The nickel concentration in the aqueous solution after treatment of the EDTA-containing wastewater could not be reduced to 0.1 mg / L or less.

[0097] [Table 4]

[0098] Comparative Examples 2 to 4 The nickel concentration in the aqueous solution after treatment was measured in the same manner as in Comparative Example 1, except that the added chemicals were changed to those shown in Table 5. The results are shown in Table 4.

[0099] Comparative Example 2 is an example in which an alkaline earth metal was added in an amount below the range of the present invention, and the nickel concentration in the aqueous solution after treatment of the EDTA-containing wastewater could not be reduced to 0.1 mg / L or less.

[0100] Comparative Example 3 is an example in which only Ca(OH)2 and the salt A of dithiocarbamic acid were added. The nickel concentration in the aqueous solution after treatment of the EDTA-containing wastewater could not be reduced to 0.1 mg / L or less.

[0101] Comparative Example 4 is an example in which only Ca(OH)2 and EA(3) were added. The nickel concentration in the aqueous solution after treatment of the EDTA-containing wastewater could not be reduced to 0.1 mg / L or less.

[0102] Comparative Example 5 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, while stirring at 150 rpm, 250 mg of calcium hydroxide (concentration: 500 mg / L) was added, and the nickel-containing aqueous solution was adjusted to pH 11.5 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0103] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg of dithiocarbamic acid salt A, concentration: 12 mg / L), and 45 mg / L of diethylenetriamine [EA(3)] was added (concentration: 90 mg / L), and the mixture was stirred at 150 rpm for 10 minutes.

[0104] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 5.

[0105] [Table 5]

[0106] Comparative Examples 6 to 7 The nickel concentration in the aqueous solution after treatment was measured in the same manner as in Comparative Example 5, except that the added chemicals were changed to those shown in Table 5. The results are shown in Table 5.

[0107] Comparative Example 8 500 mg / L of an aqueous solution containing 5 mg / L nickel ions and 50 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, while stirring at 150 rpm, 250 mg of calcium hydroxide (concentration: 500 mg / L) was added, and the nickel-containing aqueous solution was adjusted to pH 12.5 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0108] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg of dithiocarbamic acid salt A, concentration: 12 mg / L), and 45 mg / L of diethylenetriamine [EA(3)] was added (concentration: 90 mg / L), and the mixture was stirred at 150 rpm for 10 minutes.

[0109] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 5.

[0110] Reference example 1 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, while stirring at 150 rpm, 350 mg of calcium hydroxide (concentration: 700 mg / L) was added, and the nickel-containing aqueous solution was adjusted to pH 11.5 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0111] Next, 24 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (30 mg of dithiocarbamic acid salt A, concentration 60 mg / L), and 135 mg / L of diethylenetriamine [EA(3)] was added (concentration 270 mg / L), and the mixture was stirred at 150 rpm for 60 minutes.

[0112] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was further added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 5.

[0113] Comparative Examples 5 to 7 are examples in which the aqueous solution pH was changed outside the range of the present invention after the addition of an alkaline earth metal, and the nickel concentration in the aqueous solution after treatment of the EDTA-containing wastewater could not be reduced to 0.1 mg / L or less.

[0114] Comparative Example 8 is a treatment example in which the nickel concentration in the aqueous solution containing nickel and ethylenediaminetetraacetic acid exceeded the range of the present invention. The nickel concentration in the aqueous solution after treatment of the EDTA-containing wastewater could not be reduced to 0.1 mg / L or less.

[0115] Reference Example 1 is an example in which the reaction time was changed from 10 to 60 minutes with the same amount of chemicals and the same pH as in Comparative Example 7. The nickel concentration in the aqueous solution after treatment was almost the same as in Example 1, which had a pH of 12.5, but the reaction time was long.

[0116] Comparative Example 9 500 mg / L of an aqueous solution containing 1 mg / L nickel ions and 10 mg / L EDTA was added to a 1000 mL beaker placed in a Jar Tester. Next, while stirring at 150 rpm, the nickel-containing aqueous solution was adjusted to pH 12.5 using sodium hydroxide or hydrochloric acid as a pH adjuster.

[0117] Next, 15 mg of an aqueous solution containing 40% by weight of the compound represented by the above formula (5) (dithiocarbamic acid salt A) was added (6 mg of dithiocarbamic acid salt A, concentration: 12 mg / L), and 45 mg / L of ethylenediamine [EA(2)] was added (concentration: 90 mg / L), and the mixture was stirred at 150 rpm for 60 minutes.

[0118] Next, 500 mg of 30 wt% polyaluminum chloride aqueous solution was added (150 mg of polyaluminum chloride, concentration 300 mg / L), and hydrochloric acid was added to adjust the pH to 7, followed by stirring at 150 rpm for 5 minutes. Next, 500 mg of OA-23 (concentration 1000 mg / L) was added as a polymer flocculant, and the mixture was stirred at 50 rpm for 5 minutes. After stirring, the mixture was left to stand for 5 minutes, and the aqueous solution was filtered using Advantec 5A filter paper, and the nickel concentration of the aqueous solution after treatment was measured. The results are shown in Table 6.

[0119] [Table 6]

[0120] Comparative Example 10 The nickel concentration in the aqueous solution after treatment was measured in the same manner as in Comparative Example 9, except that the added chemicals were changed to those shown in Table 6. The results are shown in Table 6.

[0121] Comparative Examples 9 and 10 are examples in which EA(2) or EA(6) was added as a polyamine outside the scope of the present invention. The nickel concentration in the aqueous solution after treatment of the EDTA-containing wastewater could not be reduced to 0.1 mg / L or less.

Claims

1. The invention includes the following steps 1 to 3: (Step 1) adding an alkaline earth metal compound to an aqueous solution containing nickel and a compound capable of forming a complex with nickel, and adjusting the pH of the aqueous solution to a range of more than 11.5 and less than 13.5; (Step 2) adding a salt of dithiocarbamic acid and a polyamine having 3 to 5 nitrogen atoms to the aqueous solution obtained in Step 1; (Step 3) removing the solid matter produced from the aqueous solution obtained in Step 2; the amount of the alkaline earth metal added in step 1 is more than 25 parts by weight and not more than 500 parts by weight per part by weight of the salt of dithiocarbamic acid added in step 2; the amount of the polyamine having 3 to 5 nitrogen atoms added in step 2 is 1 part by weight or more per 1 part by weight of the salt of dithiocarbamic acid added in step 2; A method for purifying an aqueous solution containing nickel.

2. 2. The method for purifying a nickel-containing aqueous solution according to claim 1, wherein the nickel concentration in the aqueous solution containing nickel and the compound capable of forming a complex with nickel is less than 5 mg / L.

3. 2. The method for purifying a nickel-containing aqueous solution according to claim 1, wherein the alkaline earth metal compound is at least one selected from the group consisting of calcium chloride, calcium hydroxide, magnesium chloride, and magnesium hydroxide.

4. 2. The method for purifying a nickel-containing aqueous solution according to claim 1, wherein the salt of dithiocarbamic acid is dipotassium piperazine-1,4-bis(carbodithioate), disodium piperazine-1,4-bis(carbodithioate), sodium N,N-diethyldithiocarbamate, or a reaction product of tetraethylenepentamine, carbon disulfide, and an alkali metal hydroxide.

5. 2. The method for purifying a nickel-containing aqueous solution according to claim 1, wherein the polyamine having 3 to 5 nitrogen atoms is at least one selected from the group consisting of triamine, triethylenetetramine, and tetraethylenepentamine.

6. 2. The method for purifying a nickel-containing aqueous solution according to claim 1, wherein the polyamine having 3 to 5 nitrogen atoms is diethylenetriamine or triethylenetetramine.

7. 2. The method for purifying a nickel-containing aqueous solution according to claim 1, further comprising the step of adding an inorganic flocculant to the aqueous solution prior to removing the solids.

8. 2. The method for purifying a nickel-containing aqueous solution according to claim 1, further comprising the step of adding an inorganic flocculant and a polymer flocculant to the aqueous solution before removing the solids.

9. The method for purifying a nickel-containing aqueous solution according to claim 7 or 8, wherein the inorganic flocculant is at least one selected from the group consisting of iron compounds and aluminum compounds.

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