Purifying agent for heavy-metal-containing aqueous solution and use thereof

Abstract

Provided are: a purifying agent with which the concentration of heavy metals (especially nickel) in a heavy-metal-containing aqueous solution, which contains an anionic multidentate ligand, an amine-type multidentate ligand, and the heavy metals, can be efficiently and greatly reduced; and a purification method in which the purifying agent is used.　This purifying agent for a heavy-metal-containing aqueous solution is characterized by comprising a dithiocarbamic acid salt compound and an organic compound having a sulfonic acid group or a sulfuric acid ester group.

Description

Purifying Agent for Aqueous Solution Containing Heavy Metals and Its Use

[0001] The present invention relates to a purifying agent for an aqueous solution containing heavy metals and its use.

[0002] Zinc-nickel alloy plating is widely used in electronic parts, automotive parts, etc. because it has superior corrosion resistance compared to zinc plating. Zinc-nickel plating is classified into two types: acidic bath and alkaline bath. The acidic bath has the advantages of fast plating speed and low chemical cost, but the plating layer has the disadvantage of being non-uniform. On the other hand, the alkaline bath has the advantage of forming a uniform plating film and is used for plating electronic parts and automotive engine parts with complex shapes.

[0003] In alkaline bath zinc-nickel plating, in order to solubilize heavy metals such as zinc and nickel in the alkaline plating solution, organic acids (anionic ligands) having complex-forming ability such as citric acid, gluconic acid, or ethylenediaminetetraacetic acid (hereinafter sometimes abbreviated as EDTA), and compounds (amine ligands) having complex-forming ability such as cyanide, amine, ammonia, polyphosphoric acid, or polyethyleneimine (hereinafter sometimes abbreviated as PEI) are added to the plating solution. Due to the characteristics of such a plating solution, heavy metals such as nickel in the wastewater discharged from an alkaline zinc-nickel plating factory form water-soluble complexes. Therefore, in many cases, it is difficult to highly purify heavy metals (especially nickel) in the said wastewater by conventionally known hydroxide methods, coagulation separation removal methods, or adsorption removal methods.

[0004] Nickel is a hazardous heavy metal designated as a Class 1 designated chemical substance under the Act on Confirmation and Promotion of Management of Releases of Chemical Substances, and is set as a monitoring item in the environmental standards for water pollution, making wastewater treatment increasingly important. In China, a discharge standard value of 0.1 mg / L has been set in Table 3 standards (GB-21900-2008, hereinafter abbreviated as Table 3 standards) for plating pollutant discharge standards, and treatment technologies that can meet discharge standards are required. A purifying agent for nickel-containing aqueous solutions containing a salt of dithiocarbamic acid and a method for purifying nickel-containing aqueous solutions using the same have been proposed (see, for example, Patent Documents 1-2). The prior art discloses a technology for purifying heavy metals such as nickel contained in wastewater containing both heavy metals such as nickel and EDTA.

[0005] Japanese Patent Publication No. 2022-094340, Japanese Patent Publication No. 2019-069434

[0006] The wastewater discharged from the above-mentioned alkaline zinc-nickel plating plant contains heavy metals such as nickel, anionic polydentate ligands such as EDTA, and amine-based polydentate ligands such as PEI. However, even when this wastewater is treated using the above-mentioned prior art, it does not meet the discharge standard value of 0.1 mg / L according to the Chinese Table 3 standards, and there is a problem that sufficient performance cannot be obtained. The present invention has been made in view of the above-mentioned background art, and its purpose is to provide a purifying agent that can efficiently and significantly reduce the concentration of heavy metals (especially nickel) from a heavy metal-containing aqueous solution containing anionic polydentate ligands, amine-based polydentate ligands, and heavy metals, and a purifying method using the same.

[0007] The present inventors, after diligent study to solve the above problems, have discovered the following invention and completed the present invention. That is, the present invention relates to the following purifying agent and a method of purification using the same. [1] A purifying agent for aqueous solutions containing heavy metals, characterized by containing a dithiocarbamate compound and an organic compound having a sulfonic acid group or a sulfate ester group. [2] The purifying agent for aqueous solutions containing heavy metals according to [1], wherein the organic compound having a sulfonic acid group or a sulfate ester group is a sulfonic acid hydrocarbon compound or a sulfate ester hydrocarbon compound. [3] The purifying agent for aqueous solutions containing heavy metals according to [1] or [2], wherein the dithiocarbamate compound is a reaction product of an amine compound having at least one group selected from the group consisting of primary amino groups and secondary amino groups, carbon disulfide, and a base. [4] The purifying agent for aqueous solutions containing heavy metals according to any one of [1] to [3], wherein the content of the organic compound having a sulfonic acid group or a sulfate ester group is 5 to 2000 parts by mass per 100 parts by mass of the dithiocarbamate compound. [5] The heavy metal-containing aqueous solution purifying agent according to any one of [1] to [4], wherein the heavy metal-containing aqueous solution is a heavy metal-containing aqueous solution containing nickel. [6] The heavy metal-containing aqueous solution purifying agent according to [1], comprising a dithiocarbamate compound, an organic compound having a sulfonic acid group or a sulfate ester group, and a solvent. [7] A method for purifying a heavy metal-containing aqueous solution, characterized by adding the heavy metal-containing aqueous solution purifying agent according to any one of [1] to [6] to a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal, and then removing the resulting solid matter. [8] The heavy metal-containing aqueous solution purifying agent according to [7], wherein the heavy metal-containing aqueous solution is a heavy metal-containing aqueous solution containing a calcium salt, an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal. [9] The heavy metal-containing aqueous solution purifying agent according to [7] or [8], wherein the heavy metal is nickel.

[10] A method for purifying a heavy metal-containing aqueous solution according to any one of [7] to [9], wherein the anionic polydentate ligand is ethylenediaminetetraacetic acid.

[11] A method for purifying an aqueous solution containing heavy metals according to any one of [7] to

[10] , wherein the amine-based polydentate ligand is polyethyleneimine or ethyleneamine.

[12] A method for purifying an aqueous solution containing heavy metals according to any one of [7] to

[11] , characterized by adding a purifying agent for aqueous solutions containing heavy metals, then adding a flocculant, and then removing the resulting solids.

[13] A method for purifying an aqueous solution containing heavy metals according to

[12] , wherein the flocculant is an inorganic flocculant or a polymer flocculant.

[14] A method for purifying an aqueous solution containing heavy metals, characterized by adding a dithiocarbamate compound and an organic compound having a sulfonic acid group or a sulfate ester group to an aqueous solution containing an anionic polydentate ligand, an amine-based polydentate ligand, and a heavy metal, and then removing the resulting solids.

[15] A method for purifying an aqueous solution containing heavy metals according to

[14] , wherein the aqueous solution containing heavy metals is an aqueous solution containing a calcium salt, an anionic polydentate ligand, an amine-based polydentate ligand, and a heavy metal.

[16] The method for purifying an aqueous solution containing heavy metals according to

[14] or

[15] , wherein the amount of the organic compound having a sulfonic acid group or a sulfate ester group added is 5 to 2000 parts by mass per 100 parts by mass of the amount of the dithiocarbamate compound added.

[0008] The present invention provides a purifying agent for heavy metal-containing aqueous solutions and a method for purifying heavy metal-containing aqueous solutions. These methods are extremely useful in industry because they can purify nickel-containing aqueous solutions (wastewater), which are extremely difficult to purify, and reduce the nickel concentration to an extremely low level (for example, 0.1 mg / L or less).

[0009] An aspect of this disclosure will be described in detail below. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or greater, B or less." This disclosure relates to a purifying agent for heavy metal-containing aqueous solutions (e.g., wastewater from a plating factory) containing heavy metals such as nickel, and to a purifying treatment technology. One aspect of this disclosure relates to a purifying agent for heavy metal-containing aqueous solutions, characterized by comprising a dithiocarbamate compound and an organic compound having a sulfonic acid group or a sulfate ester group. The dithiocarbamate compound refers to an organic compound having a dithiocarbamate group that forms a salt in the molecule, and is not particularly limited, but examples include a reaction product of an amine compound having at least one group selected from the group consisting of a primary amino group and a secondary amino group, carbon disulfide, and a base.

[0010] Here, the amine compound having at least one group selected from the group consisting of primary and secondary amino groups is not particularly limited, but examples include dimethylamine, diethylamine, piperazine, pyrrolidine, piperidine, diethylenetriamine, N-(2-aminoethyl)piperazine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, heptaethyleneoctamine, morpholine, or PEI. Of the amine compounds having at least one group selected from the group consisting of primary and secondary amino groups, dimethylamine, diethylamine, piperazine, pyrrolidine, piperidine, or PEI are preferred in terms of their excellent purifying ability as a purifying agent, and dimethylamine, diethylamine, or piperazine are more preferred. The aforementioned bases are not particularly limited, but examples include alkali metal hydroxides, alkaline earth metal hydroxides, ammonia, or amine compounds. More specifically, examples include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, strontium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, triethylamine, triethanolamine, quinuclidine, or triethylenediamine.

[0011] Regarding the aforementioned base, it is preferable that it be an alkali metal hydroxide, and more preferably potassium hydroxide or sodium hydroxide, in terms of its excellent purifying ability as a purifying agent. The dithiocarbamate compounds mentioned above are not particularly limited, but examples include potassium N,N-dimethyldithiocarbamate, sodium N,N-dimethyldithiocarbamate, ammonium N,N-dimethyldithiocarbamate, potassium N,N-diethyldithiocarbamate, sodium N,N-diethyldithiocarbamate, ammonium N,N-diethyldithiocarbamate, dipotassium = piperazine-1,4-bis(carboditiote), disodium = piperazine-1,4-bis(carboditiote), diammonium = piperazine-1,4-bis(carboditiote), potassium 1-pyrrolidinecarboditiote, sodium 1-pyrrolidinecarboditiote, ammonium 1-pyrrolidinecarboditiote, potassium 1-piperidinecarboditiote, sodium 1-piperidinecarboditiote, or ammonium 1-piperidinecarboditiote.

[0012] Regarding the dithiocarbamate compounds mentioned above, in terms of their excellent purification ability as a purifying agent, N,N-dimethyldithiocarbamate potassium salt, N,N-dimethyldithiocarbamate sodium salt, N,N-dimethyldithiocarbamate ammonium salt, N,N-diethyldithiocarbamate potassium salt, N,N-diethyldithiocarbamate sodium salt, N,N-diethyldithiocarbamate ammonium salt, dipotassium=piperazine-1,4-bis(carboditiote), disodium=piperazine-1,4-bis(carboditiote), or diammonium=piperazine-1,4-bis(carboditiote) are preferred. Regarding the organic compounds having the sulfonic acid group or sulfate ester group mentioned above, -SO ３ － An organic compound having a sulfonic acid group represented by -OSO ３ －The term represents an organic compound having a sulfate ester group, and is preferably a sulfonic acid hydrocarbon compound or a sulfate ester hydrocarbon compound in terms of its excellent purification ability as a purifying agent. The organic compound having the sulfonic acid group or sulfate ester group may be an acid type compound or a salt compound, and examples of salts are not particularly limited, but include lithium salts, sodium salts, potassium salts, rubidium salts, cesium salts, ammonium salts, organic ammonium salts, or quaternary ammonium salts.

[0013] Furthermore, regarding the organic compounds having a sulfonic acid group or a sulfate ester group, those having 1 to 30 carbon atoms are preferred, those having 1 to 24 carbon atoms are more preferred, those having 2 to 18 carbon atoms are more preferred, those having 6 to 18 carbon atoms are more preferred, and those having 8 to 18 carbon atoms are more preferred in terms of their excellent purification ability as a purifying agent. In other words, regarding the sulfonic acid hydrocarbon compound or sulfate ester hydrocarbon compound, it is preferable that the sulfonic acid hydrocarbon compound or sulfate ester hydrocarbon compound has 1 to 30 carbon atoms, it is preferable that the sulfonic acid hydrocarbon compound or sulfate ester hydrocarbon compound has 1 to 24 carbon atoms, and it is preferable that the sulfonic acid hydrocarbon compound or sulfate ester hydrocarbon compound has 6 to 18 carbon atoms.

[0014] More specifically, the organic compounds having the aforementioned sulfonic acid group or sulfuric acid ester group are, without particular limitation, examples of potassium methanesulfonate, sodium methanesulfonate, 2-aminoethanesulfonic acid, potassium butanesulfonate, sodium butanesulfonate, potassium octanesulfonate, sodium octanesulfonate, potassium decanesulfonate, sodium decanesulfonate, potassium dodecanesulfonate, sodium dodecanesulfonate, potassium tetradecanesulfonate, sodium tetradecanesulfonate, potassium hexadecanesulfonate, sodium hexadecanesulfonate, potassium octadecanesulfonate, sodium octadecanesulfonate, potassium oleylsulfonate, sodium oleylsulfonate, potassium benzenesulfonate, sodium benzenesulfonate, potassium p-toluenesulfonate, sodium p-toluenesulfonate, potassium decylbenzenesulfonate, sodium decylbenzenesulfonate, undecylbenzenesulfonate Examples include potassium sulfonate, sodium undecylbenzenesulfonate, potassium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate, potassium tridecylbenzenesulfonate, sodium tridecylbenzenesulfonate, potassium tetradecylbenzenesulfonate, sodium tetradecylbenzenesulfonate, potassium hexadecylbenzenesulfonate, sodium hexadecylbenzenesulfonate, potassium octadecylbenzenesulfonate, sodium octadecylbenzenesulfonate, potassium methyl sulfate, sodium methyl sulfate, potassium butyl sulfate, sodium butyl sulfate, potassium octyl sulfate, sodium octyl sulfate, potassium decyl sulfate, sodium decyl sulfate, potassium dodecyl sulfate, sodium dodecyl sulfate, potassium hexadecyl sulfate, sodium hexadecyl sulfate, potassium stearyl sulfate, sodium stearyl sulfate, potassium oleyl sulfate, sodium oleyl sulfate, potassium p-tolyl sulfate, or sodium p-tolyl sulfate.

[0015] Of these, sodium methanesulfonate, sodium octanesulfonate, sodium dodecanesulfonate, sodium hexadecanesulfonate, sodium octadecanesulfonate, sodium dodecylbenzenesulfonate, sodium methyl sulfate, sodium octyl sulfate, sodium dodecyl sulfate, sodium hexadecyl sulfate, or sodium stearyl sulfate are preferred in terms of their superior purification ability, and sodium octyl sulfate, sodium dodecyl sulfate, or sodium hexadecyl sulfate are more preferred. Cationic heavy metals such as nickel react with the anionic dithiocarbamate compounds to become hydrophobic and are purified from the aqueous solution. If amine-based polydentate ligands such as cationic amines or cationic polymers are present in the aqueous solution, the dithiocarbamate compounds are consumed by charge neutralization with these amine-based polydentate ligands, and as a result, the heavy metal purification treatment by the dithiocarbamate compounds is presumed to be inhibited. On the other hand, the organic compounds having the sulfonic acid group or sulfate ester group have anionic properties derived from the sulfonic acid group or sulfate ester group, and it is presumed that these anionic properties react with the amine-based polydentate ligand to neutralize the charge and reduce interference with the heavy metal purification treatment by the dithiocarbamate compound. For this reason, the purifying agent of this disclosure, which is characterized by containing a dithiocarbamate compound and an organic compound having the sulfonic acid group or sulfate ester group, is presumed to exhibit excellent effects as a purifying agent for heavy metal-containing aqueous solutions.

[0016] In the heavy metal-containing aqueous solution purifying agent of this disclosure, the content of the organic compound having a sulfonic acid group or a sulfuric acid ester group is preferably 5 to 2000 parts by mass, more preferably 10 to 1000 parts by mass, and more preferably 50 to 500 parts by mass, per 100 parts by mass of the dithiocarbamate compound, in terms of excellent purifying ability of the purifying agent. The heavy metal-containing aqueous solution purifying agent of this disclosure is characterized by containing a dithiocarbamate compound and an organic compound having a sulfonic acid group or a sulfuric acid ester group, but the purifying agent may be in a solid state (under general temperature conditions (4 to 98°C) when a heavy metal-containing aqueous solution is treated for purification), or it may further contain a solvent in addition to the dithiocarbamate compound and the sulfonic acid group or sulfuric acid ester group, or it may be a clay-like or paste-like substance kneaded with the solvent, or it may be a slurry-like substance dispersed in the solvent, or it may be a solution-like substance dissolved in the solvent, or it may be a frozen substance obtained by freezing the slurry or solution.

[0017] If the purifying agent is a solid, the dithiocarbamate compound and the organic compound having a sulfonic acid group or a sulfate ester group, which are components of the purifying agent, may each be solid, or one may be a liquid and the other a solid, resulting in a solid state when mixed. The solvent is not particularly limited, but examples include water, alcohols (ethanol, ethylene glycol, or glycerin, etc.), and highly polar organic solvents other than alcohols (N,N-dimethylformamide, dimethyl sulfoxide, or N-methyl-2-pyrrolidone). Water is preferred as the solvent from the viewpoint of preventing an increase in COD of wastewater.

[0018] When the heavy metal-containing aqueous solution purifying agent of this disclosure is in the form of a solution (liquid agent), the concentration of the dithiocarbamate compound contained in the solution (liquid agent) is preferably 5 to 40% by mass, more preferably 10 to 40% by mass, and more preferably 10 to 30% by mass, based on 100% by mass of the total amount of the heavy metal-containing aqueous solution purifying agent (liquid agent) in solution form, in terms of excellent operability. When the heavy metal-containing aqueous solution purifying agent of this disclosure is in the form of a solution (liquid agent), the concentration of the organic compound having a sulfonic acid group or a sulfate ester group contained in the solution (liquid agent) is preferably 5 to 30% by mass, more preferably 5 to 20% by mass, and more preferably 10 to 20% by mass, based on 100% by mass of the total amount of the heavy metal-containing aqueous solution purifying agent (liquid agent) in solution form, in terms of excellent operability.

[0019] Furthermore, when the heavy metal-containing aqueous solution purifying agent of this disclosure is in the form of a solution (liquid agent), the concentration of the solvent contained in the solution (liquid agent) is preferably 30 to 95% by mass, more preferably 40 to 95% by mass, and even more preferably 50 to 90% by mass, based on 100% by mass of the total amount of the heavy metal-containing aqueous solution purifying agent (liquid agent) in solution form, in terms of excellent handling properties. Note that the heavy metal-containing aqueous solution purifying agent of this disclosure may contain components other than those shown above.

[0020] The aforementioned purifying agent for heavy metal-containing aqueous solutions means an agent that is applied to a heavy metal-containing aqueous solution containing heavy metals and acts to separate and remove the dissolved heavy metals. The heavy metals are not particularly limited, but include nickel, cadmium, chromium, copper, iron, mercury, lead, zinc, palladium, gold, silver, platinum, cobalt, indium, molybdenum, antimony, tin, titanium, zirconium, manganese, or tungsten, and may consist of two or more of any heavy metals. These heavy metals may be in any form as long as they are dissolved in the aqueous solution, and the form is not particularly limited, but examples include heavy metal ions, heavy metal salts, or heavy metal organic complex compounds.

[0021] The heavy metal-containing aqueous solutions treated by the aforementioned heavy metal-containing aqueous solution purifying agent are not particularly limited, but examples include industrial wastewater and domestic wastewater, and more specifically, wastewater from plating plants, metal processing plants, or automobile factories. In addition, these common industrial wastewaters often contain nickel, or nickel and zinc together. As mentioned above, in alkaline zinc-nickel plating, organic acids (anionic ligands) with complex-forming ability such as citric acid, gluconic acid, or EDTA, and compounds (amine ligands) with complex-forming ability such as cyanide, amines, ammonia, polyphosphate, ethyleneamines, or PEI are often added to the plating solution to solubilize zinc and nickel in the alkaline plating solution.

[0022] When both anionic polydentate ligands such as EDTA and amine-based polydentate ligands such as ethyleneamines or PEI are present in a heavy metal-containing aqueous solution, purification is extremely difficult. The heavy metal-containing aqueous solution purifying agent of this disclosure exhibits the excellent effect of being able to highly purify even such heavy metal-containing aqueous solutions. For this reason, the heavy metal-containing aqueous solution in this disclosure is preferably a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine-based polydentate ligand, and a heavy metal; more preferably a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine-based polydentate ligand, and nickel; and even more preferably a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine-based polydentate ligand, nickel, and zinc.

[0023] One aspect of the present disclosure relates to a method for purifying a heavy metal-containing aqueous solution, characterized by adding the above-mentioned purifying agent for heavy metal-containing aqueous solutions to a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal, and then removing the resulting solid matter. The anionic polydentate ligand can be rephrased as an anionic chelating agent and represents a compound having two or more anionic groups (e.g., carboxyl groups) in its molecule and forming a complex with a heavy metal ion. While not particularly limited, it is preferable that the compound has two or more carboxyl groups in its molecule and forms a complex with a heavy metal ion. Examples of the anionic polydentate ligand include malonic acid, succinic acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), ethylenediamine-N,N'-disuccinic acid, trans-1,2-cyclohexanediaminetetraacetic acid, or 2,2'-[(phosphonomethyl)imino]diacetic acid.

[0024] Of the aforementioned anionic polydentate ligands, EDTA is preferred due to its superior convenience in alkaline zinc-nickel plating plants. The aforementioned amine polydentate ligands do not contain the aforementioned anionic polydentate ligands and represent compounds that have at least one nitrogen atom in their molecule, do not have anionic groups in their molecule, and have the ability to form complexes with heavy metal ions. They are not particularly limited, but examples include ethyleneamines (e.g., ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine), triethanolamine, or polyethyleneimine (PEI). Of the aforementioned amine polydentate ligands, ethyleneamines or PEI are preferred, and ethyleneamines and PEI are more preferred, due to their superior convenience in plating treatment in alkaline zinc-nickel plating plants.

[0025] Furthermore, the ethyleneamines mentioned above are preferably diethylenetriamines, as they offer superior convenience for plating processes in alkaline zinc-nickel plating plants. The purification method of the present invention is particularly effective for zinc-nickel plating wastewater from alkaline baths containing anionic polydentate ligands and amine polydentate ligands, where nickel purification is difficult, due to its high treatment efficiency. When the above-mentioned purifying agent for heavy metal-containing aqueous solutions is added to a heavy metal-containing aqueous solution containing anionic polydentate ligands, amine polydentate ligands, and heavy metals (such as nickel and zinc), and mixed and stirred, a solid substance containing the heavy metal is formed. This solid substance mainly consists of the reaction products of the heavy metal and the metal-containing aqueous solution purifying agent. Because the reaction products are hydrophobic, they are formed as solids in water.

[0026] In the method for purifying a heavy metal-containing aqueous solution according to the present disclosure, the amount of purifying agent for heavy metal-containing aqueous solutions added is not particularly limited, but in terms of excellent heavy metal purification efficiency, it is preferably 5 to 1,000 parts by mass, more preferably 5 to 500 parts by mass, and even more preferably 5 to 300 parts by mass, per 1 part by mass of heavy metal contained in the heavy metal-containing aqueous solution to be treated.

[0027] One aspect of this disclosure relates to a method for purifying a heavy metal-containing aqueous solution, characterized by adding the above-mentioned purifying agent for heavy metal-containing aqueous solutions to a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal, and then removing the resulting solid matter. In this case, instead of adding the purifying agent for heavy metal-containing aqueous solutions, a dithiocarbamate compound and an organic compound having a sulfonic acid group or a sulfate ester group, which are components of the purifying agent for heavy metal-containing aqueous solutions, may be added separately. Here, the definitions and preferred ranges of the dithiocarbamate compound and the organic compound having a sulfonic acid group or a sulfate ester group are as described above. In the case where, as in the above aspect, instead of adding the purifying agent for heavy metal-containing aqueous solutions, a dithiocarbamate compound and an organic compound having a sulfonic acid group or a sulfate ester group, which are components of the purifying agent for heavy metal-containing aqueous solutions, are added separately, the order of addition is not particularly limited, and they may be added simultaneously.

[0028] In the method for purifying a heavy metal-containing aqueous solution according to the present disclosure, the amount of dithiocarbamate compound in the added purifying agent for heavy metal-containing aqueous solutions is not particularly limited, but in terms of excellent heavy metal purification efficiency, it is preferably 1 to 50 parts by mass, more preferably 1 to 30 parts by mass, and more preferably 5 to 30 parts by mass, per 1 part by mass of heavy metal contained in the heavy metal-containing aqueous solution to be treated. In the method for purifying a heavy metal-containing aqueous solution according to the present disclosure, the amount of organic compound having a sulfonic acid group or a sulfate ester group in the added purifying agent for heavy metal-containing aqueous solutions is not particularly limited, but in terms of excellent heavy metal purification efficiency, it is preferably 1 to 2000 parts by mass, more preferably 1 to 1000 parts by mass, and more preferably 5 to 1000 parts by mass, per 100 parts by mass of anionic polydentate ligand contained in the heavy metal-containing aqueous solution to be treated.

[0029] Furthermore, regarding the amount of the organic compound having a sulfonic acid group or a sulfate ester group added, in terms of excellent heavy metal purification efficiency, it is preferably 5 to 2000 parts by mass, more preferably 20 to 2000 parts by mass, and more preferably 40 to 1000 parts by mass, per 100 parts by mass of the dithiocarbamate compound. In the above method for purifying an aqueous solution containing heavy metals, when the purifying agent for aqueous solutions containing heavy metals is added to the aqueous solution containing heavy metals, the pH of the aqueous solution containing heavy metals before the addition of the purifying agent for aqueous solutions containing heavy metals is preferably in the range of 7 to 14, more preferably in the range of 9 to 14, and more preferably in the range of 11 to 14, in order to enhance the heavy metal purification efficiency.

[0030] If the pH of the heavy metal-containing aqueous solution falls outside the preferred range described above, the pH can be adjusted using any commercially available pH adjusting agent. The pH adjusting agent may contain a calcium salt, as described later, and it is preferable that it contains a calcium salt. In the heavy metal-containing aqueous solution purification method of this disclosure, the heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal is combined with the heavy metal-containing aqueous solution, and the resulting solid matter is removed. However, it is preferable that the pH of the heavy metal-containing aqueous solution after the addition of the heavy metal-containing aqueous solution be adjusted to 5 to 9, and more preferably to 5 or more and less than 7, in order to improve the heavy metal purification efficiency. If the pH of the heavy metal-containing aqueous solution after the addition of the heavy metal-containing aqueous solution falls outside the preferred range described above, the pH can be adjusted using any commercially available pH adjusting agent.

[0031] One aspect of the present disclosure relates to a method for purifying a heavy metal-containing aqueous solution, characterized by adding the above-mentioned purifying agent for heavy metal-containing aqueous solutions to a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal, and then removing the resulting solid matter. In this case, it is preferable to add a calcium salt to the heavy metal-containing aqueous solution beforehand, in order to improve the efficiency of heavy metal purification. That is, one aspect of the present disclosure relates to a method for purifying a heavy metal-containing aqueous solution, characterized by adding the above-mentioned purifying agent for heavy metal-containing aqueous solutions to a heavy metal-containing aqueous solution containing a calcium salt, an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal, and then removing the resulting solid matter.

[0032] The calcium salts mentioned above are not particularly limited, but examples include calcium chloride, calcium bromide, calcium oxide, calcium hydroxide, calcium carbonate, calcium bicarbonate, calcium nitrate, or calcium hypochlorite. Among these, calcium chloride or calcium hydroxide is preferred in that it can improve the efficiency of heavy metal purification. In the method for purifying a heavy metal-containing aqueous solution of this disclosure, the amount (or content) of the calcium salt added is preferably 10 to 1000 parts by mass, more preferably 10 to 500 parts by mass, and even more preferably 10 to 100 parts by mass, per 1 part by mass of heavy metal contained in the heavy metal-containing aqueous solution to be treated, in order to improve the efficiency of heavy metal purification.

[0033] Furthermore, one aspect of this disclosure relates to a method for purifying a heavy metal-containing aqueous solution, characterized in that the above-mentioned purifying agent for heavy metal-containing aqueous solutions is added to a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal, and then the resulting solid matter is removed. In this case, in order to improve the efficiency of heavy metal purification, it is preferable to further add a flocculant to the heavy metal-containing aqueous solution after adding the purifying agent for heavy metal-containing aqueous solutions, and then remove the resulting solid matter. By performing such an operation, it is expected that the removal rate of heavy metals such as nickel will be improved, and the separation and removal of the resulting solid matter will be faster and more efficient.

[0034] The aforementioned flocculant is not particularly limited, but examples include inorganic flocculants and polymer flocculants. It is preferable to use both an inorganic flocculant and a polymer flocculant in combination, as this improves the removal rate of heavy metals such as nickel and allows for faster and more efficient separation and removal of the resulting solids. The inorganic flocculant is not particularly limited, but examples include iron compounds and aluminum compounds, and more specifically, ferric chloride, ferrous sulfate, aluminum sulfate, and polyaluminum chloride. It is preferable to use commercially available inorganic flocculants as they are. The polymer flocculant is not particularly limited, but examples include acrylic acid polymers, acrylamide polymers, and dimethylaminoethyl methacrylate polymers. Among these, acrylic acid polymers are preferred due to their excellent ability to purify heavy metal-containing aqueous solutions. It is preferable to use commercially available polymer flocculants as they are.

[0035] In the method for purifying a heavy metal-containing aqueous solution according to the present disclosure, the amount of inorganic flocculant used is preferably 1 to 500 parts by mass, more preferably 1 to 300 parts by mass, and more preferably 3 to 300 parts by mass, per 1 part by mass of heavy metal contained in the heavy metal-containing aqueous solution to be treated, in order to enhance the heavy metal purification efficiency. In the method for purifying a heavy metal-containing aqueous solution according to the present disclosure, the amount of polymer flocculant used is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 10 parts by mass, and more preferably 0.01 to 5 parts by mass, per 1 part by mass of heavy metal contained in the heavy metal-containing aqueous solution to be treated, in order to enhance the heavy metal purification efficiency.

[0036] When the inorganic flocculant and polymer flocculant are used in combination, there are no particular limitations on the order of addition, but it is preferable to add the polymer flocculant after the inorganic flocculant in order to improve the efficiency of heavy metal purification. The timing for adding the polymer flocculant is preferably after adding the inorganic flocculant to the heavy metal-containing aqueous solution after adding the heavy metal-containing aqueous solution and stirring for 1 to 60 minutes, more preferably after stirring for 2 to 30 minutes, and even more preferably after stirring for 5 to 10 minutes.

[0037] The heavy metal-containing aqueous solution after the addition of the polymer flocculant is preferably stirred and mixed, with the stirring and mixing time preferably being 1 minute to 2 hours, more preferably 2 minutes to 60 minutes, and even more preferably 5 minutes to 30 minutes. In the method for purifying a heavy metal-containing aqueous solution according to this disclosure, the method for removing solid matter is not particularly limited, but examples include filtration separation, centrifugation, or sedimentation separation.

[0038] The present invention will be described in detail below, but the present invention is not limited to these examples. <Method for measuring the concentration of heavy metals in a heavy metal-containing aqueous solution> The concentration of heavy metals (nickel, zinc, etc.) in a heavy metal-containing aqueous solution was measured using an ICP emission spectrometer (ICPE-9800, manufactured by Shimadzu Corporation). The following chemicals were used in the examples.

[0039] <Organic compounds having a sulfonic acid group or a sulfate ester group> Sulfate ester compound A = Hexadecyl sulfate sodium (containing approximately 40% stearyl sulfate sodium) (manufactured by Tokyo Chemical Industry Co., Ltd.) Sulfate ester compound B = Dodecyl sulfate sodium (manufactured by Tokyo Chemical Industry Co., Ltd.) Sulfate ester compound C = Octyl sulfate sodium (manufactured by Tokyo Chemical Industry Co., Ltd.) Sulfate ester compound D = Methyl sulfate sodium (manufactured by Tokyo Chemical Industry Co., Ltd.) Sulfonic acid compound A = Dodecylbenzenesulfonate sodium (hard type) (mixture) (manufactured by Tokyo Chemical Industry Co., Ltd.) Sulfonic acid compound B = p-toluenesulfonate sodium (manufactured by Tokyo Chemical Industry Co., Ltd.) Sulfonic acid compound C = Benzenesulfonate sodium (manufactured by Tokyo Chemical Industry Co., Ltd.) Sulfonic acid compound D = 2-aminoethanesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0040] As comparative examples, organic compounds having a phosphate group, a carboxyl group, or an amino group shown below were used. Phosphate compound A = sodium monododecyl phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) Carboxylic acid compound A = sodium polyacrylate (manufactured by Fujifilm Wako Pure Chemical Corporation) Amine salt compound A = triethylamine hydrochloride (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0041] <Dithiocarbamate compound> Aqueous solution of dithiocarbamate compound A = 10% by mass aqueous solution of sodium dimethyldithiocarbamate: Sodium dimethyldithiocarbamate dihydrate (manufactured by Tokyo Chemical Industry Co., Ltd.) and water were mixed to prepare a 10% by mass aqueous solution of sodium dimethyldithiocarbamate. Aqueous solution of dithiocarbamate compound B = 10% by mass aqueous solution of sodium N,N - diethyldithiocarbamate: Sodium N,N - diethyldithiocarbamate trihydrate (manufactured by Fujifilm Wako Pure Chemical Corporation) and water were mixed to prepare a 10% by mass aqueous solution of sodium N,N - diethyldithiocarbamate. Aqueous solution of dithiocarbamate compound C = forty% by mass aqueous solution of dipotassium = piperazine - 1,4 - bis(carbodithioate): 112 g of piperazine (manufactured by Tosoh Corporation) and 386 g of pure water were mixed, and then, at 25°C, while stirring in a nitrogen stream, 306 g of 48% by weight potassium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 196 g of carbon disulfide (manufactured by Kishida Chemical Co., Ltd.) were each divided into 4 portions and alternately dropped. After stirring for 1 hour, an aqueous solution containing 40% by mass of the compound shown in the following formula (3) (dipotassium = piperazine - 1,4 - bis(carbodithioate)) was obtained.

[0042] Aqueous solution of dithiocarbamate compound D = 10% by mass aqueous solution of ammonium 1 - pyrrolidinecarbodithioate: Ammonium 1 - pyrrolidinecarbodithioate (manufactured by Tokyo Chemical Industry Co., Ltd.) and water were mixed to prepare a 10% by mass aqueous solution of ammonium 1 - pyrrolidinecarbodithioate.

[0043] <Calcium Salt> Calcium chloride (manufactured by Kishida Chemical Co., Ltd.) <Coagulant> Aqueous solution of inorganic coagulant A = 30% by mass of polyaluminum chloride aqueous solution: 30 g of polyaluminum chloride (manufactured by Kishida Chemical Co., Ltd.) was mixed with water to prepare an aqueous solution with a total of 100 g. Aqueous solution of polymer coagulant A = 0.1% by mass of OA-23 aqueous solution: 0.1 g of OA-23 (manufactured by Organo Corporation) was mixed with water to prepare an aqueous solution with a total of 100 g.

[0044] <Sulfide Aqueous Solution> Sulfide aqueous solution = 20% by mass of sodium hydrosulfide aqueous solution: Sodium hydrosulfide (manufactured by Kishida Chemical Co., Ltd.) was mixed with water to prepare a 20% by mass sodium hydrosulfide aqueous solution. <Anionic Multidentate Ligand> Ethylenediamine-N,N,N',N'-tetraacetic acid tetrasodium salt tetrahydrate (manufactured by Dojindo Laboratories)

[0045] <Amine-Based Multidentate Ligand> Polyethyleneimine (average molecular weight of about 600) (manufactured by FUJIFILM Wako Pure Chemical Corporation) Polyethyleneimine (average molecular weight of about 1800) (manufactured by FUJIFILM Wako Pure Chemical Corporation) Polyethyleneimine (average molecular weight of about 10,000) (manufactured by FUJIFILM Wako Pure Chemical Corporation) Diethylenetriamine (manufactured by Tosoh Corporation) Triethylenetetramine (manufactured by Tosoh Corporation)

[0046] <Heavy Metal-Containing Aqueous Solution> Using the reagents shown below, heavy metal-containing aqueous solutions A, B, C, and D (simulation solutions of heavy metal-containing wastewater) were prepared. Nickel standard solution (Ni 1000) (manufactured by Kanto Chemical Co., Inc.) Zinc standard solution (Zn 1000) (manufactured by Kanto Chemical Co., Inc.) Polyethyleneimine (average molecular weight of about 600) (manufactured by FUJIFILM Wako Pure Chemical Corporation) Polyethyleneimine (average molecular weight of about 1800) (manufactured by FUJIFILM Wako Pure Chemical Corporation) Polyethyleneimine (average molecular weight of about 10,000) (manufactured by FUJIFILM Wako Pure Chemical Corporation) Diethylenetriamine (manufactured by Tosoh Corporation) Triethylenetetramine (manufactured by Tosoh Corporation) Ethylenediamine-N,N,N',N'-tetraacetic acid tetrasodium salt tetrahydrate (manufactured by Dojindo Laboratories)

[0047] <Heavy Metal-Containing Aqueous Solution A> The concentrations of each component in the prepared heavy metal-containing aqueous solution A are as follows: Nickel ions 10 mg / L Zinc ions 10 mg / L Ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) 10 mg / L Diethylenetriamine 1000 mg / L Polyethyleneimine (PEI) (average molecular weight approximately 1800) 1000 mg / L

[0048] <Heavy Metal-Containing Aqueous Solution B> The concentrations of each component in the prepared heavy metal-containing aqueous solution B are as follows: Nickel ions 10 mg / L Zinc ions 10 mg / L Ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) 10 mg / L Triethylenetetramine 1000 mg / L Polyethyleneimine (PEI) (average molecular weight approximately 1800) 1000 mg / L

[0049] <Heavy Metal-Containing Aqueous Solution C> The concentrations of each component in the prepared heavy metal-containing aqueous solution C are as follows: Nickel ions 10 mg / L Zinc ions 10 mg / L Ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) 10 mg / L Diethylenetriamine 1000 mg / L Polyethyleneimine (PEI) (average molecular weight approximately 600) 1000 mg / L

[0050] <Heavy Metal-Containing Aqueous Solution D> The concentrations of each component in the prepared heavy metal-containing aqueous solution D are as follows: Nickel ions 10 mg / L Zinc ions 10 mg / L Ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) 10 mg / L Diethylenetriamine 1000 mg / L Polyethyleneimine (PEI) (average molecular weight approximately 10000) 1000 mg / L

[0051] Example 1 500 mL of the heavy metal-containing aqueous solution A was placed in a 1000 mL beaker set up in a jar tester. Next, a small amount of 10% by mass sodium hydroxide aqueous solution was added to the heavy metal-containing aqueous solution to adjust the pH to 11, and then 500 mg of calcium chloride (concentration of 1000 mg / L) was added while stirring at 150 rpm. Next, a purifying agent for heavy metal-containing aqueous solutions consisting of 250 mg of sulfate ester compound A (concentration of 500 mg / L) and 500 mg of dithiocarbamate compound A aqueous solution (50 mg as dithiocarbamate compound, concentration of 100 mg / L) was added to the heavy metal-containing aqueous solution, and the mixture was stirred at 150 rpm for 10 minutes. Next, 500 mg of inorganic flocculant aqueous solution A (150 mg as polyaluminum chloride, concentration 300 mg / L) was added to the heavy metal-containing aqueous solution, and sulfuric acid was added to adjust the pH to 6. The mixture was then stirred at 150 rpm for 5 minutes. Next, 1000 mg of polymer flocculant aqueous solution A (1 mg as OA-23, concentration 2 mg / L) was added to the heavy metal-containing aqueous solution and stirred at 50 rpm for 5 minutes. The formation of solid matter was visually confirmed. After stirring, the mixture was allowed to stand for 5 minutes, and the heavy metal-containing aqueous solution was filtered using Advantec 5A filter paper to separate the solid matter (the above corresponds to the method for purifying heavy metal-containing aqueous solutions of the present invention). The nickel and zinc concentrations in the heavy metal-containing aqueous solution (filtrate) after filtration were measured. The results are shown in Table 1.

[0052] Examples 2-7 The method for purifying heavy metal-containing aqueous solutions of the present invention was carried out in the same manner as in Example 1, except that the type and amount of added chemicals were changed as shown in Table 1. The nickel and zinc concentrations in the filtered heavy metal-containing aqueous solutions (filtrate) were measured. These results are shown in Table 1.

[0053]

[0054] As shown in Examples 1 to 7, in a heavy metal-containing aqueous solution containing EDTA, an anionic polydentate ligand, ethyleneamines (diethylenetriamine), PEI, and nickel, the nickel concentration in the heavy metal-containing aqueous solution could be reduced to 0.1 mg / L or less by purification treatment with the heavy metal-containing aqueous solution purifying agent of the present invention.

[0055] Regarding zinc, there is a mix of cases where it is highly purified and cases where it is not purified to a sufficient degree. This zinc can be purified to a very high degree using a simpler method other than the purification method of the present invention. Therefore, the fact that zinc is not sufficiently and alternately removed by the purification method of the present invention is not a problem. It is important that this zinc purification treatment is carried out when nickel has been highly purified, and by going through such a stage, the overall purification performance of heavy metal-containing aqueous solutions in industrial wastewater can be greatly improved. For this reason, the technology of the present invention, which can purify nickel to a very high degree, is extremely important industrially. The effect of simultaneously removing zinc is unexpected.

[0056] Comparative Examples 1 to 6 were performed in the same manner as in Example 1, except that the type and amount of added chemicals were changed to those shown in Table 2. The nickel and zinc concentrations in the filtered heavy metal-containing aqueous solutions (filtrate) were measured. These results are shown in Table 2. In Comparative Example 5, instead of using a dithiocarbamate compound, an inorganic sulfide (sodium hydrosulfide), which is commonly used as a heavy metal wastewater purification agent, was used for evaluation.

[0057]

[0058] Comparative Examples 1 to 6 are examples of purification treatment using a purifying agent that does not meet the requirements of the heavy metal-containing aqueous solution purifying agent of the present invention. The nickel concentration of the aqueous solution after treatment did not meet the Chinese Table 3 standard, and no effect of sufficiently removing nickel was observed. Comparative Example 5 is an example in which sodium hydrosulfide, a sulfide, was used instead of a dithiocarbamate compound. The nickel concentration of the aqueous solution after treatment was 4.6 mg / L, which did not meet the Chinese Table 3 standard.

[0059] Example 9 500 mL of the heavy metal-containing aqueous solution A was placed in a 1000 mL beaker set up in a jar tester. Next, a small amount of 10% by mass sodium hydroxide aqueous solution was added to the heavy metal-containing aqueous solution to adjust the pH to 11, and then 500 mg of calcium chloride (concentration of 1000 mg / L) was added while stirring at 150 rpm. Next, 250 mg of sulfate ester compound A (concentration of 500 mg / L) and 500 mg of dithiocarbamate compound A aqueous solution (50 mg as dithiocarbamate compound, concentration of 100 mg / L) were added to the heavy metal-containing aqueous solution, and the mixture was stirred at 150 rpm for 10 minutes. Next, 500 mg of inorganic flocculant aqueous solution A (150 mg as polyaluminum chloride, concentration of 300 mg / L) was added to the heavy metal-containing aqueous solution, and sulfuric acid was added to adjust the pH to 6, and the mixture was stirred at 150 rpm for 5 minutes. Next, 1000 mg of polymer flocculant aqueous solution A (1 mg as OA-23, concentration 2 mg / L) was added to the heavy metal-containing aqueous solution and stirred at 50 rpm for 5 minutes. The formation of solid matter was visually confirmed. After stirring, the solution was allowed to stand for 5 minutes, and the heavy metal-containing aqueous solution was filtered using Advantec 5A filter paper to remove the solid matter (the above corresponds to the method for purifying heavy metal-containing aqueous solutions of the present invention). The nickel concentration and zinc concentration in the heavy metal-containing aqueous solution (filtrate) after filtration were measured. The results were the same as in Example 1.

[0060] Example 10 A heavy metal-containing aqueous solution purifying agent was prepared by mixing 250 mg of sulfate ester compound B (at a concentration of 500 mg / L), 500 mg of an aqueous solution of dithiocarbamate compound A (50 mg of dithiocarbamate compound, at a concentration of 100 mg / L), and 1.2 g of water to a total volume of 1.5 g with a concentration of 20% by mass. The procedure was the same as in Example 2, except that instead of adding the heavy metal-containing aqueous solution purifying agent consisting of 250 mg of sulfate ester compound B (at a concentration of 500 mg / L) and 500 mg of an aqueous solution of dithiocarbamate compound A (50 mg of dithiocarbamate compound, at a concentration of 100 mg / L) used in Example 2, the above 1.5 g total volume of a 20% by mass aqueous solution purifying agent for heavy metal-containing aqueous solutions was added, and the nickel and zinc concentrations in the heavy metal-containing aqueous solution (filtrate) after the final filtration treatment were measured. The results were the same as in Example 2.

[0061] Examples 8, 11-13: The method for purifying heavy metal-containing aqueous solutions of the present invention was carried out in the same manner as in Example 1, except that the type and amount of added chemicals were changed as shown in Table 3. Nickel and zinc concentrations were measured in the filtered heavy metal-containing aqueous solutions (filtrate). These results are shown in Table 3.

[0062]

[0063] As shown in Examples 8, 11-13, for heavy metal-containing aqueous solutions containing EDTA (an anionic polydentate ligand), ethyleneamines (diethylenetriamine) and PEI (amine polydentate ligands), and nickel, the nickel concentration in the heavy metal-containing aqueous solution could be reduced to 0.1 mg / L or less by purification treatment with the heavy metal-containing aqueous solution purifying agent of the present invention.

[0064] Example 14 500 mL of the heavy metal-containing aqueous solution B was placed in a 1000 mL beaker set up in a jar tester. Next, a small amount of 10% by mass sodium hydroxide aqueous solution was added to the heavy metal-containing aqueous solution to adjust the pH to 11, and then 500 mg of calcium chloride (concentration of 1000 mg / L) was added while stirring at 150 rpm. Next, a purifying agent for heavy metal-containing aqueous solutions consisting of 250 mg of sulfate ester compound A (concentration of 500 mg / L) and 500 mg of dithiocarbamate compound A aqueous solution (50 mg as dithiocarbamate compound, concentration of 100 mg / L) was added to the heavy metal-containing aqueous solution, and the mixture was stirred at 150 rpm for 10 minutes. Next, 500 mg of inorganic flocculant aqueous solution A (150 mg as polyaluminum chloride, concentration 300 mg / L) was added to the heavy metal-containing aqueous solution, and sulfuric acid was added to adjust the pH to 6. The mixture was then stirred at 150 rpm for 5 minutes. Next, 1000 mg of polymer flocculant aqueous solution A (1 mg as OA-23, concentration 2 mg / L) was added to the heavy metal-containing aqueous solution and the mixture was stirred at 50 rpm for 5 minutes. The formation of solid matter was visually confirmed. After stirring, the mixture was allowed to stand for 5 minutes, and the heavy metal-containing aqueous solution was filtered using Advantec 5A filter paper to separate the solid matter (the above corresponds to the method for purifying heavy metal-containing aqueous solutions of the present invention). The nickel and zinc concentrations in the heavy metal-containing aqueous solution (filtrate) after filtration were measured. The results are shown in Table 4.

[0065] Example 15 500 mL of the heavy metal-containing aqueous solution C was placed in a 1000 mL beaker set up in a jar tester. Next, a small amount of 10% by mass sodium hydroxide aqueous solution was added to the heavy metal-containing aqueous solution to adjust the pH to 11, and then 500 mg of calcium chloride (concentration of 1000 mg / L) was added while stirring at 150 rpm. Next, a purifying agent for heavy metal-containing aqueous solutions consisting of 250 mg of sulfate ester compound A (concentration of 500 mg / L) and 500 mg of dithiocarbamate compound A aqueous solution (50 mg as dithiocarbamate compound, concentration of 100 mg / L) was added to the heavy metal-containing aqueous solution, and the mixture was stirred at 150 rpm for 10 minutes. Next, 500 mg of inorganic flocculant aqueous solution A (150 mg as polyaluminum chloride, concentration 300 mg / L) was added to the heavy metal-containing aqueous solution, and sulfuric acid was added to adjust the pH to 6. The mixture was then stirred at 150 rpm for 5 minutes. Next, 1000 mg of polymer flocculant aqueous solution A (1 mg as OA-23, concentration 2 mg / L) was added to the heavy metal-containing aqueous solution and the mixture was stirred at 50 rpm for 5 minutes. The formation of solid matter was visually confirmed. After stirring, the mixture was allowed to stand for 5 minutes, and the heavy metal-containing aqueous solution was filtered using Advantec 5A filter paper to separate the solid matter (the above corresponds to the method for purifying heavy metal-containing aqueous solutions of the present invention). The nickel and zinc concentrations in the heavy metal-containing aqueous solution (filtrate) after filtration were measured. The results are shown in Table 4.

[0066] Example 16 500 mL of the heavy metal-containing aqueous solution D was placed in a 1000 mL beaker set up in a jar tester. Next, a small amount of 10% by mass sodium hydroxide aqueous solution was added to the heavy metal-containing aqueous solution to adjust the pH to 11, and then 500 mg of calcium chloride (concentration of 1000 mg / L) was added while stirring at 150 rpm. Next, a purifying agent for heavy metal-containing aqueous solutions consisting of 250 mg of sulfate ester compound A (concentration of 500 mg / L) and 500 mg of dithiocarbamate compound A aqueous solution (50 mg as dithiocarbamate compound, concentration of 100 mg / L) was added to the heavy metal-containing aqueous solution, and the mixture was stirred at 150 rpm for 10 minutes. Next, 500 mg of inorganic flocculant aqueous solution A (150 mg as polyaluminum chloride, concentration 300 mg / L) was added to the heavy metal-containing aqueous solution, and sulfuric acid was added to adjust the pH to 6. The mixture was then stirred at 150 rpm for 5 minutes. Next, 1000 mg of polymer flocculant aqueous solution A (1 mg as OA-23, concentration 2 mg / L) was added to the heavy metal-containing aqueous solution and the mixture was stirred at 50 rpm for 5 minutes. The formation of solid matter was visually confirmed. After stirring, the mixture was allowed to stand for 5 minutes, and the heavy metal-containing aqueous solution was filtered using Advantec 5A filter paper to separate the solid matter (the above corresponds to the method for purifying heavy metal-containing aqueous solutions of the present invention). The nickel and zinc concentrations in the heavy metal-containing aqueous solution (filtrate) after filtration were measured. The results are shown in Table 4.

[0067]

[0068] As shown in Examples 14 to 16, in heavy metal-containing aqueous solutions containing nickel, where the amine polydentate ligands, such as ethyleneamines, become triethylenetetramine, or the average molecular weight of PEI is other than 1800, the nickel concentration in the heavy metal-containing aqueous solution could be reduced to 0.1 mg / L or less by purification treatment with the heavy metal-containing aqueous solution purifying agent of the present invention.

[0069] Furthermore, the entire contents of the claims, description, and abstract of Japanese Patent Application No. 2025-005826, filed on January 15, 2025, and Japanese Patent Application No. 2025-097018, filed on June 10, 2025, are incorporated herein by reference as disclosures of the specification of this invention.

Claims

1. A purifying agent for heavy metal-containing aqueous solutions, characterized by containing a dithiocarbamate compound and an organic compound having a sulfonic acid group or a sulfate ester group.

2. The purifying agent for heavy metal-containing aqueous solutions according to claim 1, wherein the organic compound having a sulfonic acid group or a sulfate ester group is a sulfonic acid hydrocarbon compound or a sulfate ester hydrocarbon compound.

3. The purifying agent for heavy metal-containing aqueous solutions according to claim 1, wherein the dithiocarbamate compound is a reaction product of an amine compound having at least one group selected from the group consisting of a primary amino group and a secondary amino group, carbon disulfide, and a base.

4. The purifying agent for heavy metal-containing aqueous solutions according to claim 1, wherein the content of the organic compound having a sulfonic acid group or a sulfate ester group is 5 to 2000 parts by mass per 100 parts by mass of the dithiocarbamate compound.

5. The heavy metal-containing aqueous solution is a heavy metal-containing aqueous solution containing nickel, as described in claim 1.

6. A purifying agent for heavy metal-containing aqueous solutions according to claim 1, comprising a dithiocarbamate compound, an organic compound having a sulfonic acid group or a sulfate ester group, and a solvent.

7. A method for purifying a heavy metal-containing aqueous solution, characterized by adding the heavy metal-containing purifying agent described in any one of claims 1 to 6 to a heavy metal-containing aqueous solution containing an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal, and then removing the resulting solid matter.

8. The method for purifying a heavy metal-containing aqueous solution according to claim 7, wherein the heavy metal-containing aqueous solution is a heavy metal-containing aqueous solution containing a calcium salt, an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal.

9. The method for purifying an aqueous solution containing a heavy metal according to claim 7, wherein the heavy metal is nickel.

10. The method for purifying a heavy metal-containing aqueous solution according to claim 7, wherein the anionic polydentate ligand is ethylenediaminetetraacetic acid.

11. The method for purifying a heavy metal-containing aqueous solution according to claim 7, wherein the amine-based polydentate ligand is polyethyleneimine or ethyleneamine.

12. A method for purifying an aqueous solution containing heavy metals according to claim 7, characterized in that a purifying agent for aqueous solutions containing heavy metals is added, a coagulant is added, and then the resulting solid matter is removed.

13. The method for purifying a heavy metal-containing aqueous solution according to claim 12, wherein the coagulant is an inorganic coagulant or a polymer coagulant.

14. A method for purifying an aqueous solution containing heavy metals, characterized by adding a dithiocarbamate compound and an organic compound having a sulfonic acid group or a sulfate ester group to an aqueous solution containing an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal, and then removing the resulting solid matter.

15. The method for purifying a heavy metal-containing aqueous solution according to claim 14, wherein the heavy metal-containing aqueous solution is a heavy metal-containing aqueous solution containing a calcium salt, an anionic polydentate ligand, an amine polydentate ligand, and a heavy metal.

16. The method for purifying a heavy metal-containing aqueous solution according to claim 14 or 15, wherein the amount of the organic compound having a sulfonic acid group or a sulfate ester group added is 5 to 2000 parts by mass per 100 parts by mass of the dithiocarbamate compound added.

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