Water treatment system and water treatment method

Abstract

To provide a water treatment system and a water treatment method for treating water at low energy.SOLUTION: A water treatment system has: a first vessel accommodating a mixed solution of treated water and an amine solution containing one or more tertiary amines of chemical formulas (1) to (8), means for introducing carbon dioxide into the first vessel; and means for separately separating a supernatant phase and a precipitate phase of the liquid in which the mixed solution containing the treated water and the amine solution is phase-separated by introducing carbon dioxide into the first vessel.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE An embodiment of the present invention relates to a water treatment system and a water treatment method. [Background technology]

[0002] As the global population increases, the demand for water is expected to grow significantly, creating a demand for low-energy desalination technologies. There are several common desalination methods, including thermal evaporation and reverse osmosis (RO) membrane methods, and in recent years the RO membrane method, which consumes relatively little energy, has come into widespread use. The reverse osmosis membrane method is a method of desalination that applies pressure to an osmotic membrane in the opposite direction to the osmotic pressure. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Environ.Sci.Technol. 2020, 54 9124-9131 Summary of the Invention [Problem to be solved by the invention]

[0004] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments provide a water treatment system and method for treating water with low energy. [Means for solving the problem]

[0005] The water treatment system according to the embodiment includes a first container for accommodating a mixed solution of water to be treated and an amine solution containing one or more tertiary amines represented by any one of chemical formulas (1) to (3), a means for introducing carbon dioxide into the first container, and a means for introducing carbon dioxide into the first container to separate a supernatant phase and a precipitate phase of the mixed solution containing the water to be treated and the amine solution. 1-1 , the number of carbon atoms is 2 or 3 is a linear alkyl chain. R in formula (1) 1-2A , R 1-2B , R 1-6A, R 1-6B is hydrogen respectively. R in Chemical Formula (1) 1-3A , R 1-3B , R 1-4A , R 1-4B , R 1-5A , R 1-5B Among them, any one or two of them are hydrogen, methyl group or ethyl group respectively, and the rest are hydrogen. R in Chemical Formula (1) 1-7A , R 1-7B , R 1-11A , R 1-11B is hydrogen respectively. R in Chemical Formula (1) 1-8A , R 1-8B , R 1-9A , R 1-9B , R 1-10A , R 1-10B Among them, any one or two of them are hydrogen, methyl group or ethyl group respectively, and the rest are hydrogen. R in Chemical Formula (2) 2-1 is a straight-chain alkyl chain with 1 to 3 carbon atoms. R in Chemical Formula (2) 2-2A , R 2-2B , R 2-3A , R 2-3B , R 2-6A , R 2-6B , R 2-7A , R 2-7B is hydrogen respectively. R in Chemical Formula (2) 2-4A , R 2-4B , R 2-5A , R 2-5B Among them, any one or two of them are hydrogen, methyl group or ethyl group respectively, and the rest are hydrogen. R in Chemical Formula (2) 2-8A , R 2-8B , R 2-9A , R 2-9B , R 2-12A , R 2-12B , R 2-13A , R 2-13B is hydrogen respectively. R in Chemical Formula (2) 2-10A , R 2-10B , R 2-11A , R 2-11B Among them, any one or two of them are hydrogen, methyl group or ethyl group respectively, and the rest are hydrogen. R in Chemical Formula (3) 3-1 is an alkyl chain with the number of carbon atoms being 2 or is a linear alkyl chain of 3. R in Chemical Formula (3) 3-2A , R 3-2B , R 3-5A , R 3-5B is hydrogen respectively. R in Chemical Formula (3) 3-3A , R 3-3B , R 3-4A , R 3-4B , any one or two of れメ is either a butyl group or an ethyl group respectively, and the rest are hydrogen. R in Chemical Formula (3) 3-6A , R 3-6B , R 3-9A , R 3-9B is hydrogen respectively. R in Chemical Formula (3) 3-7A , R 3-7B , R 3-8A , R 3-8B , any one or two of れメ is either a butyl group or an ethyl group respectively, and the rest are hydrogen. When the temperature of the mixed solution is 0°C or higher and 50°C or lower and the carbon dioxide concentration in the mixed solution increases, the tertiary amine responds to carbon dioxide, its solubility changes, and the solubility of the tertiary amine in the water to be treated improves.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

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Figure 8

Modes for Carrying Out the Invention

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Unless otherwise specified, the values obtained by pH or other measurements are the values measured at atmospheric pressure and 25°C.

[0008] (First Embodiment) The first embodiment relates to a water treatment system and a water treatment method applied to non-evaporative desalination by salting out using a tertiary amine compound whose hydrophobicity and hydrophilicity change by reaction with carbon dioxide. FIG. 1 shows a schematic diagram of the water treatment system 100 of the first embodiment. The schematic diagram of the water treatment system 100 in FIG. 1 includes means 11 for introducing the water to be treated A into the first container B, means 12 for introducing the amine solution C into the first container B, means 13 for introducing carbon dioxide D into the first container B, and means 14 for separately separating the supernatant phase G and the precipitate phase H of the liquid F obtained by phase separation of the mixed solution E containing the water to be treated A and the amine solution C by introducing carbon dioxide D into the first container B.

[0009] In the schematic diagram of FIG. 1, the means 11 for introducing the water to be treated A into the first container B, the means 12 for introducing the amine solution C into the first container B, the means 13 for introducing carbon dioxide D into the first container B, and the means 14 for separately separating the supernatant phase G and the precipitate phase H of the liquid F obtained by phase separation of the mixed solution E containing the water to be treated A and the amine solution C by introducing carbon dioxide D into the first container B are provided outside the first container B, but these means may be provided inside the first container B.

[0010] Figure 2 shows a flowchart of the water treatment method according to the first embodiment. The water treatment method according to the embodiment preferably includes a step of mixing the water to be treated A, the amine solution C, and the carbon dioxide D to obtain a phase-separated liquid F, and a step of separating the supernatant phase G and the precipitate phase H of the phase-separated liquid F. The step of mixing the water to be treated A, the amine solution C, and the carbon dioxide D to obtain a phase-separated liquid F is performed by means 11 for introducing the water to be treated A into the first container B, means 12 for introducing the amine solution C into the first container B, and means 13 for introducing the carbon dioxide D into the first container B. The step of separating the supernatant phase G and the precipitate phase H of the phase-separated liquid F is performed by means 14 for introducing the carbon dioxide D into the first container B to separately divide the supernatant phase G and the precipitate phase H of the mixed solution E containing the water to be treated A and the amine solution C into the phase-separated liquid F. Hereinafter, the water treatment system 100 will be described. The description of the water treatment system 100 also includes the description of the water treatment method.

[0011] Means 11 for introducing the water to be treated A into the first container B introduces the water to be treated A into the first container B. Means 11 for introducing the water to be treated A into the first container B includes, for example, a pipe communicating with the first container B, instruments for grasping the properties of the water to be treated A such as a pH meter, a conductivity meter, a thermometer, and a valve, a cock, or a pump for controlling the flow rate of the water to be treated A flowing through the pipe.

[0012] The water to be treated A contains water, inorganic salts soluble in water, and / or organic substances soluble in water. The inorganic salts soluble in water and / or the organic substances soluble in water are separated by the water treatment system 100 of the embodiment. The inorganic salts and / or organic substances in the water to be treated A can be separated by phase separation. The separated inorganic salts and / or organic substances can also be recovered. The inorganic salts are dissolved in the water to be treated A, and in the water to be treated A, the inorganic salts exist as ions. When the organic substance is a water-soluble salt, the water to be treated A contains the ionized organic substance and the counter ion of the ionized organic substance. The organic substance (the organic substance recovered by precipitation) contained in the water to be treated A is preferably water-soluble and a solid compound at the treatment temperature. Even when the water to be treated A contains substantially no salt and only contains organic substances, the water to be treated A can be treated. When only the water to be treated A is written, it represents the water to be treated A before water treatment in the embodiment.

[0013] The water to be treated A is an aqueous solution. The total mass of the inorganic salts and / or organic substances and water is preferably 5 wt% or more and 300 wt% or less of the water in the water to be treated A. In addition to the inorganic salts and / or organic substances and water, the water to be treated A may contain 0.0 wt% or more and 5 wt% or less of one or more selected from the group consisting of organic substances insoluble in water, water-soluble organic substances that are liquid at the treatment temperature, metals, and metal oxides.

[0014] The concentration of the inorganic salts and / or organic substances contained in the water to be treated A is not particularly limited. In the embodiment, the inorganic salts and / or organic substances can be separated regardless of the concentration of the inorganic salts and / or organic substances contained in the water to be treated A.

[0015] Specific examples of the ions contained in the water to be treated A include one or more selected from the group consisting of sodium ion, potassium ion, lithium ion, magnesium ion, calcium ion, fluoride ion, sulfate ion, nitrate ion, nitrite ion, chloride ion, bromide ion, iodide ion, cyanide ion, acetate ion, hydrogen carbonate ion, thiocyanate ion, hydrogen sulfide ion, hydrogen oxalate ion, chlorate ion, perchlorate ion, hypochlorite ion, hydroxide ion, silver ion, copper ion, iron ion, cobalt ion, tin ion, lead ion, manganese ion, ammonium ion, aluminum ion, chromium ion, various complex ions, phosphate ion, strontium ion, barium ion, cadmium ion, nickel ion, zinc ion, mercury ion, etc. It is also preferable that non-ionized organic substances are contained.

[0016] The first container B is a container for containing the water to be treated A and the amine solution. It is preferable that the first container B is provided with means 11 for introducing the water to be treated A into the first container B, means 12 for introducing the amine solution C into the first container B, means 13 for introducing carbon dioxide D into the first container B, and means 14 for separately separating the supernatant phase G and the precipitation phase H. It is also possible to provide means 13 for introducing carbon dioxide D and / or means 14 for separately separating the supernatant phase G and the precipitation phase H in a container different from the first container B.

[0017] The total pressure inside the first container B is preferably 700 Pa or more and 1 MPa or less. The gas inside the first container B contains carbon dioxide, oxygen, nitrogen, etc. Since carbon dioxide D is introduced into the solution in the first container B, the carbon dioxide concentration inside the first container B may be higher than that in air, for example, 1% or more and 100% or less. Even if the carbon dioxide concentration inside the first container B is high, the amount of carbon dioxide dissolved in the solution inside the first container B is small. Therefore, means 13 for introducing carbon dioxide D is used even if the carbon dioxide concentration inside the first container B is high.

[0018] The means 12 for introducing the amine solution C into the first container B introduces the amine solution C into the first container B. The means 12 for introducing the amine solution C into the first container B includes, for example, a pipe leading to the first container B, instruments for grasping the properties of the amine solution C such as a pH meter, a conductivity meter, a thermometer, a valve for controlling the flow rate of the amine solution C flowing through the pipe, a cock, a pump, and the like.

[0019] The amine solution C contains a tertiary amine whose solubility changes in response to carbon dioxide. The solution containing the amine solution C changes its liquid property according to the carbon dioxide concentration in the solution.

[0020] The tertiary amine compound whose solubility changes in response to carbon dioxide is liquid and is a highly hydrophobic compound that phase-separates when mixed with water at room temperature. The tertiary amine compound whose solubility changes in response to carbon dioxide becomes hydrophilic when reacting with carbon dioxide, and its solubility in the water to be treated A is improved.

[0021] The amine compound reacts with carbon dioxide mainly through two routes. One is the route for generating bicarbonate, and the other is the route in which carbon dioxide is added to the amine moiety to generate carbamate. The tertiary amine compound takes the former route for generating bicarbonate and is more likely to release carbon dioxide than carbamate.

[0022] FIGS. 3 and 4 show the chemical formulas of the tertiary amines of the embodiments. The amine solution C contains the tertiary amines represented by the chemical formulas (1) to (8) shown in FIGS. 3 and 4. The amine solution C preferably contains one or more selected from the tertiary amines represented by the chemical formulas (1) to (8), and preferably contains one selected from the tertiary amines represented by the chemical formulas (1) to (8). The tertiary amine whose liquid property changes according to the concentration of carbon dioxide is disclosed, for example, in Structure-function study of tertiary amines as switchable polarity solvents RSC Adv., 2014, 4, 11039-11049. The amine solution C contains 80 wt% or more and 100 wt% or less of the tertiary amine whose solubility changes in response to carbon dioxide.

[0023] When the amount of the amine solution C used is small, the precipitation amount of the inorganic salts and / or organic substances contained in the water to be treated A is small. Therefore, it is preferable to use an appropriate amount of the amine solution C according to the amount of the inorganic salts and / or organic substances contained in the water to be treated A. The total molar number of the tertiary amines whose solubility changes in response to carbon dioxide contained in the amine solution C used for water treatment is preferably not less than the total molar number of the inorganic salts and / or organic substances contained in the water to be treated A, more preferably not less than twice the total molar number of the inorganic salts and / or organic substances contained in the water to be treated A, and even more preferably not less than five times the total molar number of the inorganic salts and / or organic substances contained in the water to be treated A.

[0024] In the chemical formula, hydrogen may be omitted. For example, when three of the four bonds of carbon are shown in the chemical formulas of FIGS. 3 and 4, the remaining one bond of carbon is a bond with hydrogen, and the bond with hydrogen is omitted.

[0025] The tertiary amine of the chemical formula (1) is a tertiary amine whose solubility changes in response to carbon dioxide. In the amine of the chemical formula (1), the nitrogens of two piperidines (including derivatives) are linked by an alkyl chain (R 1-1 ).

[0026] The alkyl chain (R 1-1 ) of the chemical formula (1) is preferably a straight-chain alkyl chain having 1 to 4 carbon atoms, and more preferably a straight-chain alkyl chain having 3 carbon atoms.

[0027] The two piperidine structures of the chemical formula (1) are preferably the same. Specifically, R 1-2A and R 1-7A are the same, R 1-2B and R 1-7B are the same, R 1-3A and R 1-8A are the same, R 1-3B and R 1-8B are the same, R 1-4A and R 1-9A are the same, R 1-4B and R 1-9B are the same, R1-5A and R 1-10A are the same, and R 1-5B and R 1-10B are the same, and R 1-6A and R 1-11A are the same, and R 1-6B and R 1-11B are preferably the same. Specifically, R 1-2A , R 1-2B , R 1-7A and R 1-7B are all the same, and R 1-3A , R 1-3B , R 1-8A and R 1-8B are all the same, and R 1-4A , R 1-4B , R 1-9A and R 1-9B are all the same, and R 1-5A , R 1-5B , R 1-10A and R 1-10B are all the same, and R 1-6A , R 1-6B , R 1-11A and R 1-11B are preferably all the same.

[0028] R in the piperidine structure of Chemical Formula (1) 1-2A , R 1-2B , R 1-3A , R 1-3B , R 1-4A , R 1-4B , R 1-5A , R 1-5B , R 1-6A , R 1-6B is preferably either hydrogen, a methyl group, or an ethyl group. R 1-2A , R 1-2B , R 1-3A , R 1-3B , R 1-4A , R 1-4B , R 1-5A , R 1-5B , R 1-6A , R 1-6B is each either hydrogen, a methyl group, or an ethyl group, and R 1-2A is either hydrogen, a methyl group, or an ethyl group, and R 1-2B is either hydrogen, a methyl group, or an ethyl group, and R 1-3Ais either hydrogen, a methyl group or an ethyl group, R 1-3B is either hydrogen, a methyl group or an ethyl group, R 1-4A is either hydrogen, a methyl group or an ethyl group, R 1-4B is either hydrogen, a methyl group or an ethyl group, R 1-5A is either hydrogen, a methyl group or an ethyl group, R 1-5B is either hydrogen, a methyl group or an ethyl group, R 1-6A is either hydrogen, a methyl group or an ethyl group, R 1-6B means that it is either hydrogen, a methyl group or an ethyl group, and the same applies hereinafter. R 1-2A R 1-2B R 1-6A R 1-6B is preferably hydrogen respectively. R 1-3A R 1-3B R 1-4A R 1-4B R 1-5A R 1-5B is preferably either hydrogen, a methyl group, an ethyl group, a methoxy group or an ethoxy group respectively. R 1-3A R 1-3B R 1-4A R 1-4B R 1-5A R 1-5B Among them, it is preferable that any one or two of them are respectively either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. Having too many substituents is not preferable because the separability from water deteriorates. Also, having a hydroxyl group, a carboxyl group or a halogen in the substituent is not preferable because the solubility in water increases.

[0029] R of the piperidine structure of Chemical Formula (1) 1-7A R 1-7B R 1-8A R 1-8B R 1-9A R 1-9B R 1-10A R 1-10B R 1-11A R 1-11B is preferably either hydrogen, a methyl group or an ethyl group respectively. R1-7A 、R 1-7B 、R 1-11A 、R 1-11B is preferably hydrogen in each case. R 1-8A 、R 1-8B 、R 1-9A 、R 1-9B 、R 1-10A 、R 1-10B is preferably either hydrogen, a methyl group or an ethyl group in each case. R 1-8A 、R 1-8B 、R 1-9A 、R 1-9B 、R 1-10A 、R 1-11B Among them, it is preferable that any one or two of them are each either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. Having too many substituents is not preferable because the separability from water deteriorates. Also, having a hydroxyl group, a carboxyl group or a halogen in the substituent is not preferable because the solubility in water increases.

[0030] The R of the alkyl chain 1-1 is a straight-chain alkyl chain with 3 carbon atoms (propyl), and R 1-2A 、R 1-2B 、R 1-3A 、R 1-3B 、R 1-4A 、R 1-4B 、R 1-5A 、R 1-5B 、R 1-6A 、R 1-6B 、R 1-7A 、R 1-7B 、R 1-8A 、R 1-8B 、R 1-9A 、R 1-9B 、R 1-10A 、R 1-10B 、R 1-11A 、R 1-11B of the tertiary amine of the chemical formula (1) having a piperidine structure in which all are hydrogen, and / or the R of the alkyl chain 1-1 is a straight-chain alkyl chain with 3 carbon atoms (propyl), and R 1-2A 、R 1-2B 、R 1-3A 、R 1-3B 、R 1-4A 、R 1-5A 、R 1-5B 、R1-6A , R 1-6B , R 1-7A , R 1-8B , R 1-8A , R 1-8B , R 1-9A , R 1-10A , R 1-10B , R 1-11A , R 1-11B All of them are hydrogen, and R 1-4B and R 1-9B A tertiary amine of Chemical Formula (1) having a piperidine structure in which both are methyl groups or ethyl groups is likely to phase-separate, and the recovery rate of inorganic salts and / or organic substances is high.

[0031] The synthesis method of the compound of Chemical Formula (1) will be briefly described. For example, piperidine (or its derivative) and 1,3-dibromopropane (depending on the number of carbon atoms in the alkyl chain, dibromomethane or 1,2-dibromoethane may be used instead) are heated and stirred in a solvent, and piperidine is bonded to the bromines on both sides of 1,3-dibromopropane by a nucleophilic reaction. The obtained compound can be purified to obtain a tertiary amine of Chemical Formula (1).

[0032] The tertiary amine of Chemical Formula (2) is a tertiary amine whose solubility changes in response to carbon dioxide. In the amine of Chemical Formula (2), the nitrogens of two azepanes (including derivatives) are linked by an alkyl chain (R 2-1 ).

[0033] The alkyl chain (R 2-1 ) of Chemical Formula (2) is preferably a straight-chain alkyl chain having 1 to 3 carbon atoms, and more preferably a straight-chain alkyl chain having 3 carbon atoms.

[0034] The two azepane structures of Chemical Formula (2) are preferably the same. Specifically, R 2-2A and R 2-8A are the same, R 2-2B and R 2-8B are the same, R 2-3A and R 2-9A are the same, R 2-3B and R 2-9B are the same, R 2-4A and R 2-10A are the same, R2-4B and R 2-10B are the same, and R 2-5A and R 2-11A are the same, and R 2-5B and R 2-11B are the same, and R 2-6A and R 2-12A are the same, and R 2-6B and R 2-12B are the same, and R 2-7A and R 2-13A are the same and R 2-7B and R 2-13B are preferably the same. Specifically, R 2-2A R 2-2B R 2-8A and R 2-8B are all the same, and R 2-3A R 2-3B R 2-9A and R 2-9B are all the same, and R 2-4A R 2-4B R 2-10A and R 2-10B are all the same, and R 2-5A R 2-5B R 2-11A and R 2-11B are all the same, and R 2-6A R 2-6B R 2-12A and R 2-12B are all the same, and R 2-7A R 2-7B R 2-13A and R 2-13B are preferably all the same.

[0035] R in the azepane structure of Chemical Formula (2) 2-2A R 2-2B R 2-3A R 2-3B R 2-4A R 2-4B R 2-5A R 2-5B R 2-6A R 2-6B R 2-7A R 2-7B is preferably any one of hydrogen, a methyl group, an ethyl group, a methoxy group, or an ethoxy group. R 2-2A R 2-2B R 2-3A R 2-3B R2-6A , R 2-6B , R 2-7A , R 2-7B is preferably hydrogen for each. R 2-4A , R 2-4B , R 2-5A , R 2-5B is preferably either hydrogen, a methyl group or an ethyl group for each. R 2-4A , R 2-4B , R 2-5A , R 2-5B Among them, it is preferable that any one or two of them are each either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. It is not preferable because the separability from water deteriorates when there are many substituents. Also, it is not preferable because the solubility in water increases when the substituents contain a hydroxyl group, a carboxyl group or a halogen.

[0036] R of the azepane structure of chemical formula (2) 2-8A , R 2-8B , R 2-9A , R 2-9B , R 2-10A , R 2-10B , R 2-11A , R 2-11B , R 2-12A , R 2-12B , R 2-13A , R 2-13B is preferably either hydrogen, a methyl group or an ethyl group for each. R 2-8A , R 2-8B , R 2-9A , R 2-9B , R 2-12A , R 2-12B , R 2-13A , R 2-13B is preferably hydrogen for each. R 2-10A , R 2-10B , R 2-11A , R 2-11B is preferably either hydrogen, a methyl group or an ethyl group for each. R 2-10A , R 2-10B , R 2-11A , R 2-11BAmong them, it is preferable that any one or two of them are each one of a hydrogen atom, a methyl group or an ethyl group, and the remainder is a hydrogen atom. Having too many substituents is not preferable because the separability from water deteriorates. Further, having a hydroxyl group, a carboxyl group or a halogen in the substituent is not preferable because the solubility in water increases.

[0037] R of the alkyl chain in Chemical Formula (2) 2-1 is a straight-chain alkyl chain having 3 carbon atoms (propyl) and R 2-2A , R 2-2B , R 2-3A , R 2-3B , R 2-4A , R 2-4B , R 2-5A , R 2-5B , R 2-6A , R 2-6B , R 2-7A , R 2-7B , R 2-8A , R 2-8B , R 2-9A , R 2-9B , R 2-10A , R 2-10B , R 2-11A , R 2-11B , R 2-12A , R 2-12B , R 2-13A , R 2-13B a tertiary amine of Chemical Formula (2) having an azepane structure in which all of R are hydrogen, and / or R of the alkyl chain of Chemical Formula (2) 2-1 is a straight-chain alkyl chain having 3 carbon atoms (propyl), and R 2-2A , R 2-3A , R 2-3B , R 2-4A , R 2-4B , R 2-5A , R 2-5B , R 2-6A , R 2-6B , R 2-7A , R 2-7B , R 2-8A , R 2-9A , R 2-9B , R 2-10A , R 2-10B , R 2-11A , R 2-11B , R 2-12A , R 2-12B , R 2-13A , R2-13B All of them are hydrogen, and R 2-2B and R 2-8B The tertiary amine of Chemical Formula (2) having a piperidine structure in which both are methyl groups or ethyl groups is likely to phase-separate, and the recovery rate of inorganic salts and / or organic substances is high.

[0038] The synthesis method of the compound of Chemical Formula (2) will be briefly described. For example, azepane (or its derivative) and 1,3-dibromopropane (depending on the number of carbon atoms in the alkyl chain, dibromomethane, 1,2-dibromoethane, etc. can be used instead) are heated and stirred in a solvent, and azepane is bonded to the bromines on both sides of 1,3-dibromopropane by a nucleophilic reaction. The obtained compound can be purified to obtain the tertiary amine of Chemical Formula (2).

[0039] The tertiary amine of Chemical Formula (3) is a tertiary amine whose solubility changes in response to carbon dioxide. In the amine of Chemical Formula (3), the nitrogens of two pyrrolidines (including derivatives) are linked by an alkyl chain (R 3-1 ).

[0040] The alkyl chain (R 3-1 ) of Chemical Formula (3) is preferably a straight-chain alkyl chain having 1 to 4 carbon atoms, and more preferably a straight-chain alkyl chain having 3 carbon atoms.

[0041] The two pyrrolidine structures of Chemical Formula (3) are preferably the same. Specifically, R 3-2A and R 3-6A are the same, R 3-2B and R 3-6B are the same, R 3-3A and R 3-7A are the same, R 3-3B and R 3-7B are the same, R 3-4A and R 3-8A are the same, R 3-4B and R 3-8B are the same, R 3-5A and R 3-9A are the same, R 3-5B and R 3-9B are preferably the same. Specifically, R 3-2A , R3-2B , R 3-6A and R 3-6B are all the same, and R 3-3A , R 3-3B , R 3-7A and R 3-7B are all the same, and R 3-4A , R 3-4B , R 3-8A and R 3-8B are all the same, and R 3-5A , R 3-5B , R 3-9A and R 3-9B are preferably all the same.

[0042] R in the pyrrolidine structure of Chemical Formula (3) 3-2A , R 3-2B , R 3-3A , R 3-3B , R 3-4A , R 3-4B , R 3-5A , R 3-5B is preferably either hydrogen, a methyl group, or an ethyl group. R 3-2A , R 3-2B , R 3-5A , R 3-5B is preferably hydrogen. R 3-3A , R 3-3B , R 3-4A , R 3-4B , R 3-5A , R 3-5B Among them, it is preferable that any one or two of them are each a methyl group or an ethyl group, and the rest are hydrogen. When there is no substituent, that is, when all of R 3-2A , R 3-2B , R 3-3A , R 3-3B , R 3-4A , R 3-4B , R 3-5A , R 3-5B are hydrogen, the solubility in water does not change with the concentration of carbon dioxide D, so it is preferable that one or more substituents are included.

[0043] R in the pyrrolidine structure of Chemical Formula (3) 3-6A , R 3-6B , R 3-7A , R 3-7B , R 3-8A , R3-8B , R 3-9A , R 3-9B is preferably any one of hydrogen, a methyl group or an ethyl group. R 3-6A , R 3-6B , R 3-9A , R 3-9B is preferably hydrogen. R 3-7A , R 3-7B , R 3-8A , R 3-8B , R 3-9A , R 3-9B Among them, it is preferable that any one or two of them are either a methyl group or an ethyl group, and the rest are hydrogen. When there is no substituent, that is, when all of R 3-6A , R 3-6B , R 3-7A , R 3-7B , R 3-8A , R 3-8B , R 3-9A , R 3-9B are all hydrogen, the solubility does not change with the concentration of carbon dioxide D, so it is preferable to contain one or more substituents.

[0044] The R of the alkyl chain 3-1 is a straight-chain alkyl chain with 3 carbon atoms (propyl), and R 3-2A , R 3-2B , R 3-3A , R 3-4A , R 3-4B , R 3-5A , R 3-5B , R 3-6A , R 3-6B , R 3-7A , R 3-8A , R 3-8B , R 3-9A , R 3-9B are all hydrogen, and the tertiary amine of the chemical formula (3) having a piperidine structure in which both R 3-3B and R 3-7B are a methyl group or an ethyl group is likely to phase-separate, and the recovery rate of inorganic salts and / or organic substances is high.

[0045] The synthesis method of the compound of chemical formula (3) will be briefly described. For example, pyrrolidine (or its derivative) and 1,3-dibromopropane (depending on the number of carbon atoms in the alkyl chain, dibromomethane or 1,2-dibromoethane can also be used) are heated and stirred in a solvent, and pyrrolidine is bonded to the bromines on both sides of 1,3-dibromopropane by a nucleophilic reaction. The obtained compound can be purified to obtain the tertiary amine of chemical formula (3).

[0046] The tertiary amine of chemical formula (4) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of chemical formula (4) is a tertiary cyclohexylamine and its derivative.

[0047] R which is the alkyl group of chemical formula (4) 4-1 、R 4-2 is preferably a linear alkyl group having 1 to 3 carbon atoms or an alkyl group having a side chain, more preferably a linear alkyl group having 1 to 2 carbon atoms, and even more preferably an alkyl group having 1 carbon atom (methyl group).

[0048] R of the cyclohexane structure of chemical formula (4) 4-3A 、R 4-3B 、R 4-4A 、R 4-4B 、R 4-5A 、R 4-5B 、R 4-6A 、R 4-6B 、R 4-7A 、R 4-7B is preferably either hydrogen, a methyl group or an ethyl group. R 4-3A 、R 4-3B 、R 4-4A 、R 4-4B 、R 4-5A 、R 4-5B 、R 4-6A 、R 4-6B 、R 4-7A 、R 4-7BAmong them, it is preferable that any one or more and four or less of them are each one of a hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. Having many substituents is not preferable because the separability from water deteriorates. Further, having a hydroxyl group, a carboxyl group or a halogen in the substituent is not preferable because the solubility in water increases.

[0049] R 4-1 、R 4-2 is a methyl group, and R 4-3A 、R 4-3B 、R 4-4A 、R 4-4B 、R 4-5A 、R 4-5B 、R 4-6A 、R 4-6B 、R 4-7A 、R 4-7B A tertiary amine of chemical formula (4) having a cyclohexane structure in which all of R 4-1 and R 4-2 are both ethyl groups, and R 4-3 、R 4-4A 、R 4-5B 、R 4-5A 、R 4-5B 、R 4-6A 、R 4-6B 、R 4-7A 、R 4-7B are all hydrogen is easily phase-separated, and the recovery rate of inorganic salts and / or organic substances is high.

[0050] The synthesis method of the compound of chemical formula (4) will be briefly described. For example, aniline is hydrogenated using a nickel catalyst to obtain cyclohexylamine (primary amine). Then, cyclohexylamine and bromomethane (depending on the number of carbon atoms of the alkyl group, bromoethane or the like is used instead) are heated and stirred in a solvent, and methane is bonded to the nitrogen of cyclohexylamine by a nucleophilic reaction. The obtained compound is purified to obtain a tertiary amine of chemical formula (4).

[0051] The tertiary amine of Chemical Formula (5) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of Chemical Formula (3) is a tertiary amine to which three acyclic alkyl groups are bonded.

[0052] R, which is the alkyl group of Chemical Formula (5) 5-1 , R 5-2 , R 5-3 is preferably a linear alkyl group having 1 to 7 carbon atoms or a chain alkyl group having a side chain, R 5-1 , R 5-2 is a chain alkyl group having 1 to 4 carbon atoms, R 5-3 is a chain alkyl group having 1 to 7 carbon atoms with a linear or branched chain, R 5-1 , R 5-2 , R 5-3 is more preferably 3 or more and 10 or less in total carbon atoms, R 5-1 , R 5-2 , R 5-3 is more preferably 6 or more and 9 or less in total carbon atoms. When the alkyl group of Chemical Formula (5) is too long or the total carbon atoms are too many, phase separation becomes difficult, which is not preferable. When the total carbon atoms of Chemical Formula (5) are too few, it is easily soluble in the water to be treated A even without introducing carbon dioxide D, and it is not preferable because inorganic salts and / or organic substances are less likely to precipitate by introducing carbon dioxide D. Further, when the total carbon atoms of Chemical Formula (5) are too few, the boiling point of the amine solution C is low, which is not only difficult to handle but also emits an ammonia odor peculiar to low-boiling amines, which is not preferable.

[0053] R of Chemical Formula (5) 5-1 , R 5-2 , R 5-3 are all the same, or R 5-1 , R 5-2 are the same and R 5-3 is preferably different from R 5-1 , R 5-2 . It is not preferable that R 5-1 , R 5-2 , R 5-3 are all different because the separability from water decreases. R 5-1 , R 5-2 is preferably a chain alkyl group without a side chain, R5-3 A chain alkyl group containing one side chain or a chain alkyl group without a side chain is preferred. Having too many side chains is not preferred because the separability from water decreases. Also, having a large number of carbon atoms in Chemical Formula (5) is not preferred because it behaves like a surfactant and causes emulsification and foaming.

[0054] R 5-1 、R 5-2 、R 5-3 All being ethyl groups, the tertiary amine of Chemical Formula (5) (triethylamine), R 5-1 、R 5-2 Both being methyl groups, and R 5-3 being a butyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 Both being methyl groups, and R 5-3 being a pentyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 Both being methyl groups, and R 5-3 being a hexyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 Both being methyl groups, and R 5-3 being a heptyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 Both being ethyl groups, and R 5-3 being a butyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 Both being propyl groups, and R 5-3 being a methyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 Both being butyl groups, and R 5-3 being a methyl group, the tertiary amine of Chemical Formula (5), and, R 5-1 、R 5-2 Both being methyl groups, and R 5-3 being a 2-ethyl-hexyl group, one or more tertiary amines selected from the group consisting of the tertiary amines of Chemical Formula (5) are easily phase-separable and have a high recovery rate of inorganic salts and / or organic substances.

[0055] The synthesis method of the compound (triethylamine) of Chemical Formula (5) will be briefly described. For example, ammonia and bromoethane are heated and stirred in a solvent, and three ethanes are bonded to the nitrogen of ammonia by a nucleophilic reaction. The obtained compound is purified to obtain the tertiary amine of Chemical Formula (5). The compound of Chemical Formula (5) can be synthesized not only by the direct alkylation method but also by the indirect alkylation method.

[0056] The tertiary amine of Chemical Formula (6) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of Chemical Formula (6) is an amine having a piperidine structure.

[0057] R, which is the alkyl group of Chemical Formula (6) 6-1 is a linear alkyl group having 1 to 6 carbon atoms, a chain alkyl group having a side chain of 3 to 6 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms, and R 6-2A , R 6-2B , R 6-3A , R 6-3B , R 6-4A , R 6-4B , R 6-5A , R 6-5B , R 6-6A , R 6-6B are each preferably hydrogen, a methyl group or an ethyl group, and R 6-1 is a linear alkyl group having 1 to 6 carbon atoms, a chain alkyl group having a side chain of 3 to 6 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms, and R 6-2A , R 6-2B , R 6-3A , R 6-3B , R 6-4A , R 6-4B , R 6-5A , R 6-5B , R 6-6A , R 6-6B Among them, any three or less are each preferably hydrogen, a methyl group or an ethyl group, and the rest are more preferably hydrogen. When the alkyl group of Chemical Formula (6) is too long or the total number of carbon atoms is too large, phase separation becomes difficult, which is not preferable. The carbon number of the cyclic alkyl group of R 6-1 is more preferably 4 to 6 or 5 to 6.

[0058] R 6-1 is an ethyl group, and R 6-2A , R 6-2B , R 6-3A , R 6-3B , R 6-4A , R 6-4B , R 6-5A , R 6-5B , R 6-6A , R 6-6B the tertiary amine of chemical formula (6) in which all of them are hydrogen is prone to phase separation, and the recovery rate of inorganic salts and / or organic substances is high.

[0059] The synthesis method of the compound of chemical formula (6) will be briefly described. For example, piperidine and bromoethane (depending on the number of carbon atoms in the alkyl group, bromomethane or the like can be used instead) are heated and stirred in a solvent, and ethane is bonded to the nitrogen of piperidine by a nucleophilic reaction. The obtained compound can be purified to obtain the tertiary amine of chemical formula (6).

[0060] The tertiary amine of chemical formula (7) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of chemical formula (7) is an amine having a pyrrolidine structure.

[0061] R which is the alkyl group of chemical formula (7) 7-1 is a linear alkyl group having 1 to 6 carbon atoms, a chain alkyl group having a side chain of 3 to 6 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms, and R 7-2A , R 7-2B , R 7-3A , R 7-3B , R 7-4A , R 7-4B , R 7-5A , R 7-5B are each preferably hydrogen, a methyl group or an ethyl group, and R 7-1 is a linear alkyl group having 1 to 6 carbon atoms, a chain alkyl group having a side chain of 3 to 6 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms, and R 7-2A , R 7-2B , R 7-3A , R 7-3B , R 7-4A , R 7-4B , R 7-5A , R 7-5BAmong them, it is more preferable that any three or less of them are each a hydrogen, methyl group or ethyl group, and the rest are hydrogen. R 7-1 The number of carbon atoms in the cyclic alkyl group of is more preferably 4 to 6 or 5 to 6. When the alkyl group in Chemical Formula (7) is too long or the total number of carbon atoms is too large, phase separation becomes difficult, which is not preferable.

[0062] R 7-1 is a butyl group, and R 7-2A , R 7-2B , R 7-3A , R 7-3B , R 7-4A , R 7-4B , R 7-5A , R 7-5B are all hydrogen, and the tertiary amine of Chemical Formula (7) is easy to phase-separate and has a high recovery rate of inorganic salts and / or organic substances.

[0063] The synthesis method of the compound of Chemical Formula (7) will be briefly described. For example, pyrrolidine and n-bromobutane (depending on the number of carbon atoms in the alkyl group, bromoethane or the like can be used instead) are heated and stirred in a solvent, and butane is bonded to the nitrogen of piperidine by a nucleophilic reaction. The obtained compound can be purified to obtain the tertiary amine of Chemical Formula (7).

[0064] The tertiary amine of Chemical Formula (8) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of Chemical Formula (8) is a tertiary benzylamine.

[0065] R 8-1 which is the alkyl chain of Chemical Formula (8) is a linear alkyl group having 1 to 4 carbon atoms or a chain alkyl chain having a side chain, and R 8-2 , R 8-3 are each preferably a methyl group or an ethyl group, and R 8-1 is a linear alkyl chain having 1 to 4 carbon atoms, and R 8-2 , R 8-3 are each more preferably a methyl group or an ethyl group. When the alkyl group in Chemical Formula (8) is too long or the total number of carbon atoms is too large, phase separation becomes difficult, which is not preferable.

[0066] R 8-1 is an alkyl chain with 1 carbon atom, and R 8-2 and R 8-3 are all tertiary amines of chemical formula (8) where they are methyl groups, and / or R 8-1 is an alkyl chain with 2 carbon atoms, and R 8-2 and R 8-3 are all tertiary amines of chemical formula (8) where they are methyl groups, are prone to phase separation, and the recovery rate of inorganic salts and / or organic substances is high.

[0067] The synthesis method of the compound of chemical formula (8) will be briefly described. For example, benzylamine, which is a primary amine, and bromomethane (depending on the number of carbon atoms in the alkyl group, bromoethane or the like can be used instead) are heated and stirred in a solvent, and two methanes are bonded to the nitrogen of benzylamine by a nucleophilic reaction. The obtained compound can be purified to obtain a tertiary amine of chemical formula (8).

[0068] The means 13 for introducing carbon dioxide D into the first container B introduces carbon dioxide D into the first container B. When carbon dioxide D is introduced into the first container B, carbon dioxide D dissolves in the mixed solution E containing the water to be treated A and the amine solution. The means 13 for introducing carbon dioxide D into the first container B includes, for example, a pipe leading to the first container B, and a valve, cock, pump, or the like for controlling the flow rate (the amount transferred if it is solid carbon dioxide D) of carbon dioxide D flowing through the pipe. Solid carbon dioxide D may be stored and vaporized carbon dioxide D may be introduced into the first container B.

[0069] The mixed solution E containing the water to be treated A and the amine solution C is accommodated in the first container B. The temperature of the mixed solution E is preferably 0°C or higher and 40°C or lower. The first container B may further be provided with means for adjusting the temperature inside the container, or the temperature of the mixed solution E may be adjusted by adjusting the temperature of the water to be treated A and / or the amine solution C.

[0070] Carbon dioxide D uses one or more of gaseous carbon dioxide, solid carbon dioxide, or liquid carbon dioxide. When carbon dioxide D is contained in the solution, the liquid property of the amine solution C changes. Carbon dioxide D is introduced into the atmosphere. By introducing a large amount of carbon dioxide D, precipitation is promoted. Since there is no adverse effect even if too much carbon dioxide D is introduced, considering the treatment time, it is preferable to introduce a large amount of carbon dioxide in a short time. The volume concentration of the gaseous carbon dioxide D is preferably 5 vol% or more and 100 vol% or less, more preferably 10 vol% or more and 100 vol% or less, and even more preferably 80 vol% or more and 100 vol% or less. In addition, together with carbon dioxide D, one or more selected from the group consisting of nitrogen, oxygen, argon, and amine may be introduced into the mixed solution E as impurities.

[0071] By introducing more carbon dioxide D than the total number of moles of inorganic salts and / or organic substances contained in the water to be treated A, precipitation of inorganic salts and / or organic substances can be efficiently performed. Therefore, the total number of moles of carbon dioxide D to be introduced is preferably not less than the total number of moles of inorganic salts and / or organic substances contained in the water to be treated A, more preferably not less than twice the total number of moles of inorganic salts and / or organic substances contained in the water to be treated A, and even more preferably not less than five times the total number of moles of inorganic salts and / or organic substances contained in the water to be treated A.

[0072] In the embodiment, water treatment is performed using the above-described water to be treated A, amine solution, and carbon dioxide D. By the water treatment of the embodiment, inorganic salts and / or organic substances contained in the water to be treated A are precipitated and separated (concentrated).

[0073] Carbon dioxide D is introduced into the water to be treated A contained in the first container B, and the water to be treated A into which carbon dioxide D has been introduced is mixed with the amine solution C, or introduced into the amine solution C contained in the first container B, and the amine solution C into which carbon dioxide D has been introduced is mixed with the water to be treated A, or introduced into the mixed solution of the water to be treated A and the amine solution C contained in the first container B. Introducing carbon dioxide D means that if carbon dioxide D is a gas, carbon dioxide D is bubbled into the solution to be introduced to dissolve carbon dioxide D in the solution to be introduced. Also, introducing carbon dioxide D means that if carbon dioxide D is a solid, dry ice is put into the solution to be introduced to dissolve carbon dioxide D in the solution to be introduced. Also, introducing carbon dioxide D means that if carbon dioxide D is a liquid, the liquid carbon dioxide D is mixed with the solution to be introduced to dissolve carbon dioxide D in the solution to be introduced. The introduction of carbon dioxide D may be performed multiple times.

[0074] When the water to be treated A into which carbon dioxide D has been introduced is mixed with the amine solution C, since almost no carbon dioxide D dissolves in the water to be treated A, it is preferable to introduce carbon dioxide D again after mixing the water to be treated A into which carbon dioxide D has been introduced and the amine solution C. In addition, if the carbon dioxide D introduced into the water to be treated A is dry ice and the amine solution C is mixed within a short time after adding the dry ice, it may not be necessary to introduce carbon dioxide D again.

[0075] When the amine solution C into which carbon dioxide D has been introduced is mixed with the water to be treated A, after mixing the amine solution C into which carbon dioxide D has been introduced and the water to be treated A, it is preferable to introduce carbon dioxide D again. In addition, if the carbon dioxide D introduced into the amine solution C is dry ice and the water to be treated A is mixed within a short time after adding the dry ice, it may not be necessary to introduce carbon dioxide D again.

[0076] The pH of the mixed solution E (measured at 25°C) is preferably 3 or more and 9 or less, more preferably 6 or more and 8 or less. If the pH of the mixed solution E is less than 3, it is not preferable because carbon dioxide is less likely to dissolve. If the pH of the mixed solution E is greater than 9, it is not preferable because carbon dioxide and the metal form a salt and precipitate. For adjusting the pH, it is preferable to use an acidic solution. The acidic solution used for adjusting the pH is at least one selected from the group consisting of hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, hydroiodic acid, acetic acid, citric acid, propanoic acid, butanoic acid, methylpropanoic acid, pentanoic acid, 2,2-dimethylpropanoic acid, benzoic acid, phenylacetic acid, chloroethanoic acid, dichloroethanoic acid, trichloroethanoic acid, fluoroethanoic acid, bromoethanoic acid, iodoethanoic acid, gluconic acid, lactic acid, oxalic acid, tartaric acid, and organic acids having a sulfo group, which is practical. To adjust the pH of the mixed solution E, it is preferable to perform one or more of the adjustment of the pH of the water to be treated A, the adjustment of the pH of the amine solution C, and the adjustment of the pH of the mixed solution E.

[0077] Carbon dioxide D is introduced into the first container B, and the mixed solution E containing the water to be treated A and the amine solution C undergoes phase separation. When the water to be treated A, the amine solution C, and carbon dioxide D are mixed, the mixed solution E undergoes phase separation and separates into a supernatant phase G and a precipitate phase H. The temperature of the mixed solution E (the solution obtained by mixing the water to be treated A, the amine solution C, and carbon dioxide D) during phase separation is preferably 0°C or more and 50°C or less, more preferably 0°C or more and 40°C or less, and even more preferably 0°C or more and 35°C or less. Also, it is preferable to allow the mixed solution E to stand in the first container B for 5 minutes or more and 2 hours or less from the time when the water to be treated A, the amine solution C, and carbon dioxide D are mixed until they separate into the supernatant phase G and the precipitate phase H (the time for phase separation of the mixed solution E). Carbon dioxide D can also be introduced while the mixed solution E is standing in the first container B.

[0078] Treated water A, amine solution C, and carbon dioxide D are mixed. That is, when carbon dioxide D is introduced into the first container B and a mixed solution E containing treated water A and amine solution C begins to form a uniform phase, a liquid F separated into a supernatant phase G and a precipitate phase H is obtained. When the concentration of carbon dioxide D in the mixed solution E containing amine solution C and treated water A is low, a tertiary amine whose solubility changes in response to carbon dioxide does not have a very high solubility in treated water A. When the concentration of carbon dioxide D in the mixed solution E containing amine solution C and treated water A increases, the solubility of the tertiary amine whose solubility changes in response to carbon dioxide in treated water A improves. When carbon dioxide D is introduced and the solubility of amine solution C in treated water A improves, the inorganic salts and / or organic substances dissolved in treated water A become less soluble, and the inorganic salts and / or organic substances are likely to precipitate. By utilizing the property that the liquid property changes when carbon dioxide D is introduced, inorganic salts and / or organic substances can be precipitated.

[0079] The liquid F in which salts have precipitated contains a supernatant phase G and a precipitate phase H. The precipitate phase H is a precipitate composed of precipitates or a slurry-like substance containing precipitates. When the separation of the precipitate is insufficient, the liquid F may be cooled or centrifuged.

[0080] The means 14 for separately separating the supernatant phase G and the precipitated phase H separates the supernatant phase G and the precipitated phase H separately. The means 14 for separately separating the supernatant phase G and the precipitated phase H includes a mechanism for discharging either one or both of the supernatant phase G and the precipitated phase H from the first container B from the liquid F in which the mixed solution E has phase-separated. Examples of the means 14 for separately separating the supernatant phase G and the precipitated phase H include a pump for extracting the supernatant phase G from the upper side of the first container B. Other examples of the means 14 for separately separating the supernatant phase G and the precipitated phase H include a filter through which the precipitated phase H is filtered at the bottom of the first container B and an opening whose opening and closing can be controlled by a cock or the like. The precipitated phase H remains on the filter, and the supernatant phase G is discharged from the opening to separately separate the supernatant phase G and the precipitated phase H. Then, by recovering the precipitated phase H remaining on the filter, the supernatant phase G and the precipitated phase H can be separately discharged from the first container B. Incidentally, after transferring the liquid F in which the mixed solution E has phase-separated to another container, the supernatant phase G and the precipitated phase H can be similarly separated separately. The mesh size of the filter is appropriately selected according to the substance contained in the precipitated phase H.

[0081] In the water treatment system 100 and the water treatment method of the embodiment, a tertiary amine whose liquid property changes in response to carbon dioxide D is used, and inorganic salts and / or organic substances contained in the water to be treated A can be efficiently separated. In the water treatment system 100 and the water treatment method, inorganic salts and / or organic substances contained in the water to be treated A can be recovered without heating under low-temperature conditions. This can be performed with much lower energy than evaporating the water contained in the water to be treated A to concentrate the water to be treated A. Further, since the carbon dioxide D to be used is not limited to 100% carbon dioxide gas or the like, when the water treatment system 100 is implemented in a plant or the like, water treatment can be performed using the carbon dioxide D generated in the plant. In this case, it is preferable in that there is no increase in the amount of carbon dioxide released by performing water treatment by using the carbon dioxide that the plant has released into the atmosphere. Therefore, the water treatment system can be performed with low energy and low environmental load as a whole.

[0082] (Second Embodiment) The second embodiment relates to a water treatment system and a water treatment method applicable to non-evaporative desalination by salting out using a tertiary amine compound whose hydrophobicity and hydrophilicity change upon reaction with carbon dioxide. Fig. 5 shows a schematic diagram of the water treatment system 200 according to the second embodiment. The schematic diagram of the water treatment system 200 in Fig. 5 includes means 11 for introducing the water to be treated A into the first container B, means 12 for introducing the amine solution C into the first container B, means 13 for introducing carbon dioxide D into the first container B, and means 14 for separately separating the supernatant phase G and the precipitate phase H of the liquid F in which the mixed solution E containing the water to be treated A and the amine solution C is phase-separated after introducing carbon dioxide D into the first container B, and means 15 for phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine (organic phase K). It is preferable to provide a filter 20 between the means 14 for separately separating the supernatant phase G and the precipitate phase H and the means 15 for separating and recovering the tertiary amine. The mesh size of the filter 20 is appropriately selected according to the substance to be filtered by the filter.

[0083] The water treatment system 200 according to the second embodiment has means 15 for phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine (organic phase K), and is common to the water treatment system 100 according to the first embodiment except that the separated and recovered tertiary amine (organic phase K) is mixed into the amine solution C through the means 12 for introducing the amine solution C into the first container B. In the second embodiment, the description of the content common to the first embodiment is omitted.

[0084] Fig. 6 shows a flowchart of the water treatment method according to the second embodiment. The water treatment method according to the embodiment preferably includes a step of mixing the water to be treated A, the amine solution C, and carbon dioxide D to obtain a phase-separated liquid F, a step of separating the supernatant phase G and the precipitate phase H of the phase-separated liquid F, and a step of phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine. In the water treatment method according to the second embodiment, the step of phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine is performed by the means 15 for phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine. Hereinafter, the water treatment system 200 will be described, and the description of the water treatment system 200 also includes the description of the water treatment method.

[0085] The supernatant phase G separated by the means 14 for separately separating the supernatant phase G and the precipitated phase H is processed by the means 15 for phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine. The supernatant phase G is an aqueous solution containing carbon dioxide D and in which the tertiary amine is dissolved. The supernatant phase G may contain trace amounts of inorganic salts and / or organic substances. It is preferable to provide a filter 20 in the path from the means 14 for separately separating the supernatant phase G and the precipitated phase H to the means 15 for separating and recovering the tertiary amine. The supernatant phase G may contain partially precipitated solid inorganic salts and / or organic substances. It is preferable to provide a filter 20 to remove the solid inorganic salts and / or organic substances contained in the supernatant phase G and reduce the solid inorganic salts and / or organic substances flowing into the means 15 for phase-separating the supernatant phase G into an aqueous phase and an organic phase to separate and recover the tertiary amine.

[0086] The means 15 for phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine separates and recovers the tertiary amine contained in the supernatant phase G. As the means 15 for phase-separating the supernatant phase into an aqueous phase J and an organic phase K to separate and recover the tertiary amine, a mechanism for heating the supernatant phase G is preferable. For example, the supernatant phase G is accommodated in a second container (not shown), and the supernatant phase G is heated in the second container. When the temperature of the supernatant phase G rises, the saturation concentration of carbon dioxide D in the supernatant phase G decreases, and carbon dioxide D is released from the supernatant phase G. It is preferable to heat the supernatant phase G to 50°C or higher and 90°C or lower, and more preferably 60°C or higher and 70°C or lower from the viewpoint of reducing the energy consumption. It is preferable to use the waste heat generated in a plant or the like for heating the supernatant phase G. When the released carbon dioxide D is returned to the means 13 for introducing carbon dioxide D, the released carbon dioxide D can also be reused. Also, a solid catalyst such as zeolite can be used for the regeneration of the tertiary amine.

[0087] The release of carbon dioxide D can be promoted by blowing a gas with a carbon dioxide concentration of 3% or less, preferably 1% or less, more preferably 0.1% or less when heating the supernatant phase G. The gas blown when heating the supernatant phase G is preferably nitrogen gas or air.

[0088] When carbon dioxide is released from the supernatant phase G, the supernatant phase G phase-separates into an aqueous phase J and an organic phase K. The aqueous phase J contains a tertiary amine, an inorganic salt, and / or an organic substance dissolved in water. The organic phase K contains a tertiary amine whose polarity changes in response to carbon dioxide, and the organic phase K is returned to the amine solution C and the tertiary amine whose polarity changes in response to carbon dioxide is reused.

[0089] From the viewpoint of recovering the tertiary amine from the supernatant phase G, the tertiary amine whose polarity changes in response to carbon dioxide contained in the supernatant phase G, that is, the tertiary amine whose polarity changes in response to carbon dioxide contained in the amine solution C, has low solubility in water when the carbon dioxide concentration is low (the solution (organic phase K) from which carbon dioxide has been released from the supernatant phase G), and is preferably a tertiary amine whose polarity easily changes in response to carbon dioxide.

[0090] The tertiary amine whose polarity changes in response to the carbon dioxide contained in the amine solution C preferably contains one or more selected from the tertiary amines represented by chemical formulas (1) to (8) shown in FIGS. 3 and 4 from the two viewpoints of recovering the tertiary amine from the supernatant phase G and precipitating the inorganic salt and / or the organic substance from the water to be treated A, and preferably contains one selected from the tertiary amines represented by chemical formulas (1) to (8). More preferably, it contains one or more selected from the tertiary amines represented by chemical formulas (1) to (4), and more preferably contains one selected from the tertiary amines represented by chemical formulas (1) to (4).

[0091] The alkyl chain (R 1-1 ) of the chemical formula (1) is preferably a straight-chain alkyl chain having 1 to 3 carbon atoms, and more preferably a straight-chain alkyl chain having 3 carbon atoms.

[0092] The two piperidine structures of the chemical formula (1) are preferably the same. Specifically, R 1-2A and R 1-7A are the same, R 1-2B and R 1-7B are the same, R 1-3A and R1-8A are the same, and R 1-3B and R 1-8B are the same, and R 1-4A and R 1-9A are the same, and R 1-4B and R 1-9B are the same, and R 1-5A and R 1-10A are the same, and R 1-5B and R 1-10B are the same, and R 1-6A and R 1-11A are the same, and R 1-6B and R 1-11B are preferably the same. Specifically, R 1-2A , R 1-2B , R 1-7A and R 1-7B are all the same, and R 1-3A , R 1-3B , R 1-8A and R 1-8B are all the same, and R 1-4A , R 1-4B , R 1-9A and R 1-9B are all the same, and R 1-5A , R 1-5B , R 1-10A and R 1-10B are all the same, and R 1-6A , R 1-6B , R 1-11A and R 1-11B are preferably all the same.

[0093] R 1-2A , R 1-2B , R 1-6A , R 1-6B is preferably hydrogen in each case. R 1-3 , R 1-4A , R 1-4B , R 1-5A , R 1-5B is preferably either hydrogen, a methyl group or an ethyl group in each case. R 1-3A , R 1-3B , R 1-4A , R 1-4B , R 1-5A , R 1-5BAmong them, it is preferable that any one or two of them are each hydrogen, a methyl group, or an ethyl group, and the rest are hydrogen. It is not preferable because the separability from water will deteriorate. Further, it is not preferable because the solubility in water increases when the substituent contains a hydroxyl group, a carboxyl group, or a halogen.

[0094] R 1-7A 、R 1-7B 、R 1-11A 、R 1-11B are each preferably hydrogen. R 1-8A 、R 1-8B 、R 1-9A 、R 1-9B 、R 1-10A 、R 1-10B are each preferably hydrogen or a methyl group or an ethyl group. R 1-8A 、R 1-8B 、R 1-9A 、R 1-9B 、R 1-10A 、R 1-10B Among them, it is preferable that any one or two of them are hydrogen, a methyl group, or an ethyl group, and the rest are hydrogen. It is not preferable because the separability from water will deteriorate. Further, it is not preferable because the solubility in water increases when the substituent contains a hydroxyl group, a carboxyl group, or a halogen.

[0095] R of the alkyl chain 1-1 is a straight-chain alkyl chain having 3 carbon atoms (propyl), and R 1-2A 、R 1-2B 、R 1-3A 、R 1-3B 、R 1-4A 、R 1-4B 、R 1-5A 、R 1-5B 、R 1-6A 、R 1-6B 、R 1-7A 、R 1-7B 、R 1-8A 、R 1-8B 、R 1-9A 、R 1-9B 、R 1-10A 、R 1-10B 、R 1-11A 、R 1-11BA tertiary amine of Chemical Formula (1) having a piperidine structure in which all are hydrogen, and / or R of the alkyl chain 1-1 is a straight-chain alkyl having 3 carbon atoms (propyl group), and R 1-2A , R 1-2B , R 1-3A , R 1-3B , R 1-4A , R 1-5A , R 1-4B , R 1-6A , R 1-6B , R 1-7A , R 1-7B , R 1-8A , R 1-8B , R 1-10A , R 1-9B , R 1-11A , R 1-11B are all hydrogen, and R 1-4B and R 1-9B A tertiary amine of Chemical Formula (1) having a piperidine structure in which both are methyl groups or ethyl groups is preferable because it is likely to phase-separate by the release of carbon dioxide, has a high recovery rate of inorganic salts and / or organic substances, and also has a high recovery rate of the tertiary amine from the supernatant phase G.

[0096] The alkyl chain (R 2-1 ) of Chemical Formula (2) is preferably a straight-chain alkyl chain having 1 to 3 carbon atoms, and more preferably a straight-chain alkyl chain having 3 carbon atoms.

[0097] The two azepane structures of Chemical Formula (2) are preferably the same. Specifically, R 2-2A and R 2-8A are the same, R 2-2B and R 2-8B are the same, R 2-3A and R 2-9A are the same, R 2-3B and R 2-9B are the same, R 2-4A and R 2-10A are the same, R 2-4B and R 2-10B are the same, R 2-5A and R 2-11A are the same, R 2-5B and R 2-11B are the same, R 2-6A and R 2-12A are the same, R 2-6Band R 2-12B are the same, and R 2-7A and R 2-13A are the same, and R 2-7B and R 2-13B are preferably the same. Specifically, R 2-2A , R 2-2B , R 2-8A and R 2-8B are all the same, and R 2-3A , R 2-3B , R 2-9A and R 2-9B are all the same, and R 2-4A , R 2-4B , R 2-10A and R 2-10B are all the same, and R 2-5A , R 2-5B , R 2-11A and R 2-11B are all the same, and R 2-6A , R 2-6B , R 2-12A and R 2-12B are all the same, and R 2-7A , R 2-7B , R 2-13A and R 2-13B are preferably all the same.

[0098] R 2-2A , R 2-2B , R 2-3A , R 2-3B , R 2-6A , R 2-6B , R 2-7A , R 2-7B is preferably hydrogen respectively. R 2-4A , R 2-4B , R 2-5A , R 2-5B is preferably either hydrogen, a methyl group or an ethyl group respectively. R 2-4A , R 2-2B , R 2-5A , R 2-2B Among them, it is preferable that any one or two of them are respectively either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. Having too many substituents is not preferable because the separability from water deteriorates. Also, having a hydroxyl group, a carboxyl group or a halogen in the substituent is not preferable because the solubility in water increases.

[0099] R 2-8A 、R 2-2B 、R 2-9A 、R 2-2B 、R 2-12A 、R 2-2B 、R 2-13A 、R 2-2B are each preferably hydrogen. R 2-10A 、R 2-2B 、R 2-11A 、R 2-2B are each preferably either hydrogen, a methyl group or an ethyl group. R 2-10A 、R 2-2B 、R 2-11A 、R 2-2B Among them, it is preferable that any one or two of them are each either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. Having too many substituents is not preferable because the separability from water deteriorates. Also, having a hydroxyl group, a carboxyl group or a halogen in the substituent is not preferable because the solubility in water increases.

[0100] The R of the alkyl chain 2-1 is a straight-chain alkyl chain with 3 carbon atoms (propyl group), and R 2-2A 、R 2-2B 、R 2-3A 、R 2-3B 、R 2-4A 、R 2-4B 、R 2-5A 、R 2-5B 、R 2-6A 、R 2-6B 、R 2-7A 、R 2-7B 、R 2-8A 、R 2-8B 、R 2-9A 、R 2-9B 、R 2-10A 、R 2-10B 、R 2-11A 、R 2-11B 、R 2-12A 、R 2-12B 、R 2-13A 、R 2-13B The tertiary amine of chemical formula (2) having a piperidine structure in which all of R 1-1 is a straight-chain alkyl chain with 3 carbon atoms (propyl group), and R 2-2A 、R2-3A , R 2-3B , R 2-4A , R 2-4B , R 2-5A , R 2-5B , R 2-6A , R 2-6B , R 2-7A , R 2-7B , R 2-8A , R 2-8B , R 2-9A , R 2-9B , R 2-10A , R 2-10B , R 2-11A , R 2-11B , R 2-12A , R 2-12B , R 2-13A All of them are hydrogen, and R 2-2B and R 2-13B A tertiary amine of formula (2) having a piperidine structure in which both are a methyl group or an ethyl group is likely to phase-separate by the release of carbon dioxide, has a high recovery rate of inorganic salts and / or organic substances, and preferably has a high recovery rate of the tertiary amine from the supernatant phase G.

[0101] The alkyl chain (R 3-1 ) of formula (3) is preferably a linear alkyl chain having 1 to 3 carbon atoms, more preferably a linear alkyl chain having 3 carbon atoms.

[0102] The two pyrrolidine structures of formula (3) are preferably the same. Specifically, R 3-2A and R 3-5A are the same, R 3-2B and R 3-6B are the same, R 3-3A and R 3-7A are the same, R 3-3B and R 3-7B are the same, R 3-4A and R 3-8A are the same, R 3-4B and R 3-8B are the same, R 3-5A and R 3-9A are the same, R 3-5B and R 3-9B are preferably the same. Specifically, R 3-2A , R 3-2B , R 3-6A and R3-6B are all the same, and R 3-3A , R 3-3B , R 3-7A and R 3-7B are all the same, and R 3-4A , R 3-4B , R 3-8A and R 3-8B are all the same, and R 3-5A , R 3-5B , R 3-9A and R 3-9B are preferably all the same.

[0103] R in Chemical Formula (3) 3-2A , R 3-2B , R 3-5A , R 3-5B are each preferably hydrogen. R 3-3A , R 3-5B , R 3-4A , R 3-5B , R 3-5A , R 3-5B Among them, it is preferable that any one or two of them are each either a methyl group or an ethyl group, and the remaining two are hydrogen. When all of the substituents are absent, that is, when all of R 3-2A , R 3-2B , R 3-3A , R 3-3B , R 3-4A , R 3-4B , R 3-5A , R 3-5B are hydrogen, the polarity does not change with the concentration of carbon dioxide D, so it is preferable that one or more substituents are included. It is not preferable because the separation property from water deteriorates when there are many substituents. Also, it is not preferable because the solubility in water increases when the substituents contain hydroxyl groups, carboxyl groups, or halogens.

[0104] R in Chemical Formula (3) 3-6A , R 3-6B , R 3-9A , R 3-9B are each preferably hydrogen. R 3-7A , R 3-7B , R 3-8A , R 3-8B , R 3-9A , R 3-9BAmong them, it is preferable that any one or two of them are each either a methyl group or an ethyl group, and the remaining two are hydrogen. When there is no substituent, that is, R 3-6A 、R 3-6B 、R 3-7A 、R 3-7B 、R 3-8A 、R 3-8B 、R 3-9A 、R 3-9B are all hydrogen, the polarity does not change with the concentration of carbon dioxide D, so it is preferable to contain one or more substituents. It is not preferable because the separation property from water deteriorates when there are many substituents. Also, it is not preferable because the solubility in water increases when the substituent contains a hydroxyl group, a carboxyl group or a halogen.

[0105] The R 3-1 of the alkyl chain is a straight-chain alkyl chain (propyl) having 3 carbon atoms, and R 3-2A 、R 3-2B 、R 3-3A 、R 3-4A 、R 3-4B 、R 3-5A 、R 3-5B 、R 3-6A 、R 3-6B 、R 3-7A 、R 3-8A 、R 3-8B 、R 3-9A 、R 3-9B are all hydrogen, and the tertiary amine of Chemical Formula (3) having a piperidine structure in which both R 3-3B and R 3-7B are methyl groups is likely to phase-separate by the release of carbon dioxide, has a high recovery rate of inorganic salts and / or organic substances, and also has a high recovery rate of the tertiary amine from the supernatant phase G.

[0106] The tertiary amine of Chemical Formula (4) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of Chemical Formula (4) is a tertiary cyclohexylamine and its derivatives.

[0107] R 4-1A 、R 4-1B 、R 4-2A 、R 4-2Bis preferably an alkyl group having a linear alkyl group or a side chain with 1 to 3 carbon atoms, more preferably a linear alkyl group with 1 to 2 carbon atoms, and even more preferably an alkyl group with 1 carbon atom (methyl group).

[0108] R in Chemical Formula (4) 4-3A , R 4-3B , R 4-4A , R 4-4B , R 4-5A , R 4-5B , R 4-6A , R 4-6B , R 4-7A , R 4-7B Among them, any one or more and four or less are each either hydrogen, a methyl group or an ethyl group, and the remaining two or three are preferably hydrogen. Having too many substituents is not preferred because the separability from water deteriorates. Also, having a hydroxyl group, a carboxyl group or a halogen in the substituent is not preferred because the solubility in water increases.

[0109] R 4-1 and R 4-2 are both methyl groups, R 4-3A , R 4-3B , R 4-4A , R 4-4B , R 4-5A , R 4-5B , R 4-6A , R 4-6B , R 4-7A , R 4-7B A tertiary amine of Chemical Formula (4) having a cyclohexane structure in which all of are hydrogen, and / or R 4-1 and R 4-2 are both ethyl groups, R 4-3A , R 4-3B , R 4-4A , R 4-4B , R 4-5A , R 4-5B , R 4-6A , R 4-6B , R 4-7A , R 4-7BIt is preferable that the tertiary amine of Chemical Formula (4) having a cyclohexane structure in which all are hydrogen is liable to phase-separate by the release of carbon dioxide, the recovery rate of the inorganic salt and / or the organic substance is high, and the recovery rate of the tertiary amine from the supernatant phase G is high.

[0110] The tertiary amine of Chemical Formula (5) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of Chemical Formula (3) is a tertiary amine to which three acyclic alkyl groups are bonded.

[0111] R which is an alkyl group of Chemical Formula (5) 5-1 、R 5-2 is a linear alkyl group having 1 to 4 carbon atoms, R 5-3 is a linear or branched-chain alkyl group having 1 to 7 carbon atoms, R 5-1 、R 5-2 、R 5-3 It is more preferable that the total number of carbon atoms of is 3 or more and 10 or less, and R 5-1 、R 5-2 、R 5-3 It is more preferable that the total number of carbon atoms of is 6 or more and 9 or less. When the alkyl group of Chemical Formula (5) is too long or the total number of carbon atoms is too large, phase separation becomes difficult, which is not preferable. When the total number of carbon atoms of Chemical Formula (5) is too small, it is liable to dissolve in the water to be treated A even without introducing carbon dioxide D, and it is not preferable because it is difficult for the inorganic salt and / or the organic substance to precipitate by introducing carbon dioxide D. Further, when the total number of carbon atoms of Chemical Formula (5) is too small, the boiling point of the amine solution C is low, which is not only difficult to handle but also emits an ammonia odor peculiar to low-boiling amines, which is not preferable.

[0112] R of Chemical Formula (5) 5-1 、R 5-2 、R 5-3 are all the same, or it is preferable that R 5-1 、R 5-2 are the same and R 5-3 is different from R 5-1 、R 5-2 . It is not preferable that R 5-1 、R 5-2 、R 5-3 are all different because the separability from water decreases and synthesis becomes difficult. R5-1 、R 5-2 is preferably a linear alkyl group without a side chain, and R 5-3 is preferably a linear alkyl group with one side chain or a linear alkyl group without a side chain. Having many side chains is not preferable because the separability from water deteriorates. Also, when the number of carbon atoms in Chemical Formula (5) is large, it is difficult to phase-separate and it has an effect like a surfactant, and it is not preferable because it emulsifies or foams in the process of the present invention.

[0113] R 5-1 、R 5-2 、R 5-3 all being ethyl groups, the tertiary amine of Chemical Formula (5) (triethylamine), R 5-1 、R 5-2 both being methyl groups, and R 5-3 being a butyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 both being methyl groups, and R 5-3 being a pentyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 both being methyl groups, and R 5-3 being a hexyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 being a methyl group, and R 5-3 being a heptyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 both being ethyl groups, and R 5-3 being a butyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-1 、R 5-2 both being propyl groups, and R 5-3 being a methyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 both being butyl groups, and R 5-3 being a methyl group, the tertiary amine of Chemical Formula (5), R 5-1 、R 5-2 both being methyl groups, and R 5-3The tertiary amine of chemical formula (5) where [alkyl group] is a 2-ethyl-hexyl group is prone to phase separation by the release of carbon dioxide, is prone to phase separation, has a high recovery rate of inorganic salts and / or organic substances, and preferably has a high recovery rate of the tertiary amine from the supernatant phase G.

[0114] The tertiary amine of chemical formula (6) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of chemical formula (6) is an amine having a piperidine structure.

[0115] R in chemical formula (6) 6-1 is a linear alkyl group having 1 to 6 carbon atoms, a chain-like alkyl group having a side chain of 3 to 6 carbon atoms or a cyclic alkyl group having 3 to 6 carbon atoms, and R 6-2A , R 6-2B , R 6-3A , R 6-3B , R 6-4A , R 6-4B , R 6-5A , R 6-5B , R 6-6A , R 6-6B It is more preferable that any one or two selected from the group consisting of are a methyl group or an ethyl group and the rest are hydrogen. The number of carbon atoms of the cyclic alkyl group of R 6-1 is more preferably 4 to 6 or 5 to 6. When the alkyl group of chemical formula (6) is too long or the total number of carbon atoms is too large, it is not preferable because phase separation becomes difficult.

[0116] R in chemical formula (6) 6-1 is an ethyl group, and R 6-2A , R 6-2B , R 6-3A , R 6-3B , R 6-4A , R 6-4B , R 6-5A , R 6-5B , R 6-6A , R 6-6B It is preferable that the tertiary amine of chemical formula (6) where all are hydrogen is prone to phase separation, has a high recovery rate of inorganic salts and / or organic substances, and has a high recovery rate of the tertiary amine from the supernatant phase G.

[0117] The tertiary amine of Chemical Formula (7) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of Chemical Formula (7) is an amine having a pyrrolidine structure.

[0118] R which is the alkyl group of Chemical Formula (7) 7-1 is a linear alkyl group having 1 to 6 carbon atoms, a chain-like alkyl group having a side chain of 3 to 6 carbon atoms or a cyclic alkyl group having 3 to 6 carbon atoms, and R 7-2A , R 7-2B , R 7-3A , R 7-3B , R 7-4A , R 7-4B , R 7-5A , R 7-5B It is more preferable that any one to three selected from the group consisting of are all methyl groups or ethyl groups and the rest are hydrogen. The number of carbon atoms of the cyclic alkyl group of R 7-1 is more preferably 4 to 6 or 5 to 6. When the alkyl group of Chemical Formula (7) is too long or the total number of carbon atoms is too large, phase separation becomes difficult, which is not preferable.

[0119] R 7-1 is a butyl group, and R 7-2A , R 7-2B , R 7-3A , R 7-3B , R 7-4A , R 7-4B , R 7-5A , R 7-5B are all hydrogen. The tertiary amine of Chemical Formula (7) is easy to phase-separate, has a high recovery rate of inorganic salts and / or organic substances, and also has a high recovery rate of the tertiary amine from the supernatant phase G, which is preferable.

[0120] The tertiary amine of Chemical Formula (8) is a tertiary amine whose solubility changes in response to carbon dioxide. The amine of Chemical Formula (8) is a tertiary benzylamine.

[0121] R which is the alkyl chain of Chemical Formula (8) 8-1 is a linear alkyl chain having 1 to 3 carbon atoms, and R 8-2 , R 8-3It is more preferable that they are each a methyl group or an ethyl group. If the alkyl group in Chemical Formula (8) is too long or the total number of carbon atoms is too large, phase separation becomes difficult, which is not preferable.

[0122] R 8-1 is an alkyl chain having 1 carbon atom, and R 8-2 , R 8-3 are all tertiary amines of Chemical Formula (8) in which the groups are methyl groups, or R 8-1 is an alkyl chain having 2 carbon atoms, and R 8-2 , R 8-3 are all tertiary amines of Chemical Formula (8) in which the groups are methyl groups, which are likely to undergo phase separation by the release of carbon dioxide, have a high recovery rate of inorganic salts and / or organic substances, and also preferably have a high recovery rate of the tertiary amine from the supernatant phase G.

[0123] In the water treatment system 200 and the water treatment method of the embodiment, a tertiary amine whose liquid property changes in response to carbon dioxide D is used, and when efficiently separating inorganic salts and / or organic substances contained in the water to be treated A, the amine can be recovered from the generated supernatant phase G. In the water treatment system 200 and the water treatment method, by gently heating the supernatant phase G, carbon dioxide D can be released from the supernatant phase G to recover the amine. This can be performed with much lower energy than evaporating the water contained in the supernatant phase G to concentrate the supernatant phase G. Further, the released carbon dioxide D can be reused for introduction into the mixed solution E. In this case, it is preferable in that there is no increase in the amount of carbon dioxide released to circulate the carbon dioxide D. Therefore, the water treatment system 200 can be performed with low energy and a low environmental load as a whole.

[0124] (Third Embodiment) The third embodiment relates to a water treatment system and a water treatment method applied to non-evaporative desalination by salting out using a tertiary amine compound whose hydrophobicity and hydrophilicity change upon reaction with carbon dioxide. Fig. 7 shows a schematic diagram of the water treatment system 300 of the third embodiment. The schematic diagram of the water treatment system 300 in Fig. 7 includes means 11 for introducing the water to be treated A into the first container B, means 12 for introducing the amine solution C into the first container B, means 13 for introducing carbon dioxide D into the first container B, means 14 for separately separating the supernatant phase G and the precipitate phase H of the liquid F in which the mixed solution E containing the water to be treated A and the amine solution C is phase-separated after introducing carbon dioxide D into the first container B, means 15 for phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine (organic phase K), and means 16 for treating the aqueous phase J with a RO membrane (reverse osmosis membrane).

[0125] The water treatment system 300 of the third embodiment has means 16 for treating the aqueous phase J with a RO membrane. The highly purified water L obtained is drained, and the concentrated water M is returned to the first container B, which is the same as the water treatment system 200 of the second embodiment except for this. In the third embodiment, the description of the content common to the second embodiment is omitted.

[0126] Fig. 8 shows a flowchart of the water treatment method of the second embodiment. The water treatment method of the embodiment preferably includes a step of mixing the water to be treated A, the amine solution C, and carbon dioxide D to obtain a phase-separated liquid F, a step of separating the supernatant phase G and the precipitate phase H of the phase-separated liquid F, a step of phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine, and a step of treating the aqueous phase J with a reverse osmosis membrane (RO membrane). In the water treatment method of the third embodiment, the step of treating the aqueous phase J with the RO membrane is performed by means 16 for treating the aqueous phase J with the RO membrane. Hereinafter, the water treatment system 300 will be described, and the description of the water treatment system 300 also includes the description of the water treatment method.

[0127] Since the highly purified water L obtained has been treated with an RO membrane and contains almost no impurities, it can be discharged into a river or the like if the water quality conditions are met. Treating the water to be treated A directly with an RO membrane is very time-consuming or costly. However, by treating a water phase J that is very small in amount compared to the water to be treated A with an RO membrane, highly purified water L can be efficiently obtained.

[0128] The concentrated water M obtained by performing treatment with an RO membrane is preferably returned to the first container B through a flow path provided for return and subjected to salting-out treatment again. The concentrated water M contains, in addition to the inorganic salts and / or organic substances contained in the water to be treated A, the tertiary amine contained in the amine solution C. Therefore, by performing water treatment cyclically, the amount that can be recovered in the precipitation phase H increases. Note that the concentrated water M can also be returned to the first container B via means 11 for introducing the water to be treated A into the first container B. Further, the concentrated water M can be used as the water to be treated in another water treatment without being returned to the first container B.

[0129] When the water to be treated A contains a high concentration of salts, the osmotic pressure of the treated water is high, and a general RO membrane treatment technology cannot be applied. In any of the water treatment systems of the embodiments, treatment can be performed regardless of the concentration of the water to be treated A, and by finally performing RO membrane treatment on the low-concentration water phase J, highly purified water L can be obtained.

[0130] In the water treatment system 300 and the water treatment method of the embodiments, a tertiary amine whose liquid property changes in response to carbon dioxide D is used, and when the inorganic salts and / or organic substances contained in the water to be treated A are efficiently separated, the supernatant phase G generated is further phase-separated to obtain highly purified water L and concentrated water M. In the water treatment system 300 and the water treatment method, a cyclic water treatment can be performed to separate both the inorganic salts and / or organic substances in the precipitation phase H and the highly purified water L from the water to be treated A. As described in the water treatment system 100 of the first embodiment and the water treatment system 200 of the second embodiment, the water treatment system 200 can be performed with overall low energy and low environmental load, and highly pure water L that can be drained into a river or the like can be efficiently obtained.

[0131] Examples of the embodiments are shown below. (Example 1) To 25 ml of an aqueous solution of sodium chloride at 100 g / L, 25 ml of 1-[3-(azepan-1-yl)propyl]azepane was added. When 100% carbon dioxide gas was introduced at 0.5 L / min using a Kinoshita-type glass cylindrical filter (filter diameter 15φ, length 20 mm, filter particle No. 3 (20 - 30 μm), tube diameter 7φ, tube length 250 mm), white salt was precipitated. As a result of measuring the sodium concentration of the supernatant by ion chromatography, it was found to be about 70 ppm.

[0132] (Example 2) To 1 g of an aqueous solution of sodium chloride at 230 g / L, 1 g of an aqueous solution containing 33 wt% of 1-[3-(azepan-1-yl)propyl]azepane and made uniform by introducing carbon dioxide was added. When left standing for one day, white salt was precipitated. As a result of measuring the sodium concentration of the supernatant by ion chromatography, it was found to be about 26,000 ppm.

[0133] (Example 3) To 25 ml of an aqueous solution of sodium chloride at 150 g / L, 25 ml of dimethylcyclohexylamine was added. When 100% carbon dioxide gas was introduced at 0.5 L / min using a Pasteur pipette, white salt was precipitated. As a result of measuring the sodium concentration of the supernatant by ion chromatography, it was found to be about 800 ppm.

[0134] (Example 4) To 25 ml of an aqueous solution of sodium chloride at 150 g / L, 25 ml of N,N-dimethylbenzylamine was added. When 100% carbon dioxide gas was introduced at 0.5 L / min using a Pasteur pipette, white salt was precipitated. As a result of measuring the sodium concentration of the supernatant by ion chromatography, it was found to be about 27,000 ppm.

[0135] (Example 5) To 25 ml of an aqueous solution of sodium chloride at 150 g / L, 25 ml of N-butyldimethylamine was added. When 100% carbon dioxide gas was introduced at 0.5 L / min using a Pasteur pipette, white salt precipitated. As a result of measuring the sodium concentration of the supernatant by ion chromatography, it was found to be about 12,000 ppm.

[0136] (Example 6) To 25 ml of an aqueous solution of sodium chloride at 150 g / L, 25 ml of triethylamine was added. When 100% carbon dioxide gas was introduced at 0.5 L / min using a Pasteur pipette, white salt precipitated. As a result of measuring the sodium concentration of the supernatant by ion chromatography, it was found to be about 48,000 ppm.

[0137] (Comparative Example 1) To 25 ml of an aqueous solution of sodium chloride at 150 g / L, 25 ml of dimethyloctylamine was added. When 100% carbon dioxide gas was introduced at 0.5 L / min using a Pasteur pipette, the whole system emulsified.

[0138] (Comparative Example 2) To 25 ml of an aqueous solution of sodium chloride at 150 g / L, 25 ml of ethanol was added. When 100% carbon dioxide gas was introduced at 0.5 L / min using a Pasteur pipette, no salt precipitated.

[0139] From the above results, it was found that the salt in the aqueous solution containing salt can be precipitated using an amine whose polarity changes by reaction with carbon dioxide and carbon dioxide. Although the amount of precipitation varies depending on the amine, this is considered to depend on the solubility and polarity of the amine. By desorbing carbon dioxide from the supernatant after precipitating the salt, water and amine can be separated, and the amine and water can be recovered. Since the aqueous phase after phase separation also contains amine, highly pure water can be obtained by RO membrane treatment.

[0140] Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0141] 11: Means for introducing the water to be treated A into the first container B 12: Means for introducing the amine solution C into the first container B 13: Means for introducing carbon dioxide D into the first container B 14: Means for separately separating the supernatant phase G and the precipitate phase H of the liquid F in which the mixed solution E containing the water to be treated A and the amine solution C is phase-separated by introducing carbon dioxide D into the first container B 15: Means for phase-separating the supernatant phase G into an aqueous phase J and an organic phase K to separate and recover the tertiary amine (organic phase K) 16: Means for treating the aqueous phase J with a RO membrane (reverse osmosis membrane) 20: Filter 100: Water treatment system 200: Water treatment system 300: Water treatment system A: Water to be treated B: First container C: Amine solution D: Carbon dioxide E: Mixed solution G: Supernatant phase H: Precipitate phase J: Aqueous phase K: Organic phase L: Water M: Concentrated water

Claims

1. Means for introducing the water to be treated into the first container, Means for introducing an amine solution containing at least one tertiary amine selected from the group consisting of chemical formulas (1) to (3) into the first container, Means for introducing carbon dioxide into the first container, Means for separately separating the supernatant phase and the precipitate phase of the liquid obtained by introducing carbon dioxide into the first container and causing phase separation of the mixed solution containing the water to be treated and the amine solution, which comprises R of the chemical formula (1) １－１ is a linear alkyl chain having 2 or 3 carbon atoms, R in the chemical formula (1) １－２Ａ , R １－２Ｂ , R １－６Ａ , R １－６Ｂ are each hydrogen, R in the chemical formula (1) １－３Ａ R １－３Ｂ R １－４Ａ R １－４Ｂ R １－５Ａ R １－５Ｂ Among them, any one or two of them are each either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. R in the chemical formula (1) １－７Ａ R １－７Ｂ R １－１１Ａ R １－１１Ｂ are each hydrogen, R in the chemical formula (1) １－８Ａ R １－８Ｂ R １－９Ａ R １－９Ｂ R １－１０Ａ R １－１０Ｂ Among them, any one or two of them are each either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. R in the chemical formula (2) ２－１ is a linear alkyl chain having 1 to 3 carbon atoms, R in the chemical formula (2) ２－２Ａ R ２－２Ｂ R ２－３Ａ R ２－３Ｂ R ２－６Ａ R ２－６Ｂ R ２－７Ａ R ２－７Ｂ are each hydrogen, R of the chemical formula (2) ２－４Ａ R ２－４Ｂ R ２－５Ａ R ２－５Ｂ Among them, any one or two of them are each one of a hydrogen, a methyl group or an ethyl group, and the rest are hydrogen, R in the chemical formula (2) ２－８Ａ R ２－８Ｂ R ２－９Ａ R ２－９Ｂ R ２－１２Ａ R ２－１２Ｂ R ２－１３Ａ R ２－１３Ｂ are each hydrogen, R in the chemical formula (2) ２－１０Ａ , R ２－１０Ｂ , R ２－１１Ａ , R ２－１１Ｂ Among them, any one or two of them are each one of a hydrogen atom, a methyl group or an ethyl group, and the rest are hydrogen atoms, R in the chemical formula (3) ３－１ is a straight-chain alkyl group having 2 or 3 carbon atoms, R in the chemical formula (3) ３－２Ａ R ３－２Ｂ R ３－５Ａ R ３－５Ｂ are each hydrogen, R of the chemical formula (3) ３－３Ａ R ３－３Ｂ R ３－４Ａ R ３－４Ｂ Among them, any one or two of them are each either a methyl group or an ethyl group, and the rest are hydrogen. R in the chemical formula (3) ３－６Ａ R ３－６Ｂ R ３－９Ａ R ３－９Ｂ are each hydrogen, R in the chemical formula (3) ３－７Ａ R ３－７Ｂ R ３－８Ａ R ３－８Ｂ Among them, any one or two of them are each either a methyl group or an ethyl group, and the rest are hydrogen. A water treatment system in which the temperature of the mixed solution is 0°C or higher and 50°C or lower, and when the carbon dioxide concentration in the mixed solution increases, the tertiary amine responds to the carbon dioxide, its solubility changes, and the solubility of the tertiary amine in the water to be treated is improved. 【Chemical 1】

2. A first container for containing a mixed solution of the water to be treated and an amine solution containing at least one tertiary amine selected from the group consisting of chemical formulas (1) to (3), Means for introducing carbon dioxide into the first container, Means for separately separating the supernatant phase and the precipitate phase of the liquid obtained by introducing carbon dioxide into the first container and causing phase separation of the mixed solution containing the water to be treated and the amine solution, which comprises R in the chemical formula (1) １－１ is a linear alkyl chain having 2 or 3 carbon atoms, R in the chemical formula (1) １－２Ａ R １－２Ｂ R １－６Ａ R １－６Ｂ are each hydrogen, R in the chemical formula (1) １－３Ａ R １－３Ｂ R １－４Ａ R １－４Ｂ R １－５Ａ R １－５Ｂ Among them, any one or two of them are each either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen, R in the chemical formula (1) １－７Ａ R １－７Ｂ R １－１１Ａ R １－１１Ｂ are each hydrogen, R in the chemical formula (1) １－７Ａ R １－７Ｂ R １－８Ａ R １－８Ｂ R １－９Ａ R １－９Ｂ R １－１０Ａ R １－１０Ｂ any one or two of them are each either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen R in the chemical formula (2) ２－１ is a linear alkyl chain having 1 to 3 carbon atoms, R in the chemical formula (2) ２－２Ａ R ２－２Ｂ R ２－３Ａ R ２－３Ｂ R ２－６Ａ R ２－６Ｂ R ２－７Ａ R ２－７Ｂ is hydrogen respectively, R in the chemical formula (2) ２－４Ａ R ２－４Ｂ R ２－５Ａ R ２－５Ｂ Among them, any one or two of them are each one of a hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. R in the chemical formula (2) ２－８Ａ R ２－８Ｂ R ２－９Ａ R ２－９Ｂ R ２－１２Ａ R ２－１２Ｂ R ２－１３Ａ R ２－１３Ｂ is hydrogen respectively, R in the chemical formula (2) ２－１０Ａ R ２－１０Ｂ R ２－１１Ａ R ２－１１Ｂ is each either hydrogen, a methyl group or an ethyl group, R in the chemical formula (2) ２－１０Ａ R ２－１０Ｂ R ２－１１Ａ R ２－１１Ｂ Among them, any one or two of them are each either hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. R in the chemical formula (3) ３－１ is a straight-chain alkyl chain having 2 or 3 carbon atoms, R of the chemical formula (3) ３－２Ａ R ３－２Ｂ R ３－５Ａ R ３－５Ｂ are each hydrogen, R in the chemical formula (3) ３－３Ａ R ３－３Ｂ R ３－４Ａ R ３－４Ｂ Among them, any one or two of them are each either a methyl group or an ethyl group, and the rest are hydrogen. R of the chemical formula (3) ３－６Ａ R ３－６Ｂ R ３－９Ａ R ３－９Ｂ are each hydrogen, R in the chemical formula (3) ３－７Ａ , R ３－７Ｂ , R ３－８Ａ , R ３－８Ｂ Among them, any one or two of them are each either a methyl group or an ethyl group, and the rest are hydrogen. A water treatment system in which the temperature of the mixed solution is 0°C or higher and 50°C or lower, and when the carbon dioxide concentration in the mixed solution increases, the tertiary amine responds to the carbon dioxide, its solubility changes, and the solubility of the tertiary amine in the water to be treated is improved. [Chemical Formula 2]

3. The water treatment system according to claim 1 or 2, wherein the means for introducing carbon dioxide into the first container dissolves carbon dioxide in the mixed solution.

4. The water treatment system according to any one of claims 1 to 3, wherein the temperature of the mixed solution is 0°C or higher and 50°C or lower.

5. R in the chemical formula (1) １－１ is a straight-chain alkyl chain having 3 carbon atoms, R in the chemical formula (2) ２－１ is a straight-chain alkyl chain having 3 carbon atoms, R in the chemical formula (3) ３－１ The water treatment system according to any one of claims 1 to 4, wherein ３－１ is a linear alkyl chain having 3 carbon atoms.

6. The tertiary amine of the chemical formula (1) is R in the chemical formula (1). １－１ is a straight-chain alkyl chain with 3 carbon atoms, and R １－２Ａ R １－２Ｂ R １－３Ａ R １－３Ｂ R １－４Ａ R １－４Ｂ R １－５Ａ R １－５Ｂ R １－６Ａ R １－６Ｂ R １－７Ａ R １－７Ｂ R １－８Ａ R １－８Ｂ R １－９Ａ R １－９Ｂ R １－１０Ａ R １－１０Ｂ R １－１１Ａ R １－１１Ｂ is a tertiary amine having a piperidine structure in which all of them are hydrogen. The tertiary amine of the chemical formula (2) has an R in the chemical formula (2). ２－１ where R is a straight-chain alkyl chain with 3 carbon atoms, and R ２－２Ａ , R ２－２Ｂ , R ２－３Ａ , R ２－３Ｂ , R ２－４Ａ , R ２－４Ｂ , R ２－５Ａ , R ２－５Ｂ , R ２－６Ａ , R ２－６Ｂ , R ２－７Ａ , R ２－７Ｂ , R ２－８Ａ , R ２－８Ｂ , R ２－９Ａ , R ２－９Ｂ , R ２－１０Ａ , R ２－１０Ｂ , R ２－１１Ａ , R ２－１１Ｂ , R ２－１２Ａ , R ２－１２Ｂ , R ２－１３Ａ , R ２－１３Ｂ are all hydrogen, and it is a tertiary amine having an azepane structure. The tertiary amine of the chemical formula (3) is R in the chemical formula (3). ３－１ wherein R is a straight-chain alkyl chain having 3 carbon atoms, and R ３－２Ａ , R ３－２Ｂ , R ３－３Ａ , R ３－４Ａ , R ３－４Ｂ , R ３－５Ａ , R ３－５Ｂ , R ３－６Ａ , R ３－６Ｂ , R ３－７Ａ , R ３－８Ａ , R ３－８Ｂ , R ３－９Ａ , R ３－９Ｂ are all hydrogen, and R ３－３Ｂ and R ３－７Ｂ both have a pyrrolidine structure with methyl groups, and the water treatment system according to any one of claims 1 to 5.

7. The water treatment system according to any one of claims 1 to 4, further comprising means for phase-separating the supernatant phase into an aqueous phase and an organic phase to separate and recover the tertiary amine.

8. The water treatment system according to claim 7, wherein the separated and recovered tertiary amine is introduced into the first container.

9. The water treatment system according to claim 7 or 8, further comprising means for treating the aqueous phase with a reverse osmosis membrane.

10. The water treatment system according to any one of claims 1 to 9, wherein the amine solution contains the tertiary amine of chemical formula (2).

11. The water treatment system according to any one of claims 1 to 10, wherein the water to be treated and the precipitate phase contain inorganic salts and / or organic substances.

12. The water treatment system according to any one of claims 1 to 11, wherein the pH of the mixed solution is 3 or more and 9 or less.

13. A step of mixing the water to be treated, an amine solution containing one or more tertiary amines selected from Chemical Formulas (1) to (3), and carbon dioxide to obtain a liquid separated by phase separation, and a step of separating the supernatant phase and the precipitate phase of the liquid separated by phase separation, R in the chemical formula (1) １－１ is a linear alkyl chain having 2 or 3 carbon atoms, R in the chemical formula (1) １－２Ａ R １－２Ｂ R １－６Ａ R １－６Ｂ are each hydrogen, R in the chemical formula (1) １－３Ａ R １－３Ｂ R １－４Ａ R １－４Ｂ R １－５Ａ R １－５Ｂ Among them, any one or two of them are each one of hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. R in the chemical formula (1) １－７Ａ R １－７Ｂ R １－１１Ａ R １－１１Ｂ are each hydrogen, R in the chemical formula (1) １－８Ａ R １－８Ｂ R １－９Ａ R １－９Ｂ R １－１０Ａ R １－１０Ｂ Among them, any one or two of them are each one of a hydrogen, a methyl group or an ethyl group, and the rest are hydrogen. R in the chemical formula (2) ２－１ is a linear alkyl chain having 1 to 3 carbon atoms, R in the chemical formula (2) ２－２Ａ R ２－２Ｂ R ２－３Ａ R ２－３Ｂ R ２－６Ａ R ２－６Ｂ R ２－７Ａ R ２－７Ｂ are each hydrogen, R of the chemical formula (2) ２－４Ａ , R ２－４Ｂ , R ２－５Ａ , R ２－５Ｂ Among them, any one or two of them are each one of a hydrogen, a methyl group or an ethyl group, and the rest are hydrogen, R in the chemical formula (2) ２－８Ａ R ２－８Ｂ R ２－９Ａ R ２－９Ｂ R ２－１２Ａ R ２－１２Ｂ R ２－１３Ａ R ２－１３Ｂ are each hydrogen, R in the chemical formula (2) ２－１０Ａ R ２－１０Ｂ R ２－１１Ａ R ２－１１Ｂ Among them, any one or two of them are each one of a hydrogen atom, a methyl group or an ethyl group, and the rest are hydrogen atoms, R of the chemical formula (3) ３－１ is a straight-chain alkyl chain having 2 or 3 carbon atoms, R of the chemical formula (3) ３－２Ａ R ３－２Ｂ R ３－５Ａ R ３－５Ｂ are each hydrogen, R in the chemical formula (3) ３－３Ａ R ３－３Ｂ R ３－４Ａ R ３－４Ｂ Among them, any one or two of them are each either a methyl group or an ethyl group, and the rest are hydrogen. R of the chemical formula (3) ３－６Ａ R ３－６Ｂ R ３－９Ａ R ３－９Ｂ are each hydrogen, R of the chemical formula (3) ３－７Ａ R ３－７Ｂ R ３－８Ａ R ３－８Ｂ Among them, any one or two of them are each either a methyl group or an ethyl group, and the rest are hydrogen. wherein the temperature of the mixed solution containing the water to be treated and the amine solution is 0°C or higher and 50°C or lower, and when the carbon dioxide concentration in the mixed solution increases, the tertiary amine responds to the carbon dioxide and its solubility changes, improving the solubility of the tertiary amine in the water to be treated. 【Chemical Formula 3】

14. R in the chemical formula (1) １－１ is a straight-chain alkyl chain having 3 carbon atoms, R in the chemical formula (2) ２－１ is a linear alkyl chain having 3 carbon atoms, R in the chemical formula (3) ３－１ The water treatment method according to claim 13, wherein R is a straight-chain alkyl chain having 3 carbon atoms.

15. The tertiary amine of the chemical formula (1) is R in the chemical formula (1). １－１ a straight-chain alkyl chain having 3 carbon atoms, and R １－２Ａ R １－２Ｂ R １－３Ａ R １－３Ｂ R １－４Ａ R １－４Ｂ R １－５Ａ R １－５Ｂ R １－６Ａ R １－６Ｂ R １－７Ａ R １－７Ｂ R １－８Ａ R １－８Ｂ R １－９Ａ R １－９Ｂ R １－１０Ａ R １－１０Ｂ R １－１１Ａ R １－１１Ｂ is a tertiary amine having a piperidine structure in which all of them are hydrogen. The tertiary amine of the chemical formula (2) has an R in the chemical formula (2). ２－１ where R is a straight-chain alkyl chain with 3 carbon atoms, and R ２－２Ａ , R ２－２Ｂ , R ２－３Ａ , R ２－３Ｂ , R ２－４Ａ , R ２－４Ｂ , R ２－５Ａ , R ２－５Ｂ , R ２－６Ａ , R ２－６Ｂ , R ２－７Ａ , R ２－７Ｂ , R ２－８Ａ , R ２－８Ｂ , R ２－９Ａ , R ２－９Ｂ , R ２－１０Ａ , R ２－１０Ｂ , R ２－１１Ａ , R ２－１１Ｂ , R ２－１２Ａ , R ２－１２Ｂ , R ２－１３Ａ , R ２－１３Ｂ is a tertiary amine having an azepane structure in which all of them are hydrogen. The tertiary amine of the chemical formula (3) is R in the chemical formula (3). ３－１ wherein R is a straight-chain alkyl chain having 3 carbon atoms, and R ３－２Ａ , R ３－２Ｂ , R ３－３Ａ , R ３－４Ａ , R ３－４Ｂ , R ３－５Ａ , R ３－５Ｂ , R ３－６Ａ , R ３－６Ｂ , R ３－７Ａ , R ３－８Ａ , R ３－８Ｂ , R ３－９Ａ , R ３－９Ｂ are all hydrogen, and R ３－３Ｂ and R ３－７Ｂ are both methyl groups, and the water treatment method according to claim 13 or 14, which is a tertiary amine having a pyrrolidine structure.

16. The water treatment method according to any one of claims 13 to 15, wherein the amine solution contains the tertiary amine of Chemical Formula (2).

17. The water treatment method according to any one of claims 13 to 16, wherein the temperature of the solution obtained by mixing the water to be treated, the amine solution, and the carbon dioxide is 0°C or higher and 50°C or lower.

18. The water treatment method according to any one of claims 13 to 17, wherein the pH of the solution obtained by mixing the water to be treated, the amine solution, and the carbon dioxide is 3 or more and 9 or less.

19. Means for introducing the water to be treated into a first container, means for introducing an amine solution containing a tertiary amine of Chemical Formula (2) into the first container, means for introducing carbon dioxide into the first container, means for introducing carbon dioxide into the first container to separately divide the supernatant phase and the precipitate phase of the liquid obtained by phase separation of the mixed solution containing the water to be treated and the amine solution, and R in the chemical formula (2) ２－１ is a linear alkyl chain having 1 to 3 carbon atoms, R in the chemical formula (2) ２－２Ａ R ２－２Ｂ R ２－３Ａ R ２－３Ｂ R ２－４Ａ R ２－４Ｂ R ２－５Ａ R ２－５Ｂ R ２－６Ａ R ２－６Ｂ R ２－７Ａ R ２－７Ｂ is each either hydrogen, a methyl group or an ethyl group, R in the chemical formula (2) ２－８Ａ R ２－８Ｂ R ２－９Ａ R ２－９Ｂ R ２－１０Ａ R ２－１０Ｂ R ２－１１Ａ R ２－１１Ｂ R ２－１２Ａ R ２－１２Ｂ R ２－１３Ａ R ２－１３Ｂ is each either hydrogen, a methyl group or an ethyl group a water treatment system, wherein the temperature of the mixed solution is 0°C or higher and 50°C or lower, and when the carbon dioxide concentration in the mixed solution increases, the tertiary amine responds to the carbon dioxide and its solubility changes, improving the solubility of the tertiary amine in the water to be treated. 【Chemical Formula 4】

20. A first container for containing a mixed solution of the water to be treated and an amine solution containing a tertiary amine of Chemical Formula (2), means for introducing carbon dioxide into the first container, means for introducing carbon dioxide into the first container to separately divide the supernatant phase and the precipitate phase of the liquid obtained by phase separation of the mixed solution containing the water to be treated and the amine solution, and R in the chemical formula (2) ２－１ is a linear alkyl chain having 1 to 3 carbon atoms, R in the chemical formula (2) ２－２Ａ R ２－２Ｂ R ２－３Ａ R ２－３Ｂ R ２－４Ａ R ２－４Ｂ R ２－５Ａ R ２－５Ｂ R ２－６Ａ R ２－６Ｂ R ２－７Ａ R ２－７Ｂ is each either hydrogen, a methyl group or an ethyl group R in the chemical formula (2) ２－８Ａ R ２－８Ｂ R ２－９Ａ R ２－９Ｂ R ２－１０Ａ R ２－１０Ｂ R ２－１１Ａ R ２－１１Ｂ R ２－１２Ａ R ２－１２Ｂ R ２－１３Ａ R ２－１３Ｂ is each either hydrogen, a methyl group or an ethyl group, a water treatment system, wherein the temperature of the mixed solution is 0°C or higher and 50°C or lower, and when the carbon dioxide concentration in the mixed solution increases, the tertiary amine responds to the carbon dioxide and its solubility changes, improving the solubility of the tertiary amine in the water to be treated. 【Chemical Formula 5】 Claim 21 R in the chemical formula (1) １－２Ａ and R １－７Ａ are the same, R １－２Ｂ and R １－７Ｂ are the same, R １－３Ａ and R １－８Ａ are the same, R １－３Ｂ and R １－８Ｂ are the same, R １－４Ａ and R １－９Ａ are the same, R １－４Ｂ and R １－９Ｂ are the same, R １－５Ａ and R １－１０Ａ are the same, R １－５Ｂ and R １－１０Ｂ are the same, R １－６Ａ and R １－１１Ａ are the same, R １－６Ｂ and R １－１１Ｂ are the same, and R in the chemical formula (2) ２－２Ａ and R ２－８Ａ are the same, R ２－２Ｂ and R ２－８Ｂ are the same, R ２－３Ａ and R ２－９Ａ are the same, R ２－３Ｂ and R ２－９Ｂ are the same, R ２－４Ａ and R ２－１０Ａ are the same, R ２－４Ｂ and R ２－１０Ｂ are the same, R ２－５Ａ and R ２－１１Ａ are the same, R ２－５Ｂ and R ２－１１Ｂ are the same, R ２－６Ａ and R ２－１２Ａ are the same, R ２－６Ｂ and R ２－１２Ｂ are the same, R ２－７Ａ and R ２－１３Ａ are the same, and R ２－７Ｂ and R ２－１３Ｂ are the same, and R in the chemical formula (3) ３－２Ａ and R ３－６Ａ are the same, R ３－２Ｂ and R ３－６Ｂ are the same, R ３－３Ａ and R ３－７Ａ are the same, R ３－３Ｂ and R ３－７Ｂ are the same, R ３－４Ａ and R ３－８Ａ are the same, R ３－４Ｂ and R ３－８Ｂ are the same, R ３－５Ａ and R ３－９Ａ are the same, and R ３－５Ｂ and R ３－９Ｂ The water treatment system according to any one of claims 1 to 12, wherein are the same. Claim 22 R in the chemical formula (1) １－２Ａ and R １－７Ａ are the same, R １－２Ｂ and R １－７Ｂ are the same, R １－３Ａ and R １－８Ａ are the same, R １－３Ｂ and R １－８Ｂ are the same, R １－４Ａ and R １－９Ａ are the same, R １－４Ｂ and R １－９Ｂ are the same, R １－５Ａ and R １－１０Ａ are the same, R １－５Ｂ and R １－１０Ｂ are the same, R １－６Ａ and R １－１１Ａ are the same, R １－６Ｂ and R １－１１Ｂ are the same, and R in the chemical formula (2) ２－２Ａ and R ２－８Ａ are the same, R ２－２Ｂ and R ２－８Ｂ are the same, R ２－３Ａ and R ２－９Ａ are the same, R ２－３Ｂ and R ２－９Ｂ are the same, R ２－４Ａ and R ２－１０Ａ are the same, R ２－４Ｂ and R ２－１０Ｂ are the same, R ２－５Ａ and R ２－１１Ａ are the same, R ２－５Ｂ and R ２－１１Ｂ are the same, R ２－６Ａ and R ２－１２Ａ are the same, R ２－６Ｂ and R ２－１２Ｂ are the same, R ２－７Ａ and R ２－１３Ａ are the same and R ２－７Ｂ and R ２－１３Ｂ and R in the chemical formula (3) ３－２Ａ and R ３－６Ａ are the same, R ３－２Ｂ and R ３－６Ｂ are the same, R ３－３Ａ and R ３－７Ａ are the same, R ３－３Ｂ and R ３－７Ｂ are the same, R ３－４Ａ and R ３－８Ａ are the same, R ３－４Ｂ and R ３－８Ｂ are the same, R ３－５Ａ and R ３－９Ａ are the same, and R ３－５Ｂ and R ３－９Ｂ The water treatment method according to any one of claims 13 to 18, wherein are the same. Claim 23 R in the chemical formula (2) ２－２Ａ and R ２－８Ａ are the same, R ２－２Ｂ and R ２－８Ｂ are the same, R ２－３Ａ and R ２－９Ａ are the same, R ２－３Ｂ and R ２－９Ｂ are the same, R ２－４Ａ and R ２－１０Ａ are the same, R ２－４Ｂ and R ２－１０Ｂ are the same, R ２－５Ａ and R ２－１１Ａ are the same, R ２－５Ｂ and R ２－１１Ｂ are the same, R ２－６Ａ and R ２－１２Ａ are the same, R ２－６Ｂ and R ２－１２Ｂ are the same, R ２－７Ａ and R ２－１３Ａ are the same and R ２－７Ｂ and R ２－１３Ｂ The water treatment system according to claim 19 or 20, wherein they are the same.

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