Draw solute, draw solution, and water treatment method

Abstract

To provide a draw solute capable of achieving both low viscosity and low dilutive layer concentration, and a draw solution and a water treatment method employing the draw solute.SOLUTION: A draw solute comprises a compound represented by the following general formula (1). [In general formula (1), R1 represents a residue obtained by removing all active hydrogens from an x-valent active hydrogen-containing compound having 3 or more carbon atoms; R2 represents a methyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, aryl group, or acyl group; AO represents an ethylene oxide group, propylene oxide group, or butylene oxide group; x is an integer of 1 or more; and n is a number of 2 or more and 100 or less, provided that a plurality of AOs may be the same or different].SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to draw solutes, and draw solutions and water treatment methods using same. [Background technology]

[0002] The forward osmosis membrane method uses the phenomenon of solvent migration from the side with lower osmotic pressure to the side with higher osmotic pressure when two solutions of different concentrations are brought into contact via a semipermeable membrane, and can be used to separate the components of a solution. Compared to the reverse osmosis membrane method, which applies pressure to a solution against osmotic pressure to force the liquid through a membrane, the forward osmosis membrane method, which uses osmotic pressure to perform membrane filtration, is more energy-efficient and is expected to be applied to water treatment such as seawater desalination, wastewater treatment, and food concentration, as well as power generation.

[0003] When water is treated using the forward osmosis membrane method, a solution (draw solution) with a higher osmotic pressure than the solution to be treated (the solution to be treated) is used to move a solvent (water) from the solution to be treated to the draw solution through a semipermeable membrane. Since the solvent must then be recovered from the draw solution, the draw solution must have a property that allows for easy separation of the solvent (phase separation). Various substances with osmotic pressure-inducing properties (draw solutes) for preparing such draw solutions have been investigated. For example, Patent Document 1 proposes a draw solute made of a block copolymer containing ethylene oxide, propylene oxide, or butylene oxide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 156404 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable for the draw solute to have a low viscosity. This has the advantage of facilitating the solvent's movement through the semipermeable membrane during water treatment and reducing the energy required to transport the draw solution. Furthermore, when the draw solution is separated, it is separated into a concentrated layer containing a large amount of the draw solute and a dilute layer containing a large amount of the solvent. The solvent is obtained by removing the draw solute from the dilute layer. To reduce costs, it is desirable for the concentration of the draw solute in the dilute layer to be low (also called a "low dilute layer concentration"). However, no draw solute has been known that achieves both low viscosity and low dilute layer concentration at high levels.

[0006] Therefore, an object of the present invention is to provide a draw solute that achieves both low viscosity and low dilute layer concentration, as well as a draw solution and a water treatment method using the same. [Means for solving the problem]

[0007] In view of the above circumstances, the present inventors have conducted extensive research and have completed the inventions set forth in the following items [1] to

[11] . [1] A draw solute containing a compound represented by the following general formula (1): [ka] [In general formula (1), R 1 represents the residue obtained by removing all active hydrogens from an x-valent active hydrogen-containing compound having 3 or more carbon atoms, and R 2 represents a methyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, aryl group or acyl group, AO represents an ethylene oxide group, propylene oxide group or butylene oxide group, x is an integer of 1 or more, and n is a number of 2 or more and 100 or less, provided that multiple AOs may be the same or different.] [2] R 2 The draw solute according to [1], wherein [3] The draw solute according to [1] or [2], wherein the active hydrogen-containing compound is a monohydric aliphatic alcohol having 5 to 15 carbon atoms or a monohydric phenol having 6 to 12 carbon atoms. [4] The draw solute according to any one of [1] to [3], wherein the compound represented by the general formula (1) has a number average molecular weight of 500 to 10,000. [5] The draw solute according to any one of [1] to [4], wherein the cloud point of a 50 mass % draw solution prepared by dissolving the draw solute in water is 30°C or higher and 90°C or lower. [6] The draw solute according to any one of [1] to [5], wherein the viscosity of the draw solute at 25°C is 200 mPa·s or less. [7] The draw solute according to any one of [1] to [6], further containing a compound represented by the following general formula (2) in an amount of 0.1 ppm by mass or more and 100,000 ppm by mass or less based on the total amount of the draw solute: [ka] [In general formula (2), R 1 , AO and x are R in general formula (1). 1 , AO and x, and n1 represents a number of 1 to 100. [8] The draw solute according to any one of [1] to [7], further containing a compound represented by the following general formula (3) in an amount of 0.1 ppm by mass or more and 100,000 ppm by mass or less based on the total amount of the draw solute: [ka] [In general formula (3), R 2 and AO is R in general formula (1). 2 and AO, R 3 represents a hydroxy group or an acyloxy group, and n2 represents a number of 1 or more and 100 or less. [9] The draw solute according to any one of [1] to [8], further comprising at least one salt selected from the group consisting of sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium lactate, potassium lactate, sodium sulfate, and potassium sulfate in an amount of 0.1 ppm by mass or more and 50,000 ppm by mass or less, based on the total amount of the draw solute.

[10] A draw solution containing the draw solute according to any one of [1] to [9].

[11]

[10] A water treatment method using the draw solution described in

[10] . [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a draw solute that achieves both low viscosity and low dilute layer concentration, as well as a draw solution and a water treatment method using the same. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure will be described in detail below, but the present disclosure is not limited thereto.

[0010] <Draw solute> The draw solute of this embodiment contains a compound represented by the following general formula (1) (hereinafter also referred to as "compound of formula (1)"). [ka] [In general formula (1), R 1 represents the residue obtained by removing all active hydrogens from an x-valent active hydrogen-containing compound having 3 or more carbon atoms, and R 2 represents a methyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, aryl group or acyl group, AO represents an ethylene oxide group, propylene oxide group or butylene oxide group, x is an integer of 1 or more, and n is a number of 2 or more and 100 or less, provided that multiple AOs may be the same or different.]

[0011] The x-valent active hydrogen-containing compound having 3 or more carbon atoms may be a monovalent active hydrogen-containing compound (containing one active hydrogen) or a divalent or higher active hydrogen-containing compound (containing two or more active hydrogens).

[0012] Examples of the active hydrogen-containing functional group include a hydroxy group and an amino group.

[0013] Examples of active hydrogen-containing compounds include compounds having a hydroxy group such as aliphatic alcohols having 3 or more carbon atoms, unsaturated alcohols having 3 or more carbon atoms, aromatic alcohols having 7 or more carbon atoms, other alcohols having 3 or more carbon atoms, phenols having 6 or more carbon atoms, and carboxylic acids having 3 or more carbon atoms; and compounds having an amino group having 3 or more carbon atoms.

[0014] Specific examples of aliphatic alcohols having 3 or more carbon atoms include monohydric aliphatic alcohols such as 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-methyl-1-butanol, 2,2-dimethyl-1-propanol, 2-pentanol, 3-methyl-2-butanol, 3-pentanol, 1-octanol, 2-octanol, 1-decanol, 2-decanol, 2-propyl-1-heptanol, 1-dodecanol, and 2-dodecanol; 1,2-propanediol, 1,3- Examples of the alcohol include dihydric aliphatic alcohols such as propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, ethylene glycol, diethylene glycol, triethylene glycol, and neopentyl glycol; and trihydric or higher aliphatic alcohols such as glycerin, polyglycerol trimethylolpropane, erythritol, pentaerythritol, diglycerol, and di(trimethylolpropane).

[0015] Specific examples of unsaturated alcohols having 3 or more carbon atoms include allyl alcohol, methallyl alcohol, and isoprenol.

[0016] Specific examples of other alcohols having 3 or more carbon atoms include hydroxyacetone, tetrahydrofurfuryl alcohol, 1,4-cyclohexanedimethanol, sorbitol, sorbitan, glucose, fructose, xylitol, and methyl glucoside.

[0017] Specific examples of phenols having 6 or more carbon atoms include monohydric phenols such as phenol, cresol, picric acid, naphthol, p-nitrophenol, and pentafluorophenol; dihydric phenols such as catechol, resorcinol, and hydroquinone; and trihydric phenols such as pyrogallol and phloroglucinol.

[0018] Specific examples of carboxylic acids having 3 or more carbon atoms include acrylic acid, methacrylic acid, propionic acid, and butyric acid.

[0019] Specific examples of compounds having an amino group having 3 or more carbon atoms include polyethyleneimine, propylamine, isopropylamine, butylamine, 2-pentylamine, 3-pentylamine, neopentylamine, hexylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, pentadecylamine, cetylamine, laurylamine, stearylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, 1-adamantanamine, ethylmethylamine, diethylamine, and methylpropylamine. Amines, methyl isopropylamine, ethylpropylamine, ethylisopropylamine, butylmethylamine, methyl t-butylamine, dipropylamine, diisopropylamine, ethyl t-butylamine, N-ethyl-1,2-dimethylpropylamine, dibutylamine, diisobutylamine, di(t-butyl)amine, ethylhexylamine, dipentylamine, dihexylamine, di(2-ethylhexyl)amine, dioctylamine, didecylamine, dilaurylamine, dicetylamine, distearylamine, methylstearylamine, ethyl N-butylcyclohexylamine, dicyclohexylamine, di(2-methylcyclohexyl)amine, N,N'-dimethyl-1,3-propanediamine, 1,3-pentanediamine, ethylenediamine, diethylenetriamine, triethylenetetramine (N,N'-di(2-aminoethyl)ethylenediamine), monoethanolamine, diethanolamine, dipropanolamine, benzylamine, phenylpropylamine, phenylbutylamine ethylamine, 1,1-dimethyl-2-phenylethylamine, 3,4-dimethylbenzylamine, aniline, methylaniline, ethylaniline, propylaniline, isopropylaniline, butylaniline, laurylaniline, stearylaniline, dimethylaniline, diethylaniline, methylbenzylamine, 4,4'-methylenedianiline, naphthylamine, trimethylaniline, 4-methylphenethylamine, methylbenzylamine, ethylbenzylamine, t-butylbenzylamine, diphenylamine, dibenzylamine, N-benzyl-1,3-propanediamine, 2,4,6-trimethyl-1,3-phenylenediamine, 4-aminobenzylamine, aziridine, azetidine, pyrrolidine, 2-methylpyrrolidine, piperidine, 2-methylpiperidine, 3-methylpiperidine, 4-methylpiperidine, 2,4-dimethylpiperidine, 3,5-dimethylpiperidine, 2,6-dimethylpiperidine, 2,2,6,6-tetramethylpiperidine, piperazine, N-methylpiperazine, N-ethylpiperazine, N-isobutylpiperazine, N- Examples of suitable amines include cyclohexylpiperazine, N-cyclopentylpiperazine, N-phenylpiperazine, 1-(2-pyridyl)piperazine, 1-(4-pyridyl)piperazine, 1-(2-pyrimidyl)piperazine, morpholine, pyrrole, 2-methylpyrrole, 2,4-dimethylpyrrole, 3,4-dimethylpyrrole, pyrazole, 3,5-dimethylpyrazole, imidazole, 3-methylindole, 2-phenylindole, triethanolamine, and diethylenetriamine ethylene glycol.

[0020] The active hydrogen-containing compound is preferably an aliphatic alcohol having 3 or more carbon atoms or a phenol having 6 or more carbon atoms.

[0021] The number of carbon atoms in the aliphatic alcohol is preferably 5 to 15, and more preferably 8 to 12. The aliphatic alcohol may be linear or branched, but is preferably linear. The valence (x) of the aliphatic alcohol is preferably 1 to 3, and more preferably 1 to 2, and even more preferably 1.

[0022] The number of carbon atoms in the phenols is preferably 6 or more and 12 or less, and more preferably 6 or more and 10 or less. The valence of the phenols is preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less, and even more preferably 1.

[0023] In formula (1), R 2represents a methyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, aryl group, or acyl group. Specific examples of aryl groups include a phenyl group and a naphthyl group. Specific examples of acyl groups include a formyl group, an acetyl group, an n-propanoyl group, and a benzoyl group.

[0024] Among these, R 2 is preferably an acyl group, more preferably an acetyl group.

[0025] In formula (1), AO represents an ethylene oxide group (EO), a propylene oxide group (PO), or a butylene oxide group (BO). In formula (1), multiple AOs may be the same or different. AO is preferably an ethylene oxide group.

[0026] In formula (1), n ​​is R 1 represents the average number of moles of AO bonded to the group, and is a number of 2 or more and 100 or less. n is preferably a number of 3 or more and 70 or less, more preferably a number of 4 or more and 50 or less, even more preferably a number of 5 or more and 30 or less, and particularly preferably a number of 7 or more and 15 or less.

[0027] The number average molecular weight of the compound of formula (1) is preferably 500 to 10,000, more preferably 500 to 5,000, even more preferably 500 to 3,000, and particularly preferably 500 to 1,000. The weight average molecular weight of the compound of formula (1) is preferably 500 to 10,000, more preferably 500 to 5,000, even more preferably 500 to 3,000, and particularly preferably 500 to 1,000. The number average molecular weight and weight average molecular weight can be measured, for example, using gel permeation chromatography (GPC).

[0028] The concentration of the compound of formula (1) in the draw solute of this embodiment is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0029] The draw solute of this embodiment may further contain a compound represented by the following general formula (2) (hereinafter referred to as "compound of formula (2)"). [ka] [In general formula (2), R 1 , AO and x are R in general formula (1). 1 , AO and x, and n1 represents a number of 1 to 100.

[0030] In formula (2), n1 is R 1 n1 represents the average number of moles of AO bonded to the compound of formula (2), and is a number of 1 to 100. n1 is preferably a number of 3 to 70, more preferably a number of 4 to 50, even more preferably a number of 5 to 30, and particularly preferably a number of 7 to 15. The compound of formula (2) corresponds to a by-product generated during the synthesis of the compound of formula (1).

[0031] The concentration of the compound of formula (2) in the draw solute of this embodiment may be 0.1 ppm by mass or more and 100,000 ppm by mass or less, 1 ppm by mass or more and 80,000 ppm by mass or less, 10 ppm by mass or more and 60,000 ppm by mass or less, or 100 ppm by mass or more and 50,000 ppm by mass or less, based on the total amount of the draw solute.

[0032] The draw solute of this embodiment may further contain a compound represented by the following general formula (3) (hereinafter referred to as "compound of formula (3)"). [ka] [In general formula (3), R 2 and AO is R in general formula (1). 2 and AO, R 3 represents a hydroxy group or an acyloxy group, and n2 represents a number of 1 or more and 100 or less.

[0033] In formula (3), n2 is R3 represents the average number of moles of AO bonded to the compound of formula (3), and is a number of 1 to 100. n2 is preferably a number of 3 to 70, more preferably a number of 4 to 50, even more preferably a number of 5 to 30, and particularly preferably a number of 7 to 15. The compound of formula (3) corresponds to a by-product generated during the synthesis of the compound of formula (1).

[0034] The concentration of the compound of formula (3) in the draw solute of this embodiment may be 0.1 ppm by mass or more and 100,000 ppm by mass or less, 1 ppm by mass or more and 80,000 ppm by mass or less, 10 ppm by mass or more and 60,000 ppm by mass or less, or 100 ppm by mass or more and 50,000 ppm by mass or less, based on the total amount of the draw solute.

[0035] The draw solute of this embodiment may further contain at least one salt selected from the group consisting of sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium lactate, potassium lactate, sodium sulfate, and potassium sulfate.

[0036] The concentration of these salts in the draw solute of this embodiment may be 0.1 ppm by mass to 50,000 ppm by mass, 1 ppm by mass to 40,000 ppm by mass, 10 ppm by mass to 30,000 ppm by mass, or 100 ppm by mass to 25,000 ppm by mass, based on the total amount of the draw solute. This allows for a higher level of compatibility between high osmotic pressure and low dilute layer concentration, resulting in a draw solute that can reduce the cost of water treatment by forward osmosis. The concentrations of these salts can be analyzed by ion chromatography or electrophoresis.

[0037] When the draw solute of this embodiment is dissolved in water to prepare a 50% by mass draw solution, the cloud point of the draw solution is preferably 30°C or higher and 90°C or lower, more preferably 35°C or higher and 80°C or lower, and even more preferably 40°C or higher and 70°C or lower. When the cloud point is within these ranges, the forward osmosis membrane method can be easily applied to water treatment using low-temperature waste heat from factories, etc. The cloud point can be measured, for example, by the method described in the Examples. The draw solute of this embodiment corresponds to a lower critical solution temperature (LCST) type, which has the property of flocculating when heated.

[0038] The viscosity (25°C) of the draw solute in this embodiment is preferably 200 mPa·s (cPs) or less, more preferably 150 mPa·s or less, and even more preferably 100 mPa·s or less. Viscosities within these ranges further reduce the energy required to transport the draw solution in the forward osmosis membrane method, thereby reducing costs. The lower limit of the viscosity (25°C) of the draw solute is not particularly limited, but can be, for example, 10 mPa·s (cPs) or more. Viscosity can be measured, for example, by the method described in the Examples.

[0039] The draw solute of this embodiment can be obtained, for example, by adding ethylene oxide, propylene oxide, and / or butylene oxide (alkylene oxide) to an active hydrogen-containing compound to obtain an intermediate, and then acylating or etherifying the terminal hydroxyl group of the intermediate by a known method.

[0040] The reaction conditions for adding an alkylene oxide to an active hydrogen-containing compound are not particularly limited. For example, the active hydrogen-containing compound and the alkylene oxide can be reacted as is, or diluted with a solvent as necessary, at a temperature preferably between 0°C and 200°C, more preferably between 120°C and 180°C. An alkaline catalyst such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) may be used as a catalyst. The reaction can be carried out, for example, by adding a catalyst to the active hydrogen-containing compound and then feeding the alkylene oxide into the reaction system. The alkylene oxide may be fed in multiple batches. After feeding the alkylene oxide, the reaction rate can be further increased by aging the mixture for 1 hour to 3 hours until the reaction is complete.

[0041] The terminal hydroxyl group of the compound (intermediate) obtained by adding alkylene oxide to an active hydrogen-containing compound can be acylated by reacting the intermediate with acetic anhydride, acetyl chloride, propionyl chloride, benzoyl chloride, etc., by a known method. 2 The terminal hydroxyl group of the intermediate can be etherified by reacting the intermediate with an alkyl halide or the like in the presence of a base using a known method. 2 As a result, a methyl group or the like is introduced.

[0042] After the reaction, it is preferable to neutralize the reaction mixture by adding an acid such as acetic acid, phosphoric acid, or lactic acid, and then remove light impurities such as ethylene glycol from the product under reduced pressure at a temperature between 0°C and 200°C, more preferably between 120°C and 180°C. The draw solute is preferably stored under a nitrogen atmosphere, and an antioxidant may be added to improve stability. Suitable antioxidants include dibutylhydroxytoluene, butylhydroxyanisole, ascorbic acid, tocopherol, and sodium erythorbate.

[0043] When an antioxidant is added to the draw solute, the amount added is preferably 50 ppm by mass or more, more preferably 200 ppm by mass or more, from the viewpoint of preventing deterioration of physical properties. The upper limit of the amount added is not particularly limited, but can be, for example, 1000 ppm by mass or less.

[0044] <Drawing solution> The draw solution of this embodiment contains the draw solute. The content of the draw solute is preferably 20% by mass or more and 100% by mass or less, more preferably 50% by mass or more and 100% by mass or less, and even more preferably 75% by mass or more and 100% by mass or less, based on the total amount of the draw solution.

[0045] The draw solution may contain a solvent. The solvent may be appropriately selected depending on the conditions of the forward osmosis membrane method using the draw solution, and one or more solvents selected from water, methanol, ethanol, etc. may be used. It is more preferable that the draw solution contains the same solvent as the solvent to be treated. The content of the solvent may be, for example, 0% by mass or more and 80% by mass or less based on the total amount of the draw solution.

[0046] The draw solution may contain draw solutes other than the draw solutes (other draw solutes), but the content of the other draw solutes is preferably 20 mass % or less relative to the total amount of the draw solutes. The draw solution is preferably composed of the draw solutes, any solvent, and any other draw solutes, and more preferably composed of the draw solutes and solvent.

[0047] The draw solution preferably has a cloud point (lower critical solution temperature). The cloud point refers to the temperature at which a transparent or translucent liquid undergoes phase separation upon temperature change, resulting in an opaque liquid. A draw solution having a cloud point can undergo phase separation between the draw solute and the solvent upon heating.

[0048] For example, when the forward osmosis membrane process is applied to water treatment using low-temperature waste heat from a factory, it is preferable that the draw solution does not undergo phase separation at temperatures around room temperature where the forward osmosis membrane process is performed, but that the draw solution undergoes phase separation at a temperature similar to that of the low-temperature waste heat from the factory. The suitable cloud point of the draw solution used in such applications varies depending on the concentration of the draw solute in the draw solution, but is preferably, for example, from 30°C to 90°C, more preferably from 35°C to 80°C, and even more preferably from 40°C to 70°C.

[0049] Low-temperature waste heat from factories has traditionally been difficult to utilize, and much of it has been discarded as waste heat. Therefore, water treatment using low-temperature waste heat is particularly desirable from the perspective of energy efficiency.

[0050] <Forward osmosis membrane method (water treatment method)> In forward osmosis, the feed solution (the solution to be treated) and the draw solution are brought into contact with each other through a semipermeable membrane, and the solvent moves from the feed solution, which has a low osmotic pressure, to the draw solution, which has a high osmotic pressure. As the solvent moves, the concentration of the draw solution gradually decreases. Therefore, in order to continue forward osmosis, it is necessary to separate the draw solute and the solvent contained in the draw solution.

[0051] The draw solution having a cloud point can be heated to cause phase separation between the draw solute and the solvent.

[0052] In the forward osmosis membrane method using a draw solution having such a cloud point, the forward osmosis membrane method can be continuously carried out by repeating the following treatment, for example. The feed solution is placed on one side of the semipermeable membrane and the draw solution on the other side so that they come into contact with the semipermeable membrane, and the solvent is transferred from the feed solution side to the draw solution side through the semipermeable membrane. The reduced concentration draw solution is removed and heated to cause phase separation between the draw solute and the solvent. The phase-separated draw solute is circulated again to the other side. The phase-separated solvent is further purified, for example, using a nanofiltration membrane (NF membrane), to obtain the desired processed product (purified water, etc.).

[0053] The temperature at which the forward osmosis membrane treatment is carried out is not particularly limited, but is usually around room temperature, for example, 5°C or higher and 40°C or lower.

[0054] Conventional semipermeable membranes can be used in the forward osmosis membrane method, but to maintain the strength of the membrane, it is preferable to use a combination of a dense active layer, which determines the selective permeability of the membrane, and a porous support layer. Since the support layer adsorbs dirt more easily than the active layer, it is generally preferable to provide the active layer of the semipermeable membrane on the feed liquid (water to be treated) side from the perspective of reducing membrane fouling.

[0055] The draw solution can be applied to various applications that utilize the forward osmosis membrane method, particularly water treatment devices and power generation devices, which are expected to utilize the forward osmosis membrane method, and the draw solution can be suitably applied to these applications. [Example]

[0056] The present disclosure will be described in more detail below by showing examples, but the scope of the present disclosure is not limited to these examples, and all modifications and variations that do not deviate from the spirit of the present disclosure are included within the technical scope of the present disclosure. Unless otherwise specified, "%" means "% by mass."

[0057] [Preparation of draw solute] Draw solutes for Examples 1 to 3 and Comparative Example 1 were prepared as shown below.

[0058] Example 1 A 1-L autoclave was charged with 150.0 g of 1-decanol and 8.75 g of 48% KOH aqueous solution at room temperature, and then the pressure was reduced to 10 kPa absolute while bubbling nitrogen gas at 20 mL / min. The temperature was then raised to 125°C and the mixture was stirred for 5 hours. After the pressure was raised to 0.20 MPa, the bubbling was stopped and 375.7 g of ethylene oxide was injected over 4 hours, followed by aging for 3 hours. 35.2 g of the intermediate thus obtained and 0.32 g of acetic acid were placed in a glass container at room temperature, and then the pressure was reduced to 10-20 kPa while bubbling with nitrogen, and the mixture was heated to 110°C and stirred for 3 hours. Nitrogen gas was then blown in until the pressure reached normal pressure, after which 11.1 g of acetic anhydride was added, and the mixture was heated and stirred at 120°C for 8 hours. The pressure was reduced to 10-20 kPa while bubbling with nitrogen, and the mixture was heated at 140°C for 3 hours. This yielded the drawn solute of Example 1.

[0059] <Example 2> A 1-L autoclave was charged with 150.0 g of 1-decanol and 8.75 g of 48% KOH aqueous solution at room temperature, and then the pressure was reduced to 10 kPa absolute while bubbling nitrogen gas at 20 mL / min. The temperature was then raised to 125°C and the mixture was stirred for 5 hours. After the pressure was raised to 0.20 MPa, the bubbling was stopped and 313.1 g of ethylene oxide was injected over 4 hours, followed by aging for 3 hours. 35.2 g of the intermediate thus obtained and 0.34 g of acetic acid were placed in a glass container at room temperature, and then the pressure was reduced to 10-20 kPa while bubbling with nitrogen, and the mixture was heated to 110°C and stirred for 3 hours. Nitrogen gas was then blown in until the pressure reached normal pressure, after which 11.1 g of acetic anhydride was added, and the mixture was heated and stirred at 120°C for 8 hours. The pressure was reduced to 10-20 kPa while bubbling with nitrogen, and the mixture was heated at 140°C for 3 hours. This yielded the drawn solute of Example 2.

[0060] Example 3 A 1-L autoclave was charged with 150.0 g of p-cresol and 0.88 g of 85% KOH at room temperature, and then the pressure was reduced to 10 kPa absolute while bubbling nitrogen gas at 20 mL / min. The temperature was then raised to 125°C and the mixture was stirred for 5 hours. After the pressure was raised to 0.20 MPa, the bubbling was stopped and 549.9 g of ethylene oxide was injected over 4 hours, followed by aging for 3 hours. 35.2 g of the intermediate thus obtained and 0.04 g of acetic acid were placed in a glass container at room temperature, and then the pressure was reduced to 10-20 kPa while bubbling with nitrogen, and the mixture was heated to 110°C and stirred for 3 hours. Nitrogen gas was then blown in until the pressure reached normal pressure, after which 11.9 g of acetic anhydride was added, and the mixture was heated and stirred at 120°C for 8 hours. The pressure was reduced to 10-20 kPa while bubbling with nitrogen, and the mixture was heated at 140°C for 3 hours. This yielded the drawn solute of Example 3.

[0061] <Comparative Example 1> A 1-L autoclave was charged with 150.0 g of diethylenetriamine and 8.75 g of 48% KOH aqueous solution at room temperature, and then the pressure was reduced to 10 kPa absolute while bubbling nitrogen gas at 20 mL / min. The temperature was then raised to 125°C and the mixture was stirred for 5 hours. After the pressure was raised to 0.20 MPa, the bubbling was stopped and 640.5 g of ethylene oxide was injected over 4 hours, followed by aging for 3 hours. 150.0 g of the resulting intermediate was placed in a 1-L autoclave, and the gas phase was replaced with nitrogen. The autoclave was then heated to 125°C, the pressure increased to 0.20 MPa, and 145.3 g of ethylene oxide was added over 4 hours, followed by aging for 3 hours. 198.2 g of butylene oxide was then added over 3 hours, and the autoclave was then aged for 3 hours. After the temperature was lowered to 60°C, 2.7 g of 50% lactic acid was added and stirred. This produced the draw solute of Comparative Example 1.

[0062] [Evaluation of draw solutes] The draw solutes of Examples 1 to 3 and Comparative Example 1 were evaluated as follows. The results are shown in Table 1.

[0063] (Cloud point rating) An aqueous solution containing 50% by mass of each draw solute was prepared and sealed in a screw vial. This was placed in an oven at 97°C for 1 hour to separate the layers, and then cooled while measuring the internal temperature. The temperature at which a uniform layer was visually observed was defined as the cloud point.

[0064] (Phase separation evaluation) An aqueous solution containing 50% by mass of each draw solute was prepared and sealed in a screw vial. This was placed in a 97°C oven overnight to allow for sufficient equilibrium, after which approximately 1 g of the upper phase and approximately 1 g of the lower phase were sampled in three separate samples and placed in aluminum cups. The aluminum cups were then placed in a 97°C oven for two hours to dry, and the draw solute concentrations of the upper and lower phases were calculated from the difference in mass before and after drying. The phase with the higher draw solute concentration was designated the concentrated phase, and the phase with the lower draw solute concentration was designated the dilute phase.

[0065] (Osmolarity evaluation) Aqueous solutions containing 60%, 80%, and 90% by mass of each draw solute were prepared, and approximately 1 mL of each was placed in a dedicated sample cup. The water activity was measured at 25°C using a water activity measuring device (AquaLab Series 4 TDL). Three to five measurements were performed, and the average value was used as the water activity measurement value. The osmotic pressure (bar) was calculated from the obtained water activity measurement value using a formula and unit conversion. Osmotic pressure (bar) = ((1 - [measured water activity] / 18.015) x 10 x 8.31 x (273.15 + [measurement temperature])

[0066] (Osmotic pressure of the dense layer) Based on the relationship between the concentration and the osmotic pressure, the osmotic pressure at the concentration of the thick layer obtained by the phase separation evaluation was estimated by linear interpolation.

[0067] (viscosity) Measurements were performed using an E-type viscometer (TVE-25L, manufactured by Toki Sangyo Co., Ltd.) at 25°C, a rotation speed of 1.0 rpm, 5.0 rpm, or 10.0 rpm, and a cone plate type of 1°×R24.

[0068] (Measurement of the Contents of the Compound of General Formula (2) and the Compound of General Formula (3)) The contents of the compounds of general formula (2) and general formula (3) in the draw solute were analyzed using an Agilent Technologies 1260 Infinity II LC-MS under the following conditions, and calculated based on the TIC area ratio. Eluent: 20 mM ammonium formate / acetonitrile (70:30 to 5:95) Column: Osaka Soda Capsule Core ADME (2.7 μm, 2.1 mm x 100 mm) Flow rate: 0.2~0.5mL / min Temperature: 40℃

[0069] [Table 1]

Claims

1. A draw solute containing a compound represented by the following general formula (1): 【Chemical 1】 [In general formula (1), R １ represents a residue obtained by removing all active hydrogens from an x-valent active hydrogen-containing compound having 3 or more carbon atoms, and R ２ represents a methyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an aryl group, or an acyl group; AO represents an ethylene oxide group, a propylene oxide group, or a butylene oxide group; x is an integer of 1 or more; and n is a number of 2 or more and 100 or less. However, multiple AOs may be the same or different.]

2. R ２ The draw solute of claim 1 , wherein is an acyl group.

3. The draw solute according to claim 1 , wherein the active hydrogen-containing compound is a monohydric aliphatic alcohol having 5 to 15 carbon atoms or a monohydric phenol having 6 to 12 carbon atoms.

4. The draw solute according to claim 1, wherein the number average molecular weight of the compound represented by the general formula (1) is 500 or more and 10,000 or less.

5. The draw solute according to claim 1, wherein the cloud point of a 50% by mass draw solution prepared by dissolving the draw solute in water is 30°C or higher and 90°C or lower.

6. 10. The draw solute of claim 1, wherein the viscosity of the draw solute at 25°C is 200 mPa·s or less.

7. The draw solute according to claim 1, further comprising a compound represented by the following general formula (2) in an amount of 0.1 ppm by mass or more and 100,000 ppm by mass or less, based on the total amount of the draw solute: 【Chemistry 2】 [In general formula (2), R １ , AO and x are R in general formula (1). １ , AO and x, and n1 represents a number of 1 or more and 100 or less.

8. The draw solute according to claim 1, further comprising a compound represented by the following general formula (3) in an amount of 0.1 ppm by mass or more and 100,000 ppm by mass or less, based on the total amount of the draw solute: 【Chemistry 3】 [In general formula (3), R ２ and AO is R in general formula (1). ２ and AO, and R ３ represents a hydroxy group or an acyloxy group, and n2 represents a number of 1 or more and 100 or less.

9. 2. The draw solute according to claim 1, further comprising at least one salt selected from the group consisting of sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium lactate, potassium lactate, sodium sulfate, and potassium sulfate in an amount of 0.1 ppm by mass or more and 50,000 ppm by mass or less, based on the total amount of the draw solute.

10. A draw solution comprising the draw solute of any one of claims 1 to 9.

11. A water treatment method using the draw solution of claim 10.

Images