Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/002—Forward osmosis or direct osmosis
  • B01D61/005—Osmotic agents; Draw solutions
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
  • C02F1/445—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by forward osmosis
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
  • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
  • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
  • C08G65/26—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring from cyclic ethers and other compounds

Definitions

• the present invention relates to a draw solute, a draw solution, and a water treatment method.
• Forward osmosis uses the phenomenon in which two solutions of different concentrations come into contact with each other via a semipermeable membrane, and the solvent moves from the side with lower osmotic pressure to the side with higher osmotic pressure, and can be used to separate the components of a solution.
• reverse osmosis which applies pressure against the osmotic pressure to the solution to force it through the membrane
• forward osmosis which uses osmotic pressure to perform membrane filtration, is easier to use in energy conservation, and is expected to be applied to water treatment such as seawater desalination and power generation.
• a solution (draw solution) with a higher osmotic pressure than the solution to be treated (target solution) is used to move the solvent (water) from the target solution to the draw solution through a semipermeable membrane.
• the draw solution After moving the solvent (water) from the target solution to the draw solution through a semipermeable membrane, it is necessary to recover the solvent from the draw solution. Therefore, the draw solution must have properties that allow the solvent to be easily separated, and various osmotic pressure inducers (draw solutes) for preparing such draw solutions have been investigated.
• Patent Document 1 proposes using a block copolymer that has a glycerin skeleton as the basic skeleton and contains an ethylene oxide group as the hydrophilic portion and a group consisting of propylene oxide and/or butylene oxide as the hydrophobic portion as a temperature-sensitive water absorbent (draw solute).
• Patent Document 2 proposes a draw solute for forward osmosis membrane processing that contains an addition polymer obtained by addition polymerization of an alkylene oxide having 2 to 10 carbon atoms to polyethyleneimine.
• the objective of the present invention is to provide a novel draw solute that can be suitably used in the forward osmosis membrane process, a draw solution containing such a draw solute, and a water treatment method using such a draw solution.
• a draw solute according to an embodiment of the present invention includes a polymer having a structure derived from an amine compound and at least one structure selected from the group consisting of an oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms and a substituted oxyethylene structure derived from a glycidyl ether compound.
• the structure derived from the amine compound may be represented by general formula (1a) or general formula (1b).
• R 1 and R 2 are organic groups which may contain heteroatoms, and R 1 and R 2 in general formula (1a) may form a ring structure.
• the notation "N-*” means the structure extending from the nitrogen atom to the end of the bond.
• the structure derived from the amine compound may be represented by general formula (1c).
• the notation "N-*” means the structure from the nitrogen atom to the end of the bond extending therefrom.
• the glycidyl ether compound may be represented by general formula (2), and the substituted oxyethylene structure derived from the glycidyl ether compound may be represented by general formula (3).
• R3 is an organic group and may contain a heteroatom.
• R3 is an organic group and may contain a heteroatom.
• the notation "C-*” means a structure from a carbon atom to the end of a bond extending therefrom, and the notation "O-*” means a structure from an oxygen atom to the end of a bond extending therefrom.
• the draw solute according to any one of [1] to [4] above may have a viscosity of 500 mPa ⁇ s or less at 25°C.
• a draw solution according to an embodiment of the present invention comprises a draw solute according to any one of [1] to [5] above.
• a water treatment method according to an embodiment of the present invention uses the draw solution described in [6] above.
• the present invention provides a novel draw solute that can be suitably used in the forward osmosis membrane process, a draw solution containing such a draw solute, and a water treatment method using such a draw solution.
• the draw solute according to the embodiment of the present invention includes a polymer having at least one structure selected from the group consisting of a structure derived from an amine compound, an oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms, and a substituted oxyethylene structure derived from a glycidyl ether compound.
• the polymer may be one type only, or two or more types.
• the polymer content in the draw solute according to an embodiment of the present invention is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, particularly preferably 95% by mass to 100% by mass, and most preferably 100% by mass.
• the draw solute according to the embodiment of the present invention may contain any suitable component other than the polymer as long as the effect of the present invention is not impaired.
• the number average molecular weight Mn of the polymer in the draw solute according to an embodiment of the present invention any appropriate number average molecular weight Mn may be adopted as long as it does not impair the effects of the present invention.
• the number average molecular weight Mn of the polymer in the draw solute according to an embodiment of the present invention is preferably 100 to 5000, more preferably 200 to 3000, even more preferably 300 to 2000, particularly preferably 400 to 1500, and most preferably 500 to 1000.
• a preferred embodiment of the structure derived from an amine compound is represented by general formula (1a) or general formula (1b).
• R 1 and R 2 are organic groups and may contain heteroatoms, and R 1 and R 2 in general formula (1a) may form a ring structure.
• heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, silicon atoms, and phosphorus atoms.
• R 1 and R 2 may be the same or different.
• R 1 and R 2 include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, 2-pentyl, 3-pentyl, neopentyl, hexyl, octyl, 2-ethylhexyl, nonyl, decyl, pentadecyl, cetyl, lauryl, stearyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and 1-adamantane; and aryl groups such as phenyl, benzyl, phenylpropyl, phenylbutyl, 1,1-dimethyl-2-phenylethyl, and 3,4-dimethylbenzyl.
• alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, 2-pentyl, 3-pentyl, neopentyl
• N-* refers to the structure extending from the nitrogen atom to the end of the bond. Therefore, * can be any appropriate group, but typically is a group having at least one structure selected from the group consisting of an oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms and a substituted oxyethylene structure derived from a glycidyl ether compound.
• N-* refers to the structure extending from the nitrogen atom to the end of the bond. Therefore, * can be any appropriate group, but as in general formulas (1a) and (1b), it is typically a group having at least one structure selected from the group consisting of an oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms and a substituted oxyethylene structure derived from a glycidyl ether compound.
• the oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms is a structure formed by adding an alkylene oxide having 2 to 20 carbon atoms to an amine compound, and is an oxyalkylene structure having 2 to 20 carbon atoms, preferably an oxyalkylene structure having 2 to 10 carbon atoms, more preferably an oxyalkylene structure having 2 to 8 carbon atoms, even more preferably an oxyalkylene structure having 2 to 6 carbon atoms, and particularly preferably an oxyalkylene structure having 2 to 4 carbon atoms.
• Representative examples of such oxyalkylene structures include, for example, an oxyethylene structure, an oxypropylene structure, and an oxybutylene structure.
• the glycidyl ether compound is preferably represented by the general formula (2).
• R3 is an organic group and may contain a heteroatom, such as an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, or a phosphorus atom.
• R3 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a 2-pentyl group, a 3-pentyl group, a neopentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a pentadecyl group, a cetyl group, a lauryl group, a stearyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a 1-adamantane group; and aryl groups such as a phenyl group, a benzyl group, a phenylpropyl group, a phenylbutyl group, a n
• the substituted oxyethylene structure derived from a glycidyl ether compound is preferably represented by the general formula (3).
• R3 is the same as R3 in formula (2).
• the notation "C-*” means the structure from the carbon atom to the end of the bond extending therefrom
• the notation "O-*” means the structure from the oxygen atom to the end of the bond extending therefrom.
• polymers included in the draw solute according to the present invention include: (Polymer of embodiment 1) An embodiment having a structure in which an alkylene oxide having 2 to 20 carbon atoms is added to an amine compound, (Polymer of embodiment 2) An embodiment having a structure in which a glycidyl ether compound is added to an amine compound, (Polymer of embodiment 3) An embodiment having a structure in which both an alkylene oxide having 2 to 20 carbon atoms and a glycidyl ether compound are added to an amine compound; Examples include:
• the polymer of embodiment 1 has a structure in which an oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms is repeatedly bonded to the nitrogen atom of the amino group in the amine compound in a single arrangement (when one type of alkylene oxide is used), a block arrangement, or a random arrangement (when two or more types of alkylene oxides are used).
• the polymer of embodiment 1 may have the above structure, and the method for producing it is not particularly limited.
• the number of repetitions of the oxyalkylene structure (average number of added moles) in the polymer of embodiment 1 is preferably 1 mole to 200 moles, more preferably 5 moles to 100 moles, even more preferably 5 moles to 80 moles, even more preferably 5 moles to 70 moles, even more preferably 5 moles to 60 moles, even more preferably 10 moles to 50 moles, particularly preferably 10 moles to 40 moles, and most preferably 10 moles to 30 moles, relative to 1 mole of nitrogen atoms contained in the amine compound, in terms of being able to further exert the effects of the present invention.
• the polymer of embodiment 2 has a structure in which a substituted oxyethylene structure derived from a glycidyl ether compound is bonded to the nitrogen atom of the amino group in the amine compound in a single arrangement (when one type of glycidyl ether compound is used), a block arrangement, or a random arrangement (when two or more types of glycidyl ether compounds are used).
• the polymer of embodiment 2 may have the above structure, and the method for producing it is not particularly limited.
• the number of repeats of the substituted oxyethylene structure (average number of moles added) in the polymer of embodiment 2 is preferably 1 mole to 100 moles per mole of nitrogen atoms contained in the amine compound, in order to further exert the effects of the present invention.
• both the oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms and the substituted oxyethylene structure derived from a glycidyl ether compound are bonded to the nitrogen atom of the amino group in the amine compound in a block arrangement or random arrangement.
• the oxyalkylene structure portion derived from an alkylene oxide having 2 to 20 carbon atoms has a structure bonded in a single arrangement (when one type of alkylene oxide is used), or in a block arrangement or random arrangement (when two or more types of alkylene oxides are used).
• the substituted oxyethylene structure derived from a glycidyl ether compound has a structure bonded in a single arrangement (when one type of glycidyl ether compound is used), or in a block arrangement or random arrangement (when two or more types of glycidyl ether compounds are used).
• the polymer of embodiment 3 may have the above-mentioned structure, and the method of production is not particularly limited.
• the number of repetitions (average number of added moles) of the oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms is preferably 1 to 200 moles, more preferably 3 to 100 moles, even more preferably 5 to 80 moles, particularly preferably 5 to 60 moles, and most preferably 5 to 40 moles, relative to 1 mole of nitrogen atoms contained in the amine compound, in order to further exert the effects of the present invention.
• the number of repeats (average number of moles added) of the substituted oxyethylene structure derived from the glycidyl ether compound is preferably 1 mole to 100 moles, more preferably 1 mole to 50 moles, even more preferably 1 mole to 30 moles, particularly preferably 1 mole to 20 moles, and most preferably 1 mole to 10 moles, relative to 1 mole of nitrogen atoms contained in the amine compound, in order to further exert the effects of the present invention.
• the polymer contained in the draw solute according to the embodiment of the present invention can be obtained by any suitable method as long as the effect of the present invention is not impaired.
• the polymer contained in the draw solute according to the embodiment of the present invention is obtained by adding at least one selected from the group consisting of alkylene oxides having 2 to 20 carbon atoms and glycidyl ether compounds to an amine compound.
• any appropriate amine compound can be adopted as long as the effects of the present invention are not impaired.
• the amine compound may be one type only or two or more types. Good too.
• amine compounds include alkanolamines, aliphatic amines, aromatic amines, and heterocyclic amines.
• alkanolamines examples include 2-aminoethanol, 2-methylaminoethanol, 2-ethylaminoethanol, 2-butylaminoethanol, 2-(hydroxymethylamino)ethanol, 2-(2-aminoethoxy)ethanol, 2-[(3-aminopropyl)amino]ethanol, 1-phenyl-2-aminoethanol, 1-phenyl-2-(N-methylamino)ethanol, 1-phenyl-2-(N-ethylamino)ethanol, 1-(3-hydroxyphenyl)-2-aminoethanol, 1-(4-hydroxyphenyl)-2-aminoethanol, and 1-(3,4-dihydroxyphenyl)-2-amino.
• Ethanol 1-(3-hydroxyphenyl)-2-(N-methylamino)ethanol, 1-(4-hydroxyphenyl)-2-(N-methylamino)ethanol, 1-(3,4-dihydroxyphenyl)-2-(N-methylamino)ethanol, N-(2-hydroxyethylamino)ethylenediamine, 2-(2-hydroxypropylamino)ethylamine, 2-(3-hydroxypropylamino)ethylamine, diethanolamine, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 3-amino-2-phenylpropanol, 1,3-diamino-2-propanol, 4-amino Monoalkanolamines such as butanol, 4-methylaminobutanol, 2-dimethylaminoethanol, 2-diethylaminoethanol, 2-dibutylaminoethanol, 1-dimethylamino-2-propano
• Aliphatic amines include, for example, aliphatic primary amines such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-pentylamine, 3-pentylamine, neopentylamine, hexylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, pentadecylamine, cetylamine, laurylamine, stearylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, and 1-adamantanamine; dimethylamine, ethylmethylamine, diethylamine, methylpropylamine, methylisopropylamine, ethylpropylamine, ethylisopropylamine, butylmethylamine, methyl t-butylamine, dipropylamine, di
• Aromatic amines include, for example, aromatic primary amines such as benzylamine, phenylpropylamine, phenylbutylamine, 1,1-dimethyl-2-phenylethylamine, 3,4-dimethylbenzylamine, aniline, methylaniline, ethylaniline, propylaniline, isopropylaniline, butylaniline, laurylaniline, stearylaniline, dimethylaniline, diethylaniline, methylbenzylamine, 4,4'-methylenedianiline, naphthylamine, trimethylaniline, and 4-methylphenethylamine; aromatic secondary amines such as methylbenzylamine, ethylbenzylamine, t-butylbenzylamine, diphenylamine, and dibenzylamine; and aromatic polyamines such as N-benzyl-1,3-propanediamine, 2,4,6-trimethyl-1,3-phenylenediamine,
• Heterocyclic amines include, for example, 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, and N-cyclohexylpiperidine.
• Examples 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, and 2-phenylindole.
• the amine compound is preferably an amino compound to which at least one selected from the group consisting of alkylene oxides having 2 to 20 carbon atoms and glycidyl ether compounds can be added.
• a preferred embodiment of the amine compound is represented by general formula (4a) or general formula (4b).
• the polymer contained in the draw solute according to the embodiment of the present invention typically has a structure derived from the amine compound represented by general formula (1a).
• the polymer contained in the draw solute according to the embodiment of the present invention typically has a structure derived from the amine compound represented by general formula (1b).
• R 1 and R 2 are organic groups and may contain heteroatoms, and R 1 and R 2 in general formula (1a) may form a ring structure.
• heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, silicon atoms, and phosphorus atoms.
• R 1 and R 2 may be the same or different.
• X 1 and X 2 are a hydrogen atom or -R 4 -OH, and X 1 and X 2 may be the same or different.
• R 4 is an alkylene group having 2 to 20 carbon atoms.
• R 4 is an alkylene group having 2 to 10 carbon atoms, more preferably an alkylene group having 2 to 8 carbon atoms, even more preferably an alkylene group having 2 to 6 carbon atoms, and particularly preferably an alkylene group having 2 to 4 carbon atoms.
• Specific examples of R 4 include an ethylene group, a propylene group, and a butylene group.
• the amine compound represented by the general formula (4a) is a monoalkanolamine, an aliphatic secondary amine, or an aromatic secondary amine. Examples of these include those mentioned above.
• the amine compound represented by the general formula (4b) is a dialkanolamine, an aliphatic primary amine, or an aromatic primary amine. Examples of these include those mentioned above.
• Another preferred embodiment of the amine compound is represented by the general formula (4c).
• the polymer contained in the draw solute according to the embodiment of the present invention typically has a structure derived from the amine compound represented by the general formula (1c).
• X 1 , X 2 and X 3 are a hydrogen atom or -R 4 -OH, and X 1 , X 2 and X 3 may be the same or different.
• R 4 is an alkylene group having 2 to 20 carbon atoms.
• R 4 is an alkylene group having 2 to 10 carbon atoms, more preferably an alkylene group having 2 to 8 carbon atoms, even more preferably an alkylene group having 2 to 6 carbon atoms, and particularly preferably an alkylene group having 2 to 4 carbon atoms.
• Specific examples of R 4 include an ethylene group, a propylene group, and a butylene group.
• the amine compound represented by the general formula (4c) is preferably a trialkanolamine. Examples of such an amine compound include those mentioned above.
• any suitable alkylene oxide may be used as long as it is within the range of 2 to 20 carbon atoms and does not impair the effects of the present invention.
• the alkylene oxide having 2 to 20 carbon atoms may be only one type, or may be two or more types.
• such an alkylene oxide having 2 to 20 carbon atoms is preferably an alkylene oxide having 2 to 10 carbon atoms, more preferably an alkylene oxide having 2 to 8 carbon atoms, even more preferably an alkylene oxide having 2 to 6 carbon atoms, and particularly preferably an alkylene oxide having 2 to 4 carbon atoms.
• Representative examples of alkylene oxides having 2 to 20 carbon atoms include, for example, ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO).
• the glycidyl ether compound is preferably represented by general formula (2).
• R3 is an organic group and may contain a heteroatom, such as an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, or a phosphorus atom.
• R3 include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a 2-pentyl group, a 3-pentyl group, a neopentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a pentadecyl group, a cetyl group, a lauryl group, a stearyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a 1-adamantane group; and aryl groups such as a phenyl group, a benzyl group, a phenylpropyl group, a phenylbutyl group, a n
• Any appropriate heating temperature may be used as long as it does not impair the effects of the present invention.
• Such a heating temperature is preferably 0°C to 200°C, more preferably 20°C to 180°C, and even more preferably 50°C to 150°C.
• a catalyst may be used during the addition reaction.
• catalysts include alkaline catalysts such as potassium hydroxide (KOH) and sodium hydroxide (NaOH).
• KOH potassium hydroxide
• NaOH sodium hydroxide
• the reaction can be carried out, for example, by adding the catalyst to the amine compound and then feeding at least one compound selected from the group consisting of alkylene oxides having 2 to 20 carbon atoms and glycidyl ether compounds into the reaction system.
• the amount of catalyst used is preferably 0% to 5.0% by mass, more preferably 0.1% to 3.0% by mass, relative to the amine compound.
• the reaction rate can be further increased by maturing the mixture for a predetermined period of time until it reacts sufficiently.
• Such maturing time is preferably 0.1 to 10 hours, and more preferably 1 to 5 hours.
• an acid such as acetic acid, lactic acid, or phosphoric acid may be added to neutralize the mixture.
• the amount of acid is preferably 0% to 10.0% by mass, and more preferably 0% to 5.0% by mass, based on the amine compound.
• a step of removing impurities may also be carried out. Methods for such removal include, for example, centrifugation, filtration, evaporation, and distillation.
• Light impurities can also be removed by heating under reduced pressure, preferably at 60°C to 200°C, and more preferably at 80°C to 150°C.
• the concentration of remaining light impurities (such as alkylene oxides and glycidyl ether compounds) is preferably 0% to 2% by mass, and more preferably 0% to 1% by mass.
• the draw solute is preferably stored under a nitrogen atmosphere, and an antioxidant may be added to improve stability. Any appropriate antioxidant may be used as the antioxidant as long as it does not impair the effects of the present invention.
• antioxidants suitable for addition to the draw solute include phenolic OH-containing compounds such as dibutylhydroxytoluene and butylhydroxyanisole; ascorbic acids such as ascorbic acid and its derivatives; tocopherols such as tocopherol and tocotrienol; erythorbic acids such as erythorbic acid and sodium erythorbate; 4,4'-bis( ⁇ , ⁇ -dimethylbenzyl)diphenylamine, 4-isopropylaminodiphenylamine, 4-[(4 -methyl-2-pentyl)amino]diphenylamine and other diphenylamine compounds; N,N'-di-sec-butyl-1,4-phenylenediamine, N,N'-diphenyl-1,4-
• the viscosity of the draw solute according to the embodiment of the present invention at 25°C is preferably 500 mPa ⁇ s or less, more preferably 400 mPa ⁇ s or less, even more preferably 300 mPa ⁇ s or less, even more preferably 280 mPa ⁇ s or less, particularly preferably 260 mPa ⁇ s or less, and most preferably 240 mPa ⁇ s or less.
• the lower limit of the above viscosity is preferably as small as possible, but in reality, it is, for example, 10 mPa ⁇ s or more.
• the draw solution according to the embodiment of the present invention may contain a solvent.
• the solvent may be appropriately selected depending on the conditions of the forward osmosis membrane method in which the draw solution is used.
• the solvent preferably, at least one selected from the group consisting of water, methanol, and ethanol can be used. It is more preferable that the solvent contains the same solvent as the solution to be treated (sometimes called the supply liquid).
• the draw solution according to the embodiment of the present invention may contain draw solutes (other draw solutes) other than the draw solute according to the embodiment of the present invention.
• the content of the other draw solutes is preferably 20 mass % or less of the total amount of draw solutes in the draw solution.
• the draw solution according to an embodiment of the present invention is preferably composed of a draw solute according to an embodiment of the present invention, an optional solvent, and any other draw solute, and more preferably composed of a draw solute according to an embodiment of the present invention and an optional solvent.
• the draw solution according to the embodiment of the present invention 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 due to a change in temperature, resulting in an opaque liquid.
• a draw solution having a cloud point can be heated to cause phase separation between the draw solute and the solvent.
• the cloud point of the draw solution can be adjusted appropriately by changing the composition of the draw solute according to the embodiment of the present invention, for example, the type of amine compound, the type and content ratio of the oxyalkylene structure derived from an alkylene oxide having 2 to 20 carbon atoms, the type and content ratio of the substituted oxyethylene structure derived from a glycidyl ether compound, etc. Therefore, a draw solution with an appropriate cloud point can be selected according to the application.
• the draw solution does not phase separate at a temperature around room temperature where the forward osmosis membrane treatment is performed, and that the draw solution phase separates at a temperature about the low-temperature exhaust heat of the factory.
• the suitable cloud point of the draw solution used for such applications varies depending on the concentration of the draw solute in the draw solution. For example, when the draw solute is made into a 50 mass% aqueous solution, the cloud point is preferably 20°C to 90°C, more preferably 30°C to 90°C.
• the forward osmosis membrane process can be continuously performed by repeating the following treatment.
• a feed solution is placed on one side of a semipermeable membrane and a draw solution is placed on the other side so that they are in contact with the semipermeable membrane, and the solvent is transferred from the feed solution side through the semipermeable membrane to the draw solution side.
• the reduced concentration draw solution is removed and heated to cause phase separation of the draw solute and the solvent.
• the phase-separated draw solute is again circulated 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.).
• NF membrane nanofiltration membrane
• the temperature at which the forward osmosis membrane method is carried out may be set to any appropriate temperature. Such a temperature is usually around room temperature, and for example, 5°C to 40°C is preferable.
• any suitable semipermeable membrane may be used as the semipermeable membrane for the forward osmosis membrane method.
• ⁇ Osmotic pressure evaluation> Aqueous solutions containing 40 mass%, 50 mass%, and 60 mass% of the obtained draw solute were prepared, and about 1 mL of each was taken in a dedicated sample cup, and the water activity at 25°C was measured using a water activity measuring device (AquaLab Series 4 TDL). The measurement was performed 3 to 5 times, and the average value was taken as the measured water activity value.
• ⁇ Water transport capacity evaluation> The water transport capacity was calculated according to the following formula.
• Water carrying capacity ⁇ Water passing mass>/ ⁇ Polymer mass>
• x 100 ( ⁇ Initial polymer concentration>- ⁇ Polymer concentration after water passage>)/( ⁇ Initial polymer concentration> ⁇ Polymer concentration after water passage>) ⁇ 10000
• initial polymer concentration refers to the concentration of the polymer-rich phase in the phase separation evaluation
• polymer concentration after water passing refers to the polymer concentration when the osmotic pressure becomes 48 bar, and was calculated by back-calculating from the correlation equation of the osmotic pressure at the polymer concentration
• the viscosity of the draw solute was measured using an E-type viscometer (TVE-25L, manufactured by Toki Sangyo Co., Ltd.) at 25° C., a rotation speed of 2.0 rpm, 2.5 rpm, or 4.0 rpm, and a cone plate type of 1° ⁇ R24.
• E-type viscometer (TVE-25L, manufactured by Toki Sangyo Co., Ltd.) at 25° C., a rotation speed of 2.0 rpm, 2.5 rpm, or 4.0 rpm, and a cone plate type of 1° ⁇ R24.
• Example 1 A 1 L autoclave was charged with 132.5 g of dibutylaminoethanol and 7.73 g of 48% KOH aqueous solution at room temperature, and then the pressure was reduced to 10 kPa absolute pressure 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 0.15 MPa, the bubbling was stopped and 370.4 g of ethylene oxide (hereinafter sometimes referred to as EO) was injected over 2 hours, and the mixture was then aged for 2 hours. 180.0 g of the obtained intermediate was charged into a separable glass flask at room temperature, and the gas phase was replaced with nitrogen gas.
• EO ethylene oxide
• the temperature was raised to 100° C., and then 41.1 g of phenyl glycidyl ether (hereinafter, sometimes referred to as PhGE) was added dropwise over 3 hours and the mixture was aged for 3 hours. After the temperature was lowered to 60° C., 4.5 g of 50% lactic acid was added to obtain a draw solute (1).
• the draw solute (1) had a structure in which EO and PhGE were added to dibutylamine, and EO and PhGE were arranged in a block sequence.
• the number of moles of EO added per mole of dibutylaminoethanol was 12, the number of moles of PhGE added per mole of dibutylaminoethanol was 1, and the number average molecular weight Mn was 800.
• Table 1 The results are shown in Table 1.
• Example 2 180.0 g of the intermediate obtained in Example 1 was charged into a separable glass flask at room temperature, and the gas phase was replaced with nitrogen gas. The temperature was raised to 100° C., and then 50.7 g of 2-ethylhexyl glycidyl ether (hereinafter, sometimes referred to as EHGE) was added dropwise over a period of 3 hours, followed by aging for 3 hours. After the temperature was lowered to 60° C., 4.5 g of 50% lactic acid was added to obtain a draw solute (2).
• EHGE 2-ethylhexyl glycidyl ether
• Draw solute (2) had a structure in which EO and EHGE were added to dibutylamine, EO and EHGE were arranged in a block sequence, the number of moles of EO added per mole of dibutylaminoethanol was 12, the number of moles of EHGE added per mole of dibutylaminoethanol was 1, and the number average molecular weight Mn was 850. The results are shown in Table 1.
• the draw solute (3) had a structure in which EO and BO were added to triethylamine, and EO and BO were arranged in a block sequence.
• the number of moles of EO added per mole of triethanolamine was 10
• the number of moles of BO added per mole of triethanolamine was 5
• the number average molecular weight Mn was 800. The results are shown in Table 1.
• Example 4 A 2L autoclave was charged with 149.7 g of triethanolamine and 1.0 g of 48% KOH aqueous solution at room temperature, and then the pressure was reduced to 10 kPa absolute pressure 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 0.2 MPa, the bubbling was stopped, and 751.3 g of EO and 426.8 g of BO were injected over 10 hours, followed by aging for 4 hours. After the temperature was lowered to 60° C., 0.56 g of 50% lactic acid was added to obtain a draw solute (4).
• the draw solute (4) had a structure in which EO and BO were added to triethylamine, and EO and BO were arranged randomly.
• the number of moles of EO added per mole of triethanolamine was 20, the number of moles of BO added per mole of triethanolamine was 6, and the number average molecular weight Mn was 1,300.
• the results are shown in Table 1.
• the draw solution containing the draw solute according to the embodiment of the present invention can be applied to various applications using the forward osmosis membrane method.
• water treatment devices and power generation devices are applications where the forward osmosis membrane method is expected to be used, and the draw solution containing the draw solute according to the embodiment of the present invention can be suitably used for these applications.

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