Osmotic pressure assisted reverse osmosis membrane device and aqueous solution concentration method

Abstract

Provided is an osmotic pressure-assisted reverse osmosis membrane device that can highly concentrate an aqueous solution to be treated stably and with a high recovery rate, even if the aqueous solution is highly concentrated. [Solution] An osmotically assisted reverse osmosis membrane device used for concentrating an aqueous solution, comprising: a first osmotically assisted reverse osmosis membrane module for concentrating the aqueous solution to obtain a first concentrate and a first dilution; a second osmotically assisted reverse osmosis membrane module for concentrating the first dilution to obtain a second concentrate and a second dilution; and a reverse osmosis membrane module for concentrating the second dilution to obtain a third concentrate and a permeate.

Description

[Technical Field]

[0001] The present disclosure relates to an osmotically assisted reverse osmosis membrane device and a method for concentrating an aqueous solution. [Background technology]

[0002] Conventionally, attempts have been made to concentrate wastewater containing solutes such as organic solvents and recover valuable materials, or to reduce industrial waste disposal costs.

[0003] For example, distillation, pervaporation, and the like are used to concentrate aqueous solutions. However, these concentration methods have the problem of large energy consumption due to the phase change involved. For example, when concentrating an aqueous solution containing an organic solvent with a higher boiling point than water, evaporation of water precedes evaporation in the distillation method. Therefore, the energy consumption required for concentration is particularly large.

[0004] Meanwhile, membrane filtration, which uses reverse osmosis (RO) membranes, is also known as a method for concentrating aqueous solutions. Membrane filtration allows for energy-saving concentration because there is no phase change in the aqueous solution. However, reverse osmosis (RO) membranes, for example, can only concentrate aqueous solutions to an osmotic pressure below the applied pressure, so there is a limit to how highly concentrated they can be.

[0005] Compared to the conventional RO method, the Osmotically Assisted Reverse Osmosis Method (OARO method) is known as a reverse osmosis membrane method that can concentrate an aqueous solution at a lower pressure (see Patent Document 1, etc.). The OARO method is a method in which, when concentrating an aqueous solution with a high osmotic pressure using an RO membrane, an aqueous solution with osmotic pressure is also passed through the permeate side, thereby reducing the osmotic pressure difference with the concentrate side (high-pressure side), and enabling concentration to a concentration with a higher osmotic pressure than the applied pressure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2019-504763 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, the OARO method is capable of concentrating aqueous solutions to a higher concentration than the conventional RO method.

[0008] To achieve high recovery rates and high concentration of aqueous solutions using the OARO method, the diluted solution discharged from the OARO system must be reconcentrated using RO membranes (e.g., conventional RO methods) and returned to the OARO system. Due to the nature of the OARO system, if the concentration of the raw aqueous solution is high (e.g., the solute concentration of the aqueous solution exceeds 10% by mass), the diluted solution discharged will also be similarly high, inevitably requiring high pressure for reconcentration using the RO membrane. For example, reconcentrating a diluted solution to a concentration of more than 15% requires high operating pressures of 10 MPa or more. This makes stable concentration of diluted solutions, especially those containing organic solvents, difficult using RO membranes. This is partly because the polymers that make up the membrane soften when exposed to organic solvents, causing the membrane's pores to collapse under high pressure.

[0009] The primary object of the present disclosure is to provide an osmotic pressure-assisted reverse osmosis membrane device that can stably concentrate an aqueous solution (raw solution) to be treated with high concentration and with high recovery rate, even if the aqueous solution is highly concentrated. Another object of the present disclosure is to provide a method for concentrating an aqueous solution using the osmotic pressure-assisted reverse osmosis membrane device. [Means for solving the problem]

[0010] The inventors of the present disclosure conducted extensive research to solve the above-mentioned problems, and as a result, they found that by providing an osmotic pressure-assisted reverse osmosis membrane device used for concentrating an aqueous solution with a first osmotic pressure-assisted reverse osmosis membrane module, a second osmotic pressure-assisted reverse osmosis membrane module, and a reverse osmosis membrane module so as to satisfy the following configuration, it is possible to re-concentrate the diluted solution discharged from the first osmotic pressure-assisted reverse osmosis membrane module to a high concentration (e.g., a solute concentration of the aqueous solution of more than 10 mass%) while maintaining a low pressure in the reverse osmosis membrane module (e.g., a pressure condition in the reverse osmosis membrane module of less than 7 MPa), and that even if the aqueous solution used as a raw solution has a high concentration (e.g., a solute concentration of the aqueous solution of more than 10 mass%), the aqueous solution can be concentrated stably and with a high recovery rate.

[0011] (Configuration of osmotic pressure assisted reverse osmosis membrane device) The first osmotically assisted reverse osmosis membrane module concentrates the aqueous solution to obtain a first concentrate and a first diluate. A second osmotically assisted reverse osmosis membrane module concentrates the first dilute solution to obtain a second concentrate and a second dilute solution. The reverse osmosis membrane module concentrates the second dilute solution to obtain a third concentrate and a permeate. In the first osmotically assisted reverse osmosis membrane module, the first diluent is a liquid discharged from the permeate side and supplied to the concentrate side and the permeate side of the reverse osmosis membrane of the second osmotically assisted reverse osmosis membrane module. The second concentrate obtained from the second osmotically assisted reverse osmosis membrane module is fed together with the aqueous solution to the concentrate side of the first osmotically assisted reverse osmosis membrane module. The second dilute solution obtained from the second osmotically assisted reverse osmosis membrane module is supplied to the reverse osmosis membrane module and separated into the third retentate and the permeate. The third concentrate obtained from the reverse osmosis membrane module is fed together with the first diluent to the concentrate side and the permeate side of the second osmotically assisted reverse osmosis membrane module.

[0012] The present disclosure has been completed based on these findings and further investigations. That is, the present disclosure provides the inventions of the following aspects. Item 1. An osmotic pressure-assisted reverse osmosis membrane device used for concentrating aqueous solutions, a first osmotically assisted reverse osmosis membrane module for concentrating the aqueous solution to obtain a first concentrate and a first diluent; a second osmotically assisted reverse osmosis membrane module for concentrating the first dilute solution to obtain a second concentrate and a second dilute solution; a reverse osmosis membrane module for concentrating the second dilution liquid to obtain a third concentrate and a permeate; Equipped with In the first osmotically-assisted reverse osmosis membrane module, the first diluent is a liquid discharged from the permeate side of the reverse osmosis membrane and is supplied to the concentrate side and the permeate side of the reverse osmosis membrane of the second osmotically-assisted reverse osmosis membrane module; the second concentrate obtained from the second osmotically-assisted reverse osmosis membrane module is supplied together with the aqueous solution to a concentrate side of the first osmotically-assisted reverse osmosis membrane module; The second dilute solution obtained from the second osmotically-assisted reverse osmosis membrane module is supplied to the reverse osmosis membrane module and separated into the third retentate and the permeate; The third concentrate obtained from the reverse osmosis membrane module is supplied together with the first diluent to a concentrate side and a permeate side of the second osmotic pressure-assisted reverse osmosis membrane module. Item 2. The osmotic pressure-assisted reverse osmosis membrane device according to Item 1, further comprising at least one of a pump and a pressure reducing valve between the concentrate side of the reverse osmosis membrane module and the second osmotic pressure-assisted reverse osmosis membrane module. Item 3. The osmotic pressure-assisted reverse osmosis membrane device according to Item 1 or 2, wherein the first osmotic pressure-assisted reverse osmosis membrane module includes a plurality of osmotic pressure-assisted reverse osmosis membrane modules. Item 4. The osmotic pressure-assisted reverse osmosis membrane device according to any one of Items 1 to 3, wherein the second osmotic pressure-assisted reverse osmosis membrane module includes a plurality of osmotic pressure-assisted reverse osmosis membrane modules. Item 5. The osmotic pressure-assisted reverse osmosis membrane device according to any one of Items 1 to 4, wherein the reverse osmosis membrane module includes a plurality of reverse osmosis membrane modules. Item 6. The osmotically-assisted reverse osmosis membrane device according to any one of Items 1 to 5, wherein the aqueous solution has a solute concentration of more than 10% by mass. Item 7. The osmotically-assisted reverse osmosis membrane device according to Item 6, wherein the solute comprises at least one selected from the group consisting of organic solvents, inorganic salts, sugars, amino acids, ionic liquids, and organic acids. Item 8. The osmotically-assisted reverse osmosis membrane device according to Item 7, wherein the boiling point of the organic solvent at 1 atmosphere is 105°C or higher. Item 9. The osmotic pressure-assisted reverse osmosis membrane device according to any one of Items 1 to 8, wherein concentration is performed in the first osmotic pressure-assisted reverse osmosis membrane module and the second osmotic pressure-assisted reverse osmosis membrane module at a pressure lower than 7 MPa. Item 10. The osmotic pressure-assisted reverse osmosis membrane device according to any one of Items 1 to 9, wherein in the second osmotic pressure-assisted reverse osmosis membrane module, the pressure applied to the concentrate side of the reverse osmosis membrane is 3 MPa or more and 7 MPa or less, and the pressure applied to the permeate side of the reverse osmosis membrane is 0.01 MPa or more and 3 MPa or less. Item 11. A method for concentrating an aqueous solution, comprising concentrating an aqueous solution using the osmotic pressure-assisted reverse osmosis membrane device according to any one of Items 1 to 10. [Effects of the Invention]

[0013] The present disclosure provides an osmotic pressure-assisted reverse osmosis membrane device that can stably concentrate an aqueous solution (raw solution) with a high recovery rate, even if the aqueous solution to be treated is highly concentrated. The present disclosure also provides a method for concentrating an aqueous solution using the osmotic pressure-assisted reverse osmosis membrane device. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of an osmotic pressure-assisted reverse osmosis membrane device according to the present disclosure. FIG. [Figure 2] 1 is a schematic diagram illustrating an example of the configuration of an osmotic pressure-assisted reverse osmosis membrane device according to the present disclosure. FIG. [Figure 3] FIG. 1 is a schematic diagram showing the configuration of an osmotic pressure-assisted reverse osmosis membrane device of Example 1. [Figure 4] FIG. 1 is a schematic diagram showing the configuration of an osmotic pressure-assisted reverse osmosis membrane device of Example 2. [Figure 5] 1 is a schematic diagram illustrating an example of the configuration of an osmotic pressure-assisted reverse osmosis membrane device according to the present disclosure. FIG. [Figure 6] 1 is a schematic diagram illustrating an example of the configuration of an osmotic pressure-assisted reverse osmosis membrane device according to the present disclosure. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] The osmotic pressure-assisted reverse osmosis membrane device of the present disclosure is an osmotic pressure-assisted reverse osmosis membrane device used for concentrating an aqueous solution, and includes a first osmotic pressure-assisted reverse osmosis membrane module, a second osmotic pressure-assisted reverse osmosis membrane module, and a reverse osmosis membrane module for concentrating the aqueous solution to obtain a first concentrate and a first diluent.

[0016] The first osmotically assisted reverse osmosis membrane module concentrates the first dilute solution to obtain a second retentate and a second dilute solution. The second osmotically assisted reverse osmosis membrane module concentrates the first dilute solution to obtain a second retentate and a second dilute solution. The reverse osmosis membrane module concentrates the second dilute solution to obtain a third retentate and a permeate.

[0017] In the first osmotically assisted reverse osmosis membrane module, the first diluate is a liquid discharged from the permeate side and is supplied to the concentrate side and permeate side of the reverse osmosis membrane of the second osmotically assisted reverse osmosis membrane module. The second concentrate obtained from the second osmotically assisted reverse osmosis membrane module is supplied, together with an aqueous solution, to the concentrate side of the first osmotically assisted reverse osmosis membrane module. The second diluate obtained from the second osmotically assisted reverse osmosis membrane module is supplied to the reverse osmosis membrane module and separated into a third concentrate and a permeate. The third concentrate obtained from the reverse osmosis membrane module is supplied, together with the first diluate, to the concentrate side and permeate side of the second osmotically assisted reverse osmosis membrane module.

[0018] The osmotic pressure-assisted reverse osmosis membrane device of the present disclosure having the above configuration can stably concentrate an aqueous solution (raw solution) to be treated with high concentration and with high recovery rate.

[0019] The osmotic pressure-assisted reverse osmosis membrane device of the present disclosure and a method for concentrating an aqueous solution using the osmotic pressure-assisted reverse osmosis membrane device will be described in detail below with reference to the drawings. Note that the osmotic pressure-assisted reverse osmosis membrane devices shown in Figures 1 to 4 are specific examples of the configuration of the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure, but the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure is not limited to this configuration.

[0020] In this specification, numerical values ​​connected with "~" mean a numerical range that includes the numerical values ​​before and after "~" as the lower and upper limits. When multiple lower limits and multiple upper limits are listed separately, any lower limit and upper limit can be selected and connected with "~".

[0021] 1 and 2 are schematic diagrams of an example of an osmotic pressure-assisted reverse osmosis membrane device according to the present disclosure. The osmotic pressure-assisted reverse osmosis membrane device includes at least a first osmotic pressure-assisted reverse osmosis membrane module 1, a second osmotic pressure-assisted reverse osmosis membrane module 2, and a reverse osmosis membrane module 3. In FIGS. 1 and 2, an aqueous solution 10 to be treated is fed to the first osmotic pressure-assisted reverse osmosis membrane module 1 using a high-pressure pump (feed pump). The first osmotic pressure-assisted reverse osmosis membrane module 1 is composed of at least one stage (one unit) of osmotic pressure-assisted reverse osmosis membrane modules, and the aqueous solution 10 to be treated is fed under pressure to one side (the concentrate side (concentrate chamber), also referred to as the high-pressure side) of the osmotic pressure-assisted reverse osmosis membrane module.

[0022] (First osmotic pressure-assisted reverse osmosis membrane module 1) The aqueous solution 10 to be treated is concentrated in the first osmotic pressure-assisted reverse osmosis membrane module 1, and the aqueous solution 10 to be treated that has passed through the first osmotic pressure-assisted reverse osmosis membrane module 1 is discharged as a first concentrate 11 from the concentrate-side outlet of the first osmotic pressure-assisted reverse osmosis membrane module 1. The first concentrate 11 is discharged to the outside of the system from the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure, but as described below, a portion of the first concentrate 11 can be supplied as a reflux liquid to the opposite side of the osmotic pressure-assisted reverse osmosis membrane (the permeate side (permeate chamber), also referred to as the low-pressure side) at a pressure lower than that on the concentrate side via a branch pipe.

[0023] 1 and 2, when the first osmotic pressure-assisted reverse osmosis membrane module 1 includes two or more stages (two or more) of osmotic pressure-assisted reverse osmosis membrane modules, the concentrate sides of the osmotic pressure-assisted reverse osmosis membrane modules are connected by piping. The concentrate sides of the osmotic pressure-assisted reverse osmosis membrane modules may be connected by piping in series or in parallel.

[0024] In the first osmotic pressure-assisted reverse osmosis membrane module 1, a portion of the first concentrate 11 can be supplied as a reflux liquid to the opposite side (permeate side, low-pressure side) of the osmotic pressure-assisted reverse osmosis membrane at a pressure lower than that of the concentrate side via a branch pipe. The liquid flowing through the permeate side of the first osmotic pressure-assisted reverse osmosis membrane module 1 is diluted with the permeate and discharged as a first diluent 12.

[0025] 1 and 2, the permeate sides of the osmotic pressure-assisted reverse osmosis membrane modules included in the first osmotic pressure-assisted reverse osmosis membrane module 1 are also connected by piping. The permeate sides of the osmotic pressure-assisted reverse osmosis membrane modules may also be connected by piping in series or in parallel.

[0026] 1 and 2, five osmotic pressure-assisted reverse osmosis membrane modules are connected in series (i.e., a five-stage configuration), but the number of osmotic pressure-assisted reverse osmosis membrane modules is not limited and can be adjusted within a range of, for example, about 2 to 50 modules (i.e., about 2 to 50 stages).From the viewpoint of optimally exerting the effects of the present invention, it is preferable that the first osmotic pressure-assisted reverse osmosis membrane module 1 include multiple osmotic pressure-assisted reverse osmosis membrane modules.

[0027] In order to more effectively exert the effects of the present invention, the flow rate of the aqueous solution 10 to be treated when being supplied to the first osmotic pressure-assisted reverse osmosis membrane module 1 is set to 1 / m2 / m3. 2 The flow rate is, for example, 5 mL / min or more, preferably 10 mL / min or more, more preferably 15 mL / min or more, and is, for example, 100 mL / min or less, preferably 80 mL / min or less, more preferably 70 mL / min or less, and preferred ranges include 5 to 100 mL / min, 5 to 80 mL / min, 5 to 70 mL / min, 10 to 100 mL / min, 10 to 80 mL / min, 10 to 70 mL / min, 15 to 100 mL / min, 15 to 80 mL / min, and 15 to 70 mL / min.

[0028] From the viewpoint of more suitably exerting the effects of the present invention, the concentration of solutes in the aqueous solution to be treated 10 supplied to the first osmotic pressure-assisted reverse osmosis membrane module 1 is not particularly limited, but is preferably less than 50% by mass, more preferably 40% by mass or less, even more preferably 30% by mass or less, and may be 20% by mass or less, 15% by mass or less, 10% by mass or less, or 5% by mass or less, and may also be preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and may be 5% by mass or more, 10% by mass or more, more than 10% by mass, 12% by mass or more, etc. Preferred ranges of the solute concentration in the aqueous solution 10 to be treated include 0.1 mass% or more and less than 50 mass%, 0.1 to 40 mass%, 0.1 to 30 mass%, 0.1 to 20 mass%, 0.1 to 15 mass%, 0.1 to 10 mass%, 0.1 to 5 mass%, 0.5 mass% or more and less than 50 mass%, 0.5 to 40 mass%, 0.5 to 30 mass%, 0.5 to 20 mass%, 0.5 to 15 mass%, 0.5 to 10 mass%, 0.5 to 5 mass%, 1 mass% or more and less than 50 mass%, 1 to 40 mass%, 1 to 30 mass%, 1 to 20 mass%, 1 to 15 mass%, 1 to 10 mass%, and 1 ~5 mass%, 5 mass% or more and less than 50 mass%, 5-40 mass%, 5-30 mass%, 5-20 mass%, 5-15 mass%, 5-10 mass%, 10 mass% or more and less than 50 mass%, 10-40 mass%, 10-30 mass%, 10-20 mass%, 10-15 mass%, more than 10 mass%5 Less than 0% by mass, more than 10% by mass and not more than 40% by mass, more than 10% by mass and not more than 30% by mass, more than 10% by mass and not more than 20% by mass, more than 10% by mass and not more than 15% by mass, 12% by mass or more and less than 50% by mass, 12-40% by mass, 12-30% by mass, 12-20% by mass, and 12-15% by mass.

[0029] Furthermore, in the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure, the pressure conditions when the first osmotic pressure-assisted reverse osmosis membrane module 1 performs concentration are, from the viewpoint of more suitably exerting the effects of the present disclosure, preferably 3 MPa or more, more preferably 3.5 MPa or more, even more preferably 4 MPa or more, and are preferably 9 MPa or less, more preferably 8 MPa or less, even more preferably 7 MPa or less, even more preferably 6 MPa or less, and preferred ranges include 3 to 9 MPa, 3 to 8 MPa, 3 to 7 MPa, 3 to 6 MPa, 3.5 to 9 MPa, 3.5 to 8 MPa, 3.5 to 7 MPa, 3.5 to 6 MPa, 4 to 9 MPa, 4 to 8 MPa, 4 to 7 MPa, and 4 to 6 MPa.

[0030] (Second osmotic pressure-assisted reverse osmosis membrane module 2) As shown in FIGS. 1 and 2, a first diluent 12 discharged from a first osmotically assisted reverse osmosis membrane module 1 is supplied to the concentrate and permeate sides of the reverse osmosis membrane of a second osmotically assisted reverse osmosis membrane module 2. FIG. 1 illustrates a configuration in which the first diluent 12 passes through a tank before being supplied to the second osmotically assisted reverse osmosis membrane module 2. FIG. 1 also illustrates a configuration in which the first diluent 12 is supplied to the concentrate side of the second osmotically assisted reverse osmosis membrane module 2 directly (without passing through a tank) through piping. FIG. 2 also illustrates a configuration in which the first diluent 12 is supplied to the second osmotically assisted reverse osmosis membrane module 2 directly (without passing through a tank) through piping. FIG. 2 also illustrates a configuration in which the first diluent 12 is supplied to the concentrate side of the second osmotically assisted reverse osmosis membrane module 2.

[0031] The first diluent 12 is concentrated on the concentrate side of the second osmotically assisted reverse osmosis membrane module 2 and is discharged as a second concentrate 21 from the concentrate side outlet of the second osmotically assisted reverse osmosis membrane module 2. The first diluent 12 is also supplied to the permeate side of the second osmotically assisted reverse osmosis membrane module 2 and is discharged as a second diluent 22 from the permeate side outlet of the second osmotically assisted reverse osmosis membrane module 2.

[0032] The second osmotic pressure-assisted reverse osmosis membrane module 2 may be configured with one stage (one module) of osmotic pressure-assisted reverse osmosis membrane modules, or may include two or more stages (two or more modules) of osmotic pressure-assisted reverse osmosis membrane modules. When two or more stages (two or more modules) of osmotic pressure-assisted reverse osmosis membrane modules are included, the concentrate sides of the osmotic pressure-assisted reverse osmosis membrane modules are connected by piping. The concentrate sides of the osmotic pressure-assisted reverse osmosis membrane modules may be connected in series or in parallel by piping.

[0033] 1 and 2, the second concentrate 21 obtained from the second osmotic pressure-assisted reverse osmosis membrane module 2 is supplied together with the aqueous solution 10 to be treated to the concentrate side of the first osmotic pressure-assisted reverse osmosis membrane module 1. As shown in FIGS. 1 and 2, a back pressure valve or the like can be installed between the concentrate side outlet of the second osmotic pressure-assisted reverse osmosis membrane module 2 and the piping that supplies the aqueous solution 10 to be treated to the first osmotic pressure-assisted reverse osmosis membrane module 1 to adjust the pressure.

[0034] 1 and 2, the second diluate 22 obtained from the second osmotically-assisted reverse osmosis membrane module 2 is supplied to the concentrate side of the reverse osmosis membrane module 3 and separated into a third concentrate 31 and a permeate 32. As described below, the third concentrate 31 is supplied to the concentrate side and permeate side of the second osmotically-assisted reverse osmosis membrane module 2 together with the first diluate 12. Meanwhile, the permeate 32 is discharged outside the system of the osmotically-assisted reverse osmosis membrane apparatus of the present disclosure. As shown in FIGS. 1 and 2, a high-pressure pump or the like can be installed between the permeate side outlet of the second osmotically-assisted reverse osmosis membrane module 2 and the concentrate side inlet of the reverse osmosis membrane module 3 for the second diluate 22 to adjust the pressure.

[0035] In the second osmotic pressure-assisted reverse osmosis membrane module 2, the liquid flowing on the permeate side is also diluted with the permeate and discharged as a second diluted liquid 22. When the second osmotic pressure-assisted reverse osmosis membrane module 2 includes two or more stages (two or more modules) of osmotic pressure-assisted reverse osmosis membrane modules, the permeate sides of the osmotic pressure-assisted reverse osmosis membrane modules are also connected by piping. The permeate sides of the osmotic pressure-assisted reverse osmosis membrane modules may also be connected by piping in series or in parallel.

[0036] 1 and 2, the second osmotic pressure-assisted reverse osmosis membrane module 2 has only one stage (one module) of osmotic pressure-assisted reverse osmosis membrane modules, but there is no limit to the number of osmotic pressure-assisted reverse osmosis membrane modules and it can be adjusted to, for example, a range of about 2 to 50 modules (i.e., about 2 to 50 stages).From the viewpoint of more suitably exhibiting the effects of the present disclosure, it is preferable that the second osmotic pressure-assisted reverse osmosis membrane module 2 has a plurality of osmotic pressure-assisted reverse osmosis membrane modules.

[0037] From the viewpoint of more suitably exerting the effects of the present invention, the flow rate when the second concentrate 21 is supplied from the concentrate side outlet of the second osmotic pressure-assisted reverse osmosis membrane module 2 to the first osmotic pressure-assisted reverse osmosis membrane module 1 is set to 1 / 2 m / s. 2 The flow rate is, for example, 5 mL / min or more, preferably 10 mL / min or more, more preferably 15 mL / min or more, and is, for example, 100 mL / min or less, preferably 80 mL / min or less, more preferably 70 mL / min or less, and preferred ranges include 5 to 100 mL / min, 5 to 80 mL / min, 5 to 70 mL / min, 10 to 100 mL / min, 10 to 80 mL / min, 10 to 70 mL / min, 15 to 100 mL / min, 15 to 80 mL / min, and 15 to 70 mL / min.

[0038] In order to more effectively exert the effects of the present invention, the flow rate of the second diluent 22 when it is supplied from the permeate side outlet of the second osmotic pressure-assisted reverse osmosis membrane module 2 to the concentrate side of the reverse osmosis membrane module 3 is set to 1 / 2 m / s. 2The flow rate is, for example, 5 mL / min or more, preferably 10 mL / min or more, more preferably 15 mL / min or more, and is, for example, 100 mL / min or less, preferably 80 mL / min or less, more preferably 70 mL / min or less, and preferred ranges include 5 to 100 mL / min, 5 to 80 mL / min, 5 to 70 mL / min, 10 to 100 mL / min, 10 to 80 mL / min, 10 to 70 mL / min, 15 to 100 mL / min, 15 to 80 mL / min, and 15 to 70 mL / min.

[0039] The concentration of the solute in the second concentrated liquid 21 is not particularly limited, but from the viewpoint of more suitably exerting the effects of the present disclosure, it is, for example, 0.1 mass% or more, preferably 0.5 mass% or more, more preferably 1 mass% or more, and for example, 40 mass% or less, preferably 35 mass% or less, more preferably 30 mass% or less. Preferred ranges include 0.1 to 40 mass%, 0.1 to 35 mass%, 0.1 to 30 mass%, 0.5 to 40 mass%, 0.5 to 35 mass%, and 0.5 to 30 mass%, and a particularly preferred concentration is approximately the same as that of the aqueous solution 10 to be treated.

[0040] Furthermore, the concentration of the solute in the second diluent 22 is not particularly limited, but from the viewpoint of more suitably exerting the effects of the invention of the present disclosure, it is, for example, 0.01 mass% or more, preferably 0.1 mass% or more, and more preferably 0.5 mass% or more, and for example, 30 mass% or less, preferably 25 mass% or less, and more preferably 20 mass% or less, and preferred ranges include 0.01 to 30 mass% or less, 0.01 to 25 mass% or less, 0.01 to 20 mass% or less, 0.1 to 30 mass% or less, 0.1 to 25 mass%, 0.1 to 20 mass% or less, 0.5 to 30 mass% or less, 0.5 to 25 mass%, and 0.5 to 20 mass% or less.

[0041] Furthermore, in the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure, the pressure conditions when the second osmotic pressure-assisted reverse osmosis membrane module 2 performs concentration are, from the viewpoint of more suitably exerting the effects of the present disclosure, preferably 3 MPa or more, more preferably 3.5 MPa or more, even more preferably 4 MPa or more, and are preferably 9 MPa or less, more preferably 8 MPa or less, even more preferably 7 MPa or less, even more preferably 6 MPa or less, and preferred ranges include 3 to 9 MPa, 3 to 8 MPa, 3 to 7 MPa, 3 to 6 MPa, 3.5 to 9 MPa, 3.5 to 8 MPa, 3.5 to 7 MPa, 3.5 to 6 MPa, 4 to 9 MPa, 4 to 8 MPa, 4 to 7 MPa, and 4 to 6 MPa.

[0042] More specifically, from the viewpoint of more suitably exerting the effects of the present invention, in the second osmotic pressure-assisted reverse osmosis membrane module 2, the pressure applied to the concentrate side of the reverse osmosis membrane is preferably 3 MPa or more, more preferably 3.5 MPa or more, even more preferably 4 MPa or more, and is preferably 7 MPa or less, more preferably 6.5 MPa or less, even more preferably 6 MPa or less, with preferred ranges being approximately 3 to 7 MPa, approximately 3.5 to 7 MPa, approximately 3 to 6 MPa, approximately 4 to 7 MPa, approximately 4 to 6.5 MPa, approximately 4 to 6 MPa, etc. In addition, in the second osmotic pressure-assisted reverse osmosis membrane module 2, the pressure applied to the permeate side of the reverse osmosis membrane is preferably 0.01 MPa or more, more preferably 0.05 MPa or more, and even more preferably 0.1 MPa or more, and is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1 MPa or less, with preferred ranges being approximately 0.01 to 3 MPa, approximately 0.01 to 2 MPa, approximately 0.01 to 1 MPa, approximately 0.05 to 3 MPa, approximately 0.05 to 2 MPa, approximately 0.05 to 1 MPa, approximately 0.1 to 3 MPa, approximately 0.1 to 2 MPa, approximately 0.1 to 1 MPa, etc.

[0043] (Reverse osmosis membrane module 3) 1 and 2, the second diluent 22 discharged from the second osmotically-assisted reverse osmosis membrane module 2 is supplied to the concentrate side of the reverse osmosis membrane of the reverse osmosis membrane module 3 and separated into a third concentrate 31 and a permeate 32. The third concentrate 31, together with the first diluent 12, is supplied to the concentrate side and the permeate side of the second osmotically-assisted reverse osmosis membrane module 2, and the permeate 32 is discharged outside the system of the osmotically-assisted reverse osmosis membrane apparatus of the present disclosure.

[0044] The reverse osmosis membrane module 3 may be configured with one reverse osmosis membrane module, or may include two or more reverse osmosis membrane modules. When two or more reverse osmosis membrane modules are included, the concentrate sides of the reverse osmosis membrane modules are connected by piping. The concentrate sides of the reverse osmosis membrane modules may be connected in series or in parallel by piping. The permeate sides of the reverse osmosis membrane modules are also connected by piping. The permeate sides of the reverse osmosis membrane modules may be connected in series or in parallel by piping.

[0045] As shown in FIGS. 1 and 2, the third concentrate 31 obtained from the reverse osmosis membrane module 3 is supplied, together with the first diluent 12, to the concentrate side and the permeate side of the second osmosis-assisted reverse osmosis membrane module 2. It is preferable to provide at least one of a pump and a pressure-reducing valve between the concentrate side of the reverse osmosis membrane module 3 and the second osmosis-assisted reverse osmosis membrane module 2. In FIG. 1, pumps (a high-pressure pump on the concentrate side of the second osmosis-assisted reverse osmosis membrane module 2 and a low-pressure pump on the permeate side) are provided between the concentrate side of the reverse osmosis membrane module 3 and the second osmosis-assisted reverse osmosis membrane module 2. Meanwhile, in FIG. 2, pressure-reducing valves (more specifically, a high-pressure pump on the concentrate side and a pressure-reducing valve on the permeate side of the second osmosis-assisted reverse osmosis membrane module 2) are provided between the concentrate side of the reverse osmosis membrane module 3 and the second osmosis-assisted reverse osmosis membrane module 2.

[0046] 1 and 2, the reverse osmosis membrane module 3 has only one stage (one module), but there is no limit to the number of reverse osmosis membrane modules and it can be adjusted within a range of, for example, about 2 to 50 modules (i.e., about 2 to 50 stages). From the viewpoint of more suitably exhibiting the effects of the present invention, it is preferable that the reverse osmosis membrane module 3 has a plurality of reverse osmosis membrane modules.

[0047] From the viewpoint of more suitably exerting the effects of the present invention, the flow rate of the third concentrated liquid 31 when being supplied from the concentrated liquid side outlet of the reverse osmosis membrane module 3 to the second osmotic pressure-assisted reverse osmosis membrane module 2 is set to 1 / 2 m / s. 2 The flow rate is, for example, 10 mL / min or more, preferably 20 mL / min or more, and more preferably 30 mL / min or more, and is, for example, 1000 mL / min or less, preferably 500 mL / min or less, and more preferably 300 mL / min or less, and preferred ranges include 10 to 1000 mL / min, 10 to 500 mL / min, 10 to 300 mL / min, 20 to 1000 mL / min, 20 to 500 mL / min, 20 to 300 mL / min, 30 to 1000 mL / min, 30 to 500 mL / min, and 30 to 300 mL / min.

[0048] In order to more effectively achieve the effects of the present invention, the flow rate of the permeate 32 when it is discharged from the permeate side of the reverse osmosis membrane module 3 is set to 1 / m2 / membrane area. 2 The flow rate is, for example, 5 mL / min or more, preferably 10 mL / min or more, more preferably 15 mL / min or more, and is, for example, 200 mL / min or less, preferably 100 mL / min or less, more preferably 70 mL / min or less, and preferred ranges include 5 to 200 mL / min, 5 to 100 mL / min, 5 to 70 mL / min, 10 to 200 mL / min, 10 to 100 mL / min, 10 to 70 mL / min, 15 to 200 mL / min, 15 to 100 mL / min, and 15 to 70 mL / min.

[0049] The concentration of the solute in the third concentrated liquid 31 is not particularly limited, but from the viewpoint of more suitably exerting the effects of the present disclosure, it is, for example, 0.1 mass% or more, preferably 0.5 mass% or more, more preferably 1 mass% or more, and for example, 40 mass% or less, preferably 35 mass% or less, more preferably 30 mass% or less, and preferred ranges include 0.1 to 40 mass%, 0.1 to 35 mass%, 0.1 to 30 mass%, 0.5 to 40 mass%, 0.5 to 35 mass%, 0.5 to 30 mass%, 1 to 40 mass%, 1 to 35 mass%, and 1 to 30 mass%.

[0050] Furthermore, the concentration of the solute in the permeate 32 is not particularly limited, but from the viewpoint of more suitably exerting the effects of the present disclosure, it is, for example, 5 mass % or less, preferably 3 mass % or less, and more preferably 1 mass % or less.

[0051] Furthermore, in the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure, the pressure conditions when the reverse osmosis membrane module 3 performs concentration are, from the viewpoint of more suitably exerting the effects of the present disclosure, preferably 3 MPa or more, more preferably 3.5 MPa or more, even more preferably 4 MPa or more, and are preferably 9 MPa or less, more preferably 8 MPa or less, even more preferably 7 MPa or less, even more preferably 6 MPa or less, and preferred ranges include 3 to 9 MPa, 3 to 8 MPa, 3 to 7 MPa, 3 to 6 MPa, 3.5 to 9 MPa, 3.5 to 8 MPa, 3.5 to 7 MPa, 3.5 to 6 MPa, 4 to 9 MPa, 4 to 8 MPa, 4 to 7 MPa, and 4 to 6 MPa.

[0052] In the osmotic pressure-assisted reverse osmosis membrane apparatus of the present disclosure, pressure adjustment means such as a pump or a pressure adjusting valve (back pressure valve) can be placed at any position in the piping between the connected osmotic pressure-assisted reverse osmosis membrane modules. For example, in the osmotic pressure-assisted reverse osmosis membrane apparatus of the present disclosure, the aqueous solution to be treated 10 is supplied to the first osmotic pressure-assisted reverse osmosis membrane module 1 using a pump. Furthermore, as described above, the second concentrate 21 obtained from the second osmotic pressure-assisted reverse osmosis membrane module 2 is merged with the aqueous solution to be treated 10 and supplied to the concentrate side of the first osmotic pressure-assisted reverse osmosis membrane module. Here, in FIGS. 1 and 2 , a pump is installed at a position after the aqueous solution to be treated 10 and the second concentrate 21 are merged, and these are supplied to the first osmotic pressure-assisted reverse osmosis membrane module 1. In this case, a back pressure valve is provided at the concentrate side outlet of the second osmotic pressure-assisted reverse osmosis membrane module 2. On the other hand, for example, as shown in Figures 5 and 6, if a pump for pumping the aqueous solution 10 to be treated is installed before the position (confluence) where the aqueous solution 10 to be treated and the second concentrated solution 21 are joined (i.e., on the opposite side from the first osmotic pressure-assisted reverse osmosis membrane module 1), the back pressure valve at the concentrated solution side outlet of the second osmotic pressure-assisted reverse osmosis membrane module 2 shown in Figures 1 and 2 will not be necessary and the flow rate of the pump can be reduced, which is advantageous from the perspective of energy conservation.

[0053] Furthermore, as shown in Figures 1 and 2, pressure gauges and flow meters are placed at various locations to enable confirmation of the pressure conditions and flow rate of the osmotic pressure-assisted reverse osmosis membrane device.

[0054] In the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure, the solute contained in the aqueous solution 10 to be treated is not particularly limited as long as the effects of the present invention are achieved, and examples thereof include organic solvents, inorganic salts, sugars, amino acids, ionic liquids, organic acids, etc. The aqueous solution 10 to be treated may contain only one type of solute, or two or more types of solutes.

[0055] The organic solvent is not particularly limited as long as it can be concentrated by an osmotic pressure-assisted reverse osmosis membrane device. The osmotic pressure-assisted reverse osmosis membrane device of the present disclosure is particularly suitable for concentrating, for example, an aqueous solution of an organic solvent having a boiling point higher than that of water. The boiling point of the organic solvent contained in the water to be treated at 1 atmosphere is preferably 105°C or higher, more preferably 110°C or higher, and even more preferably 115°C or higher, and is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 230°C or lower. Preferred ranges include approximately 105 to 300°C, 105 to 250°C, 105 to 230°C, 110 to 300°C, 110 to 250°C, 110 to 230°C, 115 to 300°C, 115 to 250°C, and 115 to 230°C.

[0056] Specific examples of suitable organic solvents include water-soluble organic solvents such as ethanol, isopropanol, ethylene glycol, and glycerol, alcohols having 2 to 6 carbon atoms; acetic acid, propionic acid, and other carboxylic acids; acetonitrile, dioxane, tetrahydrofuran, and acetone; and high-boiling water-soluble organic solvents such as N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). Other examples of suitable organic solvents include organic ionic liquids that are liquid at room temperature and water-soluble, such as choline glycolate; nonionic surfactants such as Pluronic, a copolymer of ethylene oxide and propylene oxide; and water-soluble polymers such as polyethylene glycol. The aqueous solution 10 to be treated may contain one or more types of organic solvents.

[0057] Specific examples of inorganic salts include water-soluble salts such as sodium chloride, potassium chloride, magnesium chloride, magnesium sulfate, and calcium chloride. Specific examples of sugars include monosaccharides such as glucose, fructose, and galactose, disaccharides such as sucrose, maltose, and lactose, and polysaccharides such as amylose and water-soluble starch. Specific examples of amino acids include monomeric amino acids such as arginine, serine, threonine, alanine, cysteine, glycine, and glutamine, as well as oligopeptides thereof. Specific examples of ionic liquids include 1-ethyl-3-methylimidazolium bromide, 1-ethylpyridinium tetrafluoroborate, trimethylpropylammonium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-methylpyrrolidinium hexafluorophosphate, and tetrabutylphosphonium hexafluorophosphate. Specific examples of organic acids include acetic acid, propionic acid, citric acid, malic acid, maleic acid, and ascorbic acid. The aqueous solution 10 to be treated may contain only one type of inorganic salts, sugars, amino acids, ionic liquids, and organic acids, or two or more types of inorganic salts, sugars, amino acids, ionic liquids, and organic acids.

[0058] In the first osmotic pressure-assisted reverse osmosis membrane module 1 and the second osmotic pressure-assisted reverse osmosis membrane module 2, the osmotic pressure-assisted reverse osmosis membrane used in each osmotic pressure-assisted reverse osmosis membrane module is not particularly limited as long as it is an osmotic pressure-assisted reverse osmosis membrane that can be applied to the osmotic pressure-assisted reverse osmosis membrane module of the present disclosure and used to concentrate solutes, and can be appropriately selected depending on the type of solute. The osmotic pressure-assisted reverse osmosis membrane is preferably a hollow fiber membrane. For example, an osmotic pressure-assisted reverse osmosis membrane used to concentrate solutes containing organic solvents is made of a polymer selected from cellulose acetate, polyamide, and the like. An example of a commercially available osmotic pressure-assisted reverse osmosis membrane is the BC (Brine Concentration) membrane from Toyobo MC Co., Ltd. For example, the BC membrane is made of cellulose triacetate.

[0059] The reverse osmosis membrane used in the reverse osmosis membrane module 3 is not particularly limited as long as it can be applied to the osmotic pressure-assisted reverse osmosis membrane module of the present disclosure and used to concentrate solutes, and can be appropriately selected depending on the type of solute. The reverse osmosis membrane may be a hollow fiber membrane or a flat membrane. For example, a reverse osmosis membrane used to concentrate solutes containing organic solvents is made of a polymer selected from cellulose acetate, polyamide, and the like. An example of a commercially available reverse osmosis membrane of this type is the SWC4 membrane manufactured by Nitto Denko Corporation. For example, the material of the separation active layer of the SWC4 membrane is polyamide.

[0060] The concentration of the solute in the first concentrated liquid 11 discharged from the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure to the outside of the system is not particularly limited, and is, for example, 30% by mass or more, preferably 40% by mass or more, and more preferably 45% by mass or more, and is, for example, 70% by mass or less, preferably 65% ​​by mass or less, and more preferably 60% by mass or less. Preferred ranges include 30 to 70% by mass, 30 to 65% by mass, 30 to 60% by mass, 40 to 70% by mass, 40 to 65% by mass, 40 to 60% by mass, 45 to 70% by mass, 45 to 65% by mass, and 45 to 60% by mass.

[0061] During the initial operation of the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure (e.g., up to about three hours), the solute concentration of the first concentrate 11 tends to be low, but if operation is continued for, for example, four hours or more, preferably one day or more, two days or more, or even three days or more, the solute concentration of the discharged concentrate can be stably maintained at the above-mentioned high concentration for an extended period of time. That is, the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure can be continuously operated for, for example, one day or more, two days or more, three days or more, five days or more, seven days or more, or even ten days or more while discharging a concentrate of such a high concentration (e.g., 30% by mass or more, preferably 40% by mass or more, more preferably 45% by mass or more).

[0062] For example, the osmotic pressure-assisted reverse osmosis membrane device of the present disclosure can be used to realize a method for concentrating an aqueous solution, which is the aqueous solution 10 to be treated described above. [Example]

[0063] The present disclosure will be explained in more detail below by showing examples, but the present disclosure is not limited to these examples.

[0064] [Example 1] An aqueous solution 10 to be treated (aqueous organic solvent solution) was concentrated using an osmotic pressure-assisted reverse osmosis apparatus having the configuration shown in the schematic diagram of Figure 3. The osmotic pressure-assisted reverse osmosis membrane module used was a cellulose triacetate hollow fiber membrane module (HOLLOSEP® Mini BC membrane module manufactured by Toyobo MC Co., Ltd., membrane area 1.1 m). 2 ) was used. This membrane can withstand a pressure of 7 MPa in aqueous liquids such as saline. Five of these were connected in series to form a five-stage first osmotic pressure-assisted reverse osmosis membrane module 1. The second osmotic pressure-assisted reverse osmosis membrane module 2 was composed of only one of these osmotic pressure-assisted reverse osmosis membrane modules.

[0065] A 15 wt% DMF aqueous solution (10) to be treated was pumped to the concentrate side of the first osmotically-assisted reverse osmosis membrane module 1 at a flow rate of 40 mL / min and an operating pressure of 6 MPa. Half of the concentrate discharged from the final (fifth-stage) osmotically-assisted reverse osmosis membrane module of the first osmotically-assisted reverse osmosis membrane module 1 was returned to the permeate side of the final OARO membrane module via a flow control valve. The first diluent discharged from the diluent outlet on the permeate side of the first-stage osmotically-assisted reverse osmosis membrane module was collected in a tank and pumped from this tank to the concentrate side of the second osmotically-assisted reverse osmosis membrane module 2 using a high-pressure pump at an operating pressure of 4 MPa and a flow rate of 38.8 mL / min (steady state). The permeate side was pumped to the concentrate side using a low-pressure pump at an operating pressure of 0.2 MPa and a flow rate of 20.9 mL / min (steady state). The second dilution solution 22 obtained from the permeate side of the second osmotically-assisted reverse osmosis membrane module 2 was pumped to a reverse osmosis membrane module 3 (SWC4, manufactured by Nitto Denko Corporation) at an operating pressure of 6 MPa. The resulting third concentrate was collected in the tank, and the permeate 32 was discharged outside the system. When the DMF concentration of the solution discharged from the concentrate side of the second osmotically-assisted reverse osmosis membrane module 2 reached 15 wt%, it was mixed with the aqueous solution 10 to be treated, and the resulting mixture was pumped to the concentrate side of the first osmotically-assisted reverse osmosis membrane module 1 at a flow rate of 40 mL / min and an operating pressure of 6 MPa. Under these conditions, the flow rate and concentration reached steady states four hours after the start of operation. The feed rate of the 15 wt% DMF aqueous solution supplied from outside the system became constant at 10.2 mL / min. The first concentrate 11 discharged from the first osmotically-assisted reverse osmosis membrane module 1 had a DMF concentration of 40 wt% and a flow rate of 3.7 mL / min. On the other hand, the DMF concentration of the liquid discharged from the system as permeate 32 from the reverse osmosis membrane module 3 was 0.8 wt %, and the liquid volume was 6.5 mL / min. Therefore, it was confirmed that the 15 wt % DMF aqueous solution can be continuously concentrated to 40 wt % DMF with a yield of 97 wt % using the apparatus shown in Figure 1.

[0066] [Example 2] An aqueous solution 10 to be treated (aqueous organic solvent solution) was concentrated using an osmotic pressure-assisted reverse osmosis apparatus having the configuration shown in the schematic diagram of Figure 4. As in Example 1, a cellulose triacetate hollow fiber membrane module (HOLLOSEP® Mini BC membrane module manufactured by Toyobo MC Co., Ltd., membrane area 1.1 m) was used as the osmotic pressure-assisted reverse osmosis membrane module. 2 ) was used. This membrane can withstand a pressure of 7 MPa in aqueous liquids such as saline. Five of these were connected in series to form a five-stage first osmotic pressure-assisted reverse osmosis membrane module 1. The second osmotic pressure-assisted reverse osmosis membrane module 2 was composed of only one of these osmotic pressure-assisted reverse osmosis membrane modules.

[0067] In Example 2, the first diluent 12 discharged from the diluent outlet on the permeate side of the first-stage osmotic pressure-assisted reverse osmosis membrane module of the first osmotic pressure-assisted reverse osmosis membrane module 1 was branched into two. One was sent to the concentrate side of the second osmotic pressure-assisted reverse osmosis membrane module 2 using a high-pressure pump at an operating pressure of 4 MPa and a flow rate of 23.6 mL / min. The other was sent to the permeate side of the second osmotic pressure-assisted reverse osmosis membrane module 2 at a flow rate of 12.7 mL / min without pressure. The second diluent 22 obtained from the permeate side of the second osmotic pressure-assisted reverse osmosis membrane module 2 was sent to a reverse osmosis membrane module 3 (SWC4, manufactured by Nitto Denko Corporation) at an operating pressure of 6 MPa. The resulting third concentrate 31 was branched into two. One was sent to the concentrate side of the second OARO membrane module at a flow rate of 15.3 mL / min while maintaining pressure. The other half was sent via a pressure reducing valve at a pressure of 0.2 MPa and a flow rate of 8.2 mL / min to the permeate side of the second osmotically assisted reverse osmosis membrane module 2. When the DMF concentration of the second concentrate 21 discharged from the concentrate side of the second osmotically assisted reverse osmosis membrane module 2 reached 15 wt%, this was mixed with the aqueous solution 10 to be treated, and the resulting mixture was sent to the concentrate side of the first osmotically assisted reverse osmosis membrane module 1 at a flow rate of 40 mL / min and an operating pressure of 6 MPa. Under these conditions, four hours after the start of operation, both the flow rate and concentration reached steady states, the feed rate of the 15 wt% DMF aqueous solution supplied from outside the system became constant at 10.2 mL / min, and the first concentrate 11 discharged from the first osmotically assisted reverse osmosis membrane module 1 to the outside of the system had a DMF concentration of 40 wt% and a flow rate of 3.7 mL / min. On the other hand, the DMF concentration of the liquid discharged from the reverse osmosis membrane module 3 to the outside of the system as permeate 32 was 0.8 wt%, and the liquid volume was 6.5 mL / min. Therefore, it was confirmed that the apparatus shown in Figure 2 can also continuously concentrate a 15 wt% DMF aqueous solution to 40 wt% DMF with a yield of 97 wt%. [Explanation of symbols]

[0068] 1. First osmotic pressure-assisted reverse osmosis membrane module 2. Second osmotic pressure-assisted reverse osmosis membrane module 3. Reverse osmosis membrane module 10. Aqueous solution to be treated 11 First Concentrate 12 First Dilution 21 Second Concentrate 22 Second Dilution 31 Third Concentrate 32 Permeate

Claims

1. 1. An osmotically assisted reverse osmosis membrane device used for concentrating an aqueous solution, comprising: a first osmotically assisted reverse osmosis membrane module for concentrating the aqueous solution to obtain a first concentrate and a first diluent; a second osmotically assisted reverse osmosis membrane module for concentrating the first dilute solution to obtain a second concentrate and a second dilute solution; a reverse osmosis membrane module for concentrating the second dilution liquid to obtain a third concentrate and a permeate; Equipped with In the first osmotically-assisted reverse osmosis membrane module, the first dilution liquid is a liquid discharged from a permeate side of a reverse osmosis membrane and is supplied to a concentrate side and a permeate side of a reverse osmosis membrane of the second osmotically-assisted reverse osmosis membrane module; the second concentrate obtained from the second osmotically-assisted reverse osmosis membrane module is supplied together with the aqueous solution to a concentrate side of the first osmotically-assisted reverse osmosis membrane module; The second dilute solution obtained from the second osmotically-assisted reverse osmosis membrane module is supplied to the reverse osmosis membrane module and separated into the third concentrate and the permeate; the third concentrate obtained from the reverse osmosis membrane module is supplied together with the first diluent to a concentrate side and a permeate side of the second osmotically assisted reverse osmosis membrane module.

2. 2. The osmotically assisted reverse osmosis membrane device according to claim 1, further comprising at least one of a pump and a pressure reducing valve disposed between the concentrate side of the reverse osmosis membrane module and the second osmotically assisted reverse osmosis membrane module.

3. The osmotically assisted reverse osmosis membrane device of claim 1 or 2, wherein the first osmotically assisted reverse osmosis membrane module includes a plurality of osmotically assisted reverse osmosis membrane modules.

4. 3. The osmotically assisted reverse osmosis membrane apparatus of claim 1, wherein the second osmotically assisted reverse osmosis membrane module comprises a plurality of osmotically assisted reverse osmosis membrane modules.

5. The osmotically assisted reverse osmosis membrane device according to claim 1 or 2, wherein the reverse osmosis membrane module includes a plurality of reverse osmosis membrane modules.

6. 3. The osmotically-assisted reverse osmosis membrane device of claim 1, wherein the aqueous solution has a solute concentration of more than 10% by weight.

7. 7. The osmotically-assisted reverse osmosis membrane device of claim 6, wherein the solute comprises at least one selected from the group consisting of organic solvents, inorganic salts, sugars, amino acids, ionic liquids, and organic acids.

8. 8. The osmotically-assisted reverse osmosis membrane device according to claim 7, wherein the organic solvent has a boiling point of 105°C or higher at 1 atmospheric pressure.

9. 3. The osmotic pressure-assisted reverse osmosis membrane device according to claim 1, wherein concentration is performed in the first osmotic pressure-assisted reverse osmosis membrane module and the second osmotic pressure-assisted reverse osmosis membrane module under a pressure condition lower than 7 MPa.

10. 3. The osmotic pressure-assisted reverse osmosis membrane device according to claim 1, wherein the pressure applied to the concentrate side of the reverse osmosis membrane of the second osmotic pressure-assisted reverse osmosis membrane module is 3 MPa or more and 7 MPa or less, and the pressure applied to the permeate side of the reverse osmosis membrane is 0.01 MPa or more and 3 MPa or less.

11. A method for concentrating an aqueous solution, comprising concentrating an aqueous solution using the osmotic pressure-assisted reverse osmosis membrane device according to claim 1 or 2.

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