Method for producing separation / concentration product of volatile substance, and system for producing separation / concentration product of volatile substance

Abstract

[Problem] The purpose of the present invention is to provide a method and a system which are for producing a separation / concentration product of a volatile substance, and which are capable of concentrating the volatile substance to a high concentration and suppressing energy consumption and material consumption by using a small-sized apparatus. [Solution] This method for producing a separation / concentration product of a volatile substance is for concentrating an aqueous solution containing a volatile substance or for isolating the volatile substance, and is characterized by comprising the following steps. The method is characterized in that the volatile substance is selectively adsorbed in the following adsorption step and / or the volatile substance is selectively desorbed in the following desorption step. Step 1: Vaporization step Step 2: Adsorption step Step 3: Desorption step

Description

Method for producing separated and concentrated volatile substances and system for producing separated and concentrated volatile substances

[0001] The present invention relates to a method and system for concentrating and separating volatile substances from an aqueous solution containing volatile substances to produce a highly concentrated aqueous solution of volatile substances or a highly pure volatile substance.

[0002] Treatment of aqueous solutions of volatile and water-soluble substances such as ammonia and methanol, or the recovery of these substances, has been a long-standing challenge. For the purpose of treatment, i.e., detoxification, methods such as the conventional activated sludge process, combustion, and catalytic decomposition are utilized. The conventional activated sludge process utilizes biological activity, so the aqueous solution must contain an appropriate ratio of carbon and nitrogen. Therefore, it is difficult to use it when the aqueous solution is mostly ammonia or mostly methanol. On the other hand, combustion and catalytic decomposition methods require the substance to be vaporized before treatment, but the water must also be vaporized at the same time, which requires a great deal of energy.

[0003] On the other hand, there are efforts to recover and recycle these volatile substances as valuable resources by concentrating or purifying them. For example, distillation is used. However, in the case of substances such as ammonia and methanol that are water-soluble and have boiling points not significantly different from that of water, multi-stage processing is required, which poses challenges such as large equipment size and large energy losses.

[0004] The most well-known method for concentrating aqueous ammonia, a volatile substance, is the ammonia stripping method. In this method, the pH of an aqueous ammonia-containing solution is adjusted to make it alkaline, and then the temperature is raised and the solution is brought into contact with a gas phase, thereby preferentially evaporating the ammonia. For example, the evaporated ammonia can be brought into contact with an aqueous sulfuric acid solution to produce aqueous ammonium sulfate, which can then be evaporated to dryness to obtain ammonium sulfate.

[0005] Membrane distillation can also be used to concentrate volatile substances. This method uses a hydrophobic separation membrane, contacting one side of the membrane with an aqueous solution and allowing it to evaporate on the other side, thereby concentrating the volatile substance. For example, it has been reported that a 4% aqueous solution of ammonia can be concentrated to 20% or more (Non-Patent Document 1).

[0006] Another method that has been studied is a liquid-phase concentration method using an adsorbent. For example, Patent Document 1 discloses a method in which a metal cyano complex is used as an adsorbent to adsorb ammonium ions in a liquid phase from a system containing coexisting substances by ion exchange, and an aqueous solution of ammonium chloride is recovered by washing with an aqueous potassium chloride solution.

[0007] Furthermore, methods that combine membrane distillation and adsorption have also been proposed (Patent Documents 2, 3, and 4).

[0008] Patent No. 6970406 Specification JP 2019-107646 A Special Publication No. 2021-513457 Special Publication No. 2015-535301

[0009] Concentration and resource recovery technology for ammonia in water, Hideto Matsuyama, 2nd Nitrogen Cycle Symposium "Global issues related to the nitrogen cycle and efforts in Japan", https: / / www.n-cycle.jp / events / symposium20221121 / Hideto Matsuyama's presentation material, p. 11

[0010] However, the above methods have both advantages and disadvantages. The ammonia stripping method requires heating all of the water before concentration, which requires a significant amount of energy. Another issue is the large size of the equipment. The membrane distillation method described in Non-Patent Document 1 consumes less energy than the ammonia stripping method because it can vaporize volatile substances without heating. However, the evaporation of water still requires energy for the heat of vaporization. In particular, when the concentration of volatile substances in an aqueous solution is low, the amount of water vaporized relative to the target volatile substance increases, increasing the energy requirement and making it difficult to increase the concentration after concentration. Furthermore, high-concentration concentration of salt or pure ammonia requires further processes such as evaporation to dryness after ammonia stripping and membrane distillation, which requires additional energy. The method using an adsorbent described in Patent Document 1 has issues such as the need for potassium chloride as a chemical agent, the need to solidify the concentrated solution using further distillation operations to obtain solid salt, which requires energy, and the inability to obtain ammonia other than salt. Furthermore, the method combining membrane distillation and adsorption involves removing impurities by adsorption as a pre- or post-treatment of membrane distillation, but does not solve the above-mentioned energy consumption issue.

[0011] Thus, efficient concentration of volatile substances requires a method for reducing energy consumption by suppressing water evaporation. In particular, a material that can selectively adsorb or vaporize volatile substances, even when the concentration of volatile substances in raw water is low, is required. In light of this, the present invention aims to provide a method and system for producing separated and concentrated volatile substances that enables concentration of volatile substances to high concentrations and reduces energy and material consumption with a compact device.

[0012] As a result of extensive investigation, the inventors have discovered a method for solving these problems by combining a gas sweep membrane distillation method with an adsorbent that selectively adsorbs and desorbs volatile substances.

[0013] The present invention has been completed based on these findings, and provides the following means according to the present invention.

[0014] (1) A method for concentrating an aqueous solution containing a volatile substance or isolating the volatile substance, comprising the following steps, and for producing a separated and concentrated product of the volatile substance, characterized in that the volatile substance is selectively adsorbed in an adsorption step described below and / or the volatile substance is selectively desorbed in a desorption step described below: Step 1. A step of contacting an aqueous solution containing the volatile substance with a water-impermeable but gas-permeable membrane on one side thereof, which is the liquid phase side, and allowing the vaporized volatile substance and water vapor to permeate the other side of the membrane to the gas phase side, thereby obtaining a mixed gas (vaporization step); Step 2. A step of contacting the gas containing the volatile substance obtained in Step 1 with an adsorbent that adsorbs the volatile substance, thereby adsorbing the volatile substance (adsorption step); and Step 3. A step of desorbing the volatile substance from the adsorbent obtained in Step 2 that has adsorbed the volatile substance (desorption step).

[0015] (2) A method for producing a separated and concentrated product of volatile substances as described in (1), characterized in that the mixed gas obtained in step 1 is brought into contact with an adsorbent in step 2, and the gas after contact is introduced again into the gas phase side of the membrane in step 1, thereby suppressing evaporation of water.

[0016] (3) The method for producing a separated and concentrated volatile substance according to (1), characterized in that the volatile substance is ammonia.

[0017] (4) The method for producing a separated and concentrated volatile substance according to (1), characterized in that the volatile substance is methanol. (5) The method for producing a separated and concentrated volatile substance according to (1), characterized in that the adsorbent is a Prussian blue derivative represented by the following general formula (1): 　　　 A ｘ M [M' (CN) ６ ] ｙ ・zH ２O... (1) In formula (1), x is a number from 0 to 3, y is a number from 0.1 to 1.5, z is a number from 0 to 6, A is at least one cation selected from the group consisting of hydrogen, ammonium cations, alkali metal ions, and alkaline earth metal ions, or a combination of two or more cations; M and M' are each independently selected, M is at least one cation selected from the group consisting of atoms having atomic numbers of 3 to 83, or a combination of two or more cations (excluding ammonium cations, alkali metal ions, and alkaline earth metal ions), and M' is at least one cation selected from the group consisting of atoms having atomic numbers of 3 to 83, or a combination of two or more cations (excluding ammonium cations, alkali metal ions, and alkaline earth metal ions).

[0018] (6) A method for producing a separated and concentrated product of volatile substances according to (1), characterized in that in the desorption step, the volatile substances are desorbed by heating the adsorbent.

[0019] (7) A method for producing a separated and concentrated product of volatile substances described in (1), characterized in that in the desorption step, when heating the adsorbent, the temperature is adjusted to two stages, low and high, so that the volatile substances are selectively desorbed at high temperatures.

[0020] (8) A system for concentrating an aqueous solution containing a volatile substance or isolating the volatile substance, wherein the adsorption means described below selectively adsorbs the volatile substance and / or the desorption means described below selectively desorbs the volatile substance, and the system for producing a separated / concentrated product of the volatile substance comprises the following means: Means 1. A means (vaporization means) for contacting an aqueous solution containing the volatile substance with a water-impermeable, gas-permeable membrane on one side thereof, and for allowing the vaporized volatile substance and water vapor to permeate the other side of the membrane to the gas phase side, thereby obtaining a mixed gas; Means 2. A means (adsorption means) for contacting the gas containing the volatile substance obtained in Means 1 with an adsorbent that selectively adsorbs the volatile substance, thereby adsorbing the volatile substance; Means 3. A means (desorption means) for desorbing the volatile substance from the adsorbent obtained in Means 2 that has adsorbed the volatile substance.

[0021] (9) The system for producing a volatile substance separation and concentration according to (8), characterized in that the adsorbent is a Prussian blue derivative represented by the following general formula (1): 　　　 A ｘ M [M' (CN) ６ ] ｙ ・zH ２ O... (1) In formula (1), x is a number from 0 to 3, y is a number from 0.1 to 1.5, z is a number from 0 to 6, A is at least one cation selected from the group consisting of hydrogen, ammonium cation, alkali metal ion, and alkaline earth metal ion, or a combination of two or more cations, M and M' are each independently selected, M is at least one cation selected from the group consisting of atoms with atomic numbers of 3 to 83 (excluding ammonium cation, alkali metal ion, and alkaline earth metal ion), and M' is at least one cation selected from the group consisting of atoms with atomic numbers of 3 to 83, or a combination of two or more cations (excluding ammonium cation, alkali metal ion, and alkaline earth metal ion). (10) A system for producing a volatile substance separation and concentration according to (8), further comprising means 2.5 between means 2 and 3, which returns gas not adsorbed by the adsorbent to the gas phase side of the membrane, thereby enabling continuous vaporization through the membrane (return means). (11) A system for producing a volatile substance separation and concentration as described in (8), wherein in means 3, the adsorbent having adsorbed the volatile substance obtained in means 2 is removed from the reaction system, and the volatile substance is desorbed by a predetermined method, while another new adsorbent is supplied to the part from which the adsorbent has been removed, thereby maintaining a continuous cycle of vaporization of the volatile substance.

[0022] The present invention makes it possible to concentrate or purify volatile substances from raw water containing volatile substances. This compact device reduces energy consumption associated with water vaporization, and also allows for the reuse of components, thereby keeping material costs low. Furthermore, the present invention makes it possible to concentrate high concentrations of volatile substances even when the raw water has a low concentration.

[0023] 1 is an explanatory diagram of an apparatus (system) for separating and concentrating ammonia. It is a photograph (left) and a schematic diagram (right) showing a triple-tube nozzle used in the production of hollow fiber membranes. It is a side-view electron microscope photograph of the contact state of water and ammonia water on a hollow fiber membrane, used as a substitute for a drawing. It is a graph showing the results of an experiment in which ammonia and water were separated using a separation membrane. It is a graph showing the desorption profile of water and ammonia from Prussian blue during heating. It is a graph showing the transition of methanol concentration in the circulating liquid. It is a graph showing the flow of methanol liquid and water relative to the amount of methanol supplied. It is an infrared spectroscopic diagram of a manganese-cobalt cyano complex adsorbed under a methanol atmosphere. It is an infrared spectroscopic diagram when a manganese-cobalt cyano complex with methanol adsorbed is heated. It is a structural diagram showing the crystal structure of a Prussian blue derivative.

[0024] Hereinafter, an embodiment of the present invention (hereinafter sometimes referred to as "the present embodiment") will be described, but these are for the purpose of explaining the present invention and do not limit the scope of the present invention. Note that "to" indicating a range of numerical values ​​includes the numerical values ​​before and after it as the lower limit and upper limit.

[0025] The volatile substance to be concentrated and separated in the present invention (hereinafter referred to as the target volatile substance) may be any substance that dissolves in water, has a certain vapor pressure at room temperature (23° C.), and at least a portion of which evaporates from water at room temperature (23° C.). For example, compounds with relatively small molecular weights such as ammonia, methanol, and ethanol are preferred, and examples thereof include ammonia, amines having 1 to 3 carbon atoms, alcohols having 1 to 3 carbon atoms, aldehydes having 1 to 3 carbon atoms, ketones having 3 to 5 carbon atoms, ethers having 2 to 4 carbon atoms, esters having 3 to 5 carbon atoms, and carbonates having 3 to 5 carbon atoms.

[0026] The apparatus for carrying out the present invention (FIG. 1) broadly comprises a membrane distillation section (separator) 1 equipped with a separation membrane, an adsorption section (adsorbent) 7, and circulation connections 6a and 6b. Reference numeral 2 denotes an outlet for gas containing a target volatile substance (e.g., ammonia), and reference numeral 3 denotes an inlet for gas after adsorption of the target volatile substance (e.g., ammonia). Reference numeral 4 denotes an inlet for water containing the target volatile substance (e.g., dilute ammonia water), and reference numeral 5 denotes an outlet for water containing the target volatile substance (e.g., dilute ammonia water). The membrane distillation section 1 is intended to vaporize the target volatile substance from the water containing the target volatile substance. However, some water vapor may also vaporize. The adsorption section 7 is intended to selectively adsorb the target volatile substance vaporized in the membrane distillation section 1, and then selectively desorb and recover the target volatile substance. The selectivity of adsorption and desorption may be both or either one. The circulation connections 6a and 6b are intended to provide a circulation structure that allows vaporized target volatile substances, water vapor, etc. to circulate between the membrane distillation section and the adsorption section, and also return them to the membrane distillation section. The key point here is that when the target volatiles vaporized in the membrane distillation section and other substances, including water vapor, enter the adsorption section via the circulation section, the target volatiles are selectively adsorbed, thereby reducing the concentration of the target volatiles in the gas returned to the membrane distillation section. Because water vapor and other substances remain unadsorbed and remain as gas, their vaporization in the membrane distillation section progresses, increasing their concentration and eventually reaching the same partial pressure as the vapor pressure. At this point, vaporization in the membrane distillation section stops and no further vaporization occurs. Meanwhile, because the target volatiles are recovered in the adsorption section, their concentration in the circulating gas is maintained at a low level. As a result, only the target volatiles are continuously vaporized in the membrane distillation section. This suppresses the vaporization of other substances, including water vapor, and promotes the vaporization of only the target volatiles, avoiding the energy loss associated with water vapor vaporization. Furthermore, by selectively adsorbing and / or desorbing the target volatiles to the adsorbent, it is possible to recover high concentrations of the target volatiles.

[0027] The membrane distillation section uses a membrane distillation membrane that does not allow liquid water to pass through, but only allows vaporized gaseous substances to pass through. The membrane distillation membrane separates the liquid flow section from the gas flow section. Volatile substance-containing water is passed through the liquid flow section and maintained at a constant temperature, causing the volatile substances in the liquid to vaporize and pass through the membrane along with the water vapor into the gas flow section. The shape and material of the membrane distillation membrane are not limited as long as it satisfies the functions described above, but examples of shapes that can be used include hollow fiber and flat membrane. Materials that can be used include polypropylene (PP), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF: polyvinylidene difluoride), with polyvinylidene fluoride (PVDF) being particularly preferred due to its ease of processing. In an embodiment of the present invention, a gas sweep membrane distillation (SGMD) method is used, so it is preferable to use a hollow fiber membrane suitable for this method. The specifications of the hollow fiber membrane, such as its dimensions, may be determined as appropriate, and examples thereof include an outer diameter of 0.5 to 1.2 mm, an inner diameter of 0.3 to 0.8 mm, a membrane thickness of 0.07 to 0.3 mm, a porosity of 30 to 60%, an average pore size of 10 to 50 nm, a water contact angle of 100° to 140°, and an ammonia water contact angle of 100° to 140°. The molecular weight of the PVDF used here is not particularly limited, but is preferably about 400,000 to 1,000,000 in Mw, more preferably about 500,000 to 8,800,000, and particularly preferably 600,000 to 700,000.

[0028] The method for producing hollow fiber membranes is not particularly limited and may be any method commonly used in this field. However, it is preferable to use the thermally induced phase separation (TIPS) process using a triple-tube nozzle as shown in Figure 2. The bore fluid for the triple-tube nozzle can be diethyl phthalate, PEG 400, GTA (glycerol triacetate), etc. The dope solution for the intermediate layer can be, for example, a solution of polyvinylidene fluoride dissolved in diphenyl carbonate or DMP. The solution concentration is preferably 10 to 50% by mass, more preferably 15 to 35% by mass. The extrudent for the outermost layer can be acetyl tributyl citrate, PEG 400, DOP (dioctyl phthalate), etc. The extrusion temperature is not particularly limited, but extrusion at 150 to 300°C is preferred. The extruded hollow fiber membrane is quenched in water (5 to 20°C) to retain its shape. For details of the hollow fiber membrane manufacturing method (TIPS) and phase separation of ammonia by SGMD using hollow fiber membranes, see Zhan Li, Pengfei Zhang, Kecheng Guan, Ralph Rolly Gonzales, Toru Ishigami, Ming Xue c, Tomohisa Yoshioka, Hideto Matsuyama, Process Safety and Environmental Protection 171 (2023) 555-560 "An experimental study on recovering and concentrating ammonia by sweep gas membrane distillation," which can be referenced.

[0029] The liquid flow section in the membrane distillation unit is not particularly limited in shape as long as the volatile substance-containing water contacts the membrane distillation membrane. However, since a large amount of water is generally required to be treated relative to the membrane area, it is generally a flow-through type with an inlet and an outlet. As for the material, there is no particular problem as long as it meets durability requirements such as water resistance and heat resistance, and polymer materials such as polypropylene and polyvinyl chloride, and metals such as stainless steel can be used.

[0030] As described below, the gas flow section must be configured so that the gas that has passed through the adsorption section comes into contact with the membrane again. There are no particular issues with the configuration or material as long as it meets durability requirements such as water resistance and heat resistance, and a flow-through configuration is generally considered to be the preferred configuration. However, since the gas flow section is filled with a high concentration of volatile substance gas, particular attention must be paid to durability. For example, if the volatile substance is ammonia, materials lacking in corrosion resistance, such as copper or aluminum, cannot be used. Therefore, examples include ceramic piping and piping with an inner surface coated with PTFE or the like.

[0031] The adsorption section is equipped with an adsorbent that selectively adsorbs the target volatile substance, and the gas evaporated in the membrane distillation section is brought into contact with the adsorbent to recover the volatile substance. The adsorbent is selected based on the target volatile substance, but it must be able to selectively adsorb the volatile substance and desorb the adsorbed volatile substance in some way. "Selective adsorption" here means preferentially adsorbing the volatile substance when comparing the target volatile substance with water vapor. Preferential adsorption is expressed by the selectivity coefficient (molar ratio basis) of the following formula when a gas with a volatile substance and water vapor ratio of x:y is contacted with the adsorbent: Selectivity coefficient = (volatile substance adsorption amount / x) / (water vapor adsorption amount / y) ... Equation 1 In the present invention, the selectivity coefficient is preferably 1 or more, more preferably 2 or more, even more preferably 5 or more, and even more preferably 10 or more. There is no particular upper limit, but a value of 1000 or less is practical.

[0032] The adsorbent may be, but is not limited to, a metal cyano complex, a zeolite, a metal-organic framework (MOF), etc., as long as it satisfies the above requirements. In particular, a metal cyano complex is known to have the ability to selectively adsorb ammonia and methanol, and can be used to separate and concentrate them.

[0033] The metal cyano complex in this embodiment (hereinafter, including the iron-iron metal cyano complex (Prussian blue), a metal cyano complex in which the metal M and / or the metal M′ is substituted with a metal other than iron may be referred to as a Prussian blue derivative) is a type of porous coordination polymer, and is composed of a metal ion (a cation having a positive charge) and a cyano group (CN of an anion having a negative charge), which is a type of ligand that bridges the metal ion. － ) (see Figure 10). Metal cyano complexes are a series of compounds called metal cyano complexes that structurally contain hexacyanometal ions. Metal cyano complexes have a nanoporous structure that can capture target gases. The nanoporous structure, i.e., the pore size, is 0.3 to 0.6 nm. Metal cyano complexes are constructed by regularly repeating this nanoporous structure. Therefore, metal cyano complexes have a large surface area and can efficiently adsorb and desorb ammonia species with high selectivity.

[0034] The metal cyano complex in this embodiment has a face-centered cubic structure as shown in FIG. 10 as a typical crystal structure, and is represented by the following general formula (1): ｘ M [M' (CN) ６ ] ｙ ・zH ２ O... (1) Here, x is 0 to 3, y is 0.1 to 1.5, and z is 0 to 6. A is one or more cations of hydrogen, ammonium, alkali metals, and alkaline earth metals. M and M' are each independently one or more cations of atoms with atomic numbers of 3 to 83. However, M and M' are not ammonium cations or cations of alkali metals or alkaline earth metals.

[0035] A is one or more cations selected from the alkali metals hydrogen, ammonium, lithium, sodium, potassium, rubidium, cesium, and francium, and the alkaline earth metals magnesium, calcium, strontium, barium, and radium. A may be a mixture of two or more cations, and x is a value that maintains charge balance throughout the metal cyano complex.

[0036] M may be one or more metal cations of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, indium, lanthanum, europium, gadolinium, and lutetium. Two or more types of cations may be mixed in M, and they are present in the metal cyano complex to maintain the charge balance of the entire metal cyano complex. M' may be one or more metal cations of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum, and copper. From the viewpoint of the stability of the cyanide in the PB derivative, M' is preferably iron or cobalt.

[0037] By combining M and M', the characteristics of the adsorbent, such as adsorption capacity, adsorption speed, selectivity, and stability as a material, can be controlled. The appropriate combination of M and M' varies depending on the target volatile substance. For example, when the target is ammonia, M is Fe. ３＋ And M' is Fe ２＋ , M is Cu ２＋ And M' is Fe ２＋ , M is Co ２＋ And M' is Fe ３＋ , M is Ni ２＋ And M' is Fe ３＋ , M is Ni ２＋ And M' is Fe ２＋ , M is Co ２＋ And M' is Co ３＋ These are known to have adsorption properties for ammonia and can be used. Also, when the target is methanol, M is Mn ２＋ And M' is Co ２＋ , M is Mn ２＋ And M' is Fe ２＋ , M is Mn ２＋ And M' is Fe ３＋ These are known to have methanol adsorption properties and can be used.

[0038] The form of the adsorbent provided in the adsorption section may be any form that allows the adsorbent to contact the vaporized volatile substance appropriately, and may be, for example, a granulated body molded into granules, a support in which the adsorbent is supported on a substrate, or a powder. The molding method for the granules is not particularly limited as long as it properly adsorbs the vaporized volatile substance, and for example, the methods described in Japanese Patent No. 6,918,323 and Japanese Patent Application Laid-Open No. 2014-077,720 can be used. The granules may also contain other substances, such as a polymer that acts as a binder or an aggregating material to improve the efficiency of the manufacturing process. Similarly, the molding method for the support is not particularly limited as long as it properly adsorbs the vaporized volatile substance, and for example, the method described in Japanese Patent No. 6,531,889 can be used.

[0039] Existing methods can also be used to desorb volatile substances from the adsorption section. For example, when the volatile substance is ammonia and the adsorbent is a metal cyano complex, methods such as contacting with acid and water, heating, and ultraviolet irradiation, as described in Japanese Patent No. 6,345,774, contacting with carbon dioxide and water, as described in Japanese Patent No. 7,093,582, humidification, as described in Japanese Patent No. 7,209,994, and contacting with ammonium bicarbonate, as described in Japanese Patent Laid-Open No. 2022-189,786, can be used. Furthermore, as will be described in more detail below, desorption by heating may be performed, and the volatile substance may be isolated by utilizing the difference in desorption temperature between water and the volatile substance.

[0040] However, the process of recovering volatile substances using the adsorption unit and the desorption process must be separated. For example, the membrane distillation unit and the adsorption unit can be disconnected, the adsorption unit can be removed, and the desorption process can be performed. Alternatively, multiple adsorption units can be prepared, one connected to the membrane distillation unit for the adsorption process, and the other disconnected for the desorption process, allowing new adsorbent to be continuously introduced and adsorption and desorption to be performed.

[0041] The desorption temperature of the volatile substance from the adsorbent is preferably different from that of the coexisting water. Specifically, the desorption temperature of water is preferably 40 to 120°C, more preferably 50 to 100°C. The desorption temperature of the volatile substance is preferably 100 to 200°C, more preferably 110 to 180°C. The difference in desorption temperature between water and the volatile substance is preferably 10°C or more at the peak top in the desorption profile, more preferably 25°C or more, and even more preferably 50°C or more. This difference in desorption temperature can be used to selectively separate, concentrate, and recover the volatile substance. Unless otherwise specified, the peak temperature of the desorbed substance refers to the peak measured by TG-MS at a heating rate of 1°C / 1 minute. Separation using such a desorption temperature difference is referred to as one embodiment of selective desorption. Alternatively, including the above-mentioned embodiment, even if it is not temperature, for example, when desorption is performed by washing, it is possible to separate the substances with a time lag, or when desorption is performed by pressure, it is possible to separate the substances by pressure or time, and these can be called embodiments of selective desorption. In other words, the ability to separate water and the target substance (volatile substance) under certain conditions in the desorption process is called "selective desorption."

[0042] The circulation connection section is intended to connect the membrane distillation section and the adsorption section and allow gas to circulate. It is preferable to use a section commonly used in the field of the present invention, and it is preferable to select it taking into consideration corrosion resistance against volatile substances, cost, etc. When the volatile substance is alcohol, metal or resin piping, which is relatively less corrosive, can be used as appropriate. When the volatile substance is ammonia, it is preferable to select the piping material with due consideration given to corrosion resistance. For example, ceramic piping or piping with a PTFE-coated inner surface can be used.

[0043] A preferred embodiment of the present invention provides a system for producing a volatile substance separation / concentration product, which concentrates an aqueous solution containing a volatile substance or isolates the volatile substance. Specifically, the system is characterized in that the adsorption means described below selectively adsorbs the volatile substance and / or the desorption means described below selectively desorbs the volatile substance, and comprises the following means. However, Means 2.5 is optional: 1. A means (vaporization means) for contacting an aqueous solution containing the volatile substance with a water-impermeable, gas-permeable membrane on one side thereof, and allowing the vaporized volatile substance and water vapor to pass through the other side of the membrane to the gas phase side, thereby obtaining a mixed gas; 2. A means (adsorption means) for contacting the mixed gas obtained in Means / Step 1 with an adsorbent that adsorbs the volatile substance, thereby adsorbing the volatile substance; and 2.5. A means (return means) for returning the gas not adsorbed by the adsorbent in Means 2 to the gas phase side of the membrane, thereby maintaining a cycle of continuous vaporization through the membrane. A means (desorption means) for removing the adsorbent having adsorbed the volatile substance obtained in means 2 or 2.5 from the reaction system and desorbing the volatile substance by a predetermined method such as heating, while supplying a new adsorbent to the part from which the adsorbent has been removed, thereby maintaining a continuous cycle of vaporization.

[0044] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited thereto.

[0045] <Preparation Example 1> (Preparation of Copper-Iron Cyano Complex) A granulated adsorbent of a copper-iron cyano complex was prepared by the method described in Example 1 of Japanese Patent No. 6918323. Specifically, the procedure is as follows. 1. Preparation of raw aqueous solution As the raw aqueous solution, 7.77 moles of copper sulfate pentahydrate were dissolved in 9.25 kg of water to prepare 10 L of copper sulfate aqueous solution LC1. Furthermore, 4.24 moles of potassium ferrocyanide trihydrate were dissolved in 8.15 kg of water to prepare 9 L of potassium ferrocyanide aqueous solution LF1. 2. Synthesis of metal cyano complex slurry By mixing LC1 and LF1, a solution of M=Cu was obtained. ２＋ , M′=Fe ２＋A copper-iron cyano complex slurry S1 was prepared. 3. Addition of flocculating agent: After adjusting the pH of slurry S1, 24 g of a polymer flocculant composed primarily of a copolymer of acrylamide and dimethylaminoethyl methacrylate with a molecular weight of approximately 4 million was added to the slurry and stirred with a stirrer. 4. Production of dried block: Slurry S1 was compressed using an electric hydraulic press (YS-1, manufactured by Hashida Kiko Co., Ltd.) and solid-liquid separation was performed to prepare dehydrated cake C1. The dehydrated cake C1 was cut into small pieces approximately 3 cm square and dried in a shelf dryer at 40°C for 24 hours to prepare dried block B1. 5. Crushing the block into fine powder, adding a binder and a crosslinking agent, and mixing: The dried block B1 was pulverized using a cutter mixer (BLIXER6, manufactured by FMI Co., Ltd.) to obtain dry powder DP1. During this process, it was confirmed that the temperature of the cutter mixer did not exceed 40°C. Separately, a 10 weight percent aqueous solution of polyvinyl alcohol was prepared as a binder, and titanium lactate ammonium salt was prepared as a cross-linking agent. Without removing P1 from the cutter mixer, the binder and cross-linking agent were added to P1 in that order. The cutter mixer was operated and stirred for 1 minute to obtain wet powder WP1, which contained a mixture of copper-iron cyano complex, flocculating agent, binder, and cross-linking agent. 6. Granulation and Drying: The wet powder WP1 was placed in an extrusion granulator (F-5, manufactured by Dalton) to obtain hydrous granulated adsorbent WA1. This hydrous granulated adsorbent WA1 was dried in a shelf dryer at 50°C for 24 hours to obtain granulated adsorbent A1.

[0046] <Preparation Example 1> An ammonia separation membrane (hollow fiber membrane) was prepared by the following procedure: The raw material, polyvinylidene fluoride (PVDF, Solef 6020, Mw=670,000-700,000) manufactured by Solvay Specialty Polymers Japan, Ltd. was used.The effects of thermally induced phase separation (thermally induced phase separation). Zhang, S. Rajabzadeh, A. Venault, S. Wang, Q. Shen, Y. Jia, C. Fang, N. Kato, Y. Chang, and H. Matsuyama, J. Membr. Sci. 638 (2021), 119712.P. Zhang, W. Liu, S. Rajabzadeh, Y. Jia, Q. Shen, C. Fang, N. Kato, and H. Matsuyama, J. Membr. Sci. 636 (2021), 119596. Effect of polymer molecular weight on structure and performance of Pvdf hollow fiber membranes prepared via tips process with co-extrusion of solvent using a triple orifice spinneret, J. Membr. Sci. 620 ( 2021 ), 118854 .First, PVDF was dissolved in DMP (dimethyl phthalate) at 200°C to prepare a homogeneous dope solution. The PVDF concentration was controlled at 24 wt%. This dope solution was fed into a twin-screw extruder using a precisely controlled conveying screw. The dope solution was coextruded with PEG400 (polyethylene glycol, number-average molecular weight 400) and fed through a triple orifice into a 15°C water cooling bath. PEG400 flowed through the inner and outermost layers of the hollow fiber membrane, forming a controlled surface morphology with the inner pores of the hollow fiber membrane. The hollow fiber membrane was collected on a winder at a speed of 10 m / min. The hollow fiber membrane was then stored in fresh ethanol to wash off the DMP (the ethanol was changed twice daily). After 5 days, the hollow fiber membrane was removed and dried vertically at room temperature.

[0047] The conditions and parameters for producing the PVDF hollow fiber membrane are as follows: -------------------------------------------------- Production conditions Parameters ------------------------------------------------------------------ PVDF concentration (mass %) 24 Mixing temperature (°C) 200 Screw speed (rpm) 100 Extrusion rate of dope solution (g min) －１ ) 7 Bore liquid flux (g min －１ 3.5 Extrusion solvent flux (g min －１ ) 2.5 Air gap (cm) 15 Cooling bath temperature (°C) 15 Winding speed (m / min) 12

[0048] The specifications of the hollow fiber membrane obtained as described above are as shown in the table below.

[0049] ---------------------------------- Item Parameter ---------------------------------- Outer diameter 0.9 mm Inner diameter 0.6 mm Film thickness 0.15 mm Porosity 42-46% Average pore size 18 nm Water contact angle 124° 5% ammonia water contact angle 124° ----------------------------------

[0050] The outer diameter, inner diameter, and membrane thickness were measured by cutting the hollow fiber membrane in the cross-sectional direction with a fine cutter and observing the cross-section with an electron microscope.

[0051] The porosity of the membrane was measured manually by calculating the volume of the pore-filling agent (1-octanol) relative to the total volume of the membrane. The membrane was dried under vacuum at 50°C and weighed m before immersion in 1-octanol with ultrasonic irradiation for 5 min. ０ The membrane was then weighed as m, and the pores of the membrane were filled with 1-octanol. The membrane was then taken out, the excess 1-octanol was wiped off, and its weight was measured again as m. The porosity δ of the membrane was calculated using the following formula 3.

[0052] where ρ is the density of 1-octanol. ｏｕｔ and D ｉｎ are the outer and inner diameters of the membrane, respectively. l is the length of the membrane.

[0053] The average pore size was measured using a liquid-liquid accelerator (LLP-1100A, Porous Material Inc., Ithaca, USA). The membrane was cut into 8 cm lengths and both ends were sealed with epoxy adhesive. It was then immersed in IPA (isopropanol) overnight. Galwick (propylene, 1,1,2,3,3,3-hexafluorofluoric acid) was then used to displace the IPA under pressure. The flow rate under different pressures was recorded using a mass balance for measurement.

[0054] The contact angles of water and ammonia water were measured using a DropMaster 300 made by Kyowa Interface Science Co., Ltd. Figure 3 shows a side view taken with a microscope.

[0055] Example 1 The above-mentioned ammonia adsorption experiment was carried out on the obtained separation membrane (hollow fiber membrane) in the following order: without dry sweep gas circulation, without 95% wet gas circulation, and with 100% wet gas circulation and an adsorption column. The results are shown in the graph in Figure 4. When 100% wet gas circulation and an adsorption column were used, the permeation flux was 1600 g / (m ２ h) was about 450 g / (m ２ h), the adsorption capacity was reduced to less than one-third. Meanwhile, the selectivity for ammonia was significantly improved, and water evaporation was significantly reduced. This indicates that the adsorbent selectively adsorbs ammonia. Furthermore, since water evaporation was significantly reduced, it can be seen that the energy required for water evaporation was also significantly reduced. The adsorption column here refers to a column (adsorption section) made of the copper-iron cyano complex adsorbent obtained in Preparation Example 1.

[0056] Example 2 The copper-iron cyano complex obtained in Preparation Example 1 was used as an adsorbent and introduced into the separator 1 shown in FIG. 1 equipped with the separation membrane described above, and ammonia was separated and concentrated. ３ This method utilizes a combination of gas adsorbents. Specifically, a dilute aqueous ammonia solution was introduced through an inlet 4 at one end of a separator 1 equipped with a hollow fiber membrane made of PVDF. The excess dilute aqueous ammonia solution was discharged and recovered from an outlet 5 at the other end. An inlet 3 for saturated water containing ammonia (water vapor) was provided at the other end of the separator 1, and saturated water was supplied from this inlet 3 via a pipe 6a. The saturated water passing through the separator absorbed vaporized components of ammonia and was recovered from an outlet 2 containing saturated water through a pipe 6b and sent to the adsorbent 7. The adsorbent 7 adsorbed ammonia and water, and the excess saturated water was sent back to the pipe 6a and supplied to the separator 1. This cycle was repeated a predetermined number of times to allow the adsorbent 7 to adsorb ammonia and water.

[0057] The adsorbent 7, which had adsorbed ammonia and water, was sent to a heating device, where the temperature was gradually increased from room temperature. The desorption profile of water and ammonia from the copper-iron cyano complex was confirmed in advance, as shown in Figure 5. Water is desorbed primarily below approximately 100°C. Ammonia then begins to desorb at temperatures of 120-130°C. Utilizing this property, the adsorbent 7 was heated at 100°C for the first hour, and then maintained at 150°C for the next hour. This enabled the separation and concentration of ammonia, a volatile gas, to 96% by mass.

[0058] Preparation Example 2 (Preparation of Manganese-Cobalt Cyano Complex) An adsorbent powder was prepared according to the method described in WO2024048667A1. 20 mL of a 0.6 mol / L aqueous manganese chloride solution and 20 mL of a 0.3 mol / L aqueous potassium hexacyanocobaltate solution were mixed and shaken for 1 hour to obtain a precipitate. The liquid containing this precipitate was subjected to solid-liquid separation at a centrifugal force of 16,000 G for 10 minutes, and the supernatant was removed. Ultrapure water was added to the precipitate, and the container was then capped and shaken up and down to stir the precipitate in the ultrapure water. This series of steps of centrifugation, supernatant removal, addition of ultrapure water, and stirring was repeated six more times. The supernatant was then removed, and the precipitate was vacuum-dried at room temperature for 4 hours to obtain a manganese-cobalt cyano complex powder.

[0059] Example 3: The same separation membrane as in Example 1 was used to test the usable concentration range. Wet resistance was observed with methanol solutions of 30 vol% or less. A separation test was conducted using a 24.3 vol% methanol solution circulated at 27.8°C and 50 ml / min, yielding the graphs shown in Figures 6 and 7. The circulated 14.3 vol% methanol solution exhibited a decrease in concentration as the methanol was separated, reaching 8.16 vol% after 420 minutes, as shown in Figure 6. The separated methanol was obtained as a gas, with a maximum concentration of 30,000 ppmv. The graph shown in Figure 7 indicated that the concentration was 13,500 ppmv when the concentration of the circulating methanol solution was 8.16 vol%.

[0060] Example 4 Using the manganese-cobalt cyano complex obtained in Preparation Example 2 as an adsorbent, methanol adsorption was evaluated when the saturated water vapor amount at 28°C was set to 100% humidity. The methanol gas concentrations were batch adsorbed into methanol with concentrations of 30,000 ppmv and 13,500 ppmv obtained in Additional Example 1. The methanol solution and adsorbent were left stationary in a desiccator for 3 days to adsorb methanol, so that the concentrations were 30,000 ppmv and 13,500 ppmv, respectively. After batch adsorption, a gas detection tube confirmed that the methanol gas concentrations were 29,000 ppmv and 13,500 ppmv, and that the water vapor concentrations were approximately 39,000 ppmv, respectively, indicating a humidity of approximately 100%. Figure 8 shows the infrared spectroscopic spectrum of the manganese-cobalt cyano complex adsorbed in a 13,500 ppmv and 29,000 ppmv methanol atmosphere before adsorption. Comparing the spectra before and after adsorption, the peak peak peak at approximately 990 cm ―１ The presence or absence of a peak derived from methanol was confirmed, and 7.1 mmol / g and 9.9 mmol / g of methanol were adsorbed, respectively.

[0061] Example 5 The adsorbent obtained in Example 3, which had adsorbed methanol, was heated to separate methanol from water. Figure 9 shows an infrared spectroscopic spectrum of a manganese-cobalt cyano complex which had adsorbed methanol at 13,500 ppmv. Upon heating, the absorption peak at 3,300 cm ―１ The peak at around 990 cm due to water completely disappears at 100 °C. On the other hand, the peak at around 990 cm due to methanol disappears. ―１ Furthermore, this peak completely disappears when heated to 150°C, which indicates that methanol can be concentrated from the gas containing water vapor and methanol obtained through the separation membrane by using an adsorbent.

[0062] From the results of the above examples, it can be seen that even when an adsorbent made of a Prussian blue (PB) derivative is incorporated into the separation and concentration device of the present invention, it exhibits good selective adsorption and selective desorption properties, and is able to efficiently separate and concentrate water-soluble, volatile trace substances from water.

[0063] DESCRIPTION OF SYMBOLS 1 Membrane distillation section (separator) 2 Target volatile substance-containing gas outlet 3 Target volatile substance adsorbed gas inlet 4 Dilute ammonia water inlet 5 Dilute ammonia water outlet 6a Piping (circulation connection section) 6b Piping (circulation connection section) 7 Adsorption section (adsorbent, Prussian blue derivative) 10 Ammonia concentration / separation product production system

Claims

1. A method for concentrating an aqueous solution containing a volatile substance or isolating the volatile substance, comprising the following steps, and comprising selectively adsorbing the volatile substance in the adsorption step described below and / or selectively desorbing the volatile substance in the desorption step described below: Step 1. A step of contacting an aqueous solution containing the volatile substance with a liquid phase side of a membrane separated by a water-impermeable but gas-permeable membrane, the liquid phase side being one side of the membrane and the gasified volatile substance and water vapor being permeated into the gas phase side to obtain a mixed gas (vaporization step); Step 2. A step of contacting the gas containing the volatile substance obtained in step 1 with an adsorbent that adsorbs the volatile substance, thereby adsorbing the volatile substance (adsorption step); Step 3. A step of desorbing the volatile substance from the adsorbent obtained in step 2 that has adsorbed the volatile substance (desorption step).

2. A method for producing the separated and concentrated volatile substances described in claim 1, characterized in that the mixed gas obtained in step 1 is contacted with an adsorbent in step 2, and the gas after contact is reintroduced into the gas phase side of the membrane in step 1, thereby suppressing evaporation of water.

3. The method for producing a volatile substance separated and concentrated as described in claim 1, wherein the volatile substance is ammonia.

4. A method for producing a separated and concentrated volatile substance as described in claim 1, characterized in that the volatile substance is methanol.

5. A method for producing a volatile substance separation and concentration product according to claim 1, characterized in that the adsorbent is a Prussian blue derivative represented by the following general formula (1): 　　　 A ｘ M [M' (CN) ６ ] ｙ ・zH ２ In formula (1), x is a number from 0 to 3, y is a number from 0.1 to 1.5, z is a number from 0 to 6, A is at least one cation selected from the group consisting of hydrogen, ammonium cation, alkali metal ion, and alkaline earth metal ion, or a combination of two or more cations, M and M' are each independently selected, M is at least one cation selected from the group consisting of atoms having atomic numbers of 3 to 83, or a combination of two or more cations (excluding ammonium cation, alkali metal ion, and alkaline earth metal ion), and M' is at least one cation selected from the group consisting of atoms having atomic numbers of 3 to 83, or a combination of two or more cations (excluding ammonium cation, alkali metal ion, and alkaline earth metal ion).

6. A method for producing a separated and concentrated volatile substance as described in claim 1, characterized in that in the desorption step, the volatile substance is selectively desorbed by heating the adsorbent.

7. A method for producing a volatile substance separation / concentration product described in any one of claims 1 to 6, characterized in that in the desorption process, when heating the adsorbent, the temperature is adjusted to two stages, low and high, thereby selectively desorbing the volatile substances at high temperature.

8. A system for concentrating an aqueous solution containing a volatile substance or isolating the volatile substance, the system comprising the following means for producing a separated / concentrated product of the volatile substance, the adsorption means selectively adsorbing the volatile substance and / or the desorption means selectively desorbing the volatile substance, and comprising the following means: Means 1. A means for obtaining a mixed gas by contacting an aqueous solution containing the volatile substance with one side of a membrane separated by a water-impermeable but gas-permeable membrane, the other side of the membrane being the gas phase side, and allowing the vaporized volatile substance and water vapor to permeate the gas phase side (vaporization means); Means 2. A means for contacting the gas containing the volatile substance obtained in means 1 with an adsorbent that adsorbs the volatile substance, thereby adsorbing the volatile substance (adsorption means); Means 3. A means for desorbing the volatile substance from the adsorbent obtained in means 2 that has adsorbed the volatile substance (desorption means).

9. The system for separating and concentrating volatile substances according to claim 8, wherein the adsorbent is a Prussian blue derivative represented by the following general formula (1): 　　　 A ｘ M [M' (CN) ６ ] ｙ ・zH ２ In formula (1), x is a number from 0 to 3, y is a number from 0.1 to 1.5, z is a number from 0 to 6, A is at least one cation selected from the group consisting of hydrogen, ammonium cation, alkali metal ion, and alkaline earth metal ion, or a combination of two or more cations, M and M' are each independently selected, M is at least one cation selected from the group consisting of atoms having atomic numbers of 3 to 83, or a combination of two or more cations (excluding ammonium cation, alkali metal ion, and alkaline earth metal ion), and M' is at least one cation selected from the group consisting of atoms having atomic numbers of 3 to 83, or a combination of two or more cations (excluding ammonium cation, alkali metal ion, and alkaline earth metal ion).

10. A system for producing volatile substance separation and concentration as described in claim 8, in which means 2.5 is provided between means 2 and 3, for returning gas not adsorbed by the adsorbent to the gas phase side of the membrane, thereby enabling continuous evaporation through the membrane.

11. A system for producing a volatile substance separation and concentration product described in any one of claims 7 to 10, wherein in means 3, the adsorbent having adsorbed the volatile substance obtained in means 2 is removed from the reaction system and the volatile substance is desorbed by a predetermined method, while another new adsorbent is supplied to the part from which the adsorbent has been removed, thereby maintaining a continuous cycle of vaporization of the volatile substance.