Soluble-ion separation / recovery device and separation / recovery method

Abstract

The present invention comprises a separation / recovery device which comprises an adsorption column group for performing adsorption treatment of specific water-soluble ions, a desorption column group for performing desorption treatment of the ions, and an adsorption device in which void columns installed between the adsorption column group and the desorption column group are annularly disposed. Liquid in the column group in which the adsorption treatment or the desorption treatment has been completed using the separation / recovery device is extruded from the most upstream column of the column group and toward the void column adjacent to the most downstream column of the column group by using said void column, and the most upstream column from which the liquid has been extruded is isolated to form a new void column.

Description

Apparatus and method for separating and recovering water-soluble ions

[0001] The present invention relates to an apparatus and method for separating and recovering water-soluble ions.

[0002] Water-soluble ions such as phosphorus, boron, arsenic, fluorine, and cesium contained in environmental water such as industrial wastewater and treated sewage water generated by human activities are causing problems of pollution and eutrophication that affect ecosystems, and there is a demand for technologies to remove these ions. On the other hand, these environmental waters also contain useful water-soluble ions such as ammonium ions and lithium ions, and there is a demand for technologies to recover these ions as useful substances.

[0003] A method for separating and recovering specific water-soluble ions is well known, as described in the following prior art documents, in which an aqueous solution containing the ions is passed through an adsorption device (such as a column) equipped with an adsorbent capable of adsorbing the ions, the ions are selectively adsorbed onto the adsorbent, and then an aqueous solution that desorbs the ions from the adsorbent is passed through the adsorption device to perform ion exchange and desorb the ions.

[0004] Patent Document 1 describes a method for producing an aqueous solution containing 95 mol % or more of ammonium ions, in which an aqueous solution containing ammonium ions is passed through a vessel filled with an adsorbent containing a metal cyano complex as an active ingredient, the ammonium ions are adsorbed onto the adsorbent, and then an aqueous solution containing potassium ions is passed through as desorbed regenerated water.

[0005] Patent Document 2 describes a method for recovering lithium, which includes an adsorption step of supplying an aqueous solution containing lithium, sodium, and calcium to a treatment vessel containing an adsorbent and causing the lithium and calcium to be adsorbed onto the adsorbent; a desorption step of stopping the supply of the aqueous solution, supplying a lithium recovery solution having a pH of 4±1.5 to the treatment vessel, and recovering lithium; and a step of stopping the supply of the lithium recovery solution, supplying a cleaning solution having a pH of 2 or less to the treatment vessel, and desorbing calcium from the adsorbent to wash the adsorbent, in which the adsorption step and the desorption and washing steps are performed alternately on two lines.

[0006] Patent Document 3 describes a phosphorus recovery method in which phosphorus-containing water to be treated is passed through an adsorption tower filled with an adsorbent for phosphorus compounds to adsorb the phosphorus, and then a desorption chemical solution is supplied to desorb the phosphorus, and the water to be treated is continuously treated by alternately repeating a phosphorus adsorption step and a phosphorus desorption or adsorbent regeneration step in one and the other of adsorption towers connected in parallel.

[0007] Patent Document 4 describes a water treatment method in which water to be treated containing fluoride ions, magnesium ions, and sulfate ions is brought into contact with an adsorbent filled in an adsorption tower that adsorbs fluoride ions, thereby removing at least a portion of the fluoride ions in the water to be treated. The method describes that three or more adsorption towers are provided, and an adsorption step is performed using a plurality of adsorption towers connected in series, while a desorption step is performed using an adsorption tower that is not connected in series.The most upstream adsorption tower of the series-connected adsorption towers is disconnected to perform the desorption step, and the adsorption tower that has completed the desorption step is connected to the most downstream adsorption tower connected in series to perform the adsorption step, thereby repeating the adsorption step and desorption step for each adsorption tower.

[0008] Non-Patent Document 1 describes that when adsorption and desorption of ammonium ions are performed using a multi-stage column packed with an adsorbent capable of adsorbing ammonium ions, in the desorption cycle, the inlet column saturated with ammonium ions in the adsorption cycle is moved to the outlet end of the multi-stage column to perform desorption, and the inlet column after desorption is completed is reconnected to the outlet end of the adsorption cycle, and overall the order of the adsorption / desorption columns is shifted one by one in the upstream direction.

[0009] Japanese Patent No. 6970406 Japanese Patent Application Laid-Open No. 2009-161794 Japanese Patent Application Laid-Open No. 2009-226250 Japanese Patent Application Laid-Open No. 2018-130677

[0010] Environmental Pollution 284 (2021) 117495 https: / / doi.org / 10.1016 / j.envpol.2021.117495

[0011] As disclosed in the above-mentioned prior art documents, when separating and recovering specific water-soluble ions from an aqueous solution containing the ions as the target of separation and recovery, it is known to connect two systems of columns equipped with an adsorbent having ion exchange capacity in parallel, and alternately perform an adsorption step in which the aqueous solution is passed through, and a desorption step in which an aqueous solution that desorbs the water-soluble ions from the adsorbent is passed through each system (Patent Documents 2 and 3).

[0012] In addition, adsorbents generally have a limit called adsorption capacity, beyond which they cannot adsorb any more water-soluble ions, and once the amount of adsorbed water-soluble ions exceeds a certain value, they can no longer adsorb the water-soluble ions. Therefore, in order to increase the adsorption capacity, Patent Document 4 and Non-Patent Document 1 disclose a method in which a plurality of columns are connected in series to form an adsorption column group and a desorption column group, and a replacement step is performed in which the inlet column (the most upstream column) where adsorption or desorption has finished is disconnected and connected to the outlet end where the desorption or adsorption of the next cycle begins, thereby enabling continuous adsorption and desorption of specific water-soluble ions.

[0013] However, in both of the above-mentioned prior arts, the aqueous solution supplied before switching between the adsorption and desorption processes remains in the column that is being switched between, without being discharged, and this residual solution is mixed into the new solution passed through after switching. If a column that has completed the adsorption process is used in the desorption process while still containing residual solution, the aqueous solution containing the water-soluble ions to be separated and recovered contains impurities, and these impurities are mixed into the desorption treatment solution that has undergone the desorption process. As a result, it is not possible to efficiently separate and recover specific water-soluble ions. Similarly, when a column that has completed the desorption process is used in the adsorption process, the aqueous solution containing the desorbed components is mixed into the adsorption treatment solution, preventing efficient adsorption of the specific water-soluble ions.

[0014] To prevent contamination of the residual liquid, the aqueous solution in the column to be switched is drained before switching the treatment, thereby avoiding contamination of the newly passed liquid. However, if the solution used for adsorption remains in the column to be switched, the discharge of wastewater may be restricted due to the high concentration of certain water-soluble ions contained in the residual liquid. Furthermore, if the solution used for desorption remains, it may be difficult to discharge it as wastewater, and new wastewater treatment may be required.

[0015] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a separation and recovery device and a separation and recovery method that can efficiently separate and recover specific water-soluble ions without requiring additional wastewater treatment.

[0016] The present inventors have studied separation and recovery devices and methods for solving the above-mentioned problems, and have found that the above-mentioned problems can be solved by configuring a separation and recovery device in a circular arrangement of multiple columns each containing an adsorbent that adsorbs the specific water-soluble ions, dividing the multiple columns into a series-connected adsorption column group for adsorption of the ions, a series-connected desorption column group for desorption of the ions, and a void column installed between the adsorption column group and the desorption column group, and by using the separation and recovery device to push liquid from the adsorption column group or the desorption column group that has completed one of the adsorption and desorption processes from the most upstream column of the column group toward the void column adjacent to the most downstream column of the column group, and then separating the most upstream column from which the liquid has been pushed and using it as a new void column, thereby completing the present invention. Here, "annular" refers to a state in which there is no topological starting point or ending point, and each column is always sandwiched between adjacent columns. It does not necessarily have to be arranged in a circular shape; for example, it may be arranged in an elliptical or polygonal shape.

[0017] That is, one aspect of the present invention for solving the above-mentioned problems is an apparatus for separating and recovering specific water-soluble ions, comprising an adsorption device, a control device, and a liquid transfer device; the adsorption device has a plurality of columns arranged in a ring, each containing an adsorbent that preferentially adsorbs the specific water-soluble ions from a stock solution for adsorption containing the specific water-soluble ions, and the plurality of columns are separated into an adsorption column group, a desorption column group, and a void column; the adsorption column group comprises a plurality of columns connected in series that adsorb the specific water-soluble ions by passing the stock solution for adsorption and discharge an adsorption treatment liquid having a reduced concentration of the specific water-soluble ions; the desorption column group comprises a plurality of columns connected in series that desorb the specific water-soluble ions by passing a desorption stock solution that can desorb the specific water-soluble ions and discharge a desorption treatment liquid containing the specific water-soluble ions; the void column is one or more columns that does not substantially contain inside thereof an aqueous solution containing the specific water-soluble ions or a component that desorbs the specific water-soluble ions; The control device controls the connection between the most downstream column of the adsorption column group or the desorption column group and the void column adjacent to that column, and the disconnection of the most upstream column of the adsorption column group or the desorption column group from the column group, and the liquid transfer device uses a transfer liquid or a transfer gas to push the aqueous solution filling the adsorption column group or the desorption column group from the most upstream column of each column group toward the void column connected to the most downstream column of the adsorption column group or the desorption column group.This is an apparatus for separating and recovering water-soluble ions.

[0018] Another aspect of the present invention is a method for separating and recovering specific water-soluble ions, the method comprising using the following adsorption means, control means, and liquid transfer means to sequentially perform the following steps (1) to (5), or sequentially repeating steps (1), (4), (5), (2), and (3) one or more times: The adsorption means comprises a plurality of columns arranged in a ring shape, each containing an adsorbent that preferentially adsorbs the specific water-soluble ions from an adsorption stock solution, the plurality of columns being divided into: an adsorption column group consisting of a plurality of columns connected in series that adsorb the specific water-soluble ions by passing the adsorption stock solution through and discharge an adsorption-treated liquid having a reduced concentration of the specific water-soluble ions; a desorption column group consisting of a plurality of columns connected in series that desorb the specific water-soluble ions by passing a desorption stock solution capable of desorbing the specific water-soluble ions through and discharge a desorption-treated liquid containing the specific water-soluble ions; and one or more void columns substantially not containing the specific water-soluble ions or an aqueous solution containing a desorption component that desorbs the specific water-soluble ions. The control means controls the connection between the most downstream column of the adsorption column group or the desorption column group and the gap column, and the disconnection of the most upstream column of the adsorption column group or the desorption column group from the column group. The liquid transfer means causes a transfer liquid or a transfer gas to flow into the most upstream column of the adsorption column group or the desorption column group, and pushes the adsorption liquid or desorption liquid filled in the adsorption column group or the desorption column group from the most upstream column of the adsorption column group or the desorption column group toward the gap column connected to the most downstream column.

[0019] The steps (1) to (5) comprise: (1) an adsorption step in which the specific water-soluble ions are adsorbed onto the adsorbent of the adsorption column group, and a desorption step in which the specific water-soluble ions are desorbed from the adsorbent of the desorption column group; (2) a liquid transfer step in which the void column is newly connected to the most downstream column of the desorption column group that has completed the desorption step, and the desorption liquid filling the desorption column group is pushed from the most upstream column of the column group toward the void column using a transfer liquid or a transfer gas; and (3) a replacement step in which, after completing the liquid transfer step, the most upstream column is disconnected from the desorption column group, and this column is designated as a new void column adjacent to the most downstream column of the adsorption column group, and the void column to which the desorption liquid has been transferred in the liquid transfer step is designated as the most downstream column of the desorption column group. (4) A liquid transfer step is performed in which the void column is newly connected to the most downstream column of the group of adsorption columns that has completed the adsorption step, and the adsorption liquid filling the group of adsorption columns is pushed from the most upstream column of the group of columns toward the void column using a transfer liquid or a transfer gas; and (5) After completing the liquid transfer step, a replacement step is performed in which the most upstream column is disconnected from the group of adsorption columns, and this column becomes a new void column adjacent to the most downstream column of the group of desorption columns, and the void column to which the adsorption liquid has been transferred in the liquid transfer step becomes the most downstream column of the group of adsorption columns.

[0020] According to the present invention, by using a column that does not contain a specific water-soluble ion or an aqueous solution containing a desorption component that desorbs the specific water-soluble ion, the specific water-soluble ion can be efficiently and continuously separated and recovered without leaving any adsorption treatment solution or desorption treatment solution undischarged in the column constituting the adsorption device.Furthermore, by using a high-concentration desorption stock solution, it is also possible to obtain a high concentration of the specific water-soluble ion.

[0021] FIG. 1 is a diagram illustrating the adsorption, desorption, and drying process of a specific water-soluble ion according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the desorption liquid transfer process according to an embodiment of the present invention. FIG. 3 is a diagram illustrating the transfer liquid discharge process from the most upstream desorption column according to an embodiment of the present invention. FIG. 4 is a diagram illustrating the adsorption liquid transfer process according to an embodiment of the present invention. FIG. 5 is a diagram illustrating the transfer liquid discharge process from the most upstream adsorption column according to an embodiment of the present invention. FIG. 6 is a diagram illustrating the adsorption, desorption, and drying process of a specific water-soluble ion according to an embodiment of the present invention.

[0022] An embodiment for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described below, but the present invention is not limited to the following embodiment and includes various other embodiments within the scope of the technical idea described in the claims. First, definitions of terms representing each element of the present invention will be described.

[0023] <Adsorption device> (Water-soluble ions) In this specification, water-soluble ions refer to molecules that have a positive or negative charge and are composed of a single atom or a relatively small number of atoms, and examples thereof include lithium ions, sodium ions, potassium ions, ammonium ions, rubidium ions, cesium ions, calcium ions, magnesium ions, barium ions, iron ions, and manganese ions.

[0024] (Aqueous Solution) As defined herein, an aqueous solution refers to a liquid in which water-soluble ions are dissolved in water at a certain ratio. Not all water-soluble ions necessarily dissolve, and the ratio of dissolved ions may be arbitrary, as in the case of weak acids or weak alkalis. In addition to ions, aqueous solutions also include those in a suspended state.

[0025] (Stock solution for adsorption) The stock solution for adsorption refers to an aqueous solution containing specific water-soluble ions that you want to separate and remove or recover. Specific examples include wastewater or wastewater containing ions whose upper limit is set by environmental standards, and environmental water containing ions that are used as raw materials for producing useful substances.

[0026] (Adsorbent) In this specification, the term "adsorbent" refers to a solid that has the characteristic of preferentially adsorbing specific water-soluble ions contained in an aqueous solution and releasing the adsorbed water-soluble ions back into the liquid by passing another liquid through it. Here, "adsorption" refers to the function of all or part of the water-soluble ions being taken up by the solid, thereby reducing the concentration of the water-soluble ions in the aqueous solution. The mechanism of adsorption can be any form, such as physical adsorption due to weak forces such as intermolecular forces, chemical adsorption due to chemical bonds, or adsorption due to exchange with internal ions or molecules.

[0027] (Desorption stock solution) The desorption stock solution refers to a liquid that can desorb specific water-soluble ions adsorbed on an adsorbent. For example, when specific water-soluble ions are desorbed from an adsorbent by ion exchange, the specific water-soluble ions can be desorbed into the liquid by preparing an aqueous solution containing other ions (hereinafter referred to as "desorbed ions") that can be ion-exchanged with the specific water-soluble ions.

[0028] (Column) A column refers to a structure capable of containing an adsorbent material and having at least two ports through which liquid and / or gas can enter and exit. Here, the structure is not critical as long as an aqueous solution can be injected through one port, contacted with the adsorbent material contained therein, and after specific water-soluble ions have been adsorbed onto the adsorbent, the aqueous solution can be discharged through another port. Generally, a cylindrical or prismatic shape with ports at the top and bottom is used, but the structure is not particularly limited, and the location and number of ports are not limited. For example, a column may have three or more ports so that the port to be injected can be changed depending on the type of aqueous solution. When gas is injected for purposes such as drying the interior, a separate port may be provided for the aqueous solution.

[0029] (Column Group) A column group refers to a series connection of multiple columns containing an adsorbent. In this context, "series" refers to a structure in which the port of one column is repeatedly connected to the port of an adjacent column, and when an aqueous solution is injected into one port of the first column among all the connected columns, the aqueous solution passes through all the columns in order once and is discharged from the port of the last column. Here, the port through which the aqueous solution is first injected is referred to as the column group inlet, and the port through which the aqueous solution is discharged from the last column is referred to as the column group outlet. The physical structure of the column group is not important, but it can be, for example, a structure in which the columns are arranged vertically and the lower port of one adjacent column is connected to the upper port of the other. Here, the column into which the aqueous solution is first injected is referred to as the most upstream column, and the column from which the aqueous solution is last discharged is referred to as the most downstream column.

[0030] (Adsorption column group) An adsorption column group refers to a column group in which the internal adsorbent has the function of adsorbing specific water-soluble ions and is used for the purpose of adsorbing specific water-soluble ions. The columns that make up the adsorption column group are called adsorption columns. An adsorption stock solution is injected through the column group inlet of the adsorption column group, and an adsorption treatment solution is discharged through the column group outlet. In this case, the concentration of the specific aqueous ions in the adsorption treatment solution needs to be lower than the concentration in the adsorption stock solution. This process of injecting the adsorption stock solution into the adsorption column group and obtaining the adsorption treatment solution is called the adsorption process. In this specification, to distinguish between the adsorption stock solution and the adsorption treatment solution, the liquid present in the adsorption column group from the adsorption stock solution injected into the adsorption column group until it is discharged as the adsorption treatment solution is called the "adsorption liquid."

[0031] (Desorption column group) A desorption column group refers to a column group in which the internal adsorbent adsorbs specific water-soluble ions and is used for the purpose of desorbing the adsorbed specific water-soluble ions. The columns constituting the desorption column group are called desorption columns. A desorption stock solution is injected through the column group inlet of the desorption column group, and a desorption treatment solution is discharged through the column group outlet. In this case, if the concentration of the specific aqueous solution ion in the desorption treatment solution is higher than the concentration in the adsorption stock solution, the specific water-soluble ion can be concentrated. This process of injecting the desorption stock solution into the desorption column group and obtaining the desorption treatment solution is called the desorption process. In this specification, to distinguish between the desorption stock solution and the desorption treatment solution, the liquid present in the desorption column group until the desorption stock solution injected into the desorption column group is discharged as the desorption treatment solution is called the "desorption liquid."

[0032] (Void column) A void column is a group consisting of one or more columns that substantially do not contain an aqueous solution containing a specific water-soluble ion or a desorption component that desorbs the specific water-soluble ion. In an adsorption device consisting of multiple columns arranged in a ring, the void column is separated from the adsorption column group and the desorption column group and is located between the most downstream column of one of the adsorption column group or the desorption column group and the most upstream column of the other. The void column is used in a liquid transfer process (hereinafter also referred to as the "transfer process") in which the adsorption liquid or desorption liquid in the adsorption column group or the desorption column group is pushed from the most upstream column of the column group to the void column connected to the most downstream column using a transfer liquid or transfer gas, and in a replacement process in which the void column from which the liquid is pushed in the transfer process is used as a new column with adsorption or desorption function, and the most upstream column of the column group that has completed the transfer process is separated and used as a new void column. When a transfer gas is used in the transfer process, the interior of the most upstream column from which the adsorption liquid or desorption liquid is transferred is filled with the transfer gas, and the adsorption liquid or desorption liquid inside is pushed to the adjacent column. When a transfer liquid is used in the transfer step, a liquid containing no specific water-soluble ions or desorption components is used as the transfer liquid, thereby replacing the adsorption liquid or desorption liquid in the most upstream column with the transfer liquid. Alternatively, a liquid containing specific water-soluble ions or desorption components can be used as the transfer liquid. In this case, the liquid can be discharged after the most upstream column is disconnected. If the liquid is a desorption stock solution or adsorption stock solution, discharge itself can be prevented by returning the desorption stock solution or adsorption stock solution to their respective stock solution supply sources after extrusion. In the transfer step, it is preferable that the adsorption liquid or desorption liquid be completely removed from the column. However, it is sufficient that the adsorption liquid or desorption liquid be removed to an extent that contamination of the adsorption liquid with the desorption treatment liquid or the desorption liquid with the adsorption treatment liquid is suppressed to a certain extent after the replacement step, and that a desorption treatment liquid that is usable is obtained. A column from which the adsorption liquid or desorption liquid has been removed to such an extent that this requirement is met is said to be "substantially free of aqueous solutions containing specific water-soluble ions or desorption components that desorb the specific water-soluble ions."

[0033] The control device according to this embodiment is a device that can control the plurality of columns to be either adsorption columns belonging to the adsorption column group, desorption columns belonging to the desorption column group, or void columns, by connecting the void column to the most downstream column of the adsorption column group or the desorption column group, or by disconnecting the most upstream column of the adsorption column group or the desorption column group. For example, the control device may be control software for the operation of an on / off switching valve provided in the aqueous solution flow path and a PC that drives the control software.

[0034] <Liquid Transfer Device> The liquid transfer device according to this embodiment includes a means for introducing a transfer liquid or a transfer gas into the most upstream column of the column group after a predetermined amount of treatment liquid has been obtained through the adsorption process in the adsorption column group or the desorption process in the desorption column group, and forcing the adsorption liquid or desorption liquid from the most upstream column toward a newly connected void column at the most downstream column of the column group. This means may be a pump for supplying the transfer liquid or the transfer gas. The transfer liquid is preferably pure water, which is a liquid that does not contain specific water-soluble ions and desorbed components. Alternatively, a desorption stock solution or an adsorption stock solution may be used. In this case, after the adsorption liquid or desorption liquid from the most upstream column is pushed out, the transfer liquid is discharged from the most upstream column or returned to the supply device for each stock solution, thereby making the solution substantially free of aqueous solutions containing specific water-soluble ions and desorbed components. The transfer gas may be any inert gas, but may be air.

[0035] Next, the principles and methods of separation and recovery of the present invention will be described using, as an example of this embodiment, a zinc-iron Prussian blue complex as an adsorbent for ammonium ions and potassium ions as a desorbed ion. <Separation and Recovery Principle> The zinc-iron Prussian blue complex has the ability to more selectively adsorb ammonium ions than potassium ions. In this case, an aqueous solution containing an ammonium ion solution can be used as the adsorption stock solution, and an aqueous solution containing potassium ions can be used as the desorption stock solution. Because the zinc-iron Prussian blue complex selectively adsorbs ammonium ions compared to sodium ions, calcium ions, potassium ions, etc., it can preferentially adsorb ammonium ions even if the adsorption stock solution contains sodium ions or calcium ions. As a result, after contacting the adsorption stock solution with the adsorbent, an adsorption-treated solution can be obtained in which the concentration of ammonium ions is significantly reduced compared to the concentrations of other ions. While general wastewater standards in Japan do not set wastewater standards for sodium ions or calcium ions, there are concentration standards for ammonium ions, which can make it difficult to dispose of the adsorption stock solution, such as by discharging it. Even in such a case, according to this embodiment, it is possible to discharge the adsorption treatment liquid in which the concentration of ammonium ions has been sufficiently reduced.

[0036] Furthermore, ammonium ions can be desorbed by contacting the adsorbent after contacting it with a desorption stock solution. This reduces the amount of ammonium ions adsorbed on the adsorbent, making it possible to adsorb ammonium ions again. Furthermore, by selecting a liquid that does not contain sodium ions, calcium ions, etc. as the desorption stock solution, a liquid containing ammonium ions but not sodium ions or calcium ions can be obtained as a desorption treatment liquid after desorption. Furthermore, for example, by using a desorption stock solution containing potassium ions at a higher concentration than the ammonium ion concentration in the adsorption stock solution, it is possible to desorb ammonium ions at a higher concentration than in the adsorption stock solution, thereby enabling the concentration of ammonium ions.

[0037] <Separation and Recovery Method> In the adsorption process in the adsorption column group or the desorption process in the desorption column group, if the amount of specific water-soluble ions or desorbed ions adsorbed on the adsorbent exceeds the adsorption capacity, the specific water-soluble ions or desorbed ions can no longer be adsorbed. Therefore, a replacement process is required in one of the adsorption column group or the desorption column group, in which the most upstream column with the most advanced adsorption and reduced adsorption capacity is separated from the column group, the adsorption function is restored, and the column is then replaced with the lowest column of the other column group. In the present invention, this replacement process is performed using a void column. That is, when the amount of adsorption of specific water-soluble ions or desorbed ions in the most upstream column of one of the adsorption column group or the desorption column group decreases, a void column is connected to the most downstream column of the other column group, and the adsorption liquid or desorption liquid present in one column group is liquid-transferred from the most upstream column to the void column. After the liquid transfer, the most upstream column is disconnected from one of the column groups, replacing the most upstream column with a new void column, and the original void column connected to the most downstream column is replaced with the most downstream column of one of the column groups. Next, when the amount of adsorption of the specific water-soluble ion or desorbed ion in the most upstream column of the other column group decreases, a new void column is connected to the most downstream column of the other column group, and the same liquid transfer and disconnection as in the one column group are performed, followed by a similar replacement process.

[0038] Although there are no restrictions on the order in which the adsorption step and the desorption step are performed, it is practical to perform them simultaneously because they are performed using separate column groups. However, since the time required for the adsorption step and the desorption step do not necessarily coincide, it is more efficient to perform them so that the time required for one step includes the time required for the other step. Note that the time required for the adsorption step and the desorption step changes depending on the number of columns included in the adsorption column group and the desorption column group, respectively. Therefore, more efficient operation can be achieved by selecting the number of adsorption column groups and the desorption column group.

[0039] An example of a separation and recovery device and an example of a separation and recovery method according to this embodiment will be described in further detail below with reference to FIGS.

[0040] <Example of Separation and Recovery Apparatus> The adsorption apparatus A in this example consists of columns A1 to A8 arranged in a ring, with A8 adjacent to A1. Each column is filled with a zinc-iron Prussian blue complex, an adsorbent capable of adsorbing ammonium ions. In FIG. 1 , columns A1 and A2 are a group of adsorption columns connected in series to which an adsorption stock solution, which is an aqueous solution containing specific water-soluble ions, is supplied from an adsorption stock solution supplying device B. Columns A3 to A7 are a group of desorption columns connected in series to which a desorption stock solution, which is an aqueous solution containing water-soluble ions that desorb the water-soluble ions, is supplied from a desorption stock solution supplying device C. A8 is a void column installed between the most upstream column of the adsorption column group and the most downstream column of the second column group. Note that the total number of columns is not limited to eight. It is sufficient that there are two or more adsorption columns and two or more desorption columns, and one or more void column, for a total of five or more.

[0041] The liquid transfer device D is a pump for circulating a transfer liquid such as pure water or a transfer gas such as air, but may be other liquid or gas transfer means.

[0042] The adsorption treatment liquid storage unit E is a tank that stores the adsorption treatment liquid (FIG. 1) discharged from the adsorption column group (A1, A2) and the adsorption treatment liquid (FIG. 4) transferred from the adsorption column group (A1, A2) to the void column A3 and discharged from column A3. The adsorption treatment liquid storage unit E stores a solution in which the concentration of specific water-soluble ions is reduced compared to the supplied adsorption stock solution. The desorption treatment liquid storage unit F is a tank that stores the desorption treatment liquid (FIG. 1) discharged from the desorption column group (A3 to A7) and the desorption treatment liquid (FIG. 2) transferred from the desorption column group (A3 to A7) to the void column A8 and discharged from column A8. The desorption treatment liquid storage unit F stores a solution containing specific water-soluble ions.

[0043] The gas supply device G is a means for supplying gas to discharge the residual liquid remaining in the most upstream column A3 of the desorption column group (FIG. 3) or the most upstream column A1 of the adsorption column group (FIG. 5) after liquid transfer has been completed, and to form a void column. The type of gas is not particularly limited, but may be air, and the gas supply device may be an air supply pump. The residual liquid in the column is discharged, for example, through a waste path H, and a new void column is formed.

[0044] The columns A1 to A8, the adsorption stock solution supply device B, the desorption stock solution supply device C, the liquid transfer device D, the adsorption treatment liquid storage unit E, the desorption treatment liquid storage unit F, the gas supply device G, and the waste path H can be connected or disconnected between any of the same or different elements selected from this group to change the flow path of the aqueous solution, the transfer liquid, and / or the waste liquid to be discarded externally. Connection and disconnection can be achieved by opening and closing a switching valve, such as a solenoid valve or a ball valve. In Figures 1 to 6, the switching state of the switching valve is represented by a circle (open) and a cross (closed). An open valve indicates a connected state allowing liquid flow, while a closed valve indicates a disconnected state preventing liquid flow. In the figures, arrows indicate the flow direction of each liquid or gas. The adsorption liquid, desorption liquid, and transfer liquid are supplied from the bottom of each column and discharged from the top of each column, while the gas and waste liquid flow in the opposite direction to the adsorption liquid, desorption liquid, and transfer liquid. However, the adsorption liquid, desorption liquid, and transfer liquid may be supplied from the top of each column, and the treatment liquid may be discharged from the bottom of each column. Furthermore, the supply and discharge directions of the adsorption liquid and desorption liquid do not need to be the same for all columns, and the supply and discharge directions may be reversed between adjacent columns. In this case, the liquid flow path can be shortened.

[0045] <Example of Separation and Recovery Method> (Figure 1: Adsorption, Desorption, and Drying Processes) Figure 1 shows the state in which the adsorption, desorption, and drying processes are performed simultaneously. The adsorption stock solution delivered by the adsorption stock solution supply device B is sent from the most upstream column A1 of the adsorption column group to column A2 adjacent to column A1 and stored in the adsorption treatment liquid storage section E. The desorption stock solution delivered by the desorption stock solution supply device C is sent from the most upstream column A3 of the desorption column group to the adjacent columns A4 to A7 in order and stored in the desorption treatment liquid storage device F. Column A8 is a void column that is substantially free of specific water-soluble ions and aqueous solutions containing desorbed components, and is located between the most downstream column A7 of the desorption column group and the most upstream column A1 of the adsorption column group. Column A8 was the most upstream column of the adsorption column group in the adsorption process one cycle before this process and was disconnected after the adsorption treatment liquid transfer process was completed.

[0046] (Figure 2: Desorption liquid transfer step) Figure 2 shows the step of transferring the desorption liquid after a predetermined amount of desorption liquid is supplied to the desorption column group and the desorption process is completed. A gap column A8 is newly connected to the most downstream column A7 of the desorption column group, and the most upstream column A3 of the desorption columns is disconnected from the desorption liquid supply device C and connected to a liquid transfer device D. The transfer liquid supplied from the liquid transfer device D pushes the desorption liquid in column A3 into the adjacent column A4, and the desorption liquid in the desorption column group is transferred sequentially to the adjacent columns, until column A8 is filled with desorption liquid.

[0047] (FIG. 3: Transfer Liquid Discharge Step for the Most Upstream Desorption Column) FIG. 3 shows the step of discharging the transfer liquid filling the most upstream column A3 of the desorption column group after the desorption liquid transfer step shown in FIG. 2 is completed. After the supply of the transfer liquid to column A3 is stopped, air is supplied to column A3 by gas supply device G in the direction opposite to the supply direction of the transfer liquid, and the transfer liquid remaining in column A3 is discharged through waste line H connected to column A3 in conjunction with gas supply device G, thereby forming a new void column. Gas supply is preferably continued until the adsorbent in column A3 is dried.

[0048] (Figure 4: Adsorption liquid transfer step) Figure 4 shows the step of transferring the adsorption liquid after a predetermined amount of the adsorption stock solution has been supplied to the adsorption column group and the adsorption process has been completed. The newly constructed void column A3 in the transfer liquid discharge step shown in Figure 3 is connected in series to the most downstream column A2 of the adsorption column group, and the most upstream column A1 of the adsorption column group is disconnected from the adsorption stock solution supply device B and connected to the liquid transfer device D. The transfer liquid supplied from the liquid transfer device D pushes the adsorption liquid in column A1 into the adjacent column A2, and the adsorption liquid in the adsorption column group is transferred sequentially to the adjacent columns, and column A3 is filled with adsorption liquid.

[0049] (Fig. 5: Transfer liquid discharge process for most upstream adsorption column) Fig. 5 shows the process of discharging the transfer liquid from the most upstream column A1 of the adsorption column group after the adsorption liquid transfer process shown in Fig. 4 is completed. After the supply of the transfer liquid to column A1 is completed, air is supplied to column A1 by gas supply device G in the direction opposite to the supply direction of the transfer liquid, and the transfer liquid remaining in column A1 is discharged through waste line H connected to column A1 in conjunction with gas supply device G.

[0050] (FIG. 6: Adsorption, desorption, and drying steps) FIG. 6 shows a state in which gas is further supplied to column A1, from which the transfer liquid was discharged in the previous step shown in FIG. 5, and the adsorbent in the column is dried to form a new void column A1, while the adsorption stock solution is supplied to new adsorption column groups A2 and A3, and the desorption stock solution is supplied to new desorption column groups A4 to A8. This shows a state in which the adsorption column groups A1 and A2, desorption column groups A3 to A7, and void column A8 shown in FIG. 1 have shifted by one column to adsorption column groups A2 and A3, desorption column groups A4 to A8, and void column A1, respectively. Thereafter, the adsorption, desorption, and transfer steps shown in each of the above steps are repeated the required number of times.

[0051] According to the present invention, specific water-soluble ions can be efficiently adsorbed by transferring the desorption liquid from the most upstream desorption column in a group of desorption columns, where the desorption process has progressed the most and the adsorption capacity of the specific water-soluble ions has decreased, then detaching and regenerating the column as a void column, and connecting the regenerated void column to the most downstream of the group of adsorption columns. Furthermore, specific water-soluble ions can be efficiently desorbed by transferring the adsorption liquid from the most upstream adsorption column in a group of adsorption columns, where the adsorption process has progressed the most and the adsorption capacity of the specific water-soluble ions has decreased, then detaching and regenerating the column as a void column, and connecting the regenerated void column to the most downstream of the group of desorption columns. Therefore, specific water-soluble ions can be efficiently separated and recovered, and if necessary, a desorption treatment solution in which the specific water-soluble ions are concentrated can be obtained by desorbing using a desorption stock solution with a higher ion concentration than the adsorption stock solution.

[0052] 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.

[0053] The adsorbent was KZnHCF granules (K) manufactured by Fuso Co., Ltd. ２ Zn ３ [Fe(CN) ６ ] ２ ・3H ２ O) was used. Eight acrylic columns with a height of 33.3 cm and an inner diameter of 2.4 cm were filled with 114 g of the above adsorbent each and arranged in a ring shape. The supply devices for the adsorption stock solution, desorption stock solution, and transfer liquid were installed so that the liquid flowed upward within the column, and the gas supply device was installed so that the gas flow direction descended within the column to reach the waste path. First, using a double plunger pump, 10 L of pure water was passed through the eight columns from the bottom to the top at a flow rate of 10 mL / min to wash the adsorbent. Then, the washing liquid in the column was discharged using gas supplied from the gas supply device to prepare the adsorption device.

[0054] Eight columns were connected in series, and a 280 mmol / L aqueous ammonium chloride solution was passed through them at a flow rate of 10 mL / min for 17 hours, resulting in saturated adsorption of all columns. Next, three adsorption columns receiving the adsorption stock solution were connected in series, and the aqueous solution was drained from the columns, after which they were pre-filled with the adsorption stock solution to form an adsorption column group. Four desorption columns receiving the desorption stock solution were connected in series, and the aqueous solution was drained from the columns, and then pre-filled with the desorption stock solution to form a desorption column group. The column between the most downstream column of the desorption column and the most upstream column of the adsorption column, which was not connected to either group, was designated as a void column. An aqueous ammonium chloride solution with an ammonium ion concentration of 70 mmol / L was supplied as the adsorption stock solution to the most upstream column of the adsorption column group at a flow rate of 3.5 mL / min for 650 minutes, for a total volume of 2275 mL, to perform the adsorption treatment. The adsorption treatment solution flowing out from the most downstream column of the adsorption column group was stored in the adsorption treatment solution storage tank. The total amount of ammonium ions supplied was 159.25 mmol.

[0055] During this adsorption treatment, 77.5 mL of a potassium chloride aqueous solution with a potassium ion concentration of 2800 mmol / L was supplied as a desorption stock solution to the most upstream column of the desorption column group at a flow rate of 0.155 mL / min for 500 minutes to perform desorption treatment, and the desorption treatment solution flowing out from the most downstream column of the desorption column group was stored in the desorption treatment solution storage tank. The total amount of potassium ions supplied was 217 mmol.

[0056] After the desorption treatment, a void column was connected to the desorption column group, and pure water (transfer liquid) was supplied to the most upstream column at a flow rate of 0.55 mL / min for 147 minutes to sequentially transfer the aqueous solution (desorption liquid) in the desorption column group toward the connected void column. Next, the most upstream column of the desorption column group was disconnected, and gas was supplied to this column for 3 minutes to drain the water, and this was used as a new void column.

[0057] This new void column was connected to the most downstream column of the group of adsorption columns that had finished receiving the aqueous ammonium chloride solution (adsorption stock solution), and pure water (transfer liquid) was supplied from the most upstream column of the group of adsorption columns at a flow rate of 10 mL / min for 310 seconds to sequentially transfer the aqueous solution (adsorption liquid) from the group of adsorption columns toward the connected void column. Next, the most upstream column of the group of adsorption columns was disconnected, and this column was drained for 3 minutes, and this was used as a new void column.

[0058] If we count the series of steps from the above adsorption, desorption, and transfer steps through to the next adsorption, desorption, and transfer steps as one cycle, the column's function will return to normal after eight cycles. After eight preparatory cycles, measurements were started from the ninth cycle. The total volume of desorption treatment solution stored in the desorption treatment solution storage tank through the above steps was 72.4 mL per cycle, and the ammonium ion concentration was 1410 mmol / L, meaning that the desorption treatment solution contained 102 mmol of ammonium ions. Therefore, in this example, the ammonium ion concentration in the desorption treatment solution was approximately 20 times higher than the 70 mmol / L of the original adsorption solution, and approximately 64% was recovered in the desorption treatment solution. Furthermore, the potassium ion concentration in the desorption treatment solution was 130.9 mmol / L, meaning that 9.42 mmol of potassium ions were contained. Therefore, the ratio of potassium ion concentration to ammonium ion concentration in the desorption treatment solution was less than 0.1, indicating that potassium ion contamination was minimal.

[0059] The present invention can be used to selectively separate and remove water-soluble ions such as phosphorus, boron, arsenic, fluorine, and cesium from environmental water, which cause pollution and eutrophication that affect ecosystems, and to concentrate, recover, and recycle useful water-soluble ions such as ammonium ions and lithium ions contained in the environmental water.

[0060] A Adsorption device B Adsorption raw liquid supply device C Desorption raw liquid supply device D Liquid transfer device E Adsorption treatment liquid storage section F Desorption treatment liquid storage section G Gas supply device H Disposal route

Claims

1. A separation and recovery device for specific water-soluble ions, comprising an adsorption device, a control device, and a liquid transfer device, wherein the adsorption device has a plurality of columns arranged in a ring shape, each containing an adsorbent that preferentially adsorbs the specific water-soluble ions from an adsorption stock solution containing the specific water-soluble ions, and the plurality of columns are separated into an adsorption column group, a desorption column group, and a void column, wherein the adsorption column group comprises a plurality of columns connected in series that adsorb the specific water-soluble ions by passing the adsorption stock solution through the columns and discharge an adsorption treatment liquid in which the concentration of the specific water-soluble ions has been reduced, and wherein the desorption column group comprises a plurality of columns connected in series that desorb the specific water-soluble ions by passing a desorption stock solution capable of desorbing the specific water-soluble ions through the columns and discharge a desorption treatment liquid containing the specific water-soluble ions, and wherein the void column is one or more columns, and does not substantially contain therein an aqueous solution containing the specific water-soluble ions or a component that desorbs the specific water-soluble ions, a control device that controls the connection between the most downstream column of the adsorption column group or the desorption column group and the gap column adjacent thereto, and the separation of the most upstream column of the adsorption column group or the desorption column group from the corresponding column group; and a liquid transfer device that uses a transfer liquid or transfer gas to push the aqueous solution filling the adsorption column group or the desorption column group from the most upstream column of each column group toward the gap column connected to the most downstream column of the adsorption column group or the desorption column group.

2. The water-soluble ion separation and recovery device as described in claim 1, wherein the columns constituting the adsorption device have an inlet for the aqueous solution at the top and a drainage port at the bottom, or an inlet at the bottom and a drainage port at the top, and the inlet and drainage ports for the aqueous solution of adjacent columns are either provided on the same side vertically or on opposite sides vertically.

3. The water-soluble ion separation and recovery device according to claim 2, wherein the column constituting the adsorption device has an inlet for the aqueous solution at the bottom and a drainage outlet at the top.

4. The water-soluble ion separation and recovery device according to claim 1, wherein the transfer liquid is pure water, a desorption stock solution or an adsorption stock solution.

5. The water-soluble ion separation and recovery apparatus according to claim 1, further comprising a gas supply device for drying the transfer liquid.

6. A method for separating and recovering specific water-soluble ions, comprising using the following adsorption means, control means, and liquid transfer means, and repeating the following steps (1) to (5) in order, or steps (1), (4), (5), (2), and (3) in order, one or more times, wherein the adsorption means is arranged in a ring shape in which a plurality of columns containing an adsorbent that preferentially adsorbs the specific water-soluble ions from an adsorption stock solution are arranged, and the plurality of columns are divided into: an adsorption column group in which a plurality of columns are connected in series to adsorb the specific water-soluble ions by passing the adsorption stock solution through and discharge an adsorption treatment liquid in which the concentration of the specific water-soluble ions has been reduced; a desorption column group in which a plurality of columns are connected in series to desorb the specific water-soluble ions by passing a desorption stock solution capable of desorbing the specific water-soluble ions through and discharge a desorption treatment liquid containing the specific water-soluble ions; and one or more void columns that do not substantially contain an aqueous solution containing the specific water-soluble ions or desorption components that desorb the specific water-soluble ions therein; the control means controls the connection between the most downstream column of the adsorption column group or the desorption column group and the gap column, and the separation of the most upstream column of the adsorption column group or the desorption column group from the column group; the liquid transfer means causes a transfer liquid or a transfer gas to flow into the most upstream column of the adsorption column group or the desorption column group, and pushes the adsorption liquid or desorption liquid filling the adsorption column group or the desorption column group from the most upstream column of the adsorption column group or the desorption column group toward the gap column connected to the most downstream column; and the steps (1) to (5) include: (1) performing an adsorption step of adsorbing the specific water-soluble ion to an adsorbent of the adsorption column group, and a desorption step of desorbing the specific water-soluble ion from the adsorbent of the desorption column group; and (2) performing a liquid transfer step of newly connecting the gap column to the most downstream column of the desorption column group that has completed the desorption step, and pushing the desorption liquid filling the desorption column group from the most upstream column of the column group toward the gap column using a transfer liquid or a transfer gas.(3) after completing the liquid transfer process, a replacement process is performed in which the most upstream column is disconnected from the desorption column group, this column is used as a new void column adjacent to the most downstream column of the adsorption column group, and the void column to which the desorption liquid has been transferred in the liquid transfer process is used as the most downstream column of the desorption column group; (4) a liquid transfer process is performed in which the void column is newly connected to the most downstream column of the adsorption column group that has completed the adsorption process, and the adsorption liquid filling the adsorption column group is pushed from the most upstream column of the column group toward the void column using a transfer liquid or transfer gas; (5) after completing the liquid transfer process, a replacement process is performed in which the most upstream column is disconnected from the adsorption column group, this column is used as a new void column adjacent to the most downstream column of the desorption column group, and the void column to which the adsorption liquid has been transferred in the liquid transfer process is used as the most downstream column of the adsorption column group.

7. A method for separating and recovering water-soluble ions as described in claim 6, wherein the aqueous solution is supplied from the top of the column constituting the adsorption means and discharged from the bottom, or is supplied from the bottom of the column constituting the adsorption means and discharged from the top, and the direction in which the aqueous solution flows between adjacent columns is the same or opposite.

8. The method for separating and recovering water-soluble ions according to claim 6, wherein the aqueous solution is supplied from the lower part of each column constituting the adsorption means and discharged from the upper part.

9. The method for separating and recovering water-soluble ions according to claim 6, wherein the liquid transfer liquid is pure water, a desorption stock solution or an adsorption stock solution.

10. The method for separating and recovering water-soluble ions according to claim 6, further comprising a step of supplying a gas to the most upstream column after the liquid transfer step using the transfer liquid, to dry the column.

11. A method for separating and recovering water-soluble ions as described in claim 6, comprising obtaining a desorption treatment solution in which the specific water-soluble ions are concentrated, using a desorption stock solution containing a desorption component at a concentration higher than the molar concentration of the specific water-soluble ion contained in the adsorption stock solution.

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