JP2011161361A - Water clarifying apparatus and water clarifying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water clarifying apparatus in which hydrated anions are recovered by using an ion permeable membrane, the hydrated anions are dehydrated to obtain water and thereby leakage of dehydrated anions to water to be clarified and deposition of salts can be prevented and clarified water can be efficiently recovered. <P>SOLUTION: The water clarifying apparatus has a dilution means for bringing the water to be clarified into contact via a semi-permeable membrane with an ion-containing aqueous solution containing nonvolatile cations and the hydrated ions that becomes volatile by dehydration and for diluting the ion-containing aqueous solution with water separated from the water to be clarified by the semi-permeable membrane, a separation means for separating the hydrated anions and the nonvolatile cations via an ion exchange membrane from the ion-containing aqueous solution diluted by the dilution means, a volatilization means for obtaining clarified water where dehydrated anions are removed and recovered by dehydrating and volatilizing separated hydrated anions, and a dissolving means for dissolving the dehydrated anions recovered and removed by the volatilization means in the aqueous solution containing at least the non-volatile cations. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water purification apparatus and a water purification method to which a forward osmosis method using an ion-containing aqueous solution containing a hydratable anion and a non-volatile cation that are dehydrated and become volatile is applied.

As a method of selectively separating and moving water between two aqueous solutions having a difference in osmotic pressure, a reverse osmosis (RO) method using external pressure and a forward osmosis (which uses osmotic pressure to perform separation with low energy) The FO) method is known.
As one of the forward osmosis methods, there is a method using a volatile ion-containing aqueous solution containing a volatile anion and a volatile cation. For example, as shown in FIG. 1, the water to be purified is brought into contact with a volatile ion-containing aqueous solution containing volatile anions and volatile cations via a semipermeable membrane 1, and the semipermeable membrane 1 allows the water to be purified to be purified. Diluting means 11 for diluting the volatile ion-containing aqueous solution with separated water;
Separation means 15 including a distillation column 7 for obtaining purified water by volatilizing the volatile anions and the volatile cations from the diluted aqueous solution containing volatile ions,
There has been proposed a water purifier having a dissolving means 14 including a gas absorber 6 for returning the vaporized and separated anion gas and cation gas to the diluted aqueous solution containing volatile ions and dissolving them (see Patent Document 1). ).

  However, in the proposed water purification apparatus shown in FIG. 1, ammonia is used as a volatile cation, so that ammonia leaks from the semipermeable membrane 1 to the purification target water. Since ammonia has physical properties such as molecular size that are very close to water, it is very difficult to suppress the permeation of ammonia in a membrane that selectively permeates water, such as the semipermeable membrane used in the present invention. As a result, not only replenishment of a large amount of cations is required, but a large amount of ammonia is released to the environment through the water to be purified after the treatment, and therefore an improvement is desired.

  In the water purification apparatus shown in FIG. 1, in the separation step using the separation means 15, carbon dioxide, water, and ammonia come into contact with each other, and a salt such as ammonium hydrogen carbonate, ammonium carbonate, or ammonium carbamate is distilled into a distillation column. There is a problem that the efficiency of the water purification treatment decreases or clogging occurs due to precipitation on packings, trays, piping, etc. in the distillation column.

  Moreover, the water purification system using the ion-containing aqueous solution containing a non-volatile cation and a volatile anion is proposed (refer patent document 2). According to this proposed water purification system, the rate of leakage of non-volatile cations from the semipermeable membrane into the water to be purified can be suppressed slower than when ammonia, which is a volatile cation, is used. However, since the water purification system of Patent Document 2 handles a part of the solute as an undissolved component, there is a problem that its handling property is remarkably poor. For example, when removing undissolved components with a filter, it is very difficult to maintain the removal performance due to clogging, and it is difficult to sufficiently recover the undissolved components remaining on the filter. Moreover, when precipitating an undissolved component, a long time is required and it cannot be handled stably. Furthermore, large-scale equipment such as a centrifuge is required.

  Therefore, the present situation is that it is desired to provide a water purification system capable of efficiently recovering purified water without having to handle non-dissolved components as described above.

US Patent Application Publication No. 2005/0145568 US Pat. No. 6,391,205

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention recovers a hydratable anion by using an ion permeable membrane by using a non-volatile cation without using volatile ammonia having a high membrane permeability, It is an object of the present invention to provide a water purification device and a water purification method that can prevent cation leakage and salt precipitation to the water to be purified by dehydrating to obtain water, and can efficiently recover the purified water. To do.

Means for solving the problems are as follows. That is,
<1> A purification target water and an ion-containing aqueous solution containing a hydrating anion and a non-volatile cation that are dehydrated and become volatile are brought into contact with each other through the semipermeable membrane, and the purification target water is made to pass through the semipermeable membrane. Dilution means for diluting the ion-containing aqueous solution with water separated from
Separation means for separating the hydratable anion and the non-volatile cation from the ion-containing aqueous solution diluted by the dilution means via an ion exchange membrane;
Volatilizing means for obtaining purified water from which the dehydrated anion has been removed and recovered by dehydrating and volatilizing the separated hydratable anion,
Dissolving means for dissolving the dehydrated anion recovered and removed by the volatilization means in an aqueous solution containing at least a non-volatile cation;
It is a water purification apparatus characterized by having.
The water purification apparatus according to <1> includes a diluting unit, a separating unit, a volatilizing unit, and a dissolving unit.
The water to be purified by the diluting means and an ion-containing aqueous solution containing a hydrating anion and a non-volatile cation that are dehydrated to become volatile are brought into contact with each other through a semipermeable membrane, and the purification object is obtained by the semipermeable membrane. The ion-containing aqueous solution is diluted with water separated from water.
The hydratable anion and the non-volatile cation are separated from the ion-containing aqueous solution diluted by the diluting means by the separating means through an ion exchange membrane.
The separated hydratable anion is dehydrated by the volatilizing means and volatilized to obtain purified water from which the dehydrated anion has been removed and recovered.
The dehydrating anion recovered and removed by the volatilizing unit is dissolved in an aqueous solution containing at least a non-volatile cation by the dissolving unit. As a result, the permeable anion is recovered by using the ion permeable membrane by using the non-volatile cation without using the volatile ammonia having a high permeability of the membrane, and dehydrating the hydratable anion. By obtaining water, it is possible to prevent cation leakage and salt precipitation to the water to be purified, and it is possible to efficiently collect the purified water.
<2> The water purification apparatus according to <1>, wherein the hydratable anion is any one of carbonic acid (H ₂ CO ₃ ) and sulfurous acid (H ₂ SO ₃ ).
<3> The water purification apparatus according to any one of <1> to <2>, wherein the non-volatile cation source is a compound having a molecular weight of 50 or more and 500 or less.
<4> The water purification apparatus according to any one of <1> to <3>, wherein the non-volatile cation source is a quaternary ammonium compound.
<5> The method according to any one of <1> to <4>, wherein the separation means is any one of diffusion dialysis using an ion exchange membrane, electrodialysis using an ion exchange membrane, and ion selective membrane distillation. It is a water purification device.
<6> The water purification apparatus according to any one of <1> to <5>, wherein the volatilization unit is a membrane process unit.
<7> The water purifier according to any one of <1> to <6>, wherein at least a part of the dissolving means is combined with the separating means.
<8> The water purification device according to any one of <1> to <7>, wherein the semipermeable membrane is a forward osmosis semipermeable membrane that selectively transmits water.
<9> The water purification device according to any one of <1> to <8>, wherein the water to be purified is seawater.
<10> A purification target water and an ion-containing aqueous solution containing a hydrating anion and a non-volatile cation that are dehydrated and become volatile are brought into contact with each other through the semipermeable membrane, and the purification target water is made by the semipermeable membrane. A diluting step of diluting the ion-containing aqueous solution with water separated from
A separation step of separating the hydratable anion and the non-volatile cation from the ion-containing aqueous solution diluted in the dilution step via an ion exchange membrane;
A volatilizing step for obtaining purified water from which the dehydrated anion is removed and recovered by dehydrating and volatilizing the separated hydratable anion;
A dissolution step of dissolving the dehydration anion recovered and removed in the volatilization step in an aqueous solution containing at least a non-volatile cation;
It is the water purification method characterized by including.
The water purification method according to <10> includes a dilution step, a separation step, a volatilization step, and a dissolution step.
In the dilution step, the water to be purified is brought into contact with a water-containing ion-containing aqueous solution containing a hydrating anion and a non-volatile cation that becomes volatile by dehydration, and the purification is performed by the semipermeable membrane. The ion-containing aqueous solution is diluted with water separated from the target water.
Next, in the separation step, the hydratable anion and the nonvolatile cation are separated from the ion-containing aqueous solution diluted in the dilution step via an ion exchange membrane.
Next, the separated hydratable anion is dehydrated and volatilized by the volatilizer to obtain purified water from which the dehydrated anion has been removed and recovered.
Next, in the dissolution step, the dehydration anion recovered and removed in the volatilization step is dissolved in an aqueous solution containing at least a non-volatile cation.
As a result, the permeable anion is recovered by using the ion permeable membrane by using the non-volatile cation without using the volatile ammonia having a high permeability of the membrane, and dehydrating the hydratable anion. By obtaining water, it is possible to prevent cation leakage and salt precipitation to the water to be purified, and it is possible to efficiently collect the purified water.

  According to the present invention, the conventional problems described above can be solved, and hydration is achieved by using an ion permeable membrane using a non-volatile cation without using volatile ammonia having a high membrane permeability. A water purification device capable of efficiently recovering purified water by recovering anions and dehydrating the hydratable anions to obtain water, thereby preventing leakage of cations and salt precipitation into the water to be purified. And a water purification method can be provided.

FIG. 1 is a schematic view showing an example of a conventional water purification device. FIG. 2 is a schematic view showing an example of the water purification apparatus of the present invention. FIG. 3 is a schematic view showing diffusion dialysis using an ion exchange membrane as a separation means. FIG. 4 is a schematic view showing electrodialysis using an ion exchange membrane as a separation means. FIG. 5 is a schematic diagram showing ion-selective membrane distillation as a separation means. FIG. 6 is a schematic view showing another example of the water purification apparatus of the present invention.

(Water purification device and water purification method)
The water purification apparatus of the present invention includes a diluting unit, a separating unit, a volatilizing unit, and a dissolving unit, and further includes other units as necessary.
The water purification method of the present invention includes a dilution step, a separation step, a volatilization step, and a dissolution step, and further includes other steps as necessary.

  The water purification method of the present invention can be preferably implemented by the water purification apparatus of the present invention, the dilution step can be performed by the dilution means, the separation step can be performed by the separation means, The volatilization step can be performed by the volatilization unit, the dissolution step can be performed by the dissolution unit, and the other steps can be performed by the other unit.

<Dilution means and dilution process>
In the dilution step, the water to be purified and an ion-containing aqueous solution containing a hydrating anion and a non-volatile cation that are dehydrated and become volatile are brought into contact with each other through a semipermeable membrane, and the purification is performed by the semipermeable membrane. This is a step of diluting the ion-containing aqueous solution with water separated from the target water, and can be performed by a diluting means.

<< Purified water >>
The water to be purified is not particularly limited and can be appropriately selected according to the purpose. For example, water obtained from the natural world such as seawater, British water, rivers, lakes, swamps, ponds, factories and various industrial facilities Industrial wastewater discharged from households, and general wastewater discharged from households and general facilities. Among these, seawater is particularly preferable from the viewpoints of availability that can be obtained stably and in large quantities and the necessity of purification.
In the present invention, the purified water means an aqueous solution having a small content of impurities such as salt. The impurity content can be appropriately adjusted according to the purpose of using the purified water and the type of impurities.

<< Ion-containing aqueous solution >>
The ion-containing aqueous solution contains a hydratable anion and a non-volatile cation that are dehydrated and become volatile.

-Hydrating anion-
As the hydratable anion, an anionic compound that is dehydrated and becomes volatile is selected.
Here, a substance having higher volatility than water at a specific temperature is selected as the volatility. Examples of the volatility index include that the Henry's constant and the saturated vapor pressure at each temperature of the substance are larger than the saturated vapor pressure of water. The Henry's constant is a physical property value indicating the relationship between the molar fraction of a substance and the saturated vapor partial pressure in a solution in which the substance is dissolved in a large amount of solvent, and the larger the value, the higher the volatility in the solution. It is described in books such as “Chemical Handbook, published by Maruzen Co., Ltd.” and books “Augmented Gas Absorption, Published by Chemical Industry Co., Ltd.”.
Specific examples of the hydratable anion include carbonic acid (H ₂ CO ₃ ), sulfurous acid (H ₂ SO ₃ ), etc., and volatile dehydrates include carbon dioxide (CO ₂ ), And sulfur dioxide (SO ₂ ). Among these, carbon dioxide (CO ₂ ) is particularly preferable because of high volatility and chemical stability of the dehydrate.

-Nonvolatile cation source-
Since the non-volatile cation source tends to have a low permeability of the semipermeable membrane as compared with a non-volatile cation source such as ammonia, the problem of cation leakage to the purification target water can be solved. .
As the non-volatile cation source, a substance having a lower volatility than water at a specific temperature is selected. Examples of the volatility index include that the Henry's constant and the saturated vapor pressure at each temperature of the substance are larger than the saturated vapor pressure of water. The Henry's constant is a physical property value indicating the relationship between the molar fraction of a substance and the saturated vapor partial pressure in a solution in which the substance is dissolved in a large amount of solvent, and the larger the value, the higher the volatility in the solution. For example, it is described in the book “Chemical Handbook, published by Maruzen Co., Ltd.” and the book “Augmented Gas Absorption, Published by Chemical Industry Co., Ltd.”.
Moreover, since the permeability | transmittance of a semipermeable membrane is suppressed, so that the molecular weight (or atomic weight) of a non-volatile cation source is large, it is preferable. On the other hand, if the molecular weight (or atomic weight) is too large, the dilution rate in the dilution means becomes slow at the same mass% concentration, which is not preferable. Specifically, the molecular weight (or atomic weight) is preferably from 50 to 500, more preferably from 100 to 200. More specifically, monoethanolamine (molecular weight 61), ethylenediamine (molecular weight 60), diethanolamine (molecular weight 105), 2- (2-aminoethylamino) ethanol (molecular weight 104), diethylenetriamine (molecular weight 103), triethylenetetramine (Molecular weight 146), Tris (2-aminoethyl) amine (Molecular weight 146), Tetraethylenepentamine (Molecular weight 189), Low molecular weight polyethyleneimine (Molecular weight 200-500), etc. are mentioned. Further, a quaternary ammonium compound is preferably selected from the viewpoint that the pH can be adjusted to near neutral, a hydrated anion and a conjugate are not formed, and the basicity is high. More specifically, tri (2-hydroxymethyl) methylammonium (molecular weight 139), tri (2-hydroxyethyl) methylammonium (molecular weight 181), choline (2-hydroxyethyltrimethylammonium) (molecular weight 121) is preferably selected. Is done.

Regarding the leakage rate of volatile cations in the semipermeable membrane, for example, as the ion-containing aqueous solution, the concentration of carbonic acid-derived components is 300 mmol / L, the concentration of ammonia as volatile cations is 420 mmol / L, and the purification target water is 2 mg / L. When an aqueous membrane containing Hydration Technology Innovations (hereinafter referred to as “HT membrane”) was used as the aqueous sodium humate solution and semi-permeable membrane, the leakage rate was 0.42 mol / m ² hr. And very early. If leakage occurs at such a rate, not only a large amount of cations need to be replenished, but also a large amount of ammonia is released to the environment through the water to be purified after treatment, which is practically impossible. It is. On the other hand, when monoethanolamine which is a non-volatile cation is used instead of ammonia in the same manner, it is less than 1/10, and when diethanolamine is used, less than 1/15, tri (2-hydroxyethyl) When methylammonium is used, it is greatly suppressed to less than 1/20.

The content (concentration) of the hydratable anion in the ion-containing aqueous solution is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of increasing the speed of separating water from the purification target water, the concentration (concentration) is high Preferably there is.
The content (concentration) of the non-volatile cation in the ion-containing aqueous solution is not particularly limited and can be appropriately selected according to the purpose. From the viewpoint of increasing the speed of separating water from the purification target water, the concentration (concentration) is high. Preferably there is. However, the concentration may be reduced as appropriate in order to suppress the precipitation of salt or the generation of bubbles in the solution. In addition, when the ion-containing aqueous solution is acidic or alkaline, a member such as the semipermeable membrane is deteriorated. Therefore, the ratio between the hydratable anion and the non-volatile cation can be appropriately adjusted. preferable.

-Semi-permeable membrane-
The semipermeable membrane is not particularly limited as to its material, shape, size, structure, etc., and can be appropriately selected according to the purpose, but is a forward osmotic semipermeable membrane that selectively permeates water. It is preferable.
The forward osmosis semipermeable membrane is not particularly limited as long as it has semipermeable membrane properties and can be appropriately selected according to the purpose. Examples of the material include cellulose acetate, aromatic polyamide, aromatic polysulfone, poly And benzimidazole. Examples of the shape include a flat membrane, a spiral type module using a flat membrane, a hollow fiber type module, a tubular type module, and the like.

<Separation process and separation means>
The separation step is a step of separating the hydratable anion and the non-volatile cation from the ion-containing aqueous solution diluted in the dilution step through an ion exchange membrane, and is performed by a separation unit.

  The separation means is not particularly limited as long as the hydratable anion and the non-volatile cation can be separated at least partially, and can be appropriately selected according to the purpose. For example, an ion exchange membrane is used. Examples include diffusion dialysis used, electrodialysis using an ion exchange membrane, and ion selective membrane distillation.

As shown in FIG. 3, the diffusion dialysis using the ion exchange membrane is performed by bringing the diluted ion-containing aqueous solution into contact with the anion exchange membrane and bringing pure water into contact with the back side, thereby allowing the concentration of the hydratable anion. It is a method of selectively permeating it according to a gradient. At this time, as a counter ion of the hydratable anion, protons selectively permeate the membrane because of its small size.
Diffusion dialysis using this ion exchange membrane is energetically advantageous because permeation of hydratable anions is achieved without the need for external forces. The diffusion dialysis requires high selectivity between protons and non-volatile cations in the anion exchange membrane. The non-volatile cation having low permeability in the semipermeable membrane is more preferably selected because of its high permeation selectivity with protons in the anion exchange membrane even in diffusion dialysis.

As shown in FIG. 4, the electrodialysis using the ion exchange membrane includes a diluted ion-containing aqueous solution sandwiched between an anion exchange membrane and a cation exchange membrane, and an anode and a cation exchange membrane outside the anion exchange membrane. This is a method in which a cathode is arranged outside the electrode and a voltage is applied between both electrodes. More preferably, between the anion exchange membrane and the anode, between the cation exchange membrane and the cathode, a bilayer membrane of an anion exchange membrane and a cation exchange membrane (hereinafter simply referred to as “bilayer membrane”), respectively. Deploy.
In the electrodialysis, a hydratable anion is attracted to the anode side (anion exchange membrane side) and a non-volatile cation is attracted to the cathode side (cation exchange membrane side) by applying a voltage between both electrodes. Thus, each membrane can be selectively permeated and separated. At this time, protons are generated and attracted from the intermembrane interface of the bilayer membrane as the counter ion of the hydratable anion, and hydroxy ions are also generated from the intermembrane interface of the bilayer membrane as the counter ion of the volatile cation. Attracted.
The electrodialysis has an increased energy load compared to the diffusion dialysis. However, the electrodialysis is advantageous because it requires less selectivity than the diffusion dialysis and can sufficiently increase the separation rate.

  In the ion selective membrane distillation, as shown in FIG. 5, an ion-containing aqueous solution diluted in the same manner as the diffusion dialysis is brought into contact with an anion exchange membrane. At this time, the hydrated anion dehydrated at the membrane interface is volatilized by contacting the back side with air instead of pure water.

<Volatilization process and volatilization means>
The volatilization step is a step of obtaining purified water from which the dehydrated anion has been removed and recovered by dehydrating and volatilizing the separated hydratable anion, and can be carried out by a volatilizing means.

The volatilization means is not particularly limited and may be appropriately selected depending on the purpose. For example, a control mechanism for a microfluid such as a distillation column, a distillation apparatus, a membrane process unit, or a microreactor used for general distillation, Etc. Among these, a membrane process unit such as a membrane distillation unit is preferable from the viewpoint that a volatile interface is relatively wide and suitable for downsizing, and is particularly preferable when carbonic acid is used as a hydratable anion.
There is no restriction | limiting in particular as said distillation tower, According to the objective, it can select suitably, For example, a plate tower, a packed tower, etc. are mentioned.
Examples of the plate tower include structures described in p139 to p143 of the book “Distillation Technology, Chemical Engineering Association” and p141 to p142 of the book “Commentary Chemical Engineering, Issued by Baifukan”. Bubble cap) tray, valve tray, perforated plate (sieve) tray, and the like.
The packing to be packed in the packed tower may be regular packing or irregular packing, for example, p155 to p157 of the book “Commentary Chemical Engineering, Bafukan Issue”, p221 of the book “Supplementary Gas Absorption, Chemical Industry Co., Ltd.”. ˜p242 can be arbitrarily selected from the packing materials described in p242.
As the membrane process unit, for example, a membrane distillation unit described in an academic paper “Journal of Membrane Science Vol. 124, Issue 1, p1 to p25” can be used.
As the microreactor, for example, the microreactor described in the book “Technology and application of microchemical chip, published by Maruzen Co., Ltd.” can be used.
As the separation means, these means may be used alone or in combination.

<Dissolution process and dissolution means>
The dissolution step is a step of dissolving the dehydration anion recovered and removed in the volatilization step in an aqueous solution containing at least a non-volatile cation, and can be performed by a dissolution means.

The dissolving means is not particularly limited, and an apparatus used for general gas absorption can be arbitrarily used. For example, the book “Additional Gas Absorption, Chemical Industry Co., Ltd.” p. 49-p. 54, p. 83-p. The apparatus, parts, and conditions described in 144 can be arbitrarily selected. Specific examples include a system using a packed tower, a plate tower, a spray tower, and a fluid packed tower, a liquid film cross flow contact system, a high-speed swirl flow system, and a mechanical force utilization system. Further, a thin gas-liquid layer may be constructed and absorbed using a microfluidic control mechanism such as a microreactor or a membrane reactor.
The packing to be packed in the packed tower may be either regular packing or irregular packing. For example, p. 221-p. The packing described in 242 can be arbitrarily selected. Component materials such as packings, towers, distributors, supports, etc. include steel-based materials such as stainless steel and aluminum killed steel, non-ferrous materials such as titanium and aluminum, ceramics such as glass and alumina, carbon, synthetic polymers, rubber Such materials can be arbitrarily selected and used.

Further, as a more preferable form of the dissolving means used in the present invention, an embodiment in which the separating means and the dissolving means can be carried out alternately or simultaneously can be preferably selected. From the viewpoint of water recovery efficiency, it is more preferred to carry out simultaneously. A possible form is selected.
As an embodiment in which such separation and dissolution can be performed at the same time, for example, as shown in FIG. 2, an anion exchange membrane 21 as a separation means is brought into contact with one side of a diluted ion-containing aqueous solution, and hydrated anions are permeated. At the back of the film, dehydration is carried out through the membrane process unit 22 in the form of membrane distillation as a volatilization means, and the gas of the hydrated anion volatilized subsequently is absorbed through the membrane process unit 23 in the form of membrane distillation as a dissolution means. And a method of dissolving them.

-Other processes and other means-
Examples of the other steps include a control step and a driving step, which are performed by a control unit and a driving unit.
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as a sequencer and a computer.

<First Embodiment>
FIG. 2 is a schematic view showing a first embodiment of the water purification apparatus of the present invention. In the water purification apparatus of FIG. 2, carbonic acid (H ₂ CO ₃ ) is used as a hydratable anion, and tri (2-hydroxymethyl) methylammonium is used as a non-volatile cation.
Further, as the forward osmosis semipermeable membrane 1, an Expedition built-in membrane (hereinafter referred to as “HT membrane”) manufactured by Hydration Technology Innovations is used.
As the separation means 21, diffusion dialysis using an ion exchange membrane shown in FIG. 3, electrodialysis using an ion exchange membrane shown in FIG. 4, or ion selective membrane distillation shown in FIG. 5 can be used.
In the water purification apparatus of FIG. 2, diffusion dialysis using the ion exchange membrane 21 shown in FIG. 3 is used as the separation means. Further, the membrane process unit 22 in the form of membrane distillation is used as the volatilizing means, and the membrane process unit 23 in the form of membrane distillation is used as the dissolving means. Thereby, the input amount of CO ₂ can be increased, and a large amount of purified water can be obtained.

In the water purification apparatus shown in FIG. 2, the water to be purified is brought into contact with an aqueous solution containing ions containing hydrating anions and non-volatile cations that are dehydrated and become volatile through a semipermeable membrane. The ion-containing aqueous solution is diluted with water separated from the purification target water by a permeable membrane.
Next, the hydratable anion and the non-volatile cation are separated from the diluted ion-containing aqueous solution through an ion exchange membrane.
Next, by dehydrating the separated hydratable anion and volatilizing it, the dehydrated anion is removed and recovered, and purified water is obtained.
Next, the recovered dehydrated anion is dissolved in an aqueous solution containing at least a non-volatile cation to regenerate the ion-containing aqueous solution.

<Second Embodiment>
FIG. 6 is a schematic view showing a second embodiment of the water purification apparatus of the present invention. The water purification apparatus of FIG. 6 uses a gas absorption tower 24 as a dissolving means. In addition, in the water purification apparatus of FIG. 6, the same thing as the water purification apparatus of FIG. 2 was shown with the same sign.

  The water purification apparatus and the water purification method of the present invention recover hydratable anions by using an ion permeable membrane without using volatile ammonia having high membrane permeability, and dehydrate the hydratable anions. Thus, by obtaining water, it is possible to prevent cation leakage and salt precipitation to the water to be purified, and to efficiently recover the purified water. It is suitably used for water purification.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
The water purification apparatus of this invention shown in FIG. 2 was assembled using the member shown below.
As the water to be purified, a 3.5% by mass sodium chloride aqueous solution was used as a seawater model.
Carbonic acid (H ₂ CO ₃ ) was used as the hydratable anion.
Tri (2-hydroxymethyl) methylammonium was used as a non-volatile cation source.
An ion-containing aqueous solution containing 1.8 mol / L of carbonic acid (H ₂ CO ₃ ) and 2.5 mol / L of a non-volatile cation source tri (2-hydroxymethyl) methylammonium was used.
As the forward osmosis semipermeable membrane 1, an HT membrane was used.
As the separation means, an electrodialysis unit using the ion exchange membrane 21 shown in FIG. 4 was used.
As a volatilization means, (a membrane distillation unit using a PTFE porous membrane (pore diameter 0.2 μm, thickness 40 μm)) 22 was used.
As a dissolution means, (a membrane distillation unit using a PTFE porous membrane (pore diameter 0.2 μm, thickness 40 μm)) 23 was used by being arranged downstream of the separation means.

  Next, using the water purification apparatus of FIG. 2, the amount of salt precipitation and cation leakage into the purification target water was evaluated as follows. The results are shown in Table 1.

<Evaluation method of salt precipitation>
As an evaluation method of salt precipitation, after performing this purification operation for 24 hours, the inside of the bent part of the pipe where the volatilized gas collides is observed at the position above the membrane distillation unit, which is the volatilization means, and the salt precipitation The presence or absence was confirmed.

<Amount of cation leaking into the purification target water>
Concentrated sodium chloride aqueous solution obtained by performing this purification operation (concentrated sodium chloride aqueous solution because water was separated and removed through a semi-permeable membrane) as a method for measuring the amount of cation leaking into the water to be purified The amount of cation leaked was determined by quantifying the amount of cation contained therein, and the amount of cation leaked per unit area per unit time was determined by dividing it by the semipermeable membrane area and the membrane surface passage time. . The cation quantification method was determined by degassing the obtained concentrated sodium chloride aqueous solution to remove carbon dioxide and titrating the solution with a hydrochloric acid aqueous solution.

(Example 2)
A water purification apparatus of the present invention shown in FIG. 6 was assembled in the same manner as in Example 1 except that the following members were used.
A gas absorption tower (glass tube packed with Sulzer Chemtech's Lab Packing EX (hereinafter referred to as “Lab Packing EX”) 24) was used as a dissolving means.

  Next, using the water purification apparatus shown in FIG. 6, the amount of salt precipitation and cation leakage into the purification target water was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
The conventional water purification apparatus shown in FIG. 1 was assembled in the same manner as in Example 1 except that the following members were used.
As the distillation column 7 in the separation means 15, a distillation column incorporating “Lab Packing EX” was used.
As the gas absorber 6 in the dissolving means 14, an absorption tower incorporating “Lab Packing EX” was used.
Carbon dioxide was used as the volatile anion source.
Ammonia was used as the volatile cation source.
A volatile ion-containing aqueous solution containing 1.8 mol / L of carbon dioxide and 2.5 mol / L of ammonia was used.

  Next, using the water purification apparatus shown in FIG. 1, the amount of salt precipitation and the leakage of cations (ammonia) into the water to be purified was evaluated in the same manner as in Example 1. The results are shown in Table 1.

  As mentioned above, although the water purification apparatus and the water purification method of this invention were demonstrated in detail, this invention is not limited to the said Example, A various change may be carried out in the range which does not deviate from the summary of this invention.

  The water purification apparatus and the water purification method of the present invention use a non-volatile cation without using volatile ammonia having a high membrane permeability, and recover a hydratable anion by using an ion permeable membrane. By dehydrating the hydratable anion to obtain water, it is possible to prevent cations from leaking into the water to be purified and salt precipitation, and the recovered purified water can be efficiently recovered. In particular, it is suitable for purification of seawater.

DESCRIPTION OF SYMBOLS 1 Semipermeable membrane 6 Gas absorber 7 Distillation tower 11 Dilution means 14 Dissolution means 15 Separation means 21 Ion exchange membrane (separation means)
22 Gas exchange membrane (volatilization means)
23 Membrane process unit (dissolution means)
24 Gas absorption tower (dissolution means)

Claims (10)

The water to be purified is brought into contact with the aqueous solution containing ions containing hydratable anions and non-volatile cations that are hydrated by dehydration through a semipermeable membrane and separated from the water to be purified by the semipermeable membrane. Dilution means for diluting the ion-containing aqueous solution with hot water;
Separation means for separating the hydratable anion and the non-volatile cation from the ion-containing aqueous solution diluted by the dilution means via an ion exchange membrane;
Volatilizing means for obtaining purified water from which the dehydrated anion has been removed and recovered by dehydrating and volatilizing the separated hydratable anion,
Dissolving means for dissolving the dehydrated anion recovered and removed by the volatilization means in an aqueous solution containing at least a non-volatile cation;
The water purification apparatus characterized by having. The water purification apparatus according to claim 1, wherein the hydratable anion is any one of carbonic acid (H ₂ CO ₃ ) and sulfurous acid (H ₂ SO ₃ ).   The water purification apparatus according to claim 1, wherein the non-volatile cation source is a compound having a molecular weight of 50 or more and 500 or less.   The water purification apparatus according to any one of claims 1 to 3, wherein the non-volatile cation source is a quaternary ammonium compound.   The water purification apparatus according to any one of claims 1 to 4, wherein the separation means is any one of diffusion dialysis using an ion exchange membrane, electrodialysis using an ion exchange membrane, and ion selective membrane distillation.   The water purifier according to any one of claims 1 to 5, wherein the volatilizing means is a membrane process unit.   The water purifier according to any one of claims 1 to 6, wherein at least a part of the dissolving means is combined with the separating means.   The water purification apparatus according to any one of claims 1 to 7, wherein the semipermeable membrane is a forward osmosis semipermeable membrane that selectively permeates water.   The water purification apparatus according to any one of claims 1 to 8, wherein the water to be purified is seawater. The water to be purified is brought into contact with the aqueous solution containing ions containing hydratable anions and non-volatile cations that are hydrated by dehydration through a semipermeable membrane and separated from the water to be purified by the semipermeable membrane. Diluting the ion-containing aqueous solution with water,
A separation step of separating the hydratable anion and the non-volatile cation from the ion-containing aqueous solution diluted in the dilution step via an ion exchange membrane;
A volatilizing step for obtaining purified water from which the dehydrated anion is removed and recovered by dehydrating and volatilizing the separated hydratable anion;
A dissolution step of dissolving the dehydration anion recovered and removed in the volatilization step in an aqueous solution containing at least a non-volatile cation;
Water purification method characterized by including.