KR102041413B1 - A Draw Solution for forward osmosis using salt of polyethyleneimine and use thereof - Google Patents

Abstract

The present invention provides a forward osmosis induction solution characterized in that it contains a polyethyleneimine (PEI) salt having a number average molecular weight of polyethyleneimine (PEI) of 4,000 or less as an induction osmotic solute. In addition, the present invention is a method for producing a fluid (fluid) purified by the osmotic pressure of the forward osmotic induction solution containing the forward osmotic induction solute, the fluid in the fluid (fluid source) through the first membrane to the osmotic pressure A first step of permeating toward the forward osmosis inducing solution; And a second step of permeating the fluid passing through the first membrane through a second membrane through which the forward osmosis inducing solute does not pass, and using the forward osmosis induction solution according to the present invention. Provide a method.
Induction solution for forward osmosis of the present invention can be easily recovered by the excellent osmotic pressure and induced solute by using polyethyleneimine salt as a polymer salt as an inducing solute, the water treatment apparatus and water treatment method using the same energy is required to separate and recover the induced solute. It is reduced and the water treatment effect is excellent.

Description

A solution for forward osmosis using polyethyleneimine salt and its use {A Draw Solution for forward osmosis using salt of polyethyleneimine and use etc}

The present invention relates to an induction solution for forward osmosis using polyethyleneimine salt and its use.

Forward osmosis (FO) is a technology that uses osmotic pressure caused by concentration differences. Osmotic pressure is generated by the difference in salt concentration between semipermeable membranes when a draw solution containing a low concentration salt is applied to one side and a high concentration salt is applied to the other side with a semipermeable membrane that selectively permeates only water. Through this osmotic pressure, the water in the influent containing the low concentration of salt moves to a high concentration of the induction solution. At this time, as the water of the low concentration influent moves to the high concentration of the induction solution, the salt concentration of the induction solution gradually decreases, and the concentration of the low concentration influent increases. This forward osmosis process is suitable for the concentration of heat-sensitive aqueous solutions or wastewater concentration processes in which membrane fouling is severe. This is because unlike the existing reverse osmosis process can be washed by pressure. On the other hand, some of the problems occurring in the forward osmosis process include difficulty in recovery and reuse of the induction solution and reverse diffusion. Therefore, there is a limit in applying the forward osmosis process.

Representatively, in case of NaCl solution used as a conventional induction solution, it is difficult to recover and separate it, and the process does not require the recovery and recycling of the induction solution in the area where seawater and freshwater meet, or the purpose is to concentrate heat-sensitive materials. Mainly used for

In connection with the recovery and reuse of the draw solution, (NH ₄ ) ₂ CO ₃ or NH ₄ HCO ₃ is used separately or together as draw solute. (NH ₄ ) ₂ CO ₃ and NH ₄ HCO ₃ are decomposed into ammonia and carbon dioxide gas when heated to about 60 ℃ and can be easily removed, but ammonia is solubility in water that exists in recovered water depending on where it is used. There is a problem to remove ammonia. Therefore, a high temperature vacuum degassing process is needed. As described above, the induction solution using ammonium hydrogen carbonate requires a heating step in the separation process even though recovery and separation are possible, and it is difficult to prevent the loss due to water evaporation. Therefore, these characteristics lower the efficiency of the forward osmosis process is a factor that hinders the utilization of the process.

In addition, a newly proposed induction solution material includes an induction solution using nano magnetic particles to which hydrophilic peptides are attached, and attempts to recover nanoparticles by applying a magnetic field, but there are no specific recovery reports.

In addition, osmotic pressure using ionic liquid is too expensive and the proper recovery is not easy.

The role is very important because the permeation performance and the presence or absence of the problem depends on the specific characteristics and concentration of the induction solution in the forward osmosis process as described above, such induction solution has high solubility, high osmotic pressure, low solute back diffusion, easy recovery and Conditions must be in place to be nontoxic.

SUMMARY OF THE INVENTION An object of the present invention is to provide a forward osmosis inducing solute and a forward osmosis inducing solution which are excellent in osmotic pressure while solving problems of conventional forward osmosis processes such as recovery and reuse of induction solution and despreading.

A first aspect of the present invention provides an induction solution for forward osmosis, characterized by containing a polyethyleneimine (PEI) salt having a number average molecular weight of polyethyleneimine (PEI) of 4,000 or less as an induction osmotic solute.

A second aspect of the present invention provides an induction osmotic solute for osmosis characterized by containing a polyethyleneimine (PEI) salt having a number average molecular weight of polyethyleneimine (PEI) of 500 to 2,000.

According to a third aspect of the present invention, there is provided a method for producing a purified fluid by osmotic pressure of an induction solution for forward osmosis containing an induction osmotic solute for forward osmosis, wherein the fluid in a fluid source through a first membrane The first step of permeating to the osmotic induction solution by osmotic pressure; And a second step of permeating the fluid that has permeated through the first membrane through a second membrane through which the forward osmosis inducing solute does not pass, wherein the forward osmosis induction solution is a forward osmosis induction solution according to the present invention. It provides a manufacturing method characterized by.

A fourth aspect of the present invention is a device for purifying a fluid from a fluid source by osmotic pressure of an induction solution for forward osmosis containing an induction solution for forward osmosis, wherein the induction solution for forward osmosis according to the present invention is ; And it provides a purification device comprising a first membrane for separating the fluid (fluid source) and the induction solution for forward osmosis.

Hereinafter, the present invention will be described in detail.

Osmotic pressure means that a semipermeable membrane that passes through a solvent but does not pass a solute is fixed, and a solution and a pure solvent are separately added to both sides, and a certain amount of solvent penetrates into the solution to reach an equilibrium. The temperature is the same, but the pressure difference causes a difference in pressure. Such osmotic pressure-inducing substances are called draw solutes.

In the present invention, the number average molecular weight is an average molecular weight obtained by averaging the molecular weight of the component molecular species of the polymer compound having a molecular weight distribution in a water fraction or a mole fraction, and can be usually obtained by membrane osmosis.

The present invention is characterized by using a polyethyleneimine (PEI) salt having a number average molecular weight of polyethyleneimine (PEI) of 4,000 or less as an induction osmotic solute. The polyethyleneimine (PEI) salt preferably has a number average molecular weight of polyethyleneimine (PEI) of 500 to 2,000, more preferably 800 to 1,800, and even more preferably 800 to 1,200.

When purifying a fluid such as water from a fluid source by the osmotic pressure of an induction solution for forward osmosis containing an induction osmotic solution for forward osmosis, the osmotic pressure is relatively smaller as the molecular weight of the inducing solute is higher. However, the present inventors have conducted experiments using chlorides of high molecular weight polyethyleneimine (PEI) and low molecular weight NaCl as derivative solutes having the same concentration (% by weight), so that the polyethyleneimine (PEI) salt has a PEI of 4,000 or less. It was found that the flux can be comparable to or superior to NaCl within the appropriate molecular weight range, and unlike NaCl, the back diffusion of the solute was significantly reduced (Table 2 and Table 3).

In addition, when using a polymer salt having a molecular weight of 4,000 or less of PEI as an inducing solute, it can be expected that the larger the molecular weight of the polymer, the larger the flux, but through the experiment, the inventors found that there is an appropriate molecular weight range in order to increase the flux (See Table 4). That is, as long as the polymer-induced solute can be recovered by membrane filtration or centrifugation, the smaller the molecular weight of the polymer, the more advantageous in terms of flux. In addition, it was found that there is an appropriate molecular weight range in terms of back diffusion (see Table 4).

In the present invention, the polyethyleneimine (PEI) salt is a ionized primary, secondary or tertiary amine group in polyethyleneimine.

The polyethyleneimine may be represented by Formula 1, and the polyethyleneimine polymer chain may include linear (Formula 2), branched (Formula 3), dendrimer (Formula 4), and the like. However, it is not limited thereto.

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

In the present invention, the polyethyleneimine salt may be derived from an acid solution, and specifically, may be derived by adding an acid solution to an aqueous solution of polyethyleneimine. The aqueous solution of polyethyleneimine has a high pH and shows basicity. However, when the acidic solution is added, a salt is formed and the pH gradually decreases.

The forward osmosis inducing solution containing the polyethyleneimine salt of the present invention as an inducing solute may be provided by mixing the aqueous polyethyleneimine solution with an acidic solution.

The term "acid solution" used in the present invention means an acid solution having a pH not exceeding 7, and the acid solution may include hydrochloric acid, sulfuric acid, acetic acid, but preferably hydrochloric acid or acetic acid. have.

Representatively, when using hydrochloric acid, the polyethyleneimine salt of the present invention may include a form such as the following formula (5).

[Formula 5]

In the present invention, the induction solution is preferably pH 4-10, more preferably pH 5-7, most preferably around pH 6 (Table 1). As described above, the pH can be achieved by titrating an acid solution to an aqueous polyethyleneimine solution.

In the present invention, the content of polyethyleneimine (PEI) salt in the induction solution may be 5 to 30% by weight, preferably 5 to 20% by weight (Table 2).

Polyethyleneimine salt as the inducing solute is a polymer having a large molecular weight, and thus is easily recovered by simple membrane filtration or centrifugation.

On the other hand, according to the present invention, a method for producing a purified fluid by the osmotic pressure of the forward osmotic induction solution containing the forward osmotic induction solute, osmotic pressure of the fluid in the fluid (fluid source) through the first membrane A first step of permeating towards the forward osmosis inducing solution; And a second step of permeating the fluid that has permeated through the first membrane through the second membrane through which the forward osmosis inducing solute does not pass. The forward osmosis induction solution is a forward osmosis induction solution according to the present invention described above. In this case, the second step may be omitted.

On the other hand, according to the present invention, an apparatus for purifying fluid from a fluid source by osmotic pressure of an induction solution for forward osmosis containing an induction osmosis solution for forward osmosis includes an induction solution for forward osmosis according to the present invention; And a first membrane for distinguishing the fluid source from the induction solution for forward osmosis.

The fluid may be water or drinking water, but is not limited thereto.

The description of the forward osmosis induction solution is as described above. The forward osmosis induction solution may adjust the concentration, pH as well as the molecular weight of the PEI salt to achieve the desired flux.

The first membrane is preferably a semi-permeable forward osmosis membrane that is impermeable to materials other than the fluid to be permeated, and is preferably a water-permeable semi-permeable membrane when the fluid is water.

The second membrane is intended to allow the fluid to pass through the first membrane to pass through while the inductive osmotic solute does not pass through it. Non-limiting examples of the second membrane include a microfiltration membrane (MF), an ultra filtration membrane (UF) or a nano filtration membrane (NF), preferably an ultrafiltration membrane (UF: ultra). filtration memebrane or nano filtration membrane (NF).

Since the PEI polymer has a (+) charge in the PEI salt, the second membrane preferably has a (+) charge so that the PEI polymer does not pass through the second membrane by the electrostatic force.

In the present invention, the second step may include separating and recovering the forward osmosis inducing solute from the forward osmosis inducing solution by membrane filtration through the second membrane. The recovered forward osmosis inducing solute may be used by re-injection into the forward osmosis inducing solution.

For the recovery of the forward osmotic induction from the forward osmotic induction solution, a membrane such as a microfiltration membrane (MF), an ultra filtration membrane (UF), or a nano filtration membrane (NF) may be used. It is also possible through a centrifuge.

1 illustrates a purification apparatus for water treatment by osmotic pressure of an induction solution for forward osmosis containing an induction osmotic solute in accordance with one embodiment of the present invention, and one embodiment of the present invention will be described with reference to FIG. 1. do.

The operating mechanism of the forward osmosis purification apparatus moves water through the first membrane 11 to an induction solution for forward osmosis with a high concentration using osmotic pressure by using osmotic pressure in the forward osmosis system 1. In addition, the induction solution for forward osmosis containing water in the stock solution may be moved to a recovery system 2 to separate and remove the inducing solute as a purified fluid. The separated inducing solute may be reused by re-injecting into the induction solution for forward osmosis contacted with the stock solution and the first membrane 11 interposed therebetween.

Separation and recovery of the forward osmosis inducing solute in the recovery system 2 may utilize the feature that the induced solute polyethyleneimine (PEI) salt has a large particle size as a polymer. That is, since it has a large particle size, it can be easily separated from the purified fluid by filtration through the second membrane 21. For example, since the microsized polyethyleneimine salt polymer particles can be separated by filtration with an ultrafiltration membrane or a nanofiltration membrane, such a recovery system 2 can greatly reduce the operating energy and facilitate easy filtration. Furthermore, since the PEI polymer has a (+) charge in the PEI salt, it may be preferable that the second membrane 21 has a (+) charge so that the PEI polymer does not pass through the second membrane 21 by electrostatic force. .

The addition and reuse of the isolated and recovered inducing solute polyethyleneimine salt to the osmotic inducing solution in contact with the stock solution can be achieved through the connecting means (3).

The connecting means 3 may include a pipe through which the separated and recovered induced solute can flow, an electrical conductivity meter on the pipe, and a flow meter to maintain a constant concentration of the forward osmosis induction solution, but is not limited thereto. no. Through the electrical conductivity meter and flow meter, it is possible to monitor whether or not the reference concentration of the induced solute separated and recovered and the flow rate.

The means for discharging the remainder of the induced solute separated by the recovery system as a purified fluid (4) includes a pipe through which the purified fluid can be discharged so as to discharge the purified water into the purified fluid by separating the induced solute, An electrical conductivity meter and a flow meter installed on the pipe may be included, but are not limited thereto. Through the electrical conductivity meter and flow meter, it is possible to monitor whether or not exceeding the reference value of impurities and the flow rate as desired.

In addition, in the forward osmosis system (1), the solvent fluid from the stock solution is passed through the first membrane 11 to the forward osmosis induction solution, whereby the stock solution from which the solvent fluid is removed is concentrated and forward osmosis as the discharge stock solution. May exit from the system 1. This can also concentrate the stock solution.

The stock solution may be sea water, brackish water, ground water, waste water, or the like. For example, drinking water that is purified fluid can be obtained by purifying seawater using the forward osmosis purification apparatus.

Induction solution for forward osmosis of the present invention can be easily recovered by the excellent osmotic pressure and induced solute by using polyethyleneimine salt as a polymer salt as an inducing solute, the water treatment apparatus and water treatment method using the same energy is required to separate and recover the induced solute. It is reduced and the water treatment effect is excellent.

1 is a schematic view of the forward osmosis purification apparatus according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples are for illustrative purposes only and the scope of the present invention is not limited to these examples.

Example  1: Preparation and Characterization of Induction Solution

Hydrochloric acid solution was used to form a salt of NH ₄ Cl in 5 wt% aqueous solution of polyethyleneimine (PEI, Sigma Aldrich, molecular weight 800), and the pH was adjusted from 13 to pH 1 by adjusting the concentration of hydrochloric acid to induce forward osmosis. The solution was prepared.

Flux and various properties of the prepared solution for forward osmosis were investigated in the following manner.

As a semipermeable membrane for forward osmosis, cellulose acetate forward osmosis membrane (HTI) was used, pure water was used as a feed solution, and the prepared induction solution for forward osmosis was used as the induction solution.

Contact the pure water (conductivity 1 ~ 3μS / cm) and the induction solution with the semi-permeable membrane in the cell and measure the change in weight of the induction solution while circulating with the circulation pump to measure the permeability (permeate flow rate, Flux). The back diffusion of the induced solute to pure water was measured using a conductivity meter. The results are shown in Table 1 below.

pH 13 12 11 10 9 8 7 6 5 4 Flux
(L / m ² hr) 2.5 3.2 4.8 6.2 6.4 7.1 7.3 8.4 7.8 7.3 back diffusion
(μS / cm) 14.6 5.9 3.2 1.8 3.0 5.3 4.6 12.6 36 207 Inductive Solution Conductivity
(mS / cm) 0.4 6.8 15.0 36.4 43.0 50.0 53.8 56.5 57.0 65.0

As shown in Table 1, it can be seen that when the pH of the induction solution is 6 shows the highest permeability (Flux), the back diffusion of the induced solute is also not very high, induction for forward osmosis It was found that it could be suitable as a solution.

Example  2: Characteristics of Induction Solution According to Concentration of Inducing Solute

The pH of the induction solution was fixed to 6 and the induction solution was prepared and tested in the same manner as in Example 1 except that the concentration of polyethyleneimine salt was changed to 5, 10, 20 wt%. The results are shown in Table 2 below.

PEI salt concentration
(weight%) 5 10 20 Flux
(L / m ² hr) 8.4 11.8 19.7 back diffusion
(μS / cm) 12.6 16.1 21.2 Inductive Solution Conductivity
(mS / cm) 56.5 100 141

As shown in Table 2, it can be seen that the highest permeability (Flux) is shown when the concentration of polyethyleneimine salt is 20% by weight, which is generally increased as the osmotic pressure increases as the concentration of the induction solution (Flux) increases. It was confirmed that the improvement tendency of) was followed.

Comparative example  One: NaCl  Characteristics of Induction Solution According to Concentration

Induction solution was prepared by dissolving NaCl in water at 5, 10, 20% by weight instead of polyethyleneimine salt.

The same procedure as in Example 1 was conducted except that the prepared induction solution was used. The results are shown in Table 3 below.

NaCl concentration
(weight%) 5 10 20 Flux
(L / m ² hr) 8.1 12.3 17.2 back diffusion
(μS / cm) 122 163 280

As shown in Table 3, when the NaCl concentration was 5% by weight and 20% by weight, the permeability was lower than that of Example 2 (Table 2), and NaCl was more than 10 times higher in back diffusion than the PEI salt. It was.

Example  3: Characteristics of Derivative Solution According to Molecular Weight of Derived Solute

The pH of the induction solution was fixed at 6 and the concentration of polyethylenimine salt was fixed at 5% by weight. Was prepared and tested. The results are shown in Table 4 below.

PEI molecular weight 800 1,200 1,800 25,000 Flux
(L / m ² hr) 8.4 7.2 5.8 2.5 back diffusion
(μS / cm) 12.6 29.8 57.7 45.6 Inductive Solution Conductivity
(mS / cm) 56.5 53.2 50.3 48.0

As shown in Table 4, when the molecular weight of polyethyleneimine is 5000 or less, it can be seen that as the molecular weight of polyethyleneimine is smaller, the permeability (Flux) increases and the back diffusion decreases.

Example  4: Characteristics of Induction Solution According to Acid Solution

Polyethyleneimine was tested in the same manner as in Example 1 except for changing the type of acid to hydrochloric acid, sulfuric acid, acetic acid, etc. while fixing the molecular weight of 800, the concentration of 5% by weight, and the pH of 6. . The results are shown in Table 5 below.

mountain Hydrochloric acid Sulfuric acid Acetic acid Flux
(L / m2hr) 8.4 3.1 7.9 back diffusion
(μS / cm) 12.6 5.1 9.8

As shown in Table 5, it was found that the permeability (Flux) and the back diffusion (diffusion) were different depending on which acidic solution the polyethyleneimine salt was induced to. In particular, it was confirmed that hydrochloric acid and acetic acid can perform better as an induction solution than sulfuric acid.

Description of the main parts of the drawing
1: forward osmosis system
2: recovery system
3: inducing solute reintroduction means
4: purified fluid discharge means
11: first membrane
21: second membrane

Claims (22)

An induction solution for forward osmosis, characterized by containing a polyethyleneimine (PEI) salt having a number average molecular weight of 800-1,200 as the induction osmotic solute.
The induction solution is pH 5 to 7, wherein the content of the polyethyleneimine (PEI) salt in the induction solution is characterized in that 5 to 20% by weight induction solution for forward osmosis.
delete According to claim 1, wherein the polyethyleneimine (PEI) salt is a forward osmosis induction solution, characterized in that derived from an acidic solution.
The induction osmosis solution for forward osmosis according to claim 3, wherein the acidic solution contains hydrochloric acid or acetic acid.
delete delete delete delete In the method for producing a purified fluid by the osmotic pressure of the forward osmotic induction solution containing the forward osmotic induction solute,
A first step of permeating the fluid in the fluid source through the first membrane toward the osmotic induction solution by osmotic pressure; And
A second step of permeating the fluid that has permeated through the first membrane through a second membrane through which the forward osmosis inducing solute does not pass,
The forward osmosis induction solution is characterized in that the forward osmosis induction solution according to any one of claims 1, 3 and 4.
10. The method of claim 9, wherein the second step comprises separating and recovering the forward osmosis inducing solute from the forward osmosis inducing solution by membrane filtration through the second membrane.
The method according to claim 10, further comprising the step of re-injecting the forward osmosis inducing solute recovered in the second step into the forward osmosis inducing solution.
The method of claim 9, wherein the second membrane has a positive charge.
The method of claim 9, wherein the second membrane is an ultra filtration memebrane (UF) or a nano filtration membrane (NF).
The method of claim 9, wherein the fluid is water or drinking water.
In the method for producing a fluid (fluid) purified by the osmotic pressure of the forward osmotic induction solution containing the forward osmotic induction solute,
Permeating the fluid in the fluid source through the membrane toward the osmotic induction solution by osmotic pressure,
The forward osmosis induction solution is characterized in that the forward osmosis induction solution according to any one of claims 1, 3 and 4.
The method of claim 15, further comprising recovering the forward osmosis inducing solution from the forward osmosis inducing solution, wherein the step is performed through an ultra filtration membrane (UF) or a nano filtration membrane (NF). A manufacturing method characterized by being performed.
An apparatus for purifying fluid from a fluid source by osmotic pressure of an induction solution for forward osmosis containing an induction solution for forward osmosis,
Induction solution for forward osmosis according to any one of claims 1, 3 and 4; And
Purification device comprising a first membrane for distinguishing the fluid (fluid source) and the induction solution for forward osmosis.
18. The purification apparatus of claim 17, further comprising a second membrane that allows fluid to pass through without inducing solute for forward osmosis.
19. The method according to claim 18, further comprising means for re-injecting the forward osmosis inducing solute separated and recovered from the forward osmosis inducing solution through the second membrane into the forward osmosis inducing solution. refinery.
19. The purification apparatus of claim 18, wherein the second membrane has a positive charge.
19. The purification apparatus of claim 18, wherein the second membrane is an ultrafiltration membrane or a nanofiltration membrane.
18. The purification apparatus of claim 17, wherein the purification apparatus is used to concentrate the stock solution by removing a fluid that is a solvent from the stock solution.

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