TWI658045B - Multi-branched cationic phosphonium salt, forward osmosis extract employing the same and forward osmosis seawater desalination process - Google Patents

Abstract

Dendritic present disclosure provides a cationic phosphonium salts, having the formula (I) shown in the ^{structure: {Z [P + (R} 1) (R 2) (R 3)] n} (X -) n (I)

Among them, R ¹ , R ² and R ³ are each independently a linear or branched C1 to C10 alkyl group, X ^- is an organic or inorganic anion, and Z has a structure represented by formula (IIb) or formula (IIc):

Among them, a is an integer from 1 to 15. In formula (IIb) and formula (IIc), Z is connected with [P ⁺ (R ¹ ) (R ² ) (R ³ )] at the position indicated by an asterisk (★), n is an integer from 3 to 4.

Description

   Multi-dendritic cationic phosphonium salt, forward osmosis extract containing the same, and forward osmosis seawater desalination process   

The present disclosure relates to a multi-dendritic cationic phosphonium salt, a forward osmosis extract containing the same, and a forward osmosis seawater desalination process.

With the increase of population, rapid industrial development and changes in the environment, the world is facing a serious shortage of fresh water resources, and more and more countries have begun to develop seawater desalination technology to solve this global crisis. At present, seawater desalination technologies that are more commonly used internationally include Multi-Stage flash (MSF), Multi-effect distillation (MED), and Reverse osmosis (RO). The disadvantages of technology are generally high cost, high energy consumption, and low water yield.

In recent years, forward osmosis (FO) seawater desalination technology has received widespread attention. It uses the principle of forward osmosis and uses a high osmotic pressure extraction solution (Draw solution, DS) to separate seawater to obtain fresh water. Compared with other technologies, although the forward osmosis seawater desalination technology has the advantages of lower cost, lower energy consumption, and higher water production rate, it still needs to be matched with an appropriate extraction liquid to truly achieve a low-cost water production process.

Generally speaking, polymer materials have problems of high solubility and viscosity, so it is difficult to dispose them as high-concentration solutions, so the osmotic pressure cannot be further increased. Although known low-polymer materials have high solubility and can be formulated into high-concentration solutions, their osmotic pressure is still insufficient.

Although many extracts can generate a sufficiently high osmotic pressure, they are not suitable for practical promotion because of high energy consumption. For example, the method of introducing carbon dioxide to increase the solubility or osmotic pressure of the extraction liquid requires an additional process of heating to 60 ° C. or higher to remove carbon dioxide when recovering the extraction liquid, and therefore requires higher energy consumption. In addition, although it is reported that magnetic nano particles are used as the extraction liquid, and the extraction liquid is recycled through magnetic separation and recovery, in fact, the agglomerated magnetic particles are not easy to be dispersed again, and it is difficult to remove the magnetic nanoparticles.

Therefore, there is an urgent need for a novel extraction liquid material.

According to an embodiment, the present disclosure provides a multi-dendritic cationic phosphonium salts, having the formula (I) shown in the ^{structure: {Z [P + (R} 1) (R 2) (R 3)] n} (X -) _n (I)

Wherein R ¹ , R ² and R ³ are each independently a linear or branched C ₁ to C ₁₀ alkyl group, X ^- is an organic or inorganic anion, and Z has a structure represented by formula (IIb) or formula (IIc) :

Among them, a is an integer from 1 to 15. In formulas (IIb) and (IIc), Z is connected to [P ⁺ (R ¹ ) (R ² ) (R ³ )] with the position indicated by an asterisk (★), n It is an integer from 3 to 4.

According to another embodiment, the present disclosure provides a multi-dendritic cationic phosphonium salts, having the formula (III) shown in the ^{structure: {Z [P + (R} ) 3] n} (X -) n (III)

Among them, R is a linear or branched C ₁ to C ₁₀ alkyl group, X ^- is an organic or inorganic anion, and Z has a structure represented by formula (IIb) or formula (IIc):

Among them, a is an integer from 1 to 15. In formulae (IIb) and (IIc), Z is connected to [P ⁺ (R) ₃ ] at a position indicated by an asterisk (★), and n is an integer from 3 to 4.

According to yet another embodiment, the present disclosure provides a forward osmosis extract, comprising: a multi-dendritic cationic phosphonium salt and water. Wherein Dendritic cationic phosphonium salt having the formula (I) shown in the ^{structure: {Z [P + (R} 1) (R 2) (R 3)] n} (X -) n (I)

Among them, R ¹ , R ² and R ³ are each independently a linear or branched C ₁ to C ₁₀ alkyl group, X ^- is an organic or inorganic anion, and Z has formula (IIa), formula (IIb), formula ( IIc), or the structure shown by formula (IId):

Among them, a is an integer from 1 to 15. In formulas (IIa) to (IId), Z is connected with [P ⁺ (R ¹ ) (R ² ) (R ³ )] at the position indicated by an asterisk (★), n It is an integer of 2 to 4, in which the concentration of the forward osmosis extract is 5 wt% or more.

According to yet another embodiment, the present disclosure provides a forward osmosis seawater desalination process, which includes providing forward osmosis extraction liquid and pure water as described above on both sides of a semipermeable membrane, and desalination of the seawater in a forward osmosis (FO) mode.

In order to make the above content and other purposes, features, and advantages of this disclosure more comprehensible, the following describes the preferred embodiments in detail, as follows:

Figure 1 shows the actual osmotic pressure and ionic liquid (IL) concentration data obtained by P2-TOS.

Figure 2 shows the actual osmotic pressure and IL concentration data of P2-TMBS.

Figure 3 shows the actual osmotic pressure and IL concentration data obtained by P3-TOS.

Figure 4 shows the actual osmotic pressure and IL concentration data of P2a-TOS.

The embodiment of the present disclosure provides a multi-dendritic cationic phosphonium salt, which can be used as an extraction liquid in a forward osmosis process. For example, it can be used as a forward osmosis extract in seawater desalination. However, the application of the multi-dendritic cationic phosphonium salt provided in this disclosure is not limited to this, as long as the concentration and osmotic pressure of the extracted solution after adjustment are adjusted, it can be applied as an extraction solution in other processes using the principle of forward osmosis for separation For example, it can also be applied to wastewater treatment, concentration purification, extraction, water desalination, power generation, etc.

This disclosure uses a chemical synthesis method to modify the cationic portion of tetrabutylphosphonium p -toluenesulfonate [P ₄₄₄₄ ] [TOS] to synthesize a multi-dendritic cationic oligomer, such as a multi-dendritic Cationic dimer (P2) or multi-dendritic cationic multi-dendrimer (P3).

In an embodiment of the present disclosure, there is provided a multi-dendritic cationic phosphonium salts, having the formula (I) shown in the ^{structure: {Z [P + (R} 1) (R 2) (R 3)] n} (X - ) _n (I)

In some embodiments of the present disclosure, R ¹ , R ² and R ³ are each independently a linear or branched C ₁ to C ₁₀ alkyl group, and Z may have a structure represented by formula (IIb) or formula (IIc):

Among them, a can be an integer from 1 to 15. In the formulae (IIb) and (IIc), Z is connected to [P ⁺ (R ¹ ) (R ² ) (R ³ )] with a position indicated by an asterisk (★), and n is an integer of 3 to 4.

In some embodiments of the present disclosure, in formula (I) X ^- may be of having a monovalent organic or inorganic anion. For example, X ^- can be a _{^{CH 3 SO 3 -, I -}} , CF 3 COO -, SCN -, BF 4 -, CF 3 SO 3 -, PF 6 -, FeCl 4 -, , , Among them, R ⁴ may be -CH ₂ COOH or-(CH ₂ ) ₄ -NH ₂ ; R ⁵ and R ⁶ may be H or CH ₃ ; R ⁷ may be -CH (CH ₃ ) ₂ ,-(CH ₂ ) ₂ -CH (CH ₃ ) ₂ , -CH (CH ₃ ) -CH ₂ -CH ₃ , or -CH ₂ -C ₆ H ₅ ; R ⁸ may be CH ₃ or H.

In formula (I), the central structure Z is matched with different anions, which will make the synthesized dendritic cationic phosphonium salts have different characteristics, and a suitable anion may be selected according to actual needs.

In an embodiment of the disclosure, X ^- in the formula (I) is In the embodiment where R ⁵ and R ^{6 are} both H, X is p-toluenesulfonyl (TOS); in the embodiment where R ⁵ and R ^{6 are} both CH ₃ , X is trimethylbenzenesulfonate (TMBS).

In an embodiment of the disclosure, R ¹ , R ² , and R ³ in the formula (I) are each independently a C ₁ -C ₈ alkyl group. In another embodiment of the present disclosure, R ¹ , R ² , and R ³ in formula (I) are each independently a C ₁ -C ₅ alkyl group.

In an embodiment of the present disclosure, a in the formulae (IIb) and (IIc) may be an integer of 3-8.

In an embodiment of the present disclosure, there is provided a multi-dendritic cationic phosphonium salts, having the formula (III) shown in the ^{structure: {Z [P + (R} ) 3] n} (X -) n (III)

Wherein, R is a linear or branched C ₁ to C ₁₀ alkyl group, and Z has a structure represented by formula (IIb) or formula (IIc):

Among them, a is an integer from 1 to 15. In formulae (IIb) and (IIc), Z is connected to [P ⁺ (R) ₃ ] at a position indicated by an asterisk (★), and n is an integer from 3 to 4.

In some embodiments of the present disclosure, the formula (III) X ^- may be of having a monovalent organic or inorganic anion. For example, X ^- can be a _{^{CH 3 SO 3 -, I -}} , CF 3 COO -, SCN -, BF 4 -, CF 3 SO 3 -, PF 6 -, FeCl 4 -, , , or , Where R ⁴ may be -CH ₂ COOH or-(CH ₂ ) ₄ -NH ₂ ; R ⁵ and R ⁶ may be H or CH ₃ ; R ⁷ may be -CH (CH ₃ ) ₂ ,-(CH ₂ ) ₂ -CH (CH ₃ ) ₂ , -CH (CH ₃ ) -CH ₂ -CH ₃ , or -CH ₂ -C ₆ H ₅ ; R ⁸ may be CH ₃ or H.

In the disclosed embodiment, the multi-dendritic cationic phosphonium salt may be: Wherein R may be the C ₁ ~ C ₅ alkyl, X ^- may be a ^{_{CH 3 SO 3 -, CF 3}} COO -, CF 3 SO 3 -, , , Where R ⁴ may be -CH ₂ COOH or-(CH ₂ ) ₄ -NH ₂ ; R ⁵ and R ⁶ may be H or CH ₃ ; R ⁷ may be -CH (CH ₃ ) ₂ ,-(CH ₂ ) ₂ -CH (CH ₃ ) ₂ , -CH (CH ₃ ) -CH ₂ -CH ₃ , or -CH ₂ -C ₆ H ₅ ; R ⁸ may be CH ₃ or H.

In an embodiment of the present disclosure, the multi-dendritic cationic sulfonium salt may be trimethylolpropane tri [(tri-n-butylphosphonium) butyrate] tri (p-toluenesulfonate) (trimethylolpropane tris [(tri- n-butylphosphonium) butyrate] tri ( p -toluenesulfonate) (P3-TOS), its chemical formula is as follows:

In some embodiments of the present disclosure, the multi-dendritic cationic phosphonium salt is a temperature-sensitive material, which has a lower critical solution temperature (LCST), and its phase change temperature (Tc) may be 5 ~ 60 ℃. The phase transition temperature is the lowest temperature at which the solution begins to separate into two phases. When the temperature is lower than the phase transition temperature, the temperature sensitive material is in a dissolved state, and when it is higher than the phase transition temperature, the temperature sensitive material is in an insoluble state. Therefore, when the temperature is higher than the above-mentioned phase transition temperature, the multi-dendritic cationic phosphonium salt undergoes a phase change, separates into two phases, and causes precipitation. Because the cationic portion is modified, the minimum critical melting temperature of the multi-dendritic cationic phosphonium salt synthesized in this disclosure is reduced, so that liquid-liquid phase separation or solid-liquid phase separation in the extraction liquid can be performed at a lower temperature. Water and multi-dendritic cationic phosphonium salts are a low-energy process. In addition, since the multi-dendritic cationic phosphonium salt is a temperature-sensitive material, the multi-dendritic cationic phosphonium salt can be easily recovered and reused by changing the temperature, thereby reducing the multi-dendritic cationic phosphonium salt remaining in the water layer after phase separation. Salt, which reduces energy consumption.

Another embodiment of the present disclosure provides a forward osmosis extract, including the aforementioned multi-dendritic cationic phosphonium salt and water. The osmotic pressure of the forward osmotic extraction solution monotonously increases with the mass molar concentration of the forward osmotic extraction solution, but it is not linear.

In some embodiments of the present disclosure, the multi-dendritic cationic phosphonium salt included in the forward osmotic extraction solution has a structure represented by formula (I): {Z [P ⁺ (R ¹ ) (R ² ) (R ³ )] _{^{n} (X -) n (}} I)

Among them, R ¹ , R ² and R ³ are each independently a linear or branched C ₁ to C ₁₀ alkyl group, X ^- is an organic or inorganic anion, and Z has formula (IIa), formula (IIb), formula ( IIc), or the structure shown by formula (IId):

Among them, a is an integer from 1 to 15. In formulas (IIa) to (IId), Z is connected with [P ⁺ (R ¹ ) (R ² ) (R ³ )] at the position indicated by an asterisk (★), n It is an integer from 2 to 4. X ^- may be as defined in the aforementioned formula (I).

In some embodiments of the disclosure, the multi-dendritic cationic phosphonium salt included in the forward osmotic extraction solution may be: or Wherein X ^- may be the preceding formula (I) as defined above.

In an embodiment of the present disclosure, the multi-dendritic cationic phosphonium salt included in the forward osmotic extraction solution may be 1,8-octanediyl-bis (tri-n-butylphosphonium) bis (p-toluenesulfonate) ( 1,8-octanediyl-bis (tri-n-butylphosphonium) di ( p -toluenesulfonate)) (P2-TOS), its chemical formula is as follows:

In an embodiment of the present disclosure, the multi-dendritic cationic phosphonium salt included in the forward osmotic extraction solution may be 1,8-octanediyl-bis (tri-n-butylphosphonium) bis (2,4,6-tri Methyl-benzenesulfonate) (1,8-octanediyl-bis (tri-n-butylphosphonium) di (2,4,6-trimethyl-benzenesulfonate)) (P2-TMBS), its chemical formula is as follows:

In an embodiment of the present disclosure, the multi-dendritic cationic phosphonium salt included in the forward osmotic extraction solution may be trimethylolpropane tri [(tri-n-butylphosphonium) butyrate] tri (p-toluenesulfonate). (trimethylolpropane tris [(tri-n-butylphosphonium) butyrate] tri ( p -toluenesulfonate) (P3-TOS), its chemical formula is as follows:

In an embodiment of the present disclosure, the multi-dendritic cationic phosphonium salt included in the forward osmotic extraction solution may be dihydroxyethane-bis [(tri-n-butylphosphonium) butyrate] bis (p-toluenesulfonate) (1,2-Ethanediol bis [(tri-n-butylphosphonium) butyrate]) (P2a-TOS), its chemical formula is as follows:

In an embodiment of the disclosure, the multi-dendritic cationic phosphonium salt included in the forward osmotic extraction solution may be 1,8-octanediyl-bis (tri-n-butylphospho) bis (salicylic acid) (1, 8-octanediyl-bis (tri-n-butylphosphonium) di (salicylic acid)) (P2-SA), its chemical formula is as follows:

In an embodiment of the present disclosure, the multi-dendritic cationic phosphonium salt included in the forward osmotic extraction solution may be 1,8-octanediyl-bis (tri-n-butylphosphonium) bis (trifluoroacetic acid) (1, 8-octanediyl-bis (tri-n-butylphosphonium) di (trifluoroacetic acid) (P2-TFA), its chemical formula is as follows:

In some embodiments of the present disclosure, the concentration of the aforementioned forward osmosis extract is greater than or equal to 5 wt%. In some embodiments of the present disclosure, the forward osmosis extraction liquid may be applied to the forward osmosis seawater desalination technology. At this time, the concentration of the forward osmosis extraction liquid may be greater than, for example, 15 wt%, 30 wt%, 40 wt%, 50 wt%, or 60 wt%. It should be noted that the concentration of the forward osmotic extraction liquid is not limited to a specific range, as long as the osmotic pressure of the forward osmotic extraction liquid at this concentration is greater than the osmotic pressure of the raw material liquid (for example, seawater, protein, industrial, agricultural or domestic wastewater, etc.) , You can play the role of forward osmosis extract. Generally speaking, the larger the difference in osmotic pressure between the extraction liquid and the raw material liquid, the better the extraction effect, so a high concentration aqueous solution as the extraction liquid will have a better extraction effect. However, from the viewpoint of cost, the osmotic pressure of the forward osmotic extraction liquid at this concentration may be greater than the osmotic pressure of the raw material liquid. Taking the multi-branched cationic phosphonium salt P2-TOS provided by an embodiment of the present disclosure as an example, it is a liquid solution itself, so it can be directly used as an extraction solution at a concentration of 100% by weight. However, depending on the osmotic pressure of the raw material liquid, a P2-TOS aqueous solution of a desired concentration can also be arbitrarily prepared.

Another embodiment of the present disclosure provides a forward osmosis seawater desalination process, which includes providing forward osmosis extraction liquid and pure water as described above on both sides of a semi-permeable membrane to desalinate seawater in a forward osmosis (FO) mode.

Although the dendritic cationic phosphonium salt provided by this disclosure has a larger molecular weight because the cationic portion has been modified, its viscosity is low, and it can still be formulated as a high-concentration solution, so that the prepared extract has a high osmotic pressure. . In addition, the multi-dendritic cationic phosphonium salt provided by this disclosure has the characteristics of lower phase transition temperature, is easy to recycle and has low energy consumption in the application process. In addition, when the multi-dendritic cationic phosphonium salt provided by the present disclosure is formulated for use in an extraction liquid, the water flux can be effectively increased and the water production rate can be improved.

The following is a list of preparation examples, comparative examples, and examples to illustrate the characteristics of the multi-dendritic cationic phosphonium salt provided by this disclosure and the extracts prepared therefrom:

[Preparation Example 1] 1,8-octanediyl-bis (tri-n-butylphosphine) bis (p-toluenesulfonate) (P2-TOS)

First, 1,8-octanediyl-bis (tri-n-butylphosphonium) dibromide (hereinafter referred to as P2-Br) is synthesized:

(1) Take a 500mL round bottom bottle, put 80g (0.4mol) of tributylphosphine and 48.9g (0.18mol) of 1,8-dibromooctane, and then add anhydrous acetone 150 mL, and stirred at 40 ° C for 48 hours.

(2) After completion of the reaction, the above solution was slowly dropped into 1.5 L of ether. The white powdery solid obtained was filtered and washed several times with ether.

(3) The white solid after washing was dried to obtain 117 g of the product P2-Br.

Next, 1,8-octanediyl-bis (tri-n-butylphosphonium) bis (p-toluenesulfonate) (1,8-octanediyl-bis (tri-n-butylphosphonium) di ( p- toluenesulfonate)) was synthesized. (Hereinafter referred to as P2-TOS):

(1) Take 2.67 g (3.7 mmol) of P2-Br and 1.57 g (8.1 mmol) of sodium p- toluenesulfonate (TOS-Na) in 13 g of deionized water and stir at room temperature for 24 hour.

(2) After the reaction is completed, 10 mL of ethyl acetate is added for extraction twice. After collecting the upper ethyl acetate layer, 20 mL of deionized water is added for washing and purification for three times.

(3) The washed organic layer was concentrated to obtain about 1.6 g of the product P2-TOS.

The product P2-TOS measurement via NMR (1H-NMR, 400MHz in D 2 O): 0.81 (t, 18H, C H 3 CH 2 -), 1.09 (m, 4H, -CH 2 -), 1.1 ~ 1.5 (m , 32H, -CH _2- ), 1.9 ~ 2.1 (t, 16H, PCH _2- ), 2.25 (s, 6H, Ar-CH ₃ ), 7.21 (d, 4H, ArH), 7.58 (d, 4H, ArH ). The chemical formula of the product P2-TOS is as follows:

[Preparation Example 2] 1,8-octanediyl-bis (tri-n-butylphosphine) bis (2,4,6-trimethyl-benzenesulfonate) (P2-TMBS)

Synthesis of 1,8-octanediyl-bis (tri-n-butylphosphonium) bis (2,4,6-trimethyl-benzenesulfonate) (1,8-octanediyl-bis (tri-n-butylphosphonium) di (2,4,6-trimethyl-benzenesulfonate)) (hereinafter referred to as P2-TMBS):

(1) Take 10 g (14.7 mmol) of P2-Br and dissolve 6.8 g (29.6 mmol) of sodium 2,4,6-trimethylbenzenesulfonate (TMBS-Na) It was stirred in 40 g of deionized water at room temperature for 24 hours.

(2) After completion of the reaction, 20 mL of ethyl acetate was added for extraction.

(3) The organic layer was concentrated to obtain about 12.4 g of product P2-TMBS.

The product P2-TMBS via NMR measurement ^{(1 H-NMR, 400MHz in} D 2 O): 0.8 (t, 18H, C H 3 CH 2 -), 1.09 (m, 4H, -CH 2 -), 1.1 ~ 1.5 ( m, 32H, -CH _2- ), 1.9 ~ 2.0 (t, 16H, PCH _2- ), 2.12 (s, 6H, Ar-CH ₃ ), 2.25 (s, 12H, Ar-CH ₃ ), 6.88 (s , 4H, ArH). The chemical formula of the product P2-TMBS is as follows:

[Preparation Example 3] Trimethylolpropane tri [(tri-n-butylphosphonium) butyrate] tri (p-toluenesulfonate) (P3-TOS)

First, trimethylolpropane tris (4-bromobutyrate) is synthesized:

(1) Take a 50mL round-bottomed reaction flask, put 1g (8.3mmol) of trimethylolpropane, dissolve it in 20mL of anhydrous tetrahydrofuran (THF), and slowly add 1.1g of NaH (60%). After stirring at room temperature with a magnet for 2 hours, 4-bromobutyryl chloride (5 g (27 mmol)) was added dropwise, and the mixture was reacted at room temperature overnight.

(2) After the reaction is completed, THF is pumped to dryness, 20 mL of ether is added, the solution is filtered to remove solids, the obtained filtrate is washed three times with 50 mL of water, and then the product is pumped to dry to obtain 3.4 g of product trimethylolpropane (4-bromobutyrate).

Next, trimethylolpropane tris [(tri-n-butylphosphonium) butyrate] tribromide (trimethylolpropane tris [(tri-n-butylphosphonium) butyrate] tribromide) (hereinafter referred to as P3-Br):

(1) Take a 50mL round-bottomed reaction flask and put 1.14g (5.6mmol) of tributylphosphine and trimethylolpropane tris (4-bromobutyrate) 1.06 g (1.8 mmol), 10 mL of anhydrous acetone was added, and it stirred at 40 degreeC for 24 hours.

(2) After the reaction, the solution was drained, and 20 mL of water was added. After washing with 50 mL of ether three times, the solution was drained to obtain 1.9 g of product P3-Br.

Next, trimethylolpropane tris [(tri-n-butylphosphonium) butyrate] tri ( p- toluenesulfonate) (hereinafter (Referred to as P3-TOS):

(1) Take 3g (2.5mmol) of P3-Br and 1.5g (7.7mmol) of sodium p- toluenesulfonate (TOS-Na) in 55g of deionized water, and stir at room temperature for 24 hours .

(2) After completion of the reaction, 15 mL of ethyl acetate was added for extraction, and the organic layer was collected.

(3) The organic layer was concentrated in vacuo to obtain about 2.5 g of the product P3-TOS.

Product P3-TOS was measured by NMR ( ¹ H-NMR, 400 MHz in D ₂ O): 0.81 (t, 30H, C H ₃ CH _2- ), 1.2 to 1.5 (m, 38H, -CH _2- ), 1.6 to 1.8 (br.s, 6H, -CH _2- ), 1.95 ~ 2.1 (m, 24H, PCH _2- ), 2.26 (s, 9H, Ar-CH ₃ ), 2.42 (m, 6H, -CH ₂ CO- ), 4.0 (s, 6H, -OCH _2- ), 7.21 (d, 6H, ArH), 7.58 (d, 6H, ArH). The chemical formula of the product P3-TOS is as follows:

[Preparation Example 4] Dihydroxyethane-bis [(tri-n-butylphosphonium) butyrate] bis (p-toluenesulfonate) (P2a-TOS)

First, dihydroxyethane bis (4-bromobutyrate) (1,2-Ethanediol bis (4-bromobutyrate)) was synthesized:

(1) Take a 50mL round-bottomed reaction flask, put 0.795g (12.8mmol) of dihydroxyethane (1,2-Ethanediol), dissolve it in 20mL of tetrahydrofuran (THF), and slowly add NaH (60%) 1.23 g, and after stirring at room temperature for 2 hours, 5.35 g (2.74 mmol) of 4-bromobutyryl chloride was added dropwise, and reacted at room temperature overnight.

(2) After the reaction is completed, THF is drained, 20 mL of ether is added, and the solution is filtered to remove solids. The obtained filtrate is washed three times with 50 mL of water, and then the product is drained to obtain 3 g of the product dihydroxyethane di (4 -Bromobutyrate).

Next, dihydroxyethane-bis [(tri-n-butylphosphonium) butyrate] dibromide (1,2-Ethanediol bis [(tri-n-butylphosphonium) butyrate] dibromide)) (hereinafter referred to as P2a-Br) was synthesized. :

(1) Take a 50mL round-bottomed reaction flask and put 3.2g (15.8mmol) of tributylphosphine and dihydroxyethanebis (4-bromobutyrate) (1,2-Ethanediol bis (4-bromobutyrate) )) 2.85 g (7.9 mmol), 10 mL of anhydrous acetone was added, and it stirred at 40 degreeC for 24 hours.

(2) After the reaction, the solution was drained, 60 mL of water was added, and the solution was washed with 150 mL of ether three times, and then the aqueous solution was drained to obtain 5 g of product P2a-Br.

Next, dihydroxyethane-bis [(tri-n-butylphosphonium) butyrate] bis (p-toluenesulfonate) (1,2-Ethanediol bis [(tri-n-butylphosphonium) butyrate] di (p- toluenesulfonate)) (hereinafter referred to as P2a-TOS):

(1) 5 g (6.5 mmol) of P2a-Br and 2.79 g (14.3 mmol) of sodium p- toluenesulfonate (TOS-Na) were dissolved in 20 g of deionized water and stirred at room temperature for 24 hours .

(2) After completion of the reaction, 25 mL of ethyl acetate was added for extraction.

(3) The organic layer was concentrated in vacuo to obtain about 3 g of the product P2a-TOS.

The product P2a-TOS was measured by NMR (1H-NMR, 400MHz in D ₂ O): 0.81 (t, 18H, CH ₃ CH _2- ), 1.2 to 1.5 (m, 24H, -CH _2- ), 1.6 to 1.8 ( br.s, 4H, -CH _2- ), 1.95 ~ 2.1 (m, 16H, PCH _2- ), 2.26 (s, 6H, Ar-CH ₃ ), 2.42 (m, 4H, -CH ₂ CO-), 4.2 (s, 4H, -OCH _2- ), 7.21 (d, 4H, ArH), 7.58 (d, 4H, ArH). The chemical formula of the product P2a-TOS is as follows:

[Preparation Example 5] 1,8-octanediyl-bis (tri-n-butylphosphine) bis (salicylic acid) (P2-SA)

First, P2-Br was synthesized according to the method described in Preparation Example 1. Next, 1,8-octanediyl-bis (tri-n-butylphospho) bis (salicylic acid) (1,8-octanediyl-bis (tri-n-butylphosphonium) di (salicylic acid)) was synthesized according to the following steps. (Hereinafter referred to as P2-SA):

(1) P2-Br is first converted into P2-OH with an ion exchange resin (1,8-octanediyl-bis (tri-n-butyl phosphorus) dihydroxide; 1,8-octanediyl-bis (tri- n-butylphosphonium) dihydroxide), take 20 g (36.4 mmol) of P2-OH and 10.1 g (72.8 mmol) of salicylic acid (SA) and dissolve in 120 g of deionized water with 3 g of ethanol, and stir at room temperature for 24 hour.

(2) After completion of the reaction, 80 mL of ethyl acetate was added for extraction.

(3) The organic layer was concentrated to obtain about 16 g of the product P2-SA.

Product P2-SA was determined by NMR ( ¹ H-NMR, 400 MHz in D ₂ O; ppm): 0.8 (t, 18H, C H _3- ), 1.20 (m, 4H, -CH _2- ), 1.25 to 1.45 ( m, 32H, -CH _2- ), 1.90 to 2.05 (m, 16H, PCH _2- ), 6.81 to 6.86 (m, 4 H, ArH), 7.32 (td, 2H, ArH), 7.70 (dd, 2H, ArH). The chemical formula of the product P2-SA is as follows:

[Preparation Example 6] 1,8-octanediyl-bis (tri-n-butylphosphine) bis (trifluoroacetic acid) (P2-TFA)

First, P2-Br was synthesized according to the method described in Preparation Example 1. Next, 1,8-octanediyl-bis (tri-n-butylphospho) bis (trifluoroacetic acid) (1,8-octanediyl-bis (tri-n-butylphosphonium) di (trifluoroacetic acid) ( Hereinafter referred to as P2-TFA):

(1) First convert P2-Br to P2-OH with an ion exchange resin. Take 20 g (36.4 mmol) of P2-OH and 8.3 g (72.8 mmol) of trifluoroacetic acid (TFA) and dissolve in 30 g of deionized water. Stir at room temperature for 24 hours.

(2) After completion of the reaction, 20 mL of ethyl acetate was added for extraction.

(3) The organic layer was concentrated to obtain about 12 g of the product P2-TFA.

Product P2-TFA was measured by NMR ( ¹ H-NMR, 400 MHz in D ₂ O; ppm): 0.81 (t, 18H, C H _3- ), 1.23 (m, 4H, -CH _2- ), 1.3 to 1.5 ( m, 32H, -CH _2- ), 2.0 to 2.2 (t, 16H, PCH _2- ); ( ¹⁹ F-NMR, 400 MHz in D ₂ O; ppm): 75.54. The chemical formula of the product P2-TFA is as follows:

[Comparative Example 1]

Commercially available tetrabutylphosphonium p -toluenesulfonate (Aldrich 95wt%) [P ₄₄₄₄ ] [TOS] was used as Comparative Example 1.

[Comparative Example 2]

P2-Br synthesized in Preparation Example 1 was measured by NMR ( ¹ H-NMR, 400 MHz in D ₂ O; ppm): 0.81 (t, 18H, CH _3- ), 1.09 (m, 4H, -CH _2- ), 1.1 ~ 1.5 (m, 32H, -CH _2- ), 1.9 ~ 2.1 (t, 16H, PCH _2- ). The chemical formula of P2-Br is as follows:

[Comparative Example 3]

To synthesize dihydroxyethane-bis [(tri-n-butylphosphonium) acetate] dibromide (hereinafter referred to as P2a1-Br) :

(1) Take a 100mL round-bottomed reaction bottle, and put 1g (4.93mmol) of tributylphosphine and dihydroxyethanebis (2-bromoacetylate) (1,2-ethanediol bis (bromoacetyrate)) 0.752g (2.47) mmol), 10 mL of anhydrous acetone was added, and the mixture was stirred at 40 ° C. for 48 hours.

(2) After the reaction is completed, the solution is drained, and 40 mL of water is added, and the solution is washed with 100 mL of ether three times. After that, the aqueous solution was dried to obtain 1 g of the product P2a1-Br.

Product P2a1-Br was measured by NMR ( ¹ H-NMR, 400 MHz in D ₂ O; ppm): 0.8 (t, 18H, CH _3- ), 1.2 to 1.6 (m, 24H, -CH _2- ), 2.3 to 2.3 (m, 12H, PCH _2- ), 3.52 (d, 4H, -CH ₂ (CO)-), 4.4 (s, 4H, -OCH _2- ). The chemical formula of the product P2a1-Br is as follows:

[Comparative Example 4]

To synthesize trimethylolpropanetri [(tri-n-butylphosphonium) butyrate] tribromide ((tri-n-butylphosphonium) butyrate] tribromide) (hereinafter referred to as P3-Br):

(1) Take a 50mL round-bottomed reaction flask and put 1.14g (5.6mmol) of tributylphosphine and trimethylolpropane tris (4-bromobutyrate) 1.06g (1.8 mmol), 10 mL of anhydrous acetone was added, and the mixture was stirred at 40 ° C. for 24 hours.

(2) After completion of the reaction, the solution was drained, and 20 mL of water was added, followed by washing with 50 mL of ether three times. After that, the aqueous solution was dried to obtain 1.9 g of the product P3-Br.

Product P3-Br was measured by NMR ( ¹ H-NMR, 400 MHz in D ₂ O; ppm): 0.81 (t, 30H, CH _3- ), 1.2 to 1.5 (m, 38H, -CH _2- ), 1.6 to 1.8 (br.s, 6H, -CH _2- ), 1.95 ~ 2.1 (m, 24H, PCH _2- ), 2.42 (m, 6H, -CH ₂ CO-), 4.0 (s, 6H, -OCH _2- ) . The chemical formula of the product P3-Br is as follows:

[Example 1] Measurement of viscosity

The multi-dendritic cationic phosphonium salt P2-TOS obtained in Preparation Example 1, the multi-dendritic cationic phosphonium salt P2-TMBS obtained in Preparation Example 2, the multi-dendritic cationic phosphonium salt P3-TOS obtained in Preparation Example 3, and The multi-branched cationic sulfonium salts P2a-TOS obtained in Preparation Example 4 were each formulated into a 75 wt% aqueous solution, and the viscosity was measured at 20 ° C using a viscosity meter Brookfield DV2TLVCJ0. The results are shown in Table 1.

[Table 1]

From the viewpoint of operability, according to the operating experience, it is better that the material suitable as the extraction liquid has a viscosity value of 200 cp or less. If the viscosity value is too high, the material will not be suitable as an extraction solution due to difficulties in flow. However, polymer materials are difficult to operate due to high viscosity problems at high concentrations, so they are not suitable for extraction. It can be seen from Table 1 that although the multi-dendritic cationic phosphonium salts of Preparation Examples 1 to 4 have a larger molecular weight after cation modification, the highest viscosity value when formulated into a 75 wt% high concentration aqueous solution Only 110cp, which is still within the range of operable viscosity values. In other words, the multi-branched cationic sulfonium salts of Preparation Examples 1 to 4 do not increase the viscosity value greatly due to the increase in molecular weight, so it will not be unable to work at high concentrations due to the high viscosity value of ordinary polymer materials. As an extract.

[Example 2] Measurement of osmotic pressure

The multi-dendritic cationic phosphonium salt P2-TOS obtained in Preparation Example 1, the multi-dendritic cationic phosphonium salt P2-TMBS obtained in Preparation Example 2, and the multi-dendritic cationic phosphonium salt P3-TOS obtained in Preparation Example 3 were prepared, The multi-branched cationic phosphonium salt P2a-TOS obtained in Example 4, the multi-branched cationic phosphonium salt P2-SA obtained in Preparation Example 5, and the multi-dendritic cationic phosphonium salt P2-TFA obtained in Preparation Example 6 were prepared separately. Aqueous solutions of different concentrations were used, and the osmotic pressure value was measured by the freezing point method using a freezing point osmometer (OSMOMAT 030; GONOTEC).

It should be noted that when the concentration of the aqueous solution is greater than 30wt%, its osmotic pressure cannot usually be measured by the instrument, but the low-concentration osmotic pressure measurement result can be used to predict the penetration of the aqueous solution when the concentration of the aqueous solution is greater than 30wt%. Pressure. Therefore, in the following examples of the present disclosure, the osmotic pressure of the aqueous solution prepared in Preparation Examples 1 to 4 at low concentration was measured in advance, and a simulation function related to the osmotic pressure and the molarity of the mass was drawn. Simulation functions should be used to predict the osmotic pressure of aqueous solutions at high concentrations. Among them, the conversion formula between the molar concentration (molality) and the weight percent concentration (wt%) is: wt% = molality x Mw / [(molality x Mw) +1000]

Mw represents the molecular weight (g / mol) of the solute in the aqueous solution.

Table 2 shows the osmotic pressure value of the multi-dendritic cationic phosphonium phosphonium salt P2-TOS obtained in Preparation Example 1 when they were arranged into aqueous solutions of different concentrations. The osmotic pressure and ionic liquid (IL) concentration data obtained by measuring the P2-TOS by the freezing point method are shown in Figure 1.

Table 3 shows the osmotic pressure values of the multi-dendritic cationic phosphonium salt P2-TMBS obtained in Preparation Example 2 when they were arranged into aqueous solutions of different concentrations. Figure 2 shows the actual osmotic pressure and IL concentration data obtained by measuring P2-TMBS with the freezing point method.

Table 4 shows the osmotic pressure values of the multi-dendritic cationic phosphonium salt P3-TOS obtained in Preparation Example 3 when the aqueous solutions were arranged in different concentrations. The osmotic pressure and IL concentration data obtained by measuring the P3-TOS with the freezing point method are shown in Figure 3.

Table 5 shows the osmotic pressure values of the multi-dendritic cationic phosphonium phosphonium salt P2a-TOS obtained in Preparation Example 4 when the aqueous solutions were arranged in different concentrations. The actual osmotic pressure and IL concentration data obtained by measuring P2a-TOS by the freezing point method are shown in Figure 4.

To confirm the accuracy of the predicted values, the following tests were performed. Take a U-shaped tube with a forward osmosis (FO) membrane in the middle, put 75 wt% P2-TOS aqueous solution at one end, and 11.2 wt% NaCl aqueous solution (NaCl aqueous solution at this concentration, its osmotic pressure at the other end) (About 3.2 times the osmotic pressure of seawater). After standing at a temperature of 22 ° C for a period of time, the liquid level of a 75 wt% aqueous solution of P2-TOS rises, while the liquid level of a 11.2 wt% aqueous solution of NaCl decreases. This means that a 75 wt% aqueous solution of P2-TOS has a higher osmotic pressure than a 11.2 wt% aqueous solution of NaCl (about 3.85 Osmol / Kg). As can be seen from Table 2, the extrapolation method predicts the osmotic pressure of a 70 wt% P2-TOS aqueous solution to be 6.148 (Osmol / Kg), which is higher than 3.85 Osmol / Kg, which is consistent with the above results. It shows that the osmotic pressure predicted by extrapolation is informative.

Table 6 shows the osmotic pressure values of the multi-dendritic cationic phosphonium salt P2-SA obtained in Preparation Example 5 when the aqueous solutions were prepared in different concentrations. The osmotic pressure and IL concentration data obtained by measuring the freezing point method of P2-SA are shown in Figure X.

Table 7 shows the osmotic pressure values of the multi-dendritic cationic phosphonium salt P2-TFA obtained in Preparation Example 6 when they were configured into aqueous solutions of different concentrations.

From the results in Tables 2 to 7, it appears that the osmotic pressure of the multi-dendritic cationic phosphonium salt aqueous solution increases relatively as the concentration thereof increases. Specifically, the osmotic pressure of the multi-dendritic cationic phosphonium salt aqueous solution monotonically increases with the molar concentration, rather than a linear relationship. In particular, it can be seen from Table 2 that when the concentration of the aqueous solution prepared in Preparation Example 1 is between 30 and 40% by weight, the osmotic pressure can be greater than the osmotic pressure of seawater. Extract. Similarly, it can be found in Tables 3 to 7 that when the concentration of the aqueous solution prepared in Preparation Example 2 is between 40-50% by weight, the concentration of the aqueous solution prepared in Preparation Example 3 is between 60-70% by weight, and When the prepared aqueous solution has a concentration of 30 to 40 wt%, the aqueous solution prepared in Preparation Example 5 has a concentration of 40 to 50 wt%, and the aqueous solution prepared in Preparation Example 6 has a concentration of 30 to 40 wt%, the osmotic pressure can be greater than The osmotic pressure of seawater is 1.2 (Osmol / Kg), so it is suitable for seawater desalination as a forward osmotic extraction solution.

In addition, according to the osmotic pressure of different raw material liquids, those with ordinary knowledge in the technical field can also refer to the results shown in Tables 2 to 7 to select an appropriate multi-dendritic cationic phosphonium salt type and the concentration of the extract solution configured for application. Water extraction process of different raw material liquids.

[Example 3] Measurement of phase transition temperature

The multi-dendritic cationic phosphonium salt P2-TOS obtained in Preparation Example 1, the multi-dendritic cationic phosphonium salt P2-TMBS obtained in Preparation Example 2, and the multi-dendritic cationic phosphonium salt P3-TOS obtained in Preparation Example 3 were prepared, Multi-branched cationic phosphonium salt P2a-TOS obtained in Example 4, multi-branched cationic phosphonium salt P2-SA obtained in Preparation Example 5, multi-dendritic cationic phosphonium salt P2-TFA obtained in Preparation Example 6, and comparative examples [P ₄₄₄₄ ] [TOS] of 1, P2-Br of Comparative Example 2, P2a1-Br of Comparative Example 3, and P3-Br of Comparative Example 4 were formulated into aqueous solutions of different concentrations, and the temperature was gradually raised to the beginning of the solution. Fog. The minimum temperature (cloud point temperature; Tc) at which the solution begins to fog is the phase transition temperature. The measured Tc (° C) results are shown in Table 8.

In Table 8, "Preparation Example 1" indicates the aqueous solution prepared by the product P2-TOS, "Preparation Example 2" indicates the aqueous solution prepared by the product P2-TMBS, and "Preparation Example 3" indicates the product. Aqueous solution prepared by P3-TOS, "Preparation Example 4" indicates the aqueous solution prepared by the product P2a-TOS, "Preparation Example 5" indicates the aqueous solution prepared by the product P2-SA, and "Preparation Example 6""Indicates an aqueous solution prepared with the product P2-TFA," Comparative Example 1 "indicates an aqueous solution prepared with [P ₄₄₄₄ ] [TOS], and" Comparative Example 2 "indicates an aqueous solution prepared with product P2-Br An "aqueous solution" indicates an aqueous solution prepared by the product P2a1-Br as "Comparative Example 3", and an "aqueous solution" prepared by the product P3-Br as "Comparative Example 4". It can be seen from Table 8 that the phase transition temperature of a 40 wt% [P ₄₄₄₄ ] [TOS] aqueous solution is about 55 ° C. If it is used as an extraction solution, the phase transition temperature will be too high, which will cause the energy consumption of the extraction solution during recovery. Promotion.

In contrast, under the same concentration conditions (40wt%), the multi-dendritic cationic phosphonium salt aqueous solution prepared by the preparation examples 1 to 4 has a phase transition temperature lower than that of the [P ₄₄₄₄ ] [TOS] aqueous solution. Phase transition temperature. For example, the phase transition temperature of a 40 wt% aqueous solution of Preparation Example 1 is about 39 ° C, the phase transition temperature of a 40 wt% aqueous solution of Preparation Example 2 is about 26 ° C, and the phase transition temperature of a 40 wt% aqueous solution of Preparation Example 4 is about 41 ° C Meanwhile, the phase transition temperature of the 40% by weight aqueous solution of Preparation Example 3 was further reduced to about 15 ° C. In addition, it can be known from Table 8 that under the same concentration conditions (such as 20-50% by weight), the phase transition temperature of the multi-branched cationic phosphonium salt aqueous solution prepared in Preparation Examples 5 and 6 of the present disclosure is also lower than [P ₄₄₄₄ ] [TOS] Phase transition temperature of aqueous solution.

Therefore, it can be known that when the aqueous solutions of Preparation Examples 1 to 6 of the present disclosure are used as the extraction liquid, it is beneficial to the recovery of the extraction liquid and reduce the energy consumption.

Hereinafter, the multi-dendritic cationic sulfonium salts of Preparation Examples 1 to 4 were prepared as an extraction solution and verified by forward osmosis.

[Example 4] Forward Osmosis (FO) Verification

The semi-permeable membrane uses Dow filmtec tw30-3012-500, the area is 8x8cm, the tangential flow (cross flow) is 25cm / s, the feed solution is pure water, and the extraction solution is 75wt% P2-TOS aqueous solution, 75wt % P2-TMBS aqueous solution, 50 wt% P2a-TOS aqueous solution, or 70 wt% [P ₄₄₄₄ ] [TOS] aqueous solution. The FO mode (active layer faced the feed solution (AL-FS)) was used for forward penetration verification. The results are shown in Table 9.

It can be seen from Table 9 that when the extraction solution is a 70 wt% [P ₄₄₄₄ ] [TOS] aqueous solution, the water flux is only 1.31 (LMH). In comparison, the 75wt% P2-TOS aqueous solution prepared by the preparation example 1 has a water flux of 3.09 (LMH), and the water flux is increased by about 2.3 times; the 75wt% prepared by the preparation example 2 is 75wt%. The water flux of the% P2-TMBS aqueous solution can reach 3.04 (LMH), and the water flux increases by about 2.3 times; the water flux of the 50 wt% P2a-TOS aqueous solution formulated in Preparation Example 4 can reach 2.0 (LMH) , The water flux increased by about 1.5 times.

From the results of the above examples, it can be proved that although the dendritic cationic phosphonium salt provided by the present disclosure has been modified to increase the molecular weight, it has low viscosity, high osmotic pressure, and low phase transition temperature when it is formulated as an extract. And other characteristics. Therefore, when the multi-dendritic cationic phosphonium salt provided by the present disclosure is formulated for extraction liquid application, it has the advantages of easy recovery and low energy consumption. In addition, when the multi-dendritic cationic phosphonium salt provided by the present disclosure is formulated to be used as an extraction liquid, the water flux can be effectively improved, thereby increasing the water production rate.

Although the present disclosure has been disclosed above with several preferred embodiments, it is not intended to limit the present disclosure. Any person with ordinary knowledge in the technical field may make arbitrary changes without departing from the spirit and scope of the present disclosure. And retouching, so the scope of protection of this disclosure shall be determined by the scope of the attached patent application.

Claims (14)

A multi-dendritic cationic phosphonium salts, having the formula (I) shown in the ^{structure: {Z [P + (R} 1) (R 2) (R 3)] n} (X -) n (I) wherein, R ¹ , R ² and R ³ are each independently a linear or branched C ₁ to C ₁₀ alkyl group, X ^- is an organic or inorganic anion, and Z has a structure represented by formula (IIb) or formula (IIc): Among them, a is an integer from 1 to 15. In formula (IIb) and formula (IIc), Z is connected with [P ⁺ (R ¹ ) (R ² ) (R ³ )] at the position indicated by an asterisk (★), n is an integer from 3 to 4. The scope of the patent application many dendrite item 1 cationic phosphonium salt, wherein the X ^- is _{^{CH 3 SO 3 -, I -}} , CF 3 COO -, SCN -, BF 4 -, CF 3 SO 3 -, PF ₆ ^-, FeCl ₄ ^-, , , , Where R ⁴ is -CH ₂ COOH or-(CH ₂ ) ₄ -NH ₂ ; R ⁵ and R ⁶ are H or CH ₃ ; R ⁷ is -CH (CH ₃ ) ₂ ,-(CH ₂ ) ₂ -CH (CH ₃ ) ₂ , -CH (CH ₃ ) -CH ₂ -CH ₃ , or -CH ₂ -C ₆ H ₅ ; R ⁸ is CH ₃ or H. The multi-dendritic cationic phosphonium salt according to item 1 of the scope of the patent application, wherein R ¹ , R ² and R ³ are each independently a C ₁ to C ₈ alkyl group. The multi-dendritic cationic sulfonium salt as described in the first patent application range, wherein R ¹ , R ² and R ³ are each independently a C ₁ -C ₅ alkyl group. The multi-dendritic cationic phosphonium salt as described in the first item of the patent application range, wherein a is an integer of 3-8. A multi-dendritic cationic phosphonium salts, having the formula (III) shown in the ^{structure: {Z [P + (R} ) 3] n} (X -) n (III) wherein, R is a straight-chain or branched-chain a C ₁ ~ C ₁₀ alkyl, X ^- is an organic or inorganic anion, and Z has a structure represented by formula (IIb) or formula (IIc): Among them, a is an integer from 1 to 15. In Formula (IIb) and Formula (IIc), Z is connected to [P ⁺ (R) ₃ ] at the position indicated by an asterisk (★), and n is an integer from 3 to 4. The scope of the patent application many dendrite Item 6. The cationic phosphonium salt, wherein the X ^- is _{^{CH 3 SO 3 -, I -}} , CF 3 COO -, SCN -, BF 4 -, CF 3 SO 3 -, PF ₆ ^-, FeCl ₄ ^-, , , , Where R ⁴ is -CH ₂ COOH or-(CH ₂ ) ₄ -NH ₂ ; R ⁵ and R ⁶ are H or CH ₃ ; R ⁷ is -CH (CH ₃ ) ₂ ,-(CH ₂ ) ₂ -CH (CH ₃ ) ₂ , -CH (CH ₃ ) -CH ₂ -CH ₃ , or -CH ₂ -C ₆ H ₅ ; R ⁸ is CH ₃ or H. The multi-dendritic cationic sulfonium salt as described in item 6 of the scope of patent application, wherein the multi-dendritic cationic sulfonium salt is: Wherein R is a C ₁ ~ C ₅ alkyl group of, X ^- is _{^{CH 3 SO 3 -, CF 3}} COO -, CF 3 SO 3 -, , Where R ⁴ is -CH ₂ COOH or-(CH ₂ ) ₄ -NH ₂ ; R ⁵ and R ⁶ are H or CH ₃ ; R ⁷ is -CH (CH ₃ ) ₂ ,-(CH ₂ ) ₂ -CH (CH ₃ ) ₂ , -CH (CH ₃ ) -CH ₂ -CH ₃ , or -CH ₂ -C ₆ H ₅ ; R ⁸ is CH ₃ or H. The multi-dendritic cationic phosphonium salt as described in item 6 of the scope of patent application, wherein a is an integer from 3 to 8. The multi-dendritic cationic phosphonium salt according to item 6 of the patent application scope, wherein the multi-dendritic cationic phosphonium salt is trimethylolpropane tri [(tri-n-butylphosphonium) butyrate] tri (p-toluene) Sulfonate) (trimethylolpropane tris [(tri-n-butylphosphonium) butyrate] tri ( p- toluenesulfonate) (P3-TOS). A positive osmotic extract, comprising: a multi-dendritic cationic phosphonium salts, having the formula (I) shown in the ^{structure: {Z [P + (R} 1) (R 2) (R 3)] n} (X -) _n (I), wherein R ¹ , R ² and R ³ are each independently a linear or branched C ₁ to C ₁₀ alkyl group, X ^- is an organic or inorganic anion, and Z has the formula (IIa), (IIb) ), Formula (IIc), or formula (IId): Among them, a is an integer from 1 to 15. In formulas (IIa) to (IId), Z is connected with [P ⁺ (R ¹ ) (R ² ) (R ³ )] at the position indicated by an asterisk (★), n An integer of 2 to 4; and water, wherein the concentration of the forward osmosis extract is 5 wt% or more. The forward osmotic extraction liquid according to item 11 of the patent application scope, wherein the osmotic pressure of the forward osmotic extraction liquid monotonously increases with the mass molar concentration of the forward osmotic extraction liquid. The forward osmotic extraction solution according to item 11 of the scope of the patent application, wherein the multi-branched cationic phosphonium salt is 1,8-octanediyl-bis (tri-n-butylphosphonium) bis (p-toluenesulfonate) (1,8-octanediyl-bis (tri-n-butylphosphonium) di ( p -toluenesulfonate)) (P2-TOS), 1,8-octanediyl-bis (tri-n-butylphosphonium) di (2,4 , 6-trimethyl-benzenesulfonate) (1,8-octanediyl-bis (tri-n-butylphosphonium) di (2,4,6-trimethyl-benzenesulfonate)) (P2-TMBS), trimethylol Trimethylolpropane tris [(tri-n-butylphosphonium) butyrate] tri ( p -toluenesulfonate) (P3-TOS), dihydroxyethyl Alkane-bis [(tri-n-butylphosphonium) butyrate] bis (p-toluenesulfonate) (1,2-Ethanediol bis [(tri-n-butylphosphonium) butyrate] di (p-toluenesulfonate)) (P2a- TOS), 1,8-octanediyl-bis (tri-n-butylphospho) bis (salicylic acid) (1,8-octanediyl-bis (tri-n-butylphosphonium) di (salicylic acid)) (P2- SA), or 1,8-octanediyl-bis (tri-n-butylphospho) bis (trifluoroacetic acid) (1,8-octanediyl-bis (tri-n-butylphosphonium) di (trifluoroacetic acid) (P2- TFA). A forward osmosis seawater desalination process includes: providing a forward osmosis extraction solution and pure water as described in any one of claims 11 to 13 on the two sides of a semipermeable membrane, and applying forward osmosis (FO) mode to Desalination of sea water.