CN108043247A - A kind of Kynoar matrix seperation film and preparation method thereof - Google Patents

Abstract

The invention relates to a polyvinylidene fluoride matrix separation membrane and a preparation method thereof, and relates to the technical field of membrane materials. The invention solves the technical problem of reducing the separation effect of the composite membrane on metal or organic matter due to the fact that the plasticizer is easy to volatilize with the membrane solvent in the existing polymer composite membrane. The polyvinylidene fluoride matrix separation membrane provided by the invention comprises a polyvinylidene fluoride membrane and an extraction agent dispersed in the polyvinylidene fluoride membrane. The preparation method of the polyvinylidene fluoride matrix separation membrane provided by the present invention, in this method, the extraction agent is dispersed in the polyvinylidene fluoride membrane through the steps of dissolving, blending, film scraping, phase inversion, etc., instead of soaking in the pores In order to ensure the stability of the polyvinylidene fluoride matrix separation membrane in the later application process. When the polyvinylidene fluoride matrix separation membrane of the invention is used for separating heavy rare earth ions, it has good separation effect, strong anti-pollution ability, and good cycle reusability; and its preparation method is simple.

Description

A polyvinylidene fluoride matrix separation membrane and its preparation method

technical field

The invention relates to the technical field of membrane materials, in particular to a polyvinylidene fluoride matrix separation membrane and a preparation method thereof.

Background technique

At present, the solvent extraction method is mainly used in the heavy rare earth separation process. Although this separation method has the advantages of simple operation and stable process, it requires a large amount of extraction agent and rare earth to press the tank during the separation process, resulting in a lot of waste and separation. A large amount of acid, alkali and organic solvents will be consumed in the process. In the actual system, the concentration of heavy rare earth feed liquid is usually low, and the separation by solvent extraction requires many extraction stages, large equipment occupation, and low energy consumption. Therefore, it is urgent to develop a new separation method to solve the current heavy Problems in rare earth separation and enrichment.

The membrane separation process highly integrates the extraction and stripping processes, and has the advantages of high extraction agent utilization, less organic solvent consumption, no two-phase separation problem, simple process, low energy consumption, and no pollution. These advantages make membrane separation technology an effective supplement and replacement of traditional solvent extraction, and it has been continuously developed in recent years.

The prior art has disclosed a variety of polymer composite membranes for the separation of metals or organics, such as dissolving triacetate cellulose or polyvinyl chloride in a solvent, then mixing with an extractant and a plasticizer, and volatilizing the solvent to obtain Composite film containing extractant and plasticizer. Although these composite membranes have good separation performance, the structure of the separation membrane is complicated by the addition of plasticizers on the basis of the membrane matrix and the extractant, and the molecular type of plasticizers has high volatility. In the process of forming a composite membrane, it is easy to volatilize with the membrane solvent, which reduces the separation effect of the composite membrane on metal or organic matter.

Contents of the invention

The present invention aims to solve the technical problems in the prior art, and provides a polyvinylidene fluoride matrix separation membrane and a preparation method thereof. The polyvinylidene fluoride matrix separation membrane of the present invention has a good separation effect when used for separating heavy rare earth ions , and strong anti-pollution ability, good recycling and reusability; and its preparation method is simple.

In order to solve the problems of the technologies described above, the technical solution of the present invention is specifically as follows:

A polyvinylidene fluoride matrix separation membrane, comprising:

Polyvinylidene fluoride film;

and an extractant dispersed in the polyvinylidene fluoride film;

The extractant is a phosphoric acid type extractant.

In the above technical solution, the mass ratio of the polyvinylidene fluoride membrane to the extractant is 0.5:0.125-0.75.

In the above technical solution, the mass ratio of the polyvinylidene fluoride membrane to the extractant is 0.5:0.34.

In the above technical solution, the extractant is bis(2-ethylhexyl)phosphinic acid, 2-ethylhexyl 2-ethylhexylphosphate or bis(2-ethylhexyl)phosphate.

In the above technical solution, the pore structure of the polyvinylidene fluoride matrix separation membrane is an asymmetric pore structure.

A preparation method of a polyvinylidene fluoride matrix separation membrane, comprising the following steps:

(1) mix the polyvinylidene fluoride and the film solvent, place it at 65°C and stir for 4 hours, then lower the temperature to 50°C and stir for 1 hour to obtain the first mixed solution;

(2) Adding the extractant to the first mixed solution to obtain a second mixed solution; stirring the second mixed solution at 50° C. for 12 hours, and ultrasonically treating at room temperature to remove air bubbles to obtain a casting solution;

(3) Pour the casting solution on a glass plate and scrape it into a nascent film, and place it in the air for 1 minute;

(4) Put the glass plate with the primary membrane into deionized water to remove the solvent in the primary membrane, and obtain a polyvinylidene fluoride matrix separation membrane after drying.

In the above technical solution, the mass ratio of the polyvinylidene fluoride to the extractant is 0.5:0.125-0.75.

In the above technical solution, the mass ratio of the polyvinylidene fluoride to the extractant is 0.5:0.34.

In the above technical solution, the extractant is bis(2-ethylhexyl)phosphinic acid, 2-ethylhexyl 2-ethylhexylphosphate or bis(2-ethylhexyl)phosphate.

In the above technical solution, the pore structure of the polyvinylidene fluoride matrix separation membrane is an asymmetric pore structure.

The beneficial effects of the present invention are:

The polyvinylidene fluoride matrix separation membrane provided by the present invention includes a polyvinylidene fluoride membrane and an extractant dispersed in the polyvinylidene fluoride membrane; its composition is simple, and no additional plasticizer or porogen is needed, which reduces the cost of membrane formation. cost, simplifying the film-making process. Among them, the polyvinylidene fluoride membrane is the matrix material, which has high hydrophobicity, high chemical stability, high thermal stability and good mechanical properties; Extraction separates metal ions from the raw material liquid side. At the same time, the extractant, while serving as a carrier for extracting and separating metal elements, also acts as a plasticizer, which can change the pore structure of the polyvinylidene fluoride membrane and improve its resistance to metal ions. The transmission performance of this kind of extractant is mature and can be purchased directly.

The polyvinylidene fluoride matrix separation membrane provided by the invention can separate metal ions, and has a good separation effect and high separation efficiency, and can be used in a special separation environment with strong acid-base or strong oxidation Use, strong environmental adaptability. At the same time, the present invention disperses the extractant in the polyvinylidene fluoride membrane instead of infiltrating in the pores, so the extractant is not easy to be lost, and the stability and service life of the membrane will not be affected.

The preparation method of the polyvinylidene fluoride matrix separation membrane provided by the present invention, in this method, the extraction agent is dispersed in the polyvinylidene fluoride membrane through the steps of dissolving, blending, film scraping, phase inversion, etc., instead of soaking in the pores In order to ensure the stability of the polyvinylidene fluoride matrix separation membrane in the later application process.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a scanning electron micrograph of the polyvinylidene fluoride matrix separation membrane prepared in Example 1 of the present invention.

Fig. 2 is the variation curve of the extraction rate of Lu ³⁺ separation by the polyvinylidene fluoride matrix separation membrane prepared in Example 1 of the present invention.

Fig. 3 is the change curve of the stripping rate of the separation of Lu ³⁺ by the polyvinylidene fluoride matrix separation membrane prepared in Example 1 of the present invention.

Fig. 4 is the variation curve of the extraction rate of Lu ³⁺ separation by polyvinylidene fluoride matrix separation membranes prepared in Examples 1, 4 and 5 of the present invention.

Fig. 5 is the variation curve of the stripping rate of the separation of Lu ³⁺ by the polyvinylidene fluoride matrix separation membrane prepared in Examples 1, 4 and 5 of the present invention.

Fig. 6 is the variation curve of Lu ³⁺ concentration and time in the raw material solution and stripping solution for the separation of Lu ³⁺ by the polyvinylidene fluoride matrix separation membrane prepared in Example 1 of the present invention.

Fig. 7 is that the polyvinylidene fluoride matrix separation membrane containing ionic liquid in the prior art separates the rare earth elements Lu ³⁺ (hollow dots) and Yb ³⁺ (solid dots) in the raw material solution and stripping liquid Lu ³⁺ and Yb ³⁺ concentration versus time curves.

Fig. 8 is a graph showing the relationship between the flux value J and the number of cycles of the change in Lu ³⁺ separation efficiency of the polyvinylidene fluoride matrix separation membrane provided in Example 1 of the present invention.

Fig. 9 is a graph showing the variation of ln(c/c _i ) with time when different masses of extractants are added in Examples 1, 2 and 3.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings.

The polyvinylidene fluoride matrix separation membrane provided by the invention is applied in the separation process of heavy rare earths. The polyvinylidene fluoride matrix separation membrane is a polyvinylidene fluoride matrix separation membrane containing an extraction agent prepared by using a phosphoric acid-type extractant as an added phase carrier and polyvinylidene fluoride as a matrix by using a non-solvent-induced phase separation method. In the present invention, the extractant carrier is dispersed in the polyvinylidene fluoride membrane through dissolution, blending, film scraping, phase inversion, etc., so that the extractant is not easy to lose It affects the stability and service life of the polyvinylidene fluoride matrix separation membrane. Compared with the prior art, the preparation process of the polyvinylidene fluoride matrix separation membrane provided by the invention is simple, and has a good effect on the separation and enrichment of heavy rare earths. Compared with the traditional solvent extraction method, the membrane separation process is highly integrated, which can reduce the footprint of equipment, reduce the consumption of acid, alkali and organic solvents, and is a new separation and enrichment method with great development potential.

A polyvinylidene fluoride matrix separation membrane provided by the present invention comprises: a polyvinylidene fluoride membrane; and an extraction agent dispersed in the polyvinylidene fluoride membrane; the extraction agent is a phosphoric acid type extraction agent. The mass ratio of the polyvinylidene fluoride film to the extractant is preferably 0.5:0.125-0.75, and most preferably the mass ratio of the polyvinylidene fluoride film to the extractant is 0.5:0.34. The extractant is preferably two (2-ethylhexyl) phosphinic acid (P227), 2-ethylhexyl phosphate (P507) or two (2-ethylhexyl) phosphate (P204) , most preferably bis(2-ethylhexyl)phosphinic acid (P227). The pore structure of the polyvinylidene fluoride matrix separation membrane is an asymmetric pore structure, and the separation and transmission direction is from the small pore side of the membrane to the large pore side of the membrane.

The present invention also provides a preparation method of a polyvinylidene fluoride matrix separation membrane, comprising the following steps:

(1) mix the polyvinylidene fluoride and the film solvent, place it at 65°C and stir for 4 hours, then lower the temperature to 50°C and stir for 1 hour to obtain the first mixed solution;

(2) Adding the extractant to the first mixed solution to obtain a second mixed solution; stirring the second mixed solution at 50° C. for 12 hours, and ultrasonically treating at room temperature to remove air bubbles to obtain a casting solution;

(3) Pour the casting solution on a glass plate and scrape it into a nascent film, and place it in the air for 1 minute;

(4) Put the glass plate with the primary film into deionized water to remove the solvent in the primary film, and obtain a polyvinylidene fluoride matrix separation membrane after drying; wherein, the mass ratio of the polyvinylidene fluoride to the extraction agent is preferably 0.5:0.125-0.75, most preferably the mass ratio of polyvinylidene fluoride to extractant is 0.5:0.34. Preferably the extractant is two (2-ethylhexyl) phosphinic acid (P227), 2-ethylhexyl phosphate (P507) or two (2-ethylhexyl) phosphate (P204) , most preferably bis(2-ethylhexyl)phosphinic acid (P227).

Example 1

Mix 0.50g of Solef6010 polyvinylidene fluoride powder and 5.0mL N,N-dimethylacetamide, stir at 65°C for 4 hours, then lower the temperature to 50°C and stir for 1 hour, then add 0.34g of bis(2-ethyl Hexyl)phosphinic acid was added to the mixed solution, stirred at 50°C for 12 hours, and then the casting solution was ultrasonically treated at room temperature for 10 minutes to obtain the casting solution. Scrape the casting solution on a smooth glass plate at room temperature, and place it in the air for 1 minute, then put the glass plate with the casting solution into the deionized water coagulation solution at 25°C to make the casting solution phase After the transformation, the formed film floats naturally to obtain the primary film. The nascent film was soaked in deionized water for 3 hours to remove N,N-dimethylacetamide, picked up and dried to obtain poly(2-ethylhexyl)phosphinic acid containing 0.34 g of extractant. Vinylidene fluoride matrix separation membrane.

Put the polyvinylidene fluoride matrix separation membrane under a scanning electron microscope to obtain the electron micrograph as shown in Figure 1. Figure 1 is a scanning electron micrograph of the polyvinylidene fluoride matrix separation membrane provided in Example 1 of the present invention. It can be known that the prepared The pore structure of the polyvinylidene fluoride matrix separation membrane is an asymmetric pore structure.

Example 2

The difference with Example 1 is that the quality of adding two (2-ethylhexyl) phosphinic acid is 0.125g, and others are the same as in Example 1, and the two (2-ethylhexyl) phosphinic acid containing extractant quality of 0.125g is obtained. acid polyvinylidene fluoride matrix separation membrane.

Example 3

The difference with Example 1 is that the quality of adding two (2-ethylhexyl) phosphinic acid is 0.75g, and others are the same as in Example 1, and it is two (2-ethylhexyl) phosphinic acid that the extraction agent quality is 0.75g to be obtained. acid polyvinylidene fluoride matrix separation membrane.

Fig. 9 is when adding the extraction agent of different quality in embodiment 1, 2 and 3 ln (c/ _ci ) (the ratio of Lu3 ⁺ concentration and its initial concentration is taken logarithm at a certain time) time-varying graph, Fig. The larger the slope of the middle line, the better the transmission effect. Because the addition of 0.75 g of the extractant has little improvement in the transmission effect compared with the addition of 0.34 g of the extractant, the optimal choice is to add 0.34 g of the extractant as a follow-up experiment. Addition ratio in .

Example 4

The difference with Example 1 is that the extractant is replaced by 2-ethylhexyl phosphate 2-ethylhexyl ester, and its quality is 0.34g. Others are the same as in Example 1, and it is 0.34g of 2-ethylhexyl that contains the extractant quality. Polyvinylidene fluoride matrix separation membrane of 2-ethylhexyl phosphate.

Example 5

The difference with Example 1 is that the extractant is replaced by two (2-ethylhexyl) phosphate, and its quality is 0.34g, and other is the same as Example 1, and it is two (2-ethylhexyl) that the quality of the extractant is 0.34g is obtained. ) Phosphate ester polyvinylidene fluoride matrix separation membrane.

Example 6

The polyvinylidene fluoride matrix separation membrane prepared in Example 1 was fixed in the membrane separation device, and the effective contact area of the membrane was 7.07cm ² ; HCl stripping solutions of different concentrations were added to the stripping tank, and the concentrations of HCl were respectively 1.0 mol/L, 2.5mol/L and 4.0mol/L; add 100mL of 1mmol/L Lu ³⁺ raw material solution into the feed liquid pool. Turn on the stirring device and stir at a speed of 500 rpm to make Lu ³⁺ migrate, and obtain the extraction rate and stripping rate change curves of the separation of Lu ³⁺ by the membrane, the results are shown in Figure 2 and Figure 3.

It can be seen that the polyvinylidene fluoride matrix separation membrane prepared in Example 1 of the present invention can be used to separate Lu ³⁺ , and can be used under strong acidic conditions, has good environmental adaptability, and has a wide range of applications.

Example 7

The polyvinylidene fluoride matrix separation membrane prepared in Example 1, the polyvinylidene fluoride matrix separation membrane prepared in Example 4, and the polyvinylidene fluoride matrix separation membrane prepared in Example 5 were carried out according to the method and steps of Example 6. Lu ³ In the separation experiment of ⁺ , the concentration of HCl on the stripping side is preferably 2.5mol/L, and the extraction rate and stripping rate change curves of the separation of Lu ³⁺ by the membrane are respectively obtained, and the results are shown in Figure 4 and Figure 5.

It can be seen that the polyvinylidene fluoride matrix separation membranes prepared in Examples 1 and 4 of the present invention can be used to separate Lu ³⁺ . Under the condition that the HCl concentration on the back extraction side is 2.5mol/L, because the acidity of the back extraction is lower for di(2-ethylhexyl) phosphate, the polyvinylidene fluoride matrix separation membrane prepared in Example 5 is Under this condition, only Lu ³⁺ can be extracted, and there is no stripping effect.

Example 8

With the polyvinylidene fluoride matrix separation membrane prepared in Example 1, the separation experiment of Lu was carried out according to the method and steps of Example 6. The concentration of HCl on the ^stripping side was preferably 2.5mol/L, and repeated three times. The results are shown in Figure 6. And the experimental data (Fig. 7 )Compare.

It can be seen that the polyvinylidene fluoride matrix separation membrane prepared in Example 1 of the present invention has good reproducibility and stability in the process of separating Lu ³⁺ . At the same time, compared with the prior art, the separation transmission speed is greatly improved, and the maximum separation efficiency is greatly improved.

Example 9

The polyvinylidene fluoride matrix separation membrane prepared in Example 1 was used for the separation experiment of Lu ³⁺ according to the method and steps of Example 6. After the experiment was carried out for 6 hours, the feed liquid and stripping liquid were discarded, and the separation membrane was soaked with 2.5mol/L HCl for 1 h, then fresh feed liquid and stripping liquid were added, and the above steps were repeated for 6 cycles to obtain the membrane pair Lu ³⁺ The flux value J of the change in separation efficiency, the results are shown in Figure 8.

It can be seen that the polyvinylidene fluoride matrix separation membrane prepared in Example 1 of the present invention has good stability and recyclability in the process of separating Lu ³⁺ , and can be applied in the long-term separation process.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. A polyvinylidene fluoride matrix separation membrane, characterized in that, comprising: Polyvinylidene fluoride film; and an extractant dispersed in the polyvinylidene fluoride film; The extractant is a phosphoric acid type extractant. 2 . The polyvinylidene fluoride matrix separation membrane according to claim 1 , wherein the mass ratio of the polyvinylidene fluoride membrane to the extractant is 0.5:0.125-0.75. 3. The polyvinylidene fluoride matrix separation membrane according to claim 1, wherein the mass ratio of the polyvinylidene fluoride membrane to the extractant is 0.5:0.34. 4. The polyvinylidene fluoride matrix separation membrane according to any one of claims 1-3, wherein the extractant is two (2-ethylhexyl) phosphinic acid, 2-ethylhexyl phosphoric acid 2 - Ethylhexyl ester or bis(2-ethylhexyl) phosphate. 5 . The polyvinylidene fluoride matrix separation membrane according to claim 4 , wherein the pore structure of the polyvinylidene fluoride matrix separation membrane is an asymmetric channel structure. 6. a preparation method of polyvinylidene fluoride matrix separation membrane according to claim 1, is characterized in that, comprises the following steps: (1) mix the polyvinylidene fluoride and the film solvent, place it at 65°C and stir for 4 hours, then lower the temperature to 50°C and stir for 1 hour to obtain the first mixed solution; (2) Adding the extractant to the first mixed solution to obtain a second mixed solution; stirring the second mixed solution at 50° C. for 12 hours, and ultrasonically treating at room temperature to remove air bubbles to obtain a casting solution; (3) Pour the casting solution on a glass plate and scrape it into a nascent film, and place it in the air for 1 minute; (4) Put the glass plate with the primary membrane into deionized water to remove the solvent in the primary membrane, and obtain a polyvinylidene fluoride matrix separation membrane after drying. 7 . The method for preparing a polyvinylidene fluoride matrix separation membrane according to claim 6 , wherein the mass ratio of the polyvinylidene fluoride to the extractant is 0.5:0.125-0.75. 8 . The method for preparing a polyvinylidene fluoride matrix separation membrane according to claim 6 , wherein the mass ratio of the polyvinylidene fluoride to the extractant is 0.5:0.34. 9. according to the preparation method of the polyvinylidene fluoride matrix separation membrane described in any one of claim 6-8, it is characterized in that, described extraction agent is two (2-ethylhexyl) phosphinic acid, 2-ethyl 2-Ethylhexyl Hexyl Phosphate or Bis(2-Ethylhexyl) Phosphate. 10. The preparation method of the polyvinylidene fluoride matrix separation membrane according to claim 9, characterized in that the pore structure of the polyvinylidene fluoride matrix separation membrane is an asymmetric channel structure.