CN107983172B - Flat plate type mixed matrix forward osmosis membrane based on metal organic framework MIL-100(Fe) and preparation method - Google Patents

Abstract

The invention discloses a flat plate mixed matrix forward osmosis membrane based on metal-organic framework MIL-100(Fe) and a preparation method, and belongs to the technical field of membrane separation. Disperse 0.1%～2.0% (w/w) MIL-100(Fe) uniformly in 66.0%～90.9% (w/w) mixed solvent by ultrasonic, then mix with 8.0%～20.0% (w/w) Add cellulose acetate to the three-necked round-bottomed flask in a certain order. After stirring to completely dissolve the cellulose acetate, add 1.0% to 12.0% (w/w) of polyvinylpyrrolidone or polyethylene glycol-400. Stir and dissolve for 2 to 16 hours at 25 to 90 °C until completely dissolved, stand for defoaming for 3 to 16 hours, and prepare a forward osmosis membrane casting solution. After heat treatment in ionized water for 5-60 mins, a flat-plate mixed matrix forward osmosis membrane based on MIL-100(Fe) was prepared. The forward osmosis membrane prepared by the present invention uses 1M NaCl as the driving liquid and deionized water as the raw material liquid. In the test time of 1h, its pure water flux reaches more than 37.0L/m ² •h, and the reverse salt flux is less than 1.5g/m ² •h.

Description

Flat-plate mixed-matrix forward osmosis membrane based on metal-organic framework MIL-100(Fe) and preparation method

technical field

The invention relates to a polymer flat plate type forward osmosis membrane and a preparation method thereof, in particular to a plate type mixed matrix forward osmosis membrane based on a metal-organic framework MIL-100(Fe) and a preparation method.

Background technique

The scarcity of water resources and the increasingly serious water pollution have become the bottlenecks restricting social progress and economic development. Since Shanghai is extremely rich in water resources and produces a large amount of waste water, seawater desalination and waste water recycling have become a strategic choice to solve the water resources crisis. Among many seawater desalination and wastewater recycling technologies, membrane separation technology is one of the best choices. As a solution to this key problem, forward osmosis technology with low energy consumption and high water recovery rate has become a research focus and hot spot in the field of seawater desalination and sewage recycling, and has important strategic significance for solving the problem of water shortage.

Forward osmosis (FO) is a membrane separation technology driven by osmotic pressure on both sides of the membrane. It is getting more and more attention. The related theoretical and applied research has made great progress, and it has been successfully applied to seawater desalination and wastewater treatment. , food medicine, energy and other fields. At present, the common forward osmosis membranes mainly include cellulose acetate membrane, polybenzimidazole membrane, polyamide composite membrane, etc. The degree of commercialization is not high mainly due to the lack of forward osmosis membranes with good performance and suitable driving fluids, while forward osmosis membranes It is the key to the entire forward osmosis process. High-performance forward osmosis membrane is closely related to its material properties and membrane structure, and it can be seen that membrane materials with excellent performance and the preparation method of forward osmosis membrane are particularly important. There are three common preparation methods for forward osmosis membranes: interfacial polymerization, double selective layer membrane preparation and nanofiltration membrane modification. The internal concentration polarization of the forward osmosis composite membrane prepared by the interfacial polymerization method is serious; the double selective layer membrane effectively reduces the internal concentration polarization, but the preparation process is more complicated; The water fluxes are all low; therefore, it is necessary to develop new forward osmosis membrane preparation processes to improve the separation performance and the feasibility of industrialization of forward osmosis membranes.

In the 1960s, the research on forward osmosis technology began abroad, and the existing reverse osmosis membrane or nanofiltration membrane was used for the application of forward osmosis. , but also proved that the performance of the forward osmosis membrane is closely related to the membrane material and membrane structure; subsequently, many membrane scientists began basic research on the preparation of forward osmosis membranes. The research results show that forward osmosis membranes with excellent performance can be prepared by selecting appropriate membrane materials and membrane forming processes. The research on forward osmosis technology in my country started late, and the current domestic research on forward osmosis technology, whether it is membrane preparation or membrane process research, is still in the exploratory stage. Some membrane researchers have explored the preparation conditions of cellulose-based forward osmosis membranes, and studied the influence of various factors on the performance of forward osmosis membranes, but they have not yet prepared a commercial forward osmosis membrane with excellent performance; the preparation of forward osmosis membranes And applied research still has a long way to go. Previous studies have inspired us that the use of blending technology to modify membrane materials is expected to improve the water flux, salt rejection, mechanical properties and pollution resistance of forward osmosis membranes, and it is easy to achieve industrialization. Invention patents ZL201410770001.4, 201510245514.8 and ZL201410769752.4, 201510245504.4 were prepared by blending nano-titanium dioxide and graphene with cellulose acetate to prepare flat and hollow fiber forward osmosis membranes. The separation performance and permeability of the prepared forward osmosis membranes were compared. Significant improvement; invention patents 2017100954795, 2017100954780, 2017100954846 use functionalized carbon nanotubes and cellulose acetate to blend forward osmosis membranes with better performance; The separation performance and permeation performance are further improved to meet the needs of commercial production and application.

Metal-Organic Frameworks (MOFs) are a recently developed new type of materials, also known as metal-organic complex polymers, which are assembled by organic ligands containing oxygen, nitrogen, etc. and metal ions through coordination. Porous materials with infinite network structure. Compared with traditional inorganic porous materials, MOFs materials have unparalleled excellent properties of inorganic porous materials such as zeolite, activated carbon, and carbon nanotubes. , chemical structure stability and so on. These excellent properties make MOFs have great application prospects in gas storage, water pollutant adsorption and separation, and gas catalysis. As a new type of organic-inorganic hybrid materials, metal-organic frameworks are an ideal dispersed phase for mixed-matrix membranes. Therefore, if suitable MOFs materials are blended with cellulose acetate to prepare a mixed matrix forward osmosis membrane, it is expected that the forward osmosis membrane product will have pollution resistance while obtaining high water flux and salt rejection rate. The research and development and application promotion of membrane materials provide new ideas.

How to obtain the hydrophilic properties while making the forward osmosis membrane anti-fouling and maintaining the stability of water flux is a difficult problem that membrane scientists have been thinking about and researching in recent years. The present invention adopts MIL-100(Fe) to improve the structure, permeability and separation performance of mixed matrix forward osmosis membrane. There is no literature report at home and abroad.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a flat plate mixed matrix forward osmosis membrane based on metal organic framework MIL-100(Fe), and another purpose of the present invention is to provide a preparation method of the mixed matrix forward osmosis membrane.

To achieve the above object, the technical scheme adopted in the present invention is:

A flat-plate mixed matrix forward osmosis membrane based on MIL-100(Fe) is composed of the following mass percentages: 8.0% to 20.0% (w/w) of polymer membrane material, 1.0% to 12.0% of porogen % (w/w), MIL-100(Fe) 0.1%～2.0% (w/w), solvent 66.0%～90.9% (w/w);

The polymer film material is one or both of cellulose diacetate and cellulose triacetate, and the content is 8.0% to 20.0% (w/w);

The metal-organic framework MIL-100(Fe) is a self-made metal-organic framework material, the shape is an octahedral crystal shape with a smaller particle size, and the content is 0.1% to 2.0% (w/w);

The porogen is one of polyvinylpyrrolidone and polyethylene glycol-400, and the content is 1.0% to 12.0% (w/w);

The solvent is a mixed solvent of N-methylpyrrolidone and acetone, the volume ratio of which is N-methylpyrrolidone:acetone=1:0.1-7.0, and the content is 66.0%-90.9% (w/w).

A preparation method of a flat-plate mixed matrix forward osmosis membrane based on metal-organic framework MIL-100(Fe), comprising the following steps:

(1) Add a certain amount of MIL-100(Fe) into the mixed solvent, and use ultrasonic to make it fully and uniformly dispersed in it. After the dispersion is completed, add it to a three-necked round-bottomed flask, and add a certain amount of polymer membrane material. , stir evenly;

(2) Add a certain amount of porogen into a three-necked round-bottomed flask, stir and dissolve at a temperature of 25 to 90 ° C for 2 to 16 hours until completely dissolved, and prepare a flat-plate mixed matrix based on MIL-100 (Fe). The initial film casting liquid of the permeable membrane; then, the obtained film casting liquid is allowed to stand for 3-16 hours at a stirring and dissolving temperature to remove the remaining bubbles in the film casting liquid;

(3) Spread the support layer on the cleaned and dried glass plate, then pour a certain amount of casting liquid into the glass plate, scrape it with a flat film scraper to make a film; put the formed nascent film at room temperature After evaporating for 1 to 30 seconds, immerse in a constant temperature coagulation bath water tank of 15 to 60 ° C to solidify and form, and the film is automatically separated from the glass plate. After heat treatment in deionized water for 5-60 minutes, a flat-plate mixed matrix forward osmosis membrane based on MIL-100(Fe) is obtained.

The support layer is one of polyester screen mesh, non-woven fabric, cotton gauze filter cloth, filter paper and nylon cloth, and its aperture is 60-280 meshes;

The evaporation time of the nascent ecological membrane at room temperature refers to the residence time of the prepared flat-type forward osmosis membrane in the air after scraping the membrane, and the evaporation time is 1 to 30 seconds;

The heat treatment temperature and time refer to the deionized water temperature and treatment time for heat treatment of the prepared flat-type forward osmosis membrane, the heat treatment temperature is 30～90℃, and the heat treatment time is 5～60 minutes;

The coagulation bath is deionized water.

The present invention provides a flat plate mixed matrix forward osmosis membrane based on metal organic framework MIL-100(Fe) and a preparation method. The matrix forward osmosis membrane has good permeation performance, separation performance and anti-fouling performance, which is the innovation of the present invention. The test results show that the pure water flux and reverse salt flux of the prepared forward osmosis membrane are greatly improved.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The MIL-100(Fe) provided by the present invention solves the problem of collapse of the traditional metal organic framework. The flat-plate mixed matrix forward osmosis membrane prepared by its blending and modification Compared with the blended forward osmosis membrane of carbon nanotubes, its pure water flux and reverse salt flux have been significantly improved.

(2) The method for preparing a flat-plate mixed matrix forward osmosis membrane by blending and modifying MIL-100(Fe) provided by the present invention has simple and easy-to-control equipment, simple membrane preparation process, and gives the prepared positive osmosis membrane while forming the membrane. The permeable membrane has good permeation performance, separation performance and anti-pollution performance, which is easy to realize industrialization.

Detailed ways:

The present invention will be described in further detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

Example 1:

0.6% (w/w) MIL-100(Fe) was added to a mixed solvent consisting of 54.4% (w/w) N-methylpyrrolidone and 25.0% (w/w) acetone, and it was made in it by ultrasound Fully and uniformly disperse, add it to a three-necked round-bottomed flask after the dispersion is completed, add 13.0% (w/w) cellulose acetate, and stir evenly. Add 7.0% (w/w) polyethylene glycol-400 porogen into a three-necked round-bottomed flask, stir and dissolve at 65 °C for 8 hours until completely dissolved, and prepare a flat plate based on MIL-100(Fe) the initial casting solution of the mixed matrix forward osmosis membrane; then, the obtained membrane casting solution was left to stand for 9 hours at the stirring and dissolving temperature to remove the remaining bubbles in the casting solution. Spread the 180-mesh polyester screen on the cleaned and dried glass plate, then pour a certain amount of casting liquid into the glass plate, scrape it with a flat film scraper to make a film; put the formed nascent film on the glass plate. After evaporating for 10 seconds at room temperature, immersed in a constant temperature coagulation bath at 25 °C to solidify and form, and the film is automatically separated from the glass plate. After taking out the film, soak it in deionized water at room temperature for 24 hours, and then heat treatment in deionized water at 65 °C for 15 minutes. , that is, a flat-plate mixed matrix forward osmosis membrane based on MIL-100(Fe) is obtained. Using 1M NaCl as the driving fluid and deionized water as the raw material solution, the pure water flux of the prepared forward osmosis membrane reached more than 37.0L/m ² •h and the reverse salt flux was less than 1.5g/m in the test time of 1h. ² •h.

Example 2:

The contents of MIL-100(Fe) and N-methylpyrrolidone were adjusted to 0.1% (w/w) and 54.9% (w/w) respectively, and the rest were the same as those in Example 1. The properties of the prepared flat-plate mixed-matrix forward osmosis membrane based on MIL-100(Fe) are as follows: using 1M NaCl as the driving fluid and deionized water as the raw material solution, in the test time of 1h, the prepared forward osmosis membrane has the following properties: The pure water flux is above 26.0L/m ² •h, and the reverse salt flux is less than 2.5g/m ² •h.

Example 3:

The contents of MIL-100(Fe) and N-methylpyrrolidone were adjusted to 2.0% (w/w) and 53.0% (w/w) respectively, and the rest were the same as those in Example 1. The properties of the prepared flat-plate mixed-matrix forward osmosis membrane based on MIL-100(Fe) are as follows: using 1M NaCl as the driving fluid and deionized water as the raw material solution, in the test time of 1h, the prepared forward osmosis membrane has the following properties: The pure water flux is above 36.0L/m ² •h, and the reverse salt flux is less than 2.0g/m ² •h.

Example 4:

The polyethylene glycol-400 in the porogen was replaced with polyvinylpyrrolidone, and the rest were the same as those in Example 1. The properties of the prepared flat-plate mixed-matrix forward osmosis membrane based on MIL-100(Fe) are as follows: using 1M NaCl as the driving fluid and deionized water as the raw material solution, in the test time of 1h, the prepared forward osmosis membrane has the following properties: The pure water flux is above 32.0L/m ² •h, and the reverse salt flux is less than 1.5g/m ² •h.

Example 5:

The temperature of the coagulation bath was adjusted from 25°C to 60°C, and the rest were the same as those in Example 1. The properties of the prepared flat-plate mixed-matrix forward osmosis membrane based on MIL-100(Fe) are as follows: using 1M NaCl as the driving fluid and deionized water as the raw material solution, in the test time of 1h, the prepared forward osmosis membrane has the following properties: The pure water flux is above 41.0L/m ² •h, and the reverse salt flux is less than 2.5g/m ² •h.

Example 6:

The heat treatment temperature was adjusted from 65°C to 90°C, and the rest were the same as those in Example 1. The properties of the prepared flat-plate mixed-matrix forward osmosis membrane based on MIL-100(Fe) are as follows: using 1M NaCl as the driving fluid and deionized water as the raw material solution, in the test time of 1h, the prepared forward osmosis membrane has the following properties: The pure water flux is above 33.0L/m ² •h, and the reverse salt flux is less than 2.0g/m ² •h.

Example 7:

The heat treatment time was adjusted from 15 minutes to 60 minutes, and the rest were the same as in Example 1. The performance of the prepared high-performance flat-type forward osmosis membrane based on MIL-100(Fe) is as follows: using 1M NaCl as the driving fluid and deionized water as the raw material solution, in the test time of 1h, the prepared forward osmosis membrane has the following properties: The pure water flux is above 35.0L/m ² •h, and the reverse salt flux is less than 1.5g/m ² •h.

Comparative Example 1:

Add a mixed solvent of 55.0% (w/w) N-methylpyrrolidone and 25.0% (w/w) acetone into a three-neck round bottom flask, then add 13.0% (w/w) cellulose acetate, stir well . Add 7.0% (w/w) polyethylene glycol-400 porogen into a three-necked round-bottomed flask, stir and dissolve at 65 °C for 8 hours until completely dissolved, and prepare a flat cellulose acetate mixed matrix forward osmosis The initial film casting liquid of the film; then, the obtained film casting liquid was left to stand for 9 hours at the stirring and dissolving temperature to remove the remaining bubbles in the film casting liquid. Spread the 180-mesh polyester screen on the cleaned and dried glass plate, then pour a certain amount of casting liquid into the glass plate, scrape it with a flat film scraper to make a film; put the formed nascent film on the glass plate. After evaporating for 10 seconds at room temperature, immersed in a constant temperature coagulation bath at 25 °C to solidify and form, and the film is automatically separated from the glass plate. After taking out the film, soak it in deionized water at room temperature for 24 hours, and then heat treatment in deionized water at 65 °C for 15 minutes. , that is, a flat cellulose acetate mixed matrix forward osmosis membrane is obtained. Using 1M NaCl as the driving fluid and deionized water as the raw material solution, the pure water flux of the prepared forward osmosis membrane was over 33.0L/m ² •h, and the reverse salt flux was less than 4.0g/m in the 1h test time. ² •h.

Claims (3)

1. A flat plate type mixed matrix forward osmosis membrane based on metal organic framework MIL-100(Fe) is characterized in that a casting solution contains the metal organic framework MIL-100(Fe) and influences the structure and the performance of the forward osmosis membrane; the casting solution consists of the following substances in percentage by mass: polymer film material 8.0-20.0% (w/w), pore-forming agent 1.0-12.0% (w/w), MIL-100(Fe) 0.6-2.0% (w/w), solvent 66.0-90.9% (w/w);

the pore-foaming agent is polyethylene glycol-400;

the polymer membrane material is one or two of cellulose diacetate and cellulose triacetate;

the solvent is a mixed solvent of N-methyl pyrrolidone and acetone, and the volume ratio of the mixed solvent to the solvent is N-methyl pyrrolidone: acetone =1: 0.1-7.0;

the preparation method of the flat plate type mixed matrix forward osmosis membrane based on the metal organic framework MIL-100(Fe) comprises the following steps:

(1) adding a certain amount of MIL-100(Fe) into a mixed solvent, fully and uniformly dispersing the MIL-100(Fe) in the mixed solvent by using ultrasound, adding the mixture into a three-neck round-bottom flask after the dispersion is finished, adding a certain amount of polymer film material, and uniformly stirring;

(2) adding a certain amount of pore-forming agent into a three-neck round-bottom flask, stirring and dissolving at 25-90 ℃ for 2-16 hours until the pore-forming agent is completely dissolved, and preparing an initial membrane casting solution of a flat plate type mixed matrix forward osmosis membrane based on MIL-100 (Fe); standing the obtained casting solution for 3-16 hours at the stirring and dissolving temperature, and removing bubbles remained in the casting solution;

(3) spreading the support layer on a cleaned and dried glass plate, pouring a certain amount of casting solution on the glass plate, and scraping the casting solution into a film by using a flat film scraper; evaporating the formed nascent membrane for 1-30 seconds at room temperature, immersing the nascent membrane into a constant-temperature solidification bath water tank at 15-60 ℃ for solidification and formation, automatically separating the formed nascent membrane from a glass plate, taking out the nascent membrane, soaking the nascent membrane in normal-temperature deionized water for 12-48 hours, and then carrying out heat treatment on the nascent membrane in the deionized water at 30-90 ℃ for 5-60 minutes to obtain the MIL-100(Fe) -based flat mixed matrix forward osmosis membrane.

2. The MIL-100(Fe) -based flat mixed matrix forward osmosis membrane according to claim 1, wherein: the forward osmosis membrane is prepared by adopting a traditional phase inversion method, namely a dry-wet method.

3. The MIL-100(Fe) -based flat mixed matrix forward osmosis membrane according to claim 1, wherein: the supporting layer is one of a polyester screen, a non-woven fabric, a cotton yarn filter cloth, filter paper and nylon cloth, and the aperture of the supporting layer is 60-280 meshes; the coagulating bath is deionized water.