Preparation method and application of a high molecular polymer sponge for efficient separation of dimethyl sulfoxide / water mixture

Abstract

The present invention belongs to the fields of material preparation and chemical separation, and particularly relates to a preparation method and application of a polymer sponge for efficient separation of dimethyl sulfoxide / water mixtures. In the present invention, amino-terminated polydimethylsiloxane is used as a matrix, grafted and modified with 3-mercaptobenzoic acid, covalently bonded with carboxylated carbon nanotubes through a condensation reaction, and foamed by the gas generated after the reaction of a condensing agent to form a polymer sponge with a three-dimensional cross-linked network structure. The obtained polymer sponge has adsorption selectivity for dimethyl sulfoxide, and through a physical adsorption separation method, efficient separation of dimethyl sulfoxide and water is achieved, and it has good application prospects in the treatment and recycling of polar solvent wastewater.

Description

Technical Field

[0001] The present invention belongs to the fields of material preparation and chemical separation, and particularly relates to a preparation method and application of a polymer sponge for efficient separation of dimethyl sulfoxide / water mixture liquids. Background Art

[0002] Organic solvents have been widely used in the chemical and pharmaceutical industries for chemical synthesis and product purification. Since most processes require high-purity solvents, after one process cycle, solvents usually cannot be reused without proper treatment, thus generating a large amount of waste streams. Traditional wastewater treatment technologies (such as biodegradation and advanced oxidation processes) are difficult to effectively treat wastewater with high organic solvent content. Therefore, the treatment and reuse of organic solvent wastewater have always been a difficult problem. Dimethyl sulfoxide is a widely used polar organic solvent and is often used as a reaction medium in chemical and pharmaceutical production due to its strong solubility in various compounds and good compatibility with water. Due to the miscibility of dimethyl sulfoxide with water, its separation and recovery pose a challenge.

[0003] In recent years, there are roughly two technologies for separating liquid mixtures: pervaporation and membrane distillation. The pervaporation process is driven by vapor pressure and separates components by taking advantage of the differences in their solubility and diffusion rates through the membrane. For example, CN201810733838.X discloses a preparation method of a polyimide pervaporation membrane, and the obtained membrane can be used for the separation of polar solutions. Membrane distillation is a membrane separation process that uses a hydrophobic microporous membrane with the vapor pressure difference across the membrane as the mass transfer driving force, and is usually used for the distillation desalination of water and the removal of volatile substances in aqueous solutions. For example, CN201811296112.0 discloses a preparation method of an ethylene-chlorotrifluoroethylene copolymer microporous separation membrane, which can be used for the treatment of organic solvents. However, when separating dimethyl sulfoxide / water mixture liquids by the above two methods, the materials need to be heated to convert the liquid mixture into a gas and then separated. The boiling point of dimethyl sulfoxide is as high as 189 °C and it does not form an azeotrope with water. Therefore, a large amount of energy consumption is required during the separation process, resulting in energy waste and increased costs.

[0004] In recent years, some porous sponge adsorbents have been used in the field of oil-water separation. These materials have good separation effects for solvents or oils with weak water miscibility, but have low separation efficiency for solvents with strong water miscibility. For example, CN202110075962.3 discloses a preparation method of a self-foaming graphene oxide-polydimethylsiloxane sponge. The invented adsorbent has good hydrophobic and oleophilic properties and can adsorb various oils and organic solvents, but does not involve the separation of water-soluble organic solvents, especially the selective separation of dimethyl sulfoxide, a high-boiling and strong-polar solvent. Other similar oil-water separation materials in this field also do not involve the selective separation of dimethyl sulfoxide. Summary of the Invention

[0005] In view of the above problems, the present invention proposes to use an adsorbent with special functional groups for the selective adsorption of dimethyl sulfoxide, so as to achieve the efficient separation of a dimethyl sulfoxide and water mixture.

[0006] The adsorbent involved in the present invention is based on amino-terminated polydimethylsiloxane, graft-modified with 3-mercaptobenzoic acid, covalently bonded to carboxylated carbon nanotubes through a condensation reaction, and foamed using the gas generated after the reaction of the condensing agent, thereby obtaining a polymer sponge with selective adsorption for dimethyl sulfoxide.

[0007] In order to achieve the above invention object, the present invention provides a preparation method of a polymer sponge for the efficient separation of a dimethyl sulfoxide / water mixture, including the following steps: dissolving amino-terminated polydimethylsiloxane in an organic solvent, then sequentially adding 3-mercaptobenzoic acid, carboxylated carbon nanotubes, a condensing agent and glutaraldehyde, stirring evenly to form a mixed solution, and then transferring the mixed solution to a mold for heat curing for more than 10 min.

[0008] The reaction involved in the present invention is a condensation reaction, and the groups participating in the reaction are carboxyl and amino. The source of the carboxyl is carboxylated carbon nanotubes and 3-mercaptobenzoic acid, and the source of the amino is amino-terminated polydimethylsiloxane, forming a three-dimensional crosslinked network structure through the condensation reaction.

[0009] Further, the molecular weight of the amino-terminated polydimethylsiloxane is 5000 - 50000, and the specific structural formula is:

[0010]

[0011] Further, the organic solvent is any one of tetrahydrofuran, dichloromethane, chloroform or 1,4-dioxane, preferably tetrahydrofuran.

[0012] Further, the mass ratio of 3-mercaptobenzoic acid to polydimethylsiloxane is (0.5 - 5):100; the mass ratio of carboxylated carbon nanotubes to polydimethylsiloxane is (1 - 5):10000.

[0013] Further, the condensing agent is a mixture of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS), wherein the molar ratio of polydimethylsiloxane to EDC and NHS is 1:10:10; the mass ratio of polydimethylsiloxane to glutaraldehyde is 100:1.

[0014] Further, the curing temperature is 20 - 60°C.

[0015] The present invention also provides a high molecular polymer sponge prepared by the above method for selective adsorption of dimethyl sulfoxide, realizing efficient separation of a dimethyl sulfoxide / water mixture, recovering dimethyl sulfoxide and recycling it.

[0016] The recovery method of dimethyl sulfoxide is to carry out reduced-pressure extraction on the high molecular polymer sponge during the adsorption process or physically extrude the high molecular polymer sponge after adsorption. The removal rate of dimethyl sulfoxide in a dimethyl sulfoxide aqueous solution with a mass concentration of 10% reaches more than 95%, and the content of dimethyl sulfoxide in the extruded liquid is more than 85%.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] 1. The adsorption and separation method of dimethyl sulfoxide and water proposed by the present invention, compared with the existing pervaporation and membrane distillation methods, does not require heating of the material and can be separated in the liquid state, having the advantages of low energy consumption and low cost.

[0019] 2. The high molecular polymer sponge used in the present invention can selectively adsorb dimethyl sulfoxide to achieve dynamic continuous separation, and the high molecular polymer sponge can be regenerated by simple physical extrusion, and the separation performance does not decrease significantly after multiple recycling. Description of the Drawings

[0020] Figure 1 It is a scanning electron microscope image of the high molecular polymer sponge prepared in Example 1 of the present invention.

[0021] Figure 2 It is the water contact angle of the high molecular polymer sponge prepared in Example 1 of the present invention.

[0022] Figure 3 It is the adsorption-desorption cycle diagram of the high molecular polymer sponge prepared in Example 1 of the present invention for a dimethyl sulfoxide aqueous solution with a mass concentration of 10%.

[0023] Figure 4 It is the cyclic compression curve of the high molecular polymer sponge prepared in Example 1 of the present invention.

[0024] Figure 5 It is the distribution diagram of the removal rate of dimethyl sulfoxide and the concentration of dimethyl sulfoxide in the extruded liquid in the high molecular polymer sponge prepared in Example 1 of the present invention in dimethyl sulfoxide aqueous solutions with different mass concentrations.

[0025] Figure 6 It is a comparison diagram of the removal rates of organic solvents in the mixed liquids of different organic solvents and water (the solvent mass concentration is 10%) by the high molecular polymer sponges prepared in Example 1 and Comparative Example 1. Detailed Embodiments

[0026] The present invention will be further described below in conjunction with specific embodiments. The materials and reagents used in the following embodiments can be obtained from commercial sources.

[0027] Example 1

[0028] (1) Put 1 g of polydimethylsiloxane with a molecular weight of 25,000 into 1 mL of tetrahydrofuran, stir evenly, and then add 20 mg of 3-mercaptobenzoic acid and stir evenly.

[0029] (2) Prepare an aqueous dispersion of carboxylated carbon nanotubes at a concentration of 10 mg / mL, transfer 0.3 mL of the dispersion to the mixed solution in step (1), and stir evenly.

[0030] (3) Add 62 mg of EDC and 46 mg of NHS to the mixed solution in step (2) successively, stir evenly; then add 10 mg of glutaraldehyde, stir evenly and transfer to a mold, and cure at 50 °C for 0.5 h to obtain a high molecular polymer sponge.

[0031] The water contact angle of the obtained high molecular polymer sponge is 146.4°( Figure 2 ).

[0032] Use the obtained high molecular polymer sponge to carry out static adsorption separation on the dimethyl sulfoxide / water mixture. The removal rate of dimethyl sulfoxide in the dimethyl sulfoxide aqueous solution with a mass concentration of 10% is 98.4%. Recover dimethyl sulfoxide by the extrusion method. More than 90% of the liquid can be extruded. The concentration of dimethyl sulfoxide in the extruded liquid is 93.7%. Then wash the sponge with ethanol and dry it, and adsorb again. After 10 cycles, the dimethyl sulfoxide removal rate and the concentration of dimethyl sulfoxide in the extruded liquid are as Figure 3 shown. It can be seen that the performance has no obvious decline, and from Figure 4 it can be seen that the high molecular polymer sponge can recover its deformation after undergoing multiple cyclic compressions.

[0033] From Figure 5 it can be seen that the removal rate of dimethyl sulfoxide aqueous solutions with different mass concentrations and the concentration of dimethyl sulfoxide in the extruded liquid by the high molecular polymer sponge. The results show that the removal rate of dimethyl sulfoxide reaches more than 98%, and the concentration of dimethyl sulfoxide in the extruded liquid reaches more than 85%.

[0034] The principle of selective adsorption of dimethyl sulfoxide by the obtained high molecular polymer sponge is as follows: Using mercaptophenyl as a modifying group, the mercapto group of mercaptophenyl and the thiol group of dimethyl sulfoxide will form hydrogen bonds, and mercaptophenyl and dimethyl sulfoxide have relatively similar polarities, so there will be a strong intermolecular force between the two, thus realizing the selective adsorption of dimethyl sulfoxide during the adsorption process.

[0035] For a 10% dimethyl sulfoxide aqueous solution, connect the high molecular polymer sponge to a peristaltic pump. During the adsorption process, perform vacuum extraction with the peristaltic pump. Finally, the remaining concentration of dimethyl sulfoxide in the solution is 1.5%, and the concentration of dimethyl sulfoxide in the extraction liquid is 85.4%.

[0036] Example 2

[0037] (1) Put 1 g of polydimethylsiloxane with a molecular weight of 25,000 into 1 mL of tetrahydrofuran and stir evenly, then add 40 mg of 3-mercaptobenzoic acid and stir evenly.

[0038] (2) Prepare an aqueous dispersion of carboxylated carbon nanotubes at a concentration of 10 mg / mL, transfer 0.3 mL of the dispersion to the mixed solution in step (1), and stir evenly.

[0039] (3) Add 62 mg of EDC and 46 mg of NHS to the mixed solution in step (2) successively, and stir evenly; then add 10 mg of glutaraldehyde, stir evenly and transfer to a mold, and cure at 50 °C for 0.5 h to obtain a high molecular polymer sponge.

[0040] The water contact angle of the obtained high molecular polymer sponge is 143.1°. The removal rate of dimethyl sulfoxide in a 10% dimethyl sulfoxide aqueous solution is 96.3%, and the concentration of dimethyl sulfoxide in the extrusion liquid is 90.4%.

[0041] Comparative Example 1

[0042] (1) Put 1 g of polydimethylsiloxane with a molecular weight of 25,000 into 1 mL of tetrahydrofuran and stir evenly.

[0043] (2) Prepare an aqueous dispersion of carboxylated carbon nanotubes at a concentration of 10 mg / mL, transfer 0.3 mL of the dispersion to the mixed solution in step (1), and stir evenly.

[0044] (3) Add 62 mg of EDC and 46 mg of NHS to the mixed solution in step (2) successively, and stir evenly; then add 10 mg of glutaraldehyde, stir evenly and transfer to a mold, and cure at 50 °C for 0.5 h to obtain a high molecular polymer sponge.

[0045] The water contact angle of the obtained high molecular polymer sponge is 144.9°. The removal rate of dimethyl sulfoxide in a 10% dimethyl sulfoxide aqueous solution is 80.8%, and the concentration of dimethyl sulfoxide in the extrusion liquid is 77.3%.

[0046] For a 10% dimethyl sulfoxide aqueous solution, perform vacuum extraction with a peristaltic pump during the adsorption process of the high molecular polymer sponge. Finally, the remaining concentration of dimethyl sulfoxide in the solution is 3.7%, and the concentration of dimethyl sulfoxide in the extraction liquid is 68.9%.

[0047] The difference between Comparative Example 1 and Example 1 is that 3-mercaptobenzoic acid is not added during the preparation process. By Figure 6 It can be seen that the removal rate of dimethyl sulfoxide by the polymer sponge prepared in Example 1 is significantly higher than that in Comparative Example 1, while the removal rates of the two for other organic solvents are quite comparable, indicating that the polymer sponge prepared in Example 1 has selective adsorption for dimethyl sulfoxide.

[0048] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a high - efficiency separation polymer sponge for dimethyl sulfoxide / water mixture, characterized in that, Dissolve the amino-terminated polydimethylsiloxane in an organic solvent, then sequentially add 3-mercaptobenzoic acid, carboxylated carbon nanotubes, a condensing agent, and glutaraldehyde, stir evenly to form a mixed solution, and then transfer the mixed solution to a mold and add it to cure for more than 10 minutes to form a high molecular polymer sponge.

2. The preparation method of the high molecular polymer sponge for efficient separation of dimethyl sulfoxide / water mixture according to claim 1, characterized in that, The molecular weight of the amino-terminated polydimethylsiloxane is 5000 - 50000, and the specific structural formula is:

3. The preparation method of the polymer sponge for efficient separation of dimethyl sulfoxide / water mixture according to claim 1, characterized in that, The organic solvent is any one of tetrahydrofuran, dichloromethane, chloroform, or 1,4-dioxane.

4. The preparation method of the polymer sponge for efficient separation of dimethyl sulfoxide / water mixture according to claim 1, characterized in that, The mass ratio of 3-mercaptobenzoic acid to polydimethylsiloxane is (0.5 - 5):100; the mass ratio of carboxylated carbon nanotubes to polydimethylsiloxane is (1 - 5):10000.

5. The preparation method of the polymer sponge for efficient separation of dimethyl sulfoxide / water mixture according to claim 1, characterized in that, The condensing agent is a mixture of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide. Among them, the molar ratio of polydimethylsiloxane to 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide is 1:10:10; the mass ratio of polydimethylsiloxane to glutaraldehyde is 100:

1.

6. The preparation method of the polymer sponge for efficient separation of dimethyl sulfoxide / water mixture according to claim 1, characterized in that, The curing temperature is 20 - 60 °C.

7. Use of a polymer sponge prepared by the method according to any one of claims 1-6, characterized in that, The high molecular polymer sponge is applied to the selective adsorption of dimethyl sulfoxide to achieve the separation of the dimethyl sulfoxide / water mixture.

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