阅读说明：本技术 多孔石墨烯复合优先透醇的渗透汽化膜材料及其制备方法 (Porous graphene composite pervaporation membrane material with preferential alcohol permeability and preparation method thereof ) 是由 姚一一 王一菲 李恒 黄思远 何龙 于 2019-10-18 设计创作，主要内容包括：本发明公开了多孔石墨烯复合优先透醇的渗透汽化膜材料及其制备方法,主要步骤包括(1)具有疏水孔洞的多孔石墨烯的制备：通过多孔石墨烯、正庚烷、正硅酸乙酯和有机锡混合得到具有疏水孔洞的多孔石墨烯；(2)优先透醇的渗透汽化膜的制备；将溶解有PDMS、交联剂、催化剂的正庚烷混合具有疏水孔洞的石墨烯制备铸膜液,用刮刀涂覆于PVDF超滤膜上,制得石墨烯改性的渗透汽化优先透醇膜。本发明提供的多孔石墨烯复合优先透醇的渗透汽化膜自身成膜性好、力学性能好,实现优先透醇,可用于渗透汽化体系,具有良好的分离性能。(The invention discloses a porous graphene composite alcohol permselective pervaporation membrane material and a preparation method thereof, which mainly comprises the following steps of (1) preparation of porous graphene with hydrophobic pores: mixing porous graphene, n-heptane, ethyl orthosilicate and organic tin to obtain porous graphene with hydrophobic pores; (2) preparing a pervaporation membrane which is permeable to alcohol preferentially; mixing n-heptane dissolved with PDMS, a cross-linking agent and a catalyst with graphene with hydrophobic pores to prepare a membrane casting solution, and coating the membrane casting solution on a PVDF ultrafiltration membrane by using a scraper to prepare the graphene modified pervaporation alcohol permselective membrane. The porous graphene composite alcohol permselective pervaporation membrane provided by the invention has good self-film forming property and good mechanical property, realizes alcohol permselective permeation, can be used for a pervaporation system, and has good separation property.)

1. The preparation method of the porous graphene composite alcohol permselective pervaporation membrane material is characterized by comprising the following steps:

preparing porous graphene with hydrophobic pores:

adding the porous graphene into n-heptane according to the mass-to-volume ratio of 0.05-0.5g/ml, ultrasonically dispersing uniformly, then adding tetraethoxysilane and organic tin, fully stirring for 0.5-3h, and filtering to obtain the porous graphene with hydrophobic pores;

(II) preparing a pervaporation membrane with preferential alcohol permeability:

dissolving PDMS, a cross-linking agent and a catalyst in n-heptane, uniformly mixing, slowly adding the mixture into the graphene with the hydrophobic holes prepared in the step (I), and stirring for 1-3h to obtain a casting solution;

and coating the membrane casting solution on a PVDF ultrafiltration membrane by using a scraper, standing for 6h at room temperature, removing the n-heptane solution, transferring to an oven, and heating to obtain the graphene modified pervaporation alcohol permselective membrane.

2. The method for preparing the porous graphene composite ethanol permselective pervaporation membrane material according to claim 1, wherein the preparation of the porous graphene in the step (one) comprises the following steps:

preparing graphite oxide by adopting a modified Hummers method: h is to be₂SO₄、H₃PO₄、KMnO₄Mixing the crystalline flake graphite according to a proportion, heating to 20-80 ℃, stirring for 10-14H, cooling the product to room temperature, pouring ice water, and adding 30% H₂O₂When the product is observed to be converted into dark yellow, standing for 12h, washing the product to be neutral by using absolute ethyl alcohol, 30% HCl and deionized water respectively after centrifugal separation, ultrasonically dispersing for 0.5-2h, and freeze-drying to obtain graphite oxide;

preparing the prepared graphite oxide into a graphene oxide aqueous solution of 2mg/mL, performing ultrasonic dispersion for 2-5 hours, uniformly pouring into a polytetrafluoroethylene reaction kettle, performing hydrothermal reaction for 2-12 hours at 140-240 ℃, taking out a sample after the temperature is reduced to room temperature, and performing freeze drying to obtain the porous graphene.

3. The preparation method of the porous graphene composite ethanol permselective pervaporation membrane material according to claim 2, wherein the H is₂SO₄、H₃PO₄、KMnO₄The mixing ratio of the crystalline flake graphite is 120: 13: 6: 1.

4. the preparation method of the porous graphene composite alcohol permselective pervaporation membrane material according to claim 1, wherein the membrane casting solution in the step (II) comprises the following components in parts by weight: 10 parts of PDMS, 0.2-2 parts of cross-linking agent, 0.01-0.001 part of catalyst, 100 parts of n-heptane and 0.1-10 parts of graphene with hydrophobic holes.

5. The method for preparing a porous graphene composite ethanol permselective pervaporation membrane material according to claim 1, wherein the viscosity of the PDMS in the step (two) is 500-100000 mPa-s, and the PDMS is a vinyl-terminated PDMS.

6. The preparation method of the porous graphene composite ethanol permselective pervaporation membrane material according to claim 1, wherein the mass ratio of the ethyl orthosilicate and the organotin in the step (I) is 5:1-15: 1.

7. The method for preparing the porous graphene composite ethanol permselective pervaporation membrane material according to claim 1, wherein in the step (two), the catalyst is organic platinum, and the cross-linking agent is hydrogen-containing silicone oil.

8. The preparation method of the porous graphene composite permselective alcohol pervaporation membrane material according to claim 1, wherein the heating temperature and time of the oven in the step (II) are 30-90 ℃ for 8-12 h.

9. The method for preparing the porous graphene composite permselective alcohol pervaporation membrane material according to claim 1, wherein the coating thickness of the PDMS membrane in the step (II) is 5-100 um.

10. The porous graphene composite alcohol permselective pervaporation membrane material prepared by the preparation method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of pervaporation membrane separation, in particular to a porous graphene composite alcohol permselective pervaporation membrane material and a preparation method thereof.

Background

Pervaporation (PV) membrane separation technology is a new type of membrane separation technology. The technology is used for separating liquid mixture, and has the outstanding advantage of realizing separation tasks which are difficult to be completed by traditional methods such as distillation, extraction, adsorption and the like with low energy consumption. It is especially suitable for separation of near-boiling point and constant-boiling point mixture which is difficult to separate or can not be separated by ordinary rectification. Currently, pervaporation is mainly applied in three fields: (1) organic solvent dehydration such as alcohols, ethers, esters, acids dehydration, and the like; (2) removing trace organic matters in water, such as volatile organic matters, recovering aromatic organic matters, recovering biofuel from fermentation liquor, and the like; (3) separation of organic-organic mixed systems, such as methyl tert-butyl ether (MTBE)/methanol, dimethyl carbonate (DMC)/methanol, benzene/cyclohexane separation, etc.

The functional layer of the pervaporation membrane which is penetrated by organic matters preferentially is mainly polymethyl siloxane (PDMS). The hydrophobic film material has strong hydrophobicity and is a typical hydrophobic film material. But the self-film-forming property and the mechanical property are poor, the separation coefficient and the permeation flux of organic matters are low, and the modified PDMS is mainly applied to the current industrialization.

Patent 101264429a discloses a method for preparing a pervaporation alcohol permselective zeolite filled silicone rubber composite membrane, which uses MFI type zeolite to modify PDMS/PVDF, and has high separation factor and permeation flux for ethanol aqueous solution. However, the compatibility of the MFI type zeolite and PDMS is poor, and the particle size of the zeolite is large, so that the mechanical property of the pervaporation membrane is influenced.

Patent 108479423a discloses a graphene oxide @ polyvinyl alcohol mixed matrix pervaporation membrane and a preparation method thereof. And uniformly mixing the graphene oxide dispersion solution with the polyvinyl alcohol solution, removing impurities, defoaming, and coating the mixture on a pretreated base membrane to obtain the graphene oxide @ polyvinyl alcohol mixed matrix pervaporation membrane. The composite membrane utilizes the good supporting performance of the base membrane and the special physical and chemical properties of the graphene oxide, so that the composite membrane has good separation performance and can be used for separating a small amount of water in high-concentration organic matters by a pervaporation method. But because the water-permeable membrane is a pervaporation priority water-permeable system, the water-permeable membrane cannot be used for a pervaporation priority alcohol-permeable system.

Patent 106084276A discloses a method for efficiently synthesizing graphene-polydimethylsiloxane functional sponge. The sponge body can be applied to separation of oil or nonpolar organic solvents in water bodies, has high adsorption capacity, high adsorption rate, strong selectivity and good recycling capacity, and has potential application value in the fields of crude oil leakage treatment, industrial organic waste liquid treatment and the like. However, the material mainly plays a role of adsorption, and adsorption saturation is achieved. The pervaporation membrane can be used for a long time due to the adsorption and desorption processes.

Disclosure of Invention

In order to solve the problems in the prior art, the porous graphene is prepared by combining a Hummers oxidation-reduction method and a hydrothermal method, and is further subjected to hydrophobic modification to be compounded with PDMS to prepare the pervaporation membrane with preferential alcohol permeability.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a preparation method of a porous graphene composite alcohol permselective pervaporation membrane material, which comprises the following steps:

preparing porous graphene with hydrophobic pores:

adding the porous graphene into n-heptane according to the mass-volume ratio of 0.05-0.5g/ml, ultrasonically dispersing uniformly, then adding tetraethoxysilane and organic tin, fully stirring for 0.5-3h, and filtering to obtain the porous graphene with hydrophobic pores;

(II) preparing a pervaporation membrane with preferential alcohol permeability:

dissolving PDMS, a cross-linking agent and a catalyst in n-heptane, uniformly mixing, slowly adding the mixture into the graphene with the hydrophobic holes prepared in the step (I), and stirring for 1-3h to obtain a casting solution;

and coating the membrane casting solution on a PVDF ultrafiltration membrane by using a scraper, standing for 6h at room temperature, removing the n-heptane solution, transferring to an oven, and heating to obtain the graphene modified pervaporation alcohol permselective membrane.

Preferably, the preparation of the porous graphene in the step (one) comprises the following steps:

preparing graphite oxide by adopting a modified Hummers method: h is to be₂SO₄、H₃PO₄、KMnO₄Mixing the crystalline flake graphite according to a proportion, heating to 20-80 ℃, stirring for 10-14H, cooling the product to room temperature, pouring ice water, and adding 30% H₂O₂When the product is observed to be converted into dark yellow, standing for 12h, washing the product to be neutral by using absolute ethyl alcohol, 30% HCl and deionized water respectively after centrifugal separation, ultrasonically dispersing for 0.5-2h, and freeze-drying to obtain graphite oxide;

(12) preparing the graphite oxide in the step (11) into a graphene oxide aqueous solution of 2mg/mL, ultrasonically dispersing for 2-5 h, uniformly pouring into a polytetrafluoroethylene reaction kettle, carrying out hydrothermal reaction at 140-240 ℃ for 2-12 h, taking out a sample after the temperature is reduced to room temperature, and freeze-drying to obtain the porous graphene.

Preferably, said H in step (11)₂SO₄、H₃PO₄、KMnO₄The mixing ratio of the crystalline flake graphite is 120: 13: 6: 1.

preferably, the casting solution in step (3) comprises the following components in parts by weight: 10 parts of PDMS, 0.2-2 parts of cross-linking agent, 0.01-0.001 part of catalyst, 100 parts of n-heptane and 0.1-10 parts of graphene with hydrophobic holes.

Preferably, the viscosity of the PDMS in the step (3) is 500-; further, the PDMS is a vinyl terminated PDMS.

Preferably, the mass ratio of the ethyl orthosilicate to the organotin in the step (one) is 5:1-15: 1.

Preferably, the catalyst in step (two) is an organic platinum; further preferably, the catalyst is 1, 3-divinyl-1, 1, 3, 3-tetramethyldisiloxane platinum (0).

Preferably, the crosslinking agent in step (two) is hydrogen-containing silicone oil.

Preferably, the PDMS film is coated in step (two) to a thickness of 5-100 um.

Secondly, in a second aspect, the invention also provides a porous graphene composite alcohol permselective pervaporation membrane material prepared by the preparation methodAnd (5) feeding. For ethanol water solution with the concentration of 3-20 wt% and the temperature of 40-70 ℃, the permeation flux of the membrane is 1.31-5.37 kg/m²h, the separation factor is 21.4-34.1.

By adopting the technical scheme, compared with the prior art, the invention has the following technical effects:

(1) according to the invention, the porous graphene prepared by combining the Hummers oxidation-reduction method and the hydrothermal method is subjected to hydrophobic modification, the porous graphene with hydrophobic pores is compounded with PDMS, and the obtained porous graphene composite alcohol-permselective pervaporation membrane has good self-film forming property and good mechanical property, realizes alcohol permselective permeation, and can be used for a pervaporation system.

(2) The prepared pervaporation membrane can be used for a long time due to the adsorption and desorption processes.

(3) The composite membrane has good separation performance, and the permeation flux of the membrane is 1.31-5.37 kg/m for ethanol water solution with the concentration of 3-20 wt% and ethanol water solution with the temperature of 40-70 DEG C²h, the separation factor is 21.4-34.1.

Detailed Description

The present invention will be described in detail and specifically with reference to the following examples to facilitate better understanding of the present invention, but the following examples do not limit the scope of the present invention.