阅读说明：本技术 具有高效油水分离的铁基超亲水立构复合聚乳酸微孔膜及其制备方法 (iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with efficient oil-water separation function and preparation method thereof ) 是由 熊竹 贺永 于 2019-07-29 设计创作，主要内容包括：本发明提供了一种具有高效油水分离的铁基超亲水立构复合聚乳酸微孔膜,其由无纺布支撑层和聚乳酸复合膜层共同组成,所述聚乳酸复合膜层为负载铁基纳米颗粒的超亲水立构复合聚乳酸微孔膜。本发明采用聚乳酸立构复合技术与原位亲水技术制备具有多级微纳结构表面的超亲水聚乳酸微孔膜,再通过多巴胺、多乙烯多胺层层修饰,使其具有丰富的铁离子吸附位点,最后将吸附在微孔膜上的铁离子还原为具有多种电荷特性的纳米粒,从而在膜表面构筑刚性纳米粒子复合界面和增强的超亲水结合水层。该微孔膜对水包油乳液具有高效分离和长效抗污染性能,可有效解决多种含油废水净化处理过程中普遍存在的易污染、效率低、成本高等问题,具有广泛的应用和市场潜景。(The invention provides an iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with efficient oil-water separation, which consists of a non-woven fabric supporting layer and a polylactic acid composite membrane layer, wherein the polylactic acid composite membrane layer is a super-hydrophilic stereo composite polylactic acid microporous membrane loaded with iron-based nano particles. According to the invention, a super-hydrophilic polylactic acid microporous membrane with a multistage micro-nano structure surface is prepared by adopting a polylactic acid stereo composite technology and an in-situ hydrophilic technology, and is modified layer by using polybamine and polyethylene polyamine to enable the microporous membrane to have rich iron ion adsorption sites, and finally, iron ions adsorbed on the microporous membrane are reduced into nanoparticles with various charge characteristics, so that a rigid nanoparticle composite interface and a reinforced super-hydrophilic combined water layer are constructed on the membrane surface. The microporous membrane has high-efficiency separation and long-acting anti-pollution performance on oil-in-water emulsion, can effectively solve the problems of easy pollution, low efficiency, high cost and the like commonly existing in the purification treatment process of various oily wastewater, and has wide application and market prospect.)

1. The iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with efficient oil-water separation is characterized by comprising a non-woven fabric supporting layer and a polylactic acid composite membrane layer, wherein the polylactic acid composite membrane layer is a super-hydrophilic stereo composite polylactic acid microporous membrane loaded with iron-based nano particles.

2. the iron ~ based super ~ hydrophilic stereo composite polylactic acid microporous membrane with the high ~ efficiency oil ~ water separation function is characterized in that the stereo composite polylactic acid microporous membrane is formed by stereo compounding of L ~ type polylactic acid and D ~ type polylactic acid, the mass ratio of the L ~ type polylactic acid to the D ~ type polylactic acid is (80 ~ 99.5): 0.5 ~ 20), the surface of the stereo composite polylactic acid microporous membrane has multi ~ level micron ~ scale and nano ~ scale dimensions, and the roughness of the stereo composite polylactic acid microporous membrane is 10 nanometers ~ 10 micrometers.

3. the microporous membrane of claim 1, wherein the iron-based nanoparticles are iron-based nanoparticles composed of multiple charge types, including positively charged iron-based nanoparticles, negatively charged iron-based nanoparticles, and neutral iron-based nanoparticles; the iron-based nanoparticles are formed via in-situ growth, with a particle size of 0.1-100 nanometers.

4. the iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with the efficient oil-water separation function as claimed in claim 1, wherein the non-woven fabric support layer is a hydrophilic non-woven fabric, including a PET non-woven fabric, a PP non-woven fabric or a PE non-woven fabric, and the pore size distribution of the non-woven fabric support layer is 1-50 micrometers.

5. The preparation method of the iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with high-efficiency oil-water separation, which is disclosed by any one of claims 1 to 4, comprises the following steps:

(1) Under the protection of nitrogen, adding D-type polylactic acid, L-type polylactic acid and an organic solvent into a reaction kettle, stirring and dissolving at the temperature of 80-110 ℃ for 3-24 h; adding an active solution to perform in-situ polymerization reaction, keeping the temperature unchanged, and reacting for 2-48h to obtain a polylactic acid membrane casting solution; then, defoaming the polylactic acid membrane casting solution, and then coating the polylactic acid membrane casting solution on the surface of non-woven fabric in a scraping manner to prepare a polylactic acid nascent membrane; solidifying the polylactic acid primary membrane in a coagulating bath at 0-60 ℃, then soaking in water at 40-80 ℃ for more than 12h, and finally drying to obtain the super-hydrophilic stereo composite polylactic acid microporous membrane;

(2) preparing a dopamine aqueous solution with the concentration of 0.2-3 g/L, and soaking the super-hydrophilic stereo composite polylactic acid microporous membrane prepared in the step (1) in the prepared dopamine aqueous solution for 0.5-2h to obtain a modified dopamine super-hydrophilic stereo composite polylactic acid microporous membrane;

(3) Preparing a 0.5-5 g/L polyethylene polyamine solution, and soaking the dopamine-modified super-hydrophilic stereo composite polylactic acid microporous membrane prepared in the step (2) in the prepared polyethylene polyamine solution for 0.5-2h, wherein the solution temperature is 35-65 ℃, so as to obtain a further modified polyethylene polyamine super-hydrophilic stereo composite polylactic acid microporous membrane;

(4) preparing iron ion aqueous solution with the concentration of 0.01-1 mol/L; carrying out suction filtration on the obtained iron ion solution to the super-hydrophilic stereo composite polylactic acid microporous membrane modified with polyethylene polyamine prepared in the step (3) to obtain a super-hydrophilic stereo composite polylactic acid microporous membrane loaded with iron ions;

The ferric ion solution is one or more of ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate and ferrous nitrate;

(5) Soaking the iron ion-loaded super-hydrophilic stereo composite polylactic acid microporous membrane into a reducing aqueous solution for 1-24h to obtain an iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with efficient oil-water separation;

The reductive aqueous solution is NaBH₄An aqueous solution of one or more of ascorbic acid or citric acid; the concentration of the reducing agent in the reducing aqueous solution is 0.1-2 g/L.

6. the method according to claim 5, wherein the reactive solution is composed of a hydrophilic monomer, a crosslinking agent and an initiator in a ratio of (0.5-0.75): (0.25-0.5): (0.01-0.05); the hydrophilic monomer is one or a mixture of N-vinyl pyrrolidone, hydroxyethyl methacrylate or hydroxypropyl methacrylate; the cross-linking agent is one or a mixture of more of vinyltriethoxysilane, vinyltrimethoxysilane and hydroxymethyl acrylamide; the initiator is one or a mixture of more of azodiisobutyronitrile, azodiisoheptonitrile and dimethyl azodiisobutyrate.

7. The method according to claim 5, wherein the organic solvent is one or more selected from the group consisting of N-methylpyrrolidone, N-dimethylacetamide, dimethylsulfoxide, and dimethylformamide.

8. the method according to claim 5, wherein the active solution is added in an amount of 4 to 10% based on the total amount of the polylactic acid/organic solvent.

Technical Field

The invention relates to the technical field of bio-based polymer oil-water separation membranes, in particular to a preparation method of a bio-based polymer composite separation membrane for efficient oil-water separation.

background

Water is an important guarantee for human life and social sustainable development. Along with the rapid development of civilization in human society, water pollution becomes a very serious problem. The oily wastewater from oil exploitation, the oily wastewater from process, the oily wastewater from kitchen and other domestic wastewater, etc. have a large proportion in the wastewater and are difficult to treat. For the sewage with much water and little oil, the most popular treatment method at present is membrane separation technology. However, the treatment process of the sewage mainly relies on a membrane bioreactor process at present, namely a small amount of oil components in the sewage are removed in a biochemical degradation mode.

At present, a great deal of researchers expect that the separation membrane material directly plays a role in filtering and intercepting oil components in the oily wastewater through design modification of the physical structure and the chemical characteristics of the separation membrane material, so that the oily wastewater is efficiently purified. As an example (Journal of Materials Chemistry A, 2013, 1, 5758) a graft-modified PVDF membrane is disclosed, the water contact angle of which is reduced to 10^oThe separation efficiency of the oily wastewater can reach 99 percent. A paper (Journal of Materials Chemistry A, 2014, 2,10137) discloses a polyacrylonitrile/polyethylene glycol nanofiltration membrane with super-hydrophilic characteristic, and the oil residue in water can reach less than 26ppm after the membrane is separated. However, research finds that the currently reported super-hydrophilic polymer separation membrane is often short in filtering and separating time-effect on oily wastewater, and is a separation membrane material easy to pollute. When a hydration layer on the membrane surface is washed and damaged in the separation process, oil stains of water are very easy to adhere to the membrane surface, so that the wettability of the membrane surface is reduced, and the membrane loses the separation capability along with the increase of the adhesion of the oil stains.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with high-efficiency oil-water separation performance.

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

the iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with high-efficiency oil-water separation is composed of a non-woven fabric supporting layer and a polylactic acid composite membrane layer, wherein the polylactic acid composite membrane layer is a super-hydrophilic stereo composite polylactic acid microporous membrane loaded with iron-based nano particles.

furthermore, the stereocomplex polylactic acid microporous membrane is formed by stereocomplex of L ~ type polylactic acid and D ~ type polylactic acid, wherein the mass ratio of the L ~ type polylactic acid to the D ~ type polylactic acid is (80 ~ 99.5): 0.5 ~ 20), the surface of the stereocomplex polylactic acid microporous membrane has multilevel micron ~ scale and nanoscale dimensions, and the roughness of the stereocomplex polylactic acid microporous membrane is 10 nanometers ~ 10 micrometers.

Further, the iron-based nanoparticles are iron-based nanoparticles composed of a plurality of charge types, including positive charge iron-based nanoparticles, negative charge iron-based nanoparticles and neutral iron-based nanoparticles; the iron-based nanoparticles are formed via in-situ growth, with a particle size of 0.1-100 nanometers.

furthermore, the non-woven fabric support layer is a hydrophilic non-woven fabric, and comprises a PET non-woven fabric, a PP non-woven fabric or a PE non-woven fabric, and the pore size distribution of the non-woven fabric support layer is 1-50 micrometers.

a preparation method of an iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with efficient oil-water separation comprises the following steps:

(1) Under the protection of nitrogen, adding D-type polylactic acid, L-type polylactic acid and an organic solvent into a reaction kettle, stirring and dissolving at the temperature of 80-110 ℃ for 3-24 h; adding an active solution to perform in-situ polymerization reaction, keeping the temperature unchanged, and reacting for 2-48h to obtain a polylactic acid membrane casting solution; then, defoaming the polylactic acid membrane casting solution, and then coating the polylactic acid membrane casting solution on the surface of non-woven fabric in a scraping manner to prepare a polylactic acid nascent membrane; solidifying the polylactic acid primary membrane in a coagulating bath at 0-60 ℃, then soaking in water at 40-80 ℃ for more than 12h, and finally drying to obtain the super-hydrophilic stereo composite polylactic acid microporous membrane;

(2) preparing a dopamine aqueous solution with the concentration of 0.2-3 g/L, and soaking the super-hydrophilic stereo composite polylactic acid microporous membrane prepared in the step (1) in the prepared dopamine aqueous solution for 0.5-2h to obtain a modified dopamine super-hydrophilic stereo composite polylactic acid microporous membrane;

(3) Preparing a 0.5-5 g/L polyethylene Polyamine (PEI) solution, and soaking the dopamine-modified super-hydrophilic stereo composite polylactic acid microporous membrane prepared in the step (2) in the prepared polyethylene polyamine solution for 0.5-2h, wherein the temperature of the solution is 35-65 ℃, so as to obtain a further modified polyethylene polyamine super-hydrophilic stereo composite polylactic acid microporous membrane;

(4) Preparing iron ion aqueous solution with the concentration of 0.01-1 mol/L; carrying out suction filtration on the obtained iron ion solution to the super-hydrophilic stereo composite polylactic acid microporous membrane modified with polyethylene polyamine prepared in the step (3) to obtain a super-hydrophilic stereo composite polylactic acid microporous membrane loaded with iron ions;

The ferric ion solution is one or more of ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate and ferrous nitrate;

(5) soaking the iron ion-loaded super-hydrophilic stereo composite polylactic acid microporous membrane into a reducing aqueous solution for 1-24h to obtain an iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with efficient oil-water separation;

the reductive aqueous solution is NaBH₄an aqueous solution of one or more of ascorbic acid or citric acid; the concentration of the reducing agent in the reducing aqueous solution is 0.1-2 g/L.

further, the active solution consists of hydrophilic monomers, a cross-linking agent and an initiator, and the composition ratio is (0.5-0.75): (0.25-0.5): (0.01-0.05); the hydrophilic monomer is one or a mixture of N-vinyl pyrrolidone, hydroxyethyl methacrylate or hydroxypropyl methacrylate; the cross-linking agent is one or a mixture of more of vinyltriethoxysilane, vinyltrimethoxysilane and hydroxymethyl acrylamide; the initiator is one or a mixture of more of azodiisobutyronitrile, azodiisoheptonitrile and dimethyl azodiisobutyrate.

further, the organic solvent is one or a mixture of N-methyl pyrrolidone, N-dimethyl acetamide, dimethyl sulfoxide and dimethyl formamide.

Furthermore, the adding amount of the active solution is 4-10% of the total amount of the polylactic acid/the organic solvent.

Has the advantages that: compared with the prior art, the iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with high-efficiency oil-water separation and the preparation method thereof have the following advantages:

The technical method comprises the steps of preparing a super-hydrophilic polylactic acid microporous membrane with a multistage micro-nano structure surface by adopting a polylactic acid stereo composite technology and synchronously combining an in-situ hydrophilic technology, modifying the surface of the microporous membrane layer by dopamine and polyethylene polyamine to enable the polylactic acid microporous membrane to have rich iron ion adsorption sites, and finally reducing the iron ions adsorbed on the polylactic acid microporous membrane into nanoparticles with various charge characteristics. Based on the nano particles with the non-single charge characteristic, a rigid nano particle composite interface and a reinforced super-hydrophilic combined water layer are synchronously constructed on the surface of the flexible polylactic acid microporous membrane, so that the physical and mechanical stability of the super-hydrophilic surface of the multistage micro-nano structure on the surface of the polymer microporous membrane is enhanced, and the stability of the super-hydrophilic combined water layer is enhanced. Based on the above, when the iron-based super-hydrophilic polylactic acid microporous membrane designed and prepared by the technical route is used for separating oil-in-water emulsion, a super-hydrophilic interface of the iron-based super-hydrophilic polylactic acid microporous membrane has excellent characteristics of oil stain resistance and surfactant adhesion pollution resistance, has high-efficiency separation and long-acting pollution resistance on the oil-in-water emulsion, can effectively solve the problems of easy pollution, low efficiency, high cost and the like commonly existing in the purification treatment processes of kitchen waste water, oil field waste water, various industrial oily waste water and the like at present, and has wide application and market prospects.

Drawings

FIG. 1 is a surface Scanning Electron Microscope (SEM) photograph of a superhydrophilic stereocomplex polylactic acid microporous membrane prepared in comparative example 1;

FIG. 2 is an Atomic Force Microscope (AFM) photograph of the ultra-hydrophilic stereocomplex polylactic acid microporous membrane prepared in comparative example 1;

FIG. 3 is a graph of separation flux versus time for the separation of a soybean oil-in-water emulsion using a superhydrophilic stereocomplex polylactic acid microporous membrane prepared in comparative example 1;

FIG. 4 is a graph of retention versus time for the separation of a soy oil-in-water emulsion for a superhydrophilic stereocomplex polylactic acid microporous membrane prepared in comparative example 1;

FIG. 5 is a surface Scanning Electron Microscope (SEM) photograph of the iron-based super-hydrophilic stereo composite polylactic acid microporous membrane with high efficiency oil-water separation prepared in example 1;

FIG. 6 is an Atomic Force Microscope (AFM) photograph of the iron-based ultra-hydrophilic stereo composite polylactic acid microporous membrane with high efficiency oil-water separation prepared in example 1;

FIG. 7 is a graph of separation flux over time for the separation of a soy oil-in-water emulsion using the iron-based superhydrophilic stereocomplex polylactic acid microporous membrane with high efficiency oil-water separation prepared in example 1;

FIG. 8 is a graph of retention versus time for the separation of a soy oil-in-water emulsion using iron-based superhydrophilic stereocomplex polylactic acid microporous membrane with high efficiency oil-water separation prepared in example 1;

FIG. 9 is a graph of separation flux over time for the separation of a soy oil-in-water emulsion using the iron-based superhydrophilic stereocomplex polylactic acid microporous membrane with high efficiency oil-water separation prepared in example 2;

FIG. 10 is a graph of separation flux over time for the separation of a soy oil-in-water emulsion using the iron-based superhydrophilic stereocomplex polylactic acid microporous membrane with high efficiency oil-water separation prepared in example 3.

Detailed Description

The present invention is further described below with reference to specific examples, which are only exemplary and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.

The method for preparing the polylactic acid microporous membrane on the surface of the multistage micro-nano structure by steam induction according to the invention will be further described with reference to specific embodiments.

Comparative example 1

under the protection of nitrogen, adding 2g D type polylactic acid, 16g L type polylactic acid and 82g N-methyl pyrrolidone into a reaction kettle, stirring and dissolving at 90 ℃ for 4 hours; adding 0.4g N-vinyl pyrrolidone, 0.25g vinyl trimethoxy silane and 0.1g azo-diisoheptanonitrile, and reacting for 8h to obtain a polylactic acid casting solution; then, the polylactic acid casting solution is defoamed and blade-coated on 80g/m²Preparing a polylactic acid primary film on the surface of the PET non-woven fabric; soaking the polylactic acid primary membrane in water at 30 ℃ for 1min for curing, then soaking in water at 65 ℃ for more than 24h, and finally drying to obtain the super-hydrophilic stereo composite polylactic acid microporous membrane. As shown in fig. 1, in order to obtain a scanning electron micrograph of the prepared superhydrophilic stereocomplex polylactic acid microporous membrane, it can be seen at high magnification that a crystal structure formed by stereocomplex has rich pores and a micro-nano structure. As shown in fig. 2, in an atomic force microscope photograph of the prepared superhydrophilic stereocomplex polylactic acid microporous membrane, it can be seen that the roughness of the membrane surface is 139 nm, and the membrane surface has a rich microstructure.

the prepared super-hydrophilic stereo composite polylactic acid microporous membrane is used for separating the soybean oil-in-water emulsion, and the results are shown in fig. 3 and 4, wherein the separation flux of the membrane to the emulsion is obviously reduced along with the increase of the separation time, and the interception efficiency is also gradually reduced.