阅读说明：本技术 一种木质素基聚芳酯复合纳滤膜的制备 (Preparation of lignin-based polyarylester composite nanofiltration membrane ) 是由 王璐莹 詹硕 雷建都 于 2019-11-19 设计创作，主要内容包括：本发明涉及制备一种新型聚芳酯复合纳滤膜。它需要解决的技术问题是,提供一种环境友好、可再生、来源丰富、成本低廉的新型膜材料—碱木素,及基于碱木素制备纳滤膜的技术方法。本发明的特征在于,分别以碱木素的氢氧化钠水溶液和均苯三甲酰氯的有机溶液为制膜反应液,通过界面聚合法在超滤底膜上制备碱木素基活性皮层,最终得到一种新型木质素基聚芳酯复合纳滤膜。(The invention relates to a novel polyarylester composite nanofiltration membrane. The technical problem to be solved is to provide a novel membrane material, namely alkali lignin, which is environment-friendly, renewable, abundant in source and low in cost, and a technical method for preparing the nanofiltration membrane based on the alkali lignin. The method is characterized in that a sodium hydroxide aqueous solution of alkali lignin and an organic solution of trimesoyl chloride are respectively used as membrane preparation reaction solutions, and an alkali lignin-based active skin layer is prepared on an ultrafiltration basement membrane by an interfacial polymerization method, so that the novel lignin-based polyarylate composite nanofiltration membrane is finally obtained.)

1. A high-rejection-rate lignin-based polyarylate composite nanofiltration membrane is characterized in that a dense separation layer of the composite nanofiltration membrane is composed of aromatic polyester compounds, and the preparation method comprises the following steps:

1) dissolving trimesoyl chloride in n-hexane to prepare an organic phase solution, and dissolving alkali lignin and sodium hydroxide in ultrapure water according to a certain proportion to prepare an alkali lignin water phase solution; 2) immersing an ultrafiltration membrane in an alkali lignin solution, taking out the ultrafiltration membrane, removing excessive solution on the surface of the membrane, and immersing a basement membrane in a trimesoyl chloride organic phase solution to carry out interfacial polymerization reaction; 3) taking out the mixture after reacting for a certain time, naturally airing the mixture, and then carrying out heat treatment and water washing to obtain the alkali lignin/trimesoyl chloride polyarylate composite nanofiltration membrane.

2. The preparation method according to claim 1, wherein the mass ratio of the alkali lignin to the sodium hydroxide is 37.5:1, the concentration of the alkali lignin aqueous phase solution is 0.5-4 wt%, and the concentration of the trimesoyl chloride organic phase solution is 0.5-3 g/L.

3. The method according to claim 1, wherein the time for immersing in the aqueous solution is 2 to 10min and the time for immersing in the organic phase (interfacial polymerization) is 2 to 10 min.

4. The method according to claim 1, wherein the heat treatment temperature is 60 to 100 ℃ and the heat treatment time is 2 to 10 min.

Technical Field

The invention relates to a method for preparing a lignin-based polyarylate composite nanofiltration membrane, which comprises the following steps: the alkali lignin/trimesoyl chloride crosslinked active skin layer is prepared on an ultrafiltration basement membrane by an interfacial polymerization method, so that the polyarylate composite nanofiltration membrane is obtained, can effectively separate a dye aqueous solution, and is expected to be applied to the field of water treatment.

Background

The membrane separation process is a process in which the mixed components of the raw materials selectively permeate the separation membrane under the action of driving force to realize separation. Nanofiltration is a pressure-driven membrane separation technology, and has no chemical reaction, no need of heating, no phase change and no damage to biological activity during nanofiltration separation. The aperture of the nanofiltration membrane is several nanometers, and the cut-off molecular weight is within the range of 100-1000 Da; the commercial membrane is mostly an organic polymer composite membrane, namely, an ultrathin active skin layer (the thickness is about 30-400 nm) is compounded on a porous base membrane, and the active skin layer plays an absolute influence role in the separation performance of the composite nanofiltration membrane.

It has been reported that natural polymer materials used for preparing polymer films are mainly natural polymers and derivatives, such as cellulose derivatives (cellulose acetate, ethyl cellulose), chitin (chitosan and aminodextran), sodium alginate, etc. Because natural polymer materials are generally low in yield, single in performance and high in price, the natural polymer materials are limited to be used as industrial membrane materials, and a novel nanofiltration membrane needs to be developed by using the natural polymer membrane materials with high yield and low cost.

Lignin is a non-crystalline, three-dimensional, net-like, complex, natural, high-molecular polymer of phenols, is a major component constituting the cell wall of higher plants, and can be used to prepare nanofiltration membranes. Lignin is the second largest natural high molecular compound in nature with reserves second to cellulose. The basic building blocks of lignin are all composed of phenylpropane building blocks. The lignin structure has a large number of active groups of different types, which can be chemically modified, and has huge utilization prospect due to the advantages of being renewable, degradable, wide in source, low in cost, non-toxic and the like. The research and development of high-value utilization of lignin at the present stage mainly focuses on three major aspects, namely industrial surfactants including some special surfactants, materials including nano materials, composite materials and the like, and biological energy and chemicals.

The invention aims to construct a novel composite nanofiltration membrane based on a natural biomass-alkali lignin, namely, a lignin-based polyarylate composite nanofiltration membrane is prepared by reacting polyhydroxy chemical structure of alkali lignin with trimesoyl chloride through an interfacial polymerization process, and the nanofiltration separation performance of the nanofiltration membrane is evaluated.

Disclosure of Invention

The technical problem to be solved by the invention is to prepare a novel polyarylate composite nanofiltration membrane with better separation performance based on alkali lignin. The polyarylester composite nanofiltration membrane is prepared by a classical interfacial polymerization process and is characterized in that an alkali lignin solution and an aromatic acyl chloride solution are subjected to polycondensation on an ultrafiltration basement membrane to obtain a lignin-based polyarylester active skin layer.

The preparation method of the alkali lignin/trimesoyl chloride membrane polyarylate composite nanofiltration membrane provided by the invention comprises the following steps:

1) preparing aqueous phase solution and organic phase solution

Dissolving trimesoyl chloride in n-hexane to prepare an organic phase solution with a certain concentration, and dissolving alkali lignin and sodium hydroxide in ultrapure water according to a certain mass ratio to prepare an aqueous phase solution.

2) Interface polymerization preparation polyarylester composite nanofiltration membrane

Immersing the basement membrane in an alkali lignin aqueous phase solution for a certain time, taking out the basement membrane and removing the excessive aqueous phase solution on the surface of the basement membrane; then immersing the basement membrane in the trimesoyl chloride organic phase solution for a certain time to carry out interfacial polymerization reaction, taking out and airing in the air to form an alkali lignin/trimesoyl chloride composite layer.

3) Heat treatment of nascent composite membranes

And (3) carrying out heat treatment on the composite membrane obtained by the interface polymerization in the previous step at a certain temperature, finally repeatedly cleaning the composite membrane by using deionized water, and removing unreacted monomers and solvents to obtain the alkali lignin/trimesoyl chloride polyarylate composite nanofiltration membrane.

Preferably, the method comprises the following steps:

the mass ratio of the alkali lignin to the sodium hydroxide in the step 1) is 37.5:1, the concentration of an alkali lignin aqueous phase solution is 0.5-4 wt%, and the concentration of a trimesoyl chloride organic phase solution is 0.5-3 g/L.

In the step 2), the time for immersing the base film into the aqueous phase solution is 2-10min, and the time for immersing into the organic phase (interfacial polymerization) is 2-10 min.

The temperature in the post-treatment step in the step 3) is 60-100 ℃, and the heat treatment time is 2-10 min.

Has the advantages that:

the membrane preparation method takes the lignin-based material with low cost and rich reserves as a novel membrane material, and can realize the large-scale production and industrial application by preparing the composite nanofiltration membrane through the traditional membrane preparation process.

Detailed Description

The invention provides an alkali lignin/trimesoyl chloride composite membrane for nanofiltration separation of an aqueous solution and a preparation method thereof. Firstly, preparing alkali lignin aqueous phase solution and trimesoyl chloride organic phase solution with proper concentration, then preparing alkali lignin/trimesoyl chloride compact layer by interfacial polymerization method, and obtaining the described composite membrane by means of after-treatment.