Method for performing fast in-situ conversion on microfiltration or ultrafiltration membrane into nanofiltration membrane

Abstract

The invention discloses a method for performing fast in-situ conversion on a microfiltration or ultrafiltration membrane into a nanofiltration membrane, and belongs to the technical field of membrane separation. By aiming at overcoming the defects of the existing nanofiltration membrane preparation technology, the invention provides a simple, cheap and fast nanofiltration membrane in-situ preparation method. Diamine capable of taking a reaction with graphene oxide without special conditions is used as a cross-linking agent; the fitting performance of a graphene oxide sheet layer is regulated through the combined effect of water surface tension and gas pressure; specific treatment such as heating and drying is not needed in the preparation process; the in-situ preparation of the graphene oxide nanofiltration membrane is realized in a device filled with the microfiltration or ultrafiltration membrane in a simple and fast mode. The method has the advantages that the cost is low; the in-situ preparation can be realized; the regeneration is realized; the limitation by basement membrane types and shapes is avoided. The prepared nanofiltration membrane has high water flux, has a good removal effect on ions and organic matters, and has wide large-scale application prospects.

Description

technical field [0001] The invention relates to a method for quickly converting microfiltration or ultrafiltration membranes into nanofiltration membranes in situ, and belongs to the technical field of membrane separation. Background technique [0002] Nanofiltration (NF) is a pressure-driven membrane separation technology between ultrafiltration and reverse osmosis, and its effective filtration pore size is 0.5-2 nanometers. Nanofiltration usually has the advantages of low operating pressure and large water flux. It has a certain ability to remove inorganic salts and small molecular organic matter, and has good purification performance on color and odor. It is widely used in the field of water treatment. At present, the preparation methods of nanofiltration membrane mainly include phase inversion method, blending method, charging method and composite method. Among them, the composite method is currently the most used method, which is prepared by compounding a polymer thin ...

AI Technical Summary

Problems solved by technology

Mi et al. (J.Membrane Sci.,2014,469:80-87) used the layer-by-layer self-assembly method to sequentially load negatively charged graphene oxide sheets and positively charged polyacrylonitrile onto the substrate by electrostatic force The graphene oxide composite membrane is prepared on the membrane. This preparation method requires multiple alternate impregnation loads. The operation process is cumbersome, and it is difficult to scale production and application.

Wang et al. (J.Mater.Chem.A, 2015,3(8):4405-4412) synthesized a series of covalently cross-linked graphene oxide films through esterification, but the cross-linking reaction conditions are relatively harsh and the preparation The membrane area is small, it is difficult to apply engineering

Zhang et al. (J.Membrane Sci., 2016,515:204-211) introduced sulfonic acid groups on the graphene oxide sheet through sulfonation, and carried out a certain reduction treatment on the graphene oxide solution. Methods A graphene oxide film cross-linked by succinic acid was prepared. The cross-linking reaction requires heating and catalysis under strong acid conditions. The preparation process is complicated and the pressure shock resistance is poor, which limits its further application.

[0005] The above methods for preparing graphene oxide membranes have problems such as complex process, small membrane area, low membrane strength, harsh reaction conditions, and difficulty in large-scale production.

[0006] The Chinese patent with publication number 103706264A uses graphene oxide as raw material to prepare graphene oxide membrane by direct filtration. This method does not add any cross-linking agent, the stability of the membrane is not guaranteed, and it is very likely to cause the graphene oxide on the membrane to swell to In water, the service life of the membrane is affected. At the same time, the preparation process requires drying and other treatments, which fails to achieve in-situ preparation

The Chinese patent with the publication number of 103736400A uses graphene oxide as raw material, and prepares graphene oxide composite film by coating method. It is necessary to coat carboxy chitosan and heat treatment on the base film, and the crosslinking reaction of graphene oxide needs to be carried out at 60 It is carried out at a temperature of -80°C. The preparation process requires coating, heating, drying and other treatments. The process is relatively complicated and in-situ preparation cannot be realized.

The Chinese patent with the publication number 104028111A adopts the method of chemical grafting, using graphene oxide as raw material to prepare a sandwich structure of chitosan and graphene oxide. The grafting reaction of this method requires special treatments such as γ-ray irradiation and drying. , the preparation process is relatively complicated, and the in-situ preparation cannot be realized

[0007] In the above-mentioned articles and patents, although graphene oxide is used as a raw material, the water flux of the membrane is low, and operations such as heating, drying or γ-ray irradiation are required in the preparation process, and none of them can achieve in-situ Therefore, it is difficult to overcome the possible damage caused by the process of membrane preparation, transfer, transportation, installation, etc., so that the application of graphene oxide nanofiltration membrane is limited to a certain extent.

Images