Preparation method of composite nanofiltration membrane

Abstract

The invention provides a preparation method of a composite nanofiltration membrane. A trace amount of carbachol is added as a functional reactive monomer to a piperazine-containing aqueous phase solution for interfacial polymerization, and effective regulation and control of a polypiperazine amide structure can be realized. The crosslinking degree of polyamide is improved and at the same time thethickness of a finally formed functional layer is reduced, so that a high-performance composite nanofiltration membrane with high water flux and high salt rejection is prepared. The method has the advantages of simple and convenient operation process, and the addition amount of carbachol in the aqueous phase is small and is non-irritating to the human body, and application prospects of the composite nanofiltration membrane in large-scale production is very broad.

Description

technical field [0001] The invention belongs to the technical field of nanofiltration and relates to a preparation method of a composite nanofiltration membrane. Background technique [0002] Nanofiltration is a pressure-driven membrane separation process between reverse osmosis and ultrafiltration. The core of nanofiltration technology is nanofiltration membrane. It is generally believed that the pore size of the nanofiltration membrane is about 1nm, which can effectively separate nanoscale components, such as the removal of high-priced salts, small molecular organics, and micro-pollutants, or as a molecular sieve to classify, purify, and filter high-value molecules. desalination etc. Nanofiltration technology with high separation precision has been widely used in water treatment, chemical industry, food, pharmaceutical and other industries in recent years, and has become one of the most commonly used treatment methods in the process of separation, concentration and purifi...

AI Technical Summary

Problems solved by technology

For example, using a phase transfer catalyst can promote the transfer of the reaction monomer from the water phase to the oil phase interface or directly increase the concentration of the reaction monomer in the water phase, which can increase the interface reaction rate and improve the crosslinking degree of the polyamide functional layer, thereby making the preparation The salt rejection rate of the composite nanofiltration membrane is improved, but the water flux does not change significantly or even decreases; if the hydrophilic component is added to the water phase or the concentration of the reaction monomer is reduced, the unreacted acid chloride group in the polyamide structure will The content of the acid chloride increases, and the acid chloride group is finally hydrolyzed into a carboxylic acid, so that the water flux of the prepared composite nanofiltration membrane increases, but the rejection rate of the salt decreases.

It can be seen that none of the currently reported methods for preparing or modifying composite nanofiltration membranes can achieve simultaneous increases in membrane water flux and salt rejection. Increasing membrane water flux is often accompanied by a decrease in salt rejection, and vice versa.

[0006] Compared with the formation process of the polyarylamide functional layer, the reactivity between piperazine and trimesoyl chloride is lower, and the formed cross-linked polyamide structure is relatively loose, which hinders the unreacted monomer from passing through the nascent film layer. Therefore, it is greatly affected by the contact conditions between the two-phase monomers, and it is more difficult to control the structure of the generated polypiperazine amide. The prepared composite nanofiltration membranes often cannot have both high water flux and high rejection.

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