Preparation method of nanofiltration membrane with adjustable desalination rate

Abstract

The invention relates to a preparation method of a nanofiltration membrane with an adjustable desalination rate. The preparation method is characterized by comprising the following steps: (1) preparing a membrane casting solution; (2) preparing a hollow fiber base membrane, namely metering the membrane casting solution and a core solution, pumping the membrane casting solution and the core solution into a spinning nozzle, extruding feed liquid from the spinning nozzle, enabling the extruded feed liquid to pass through an air gap and enter a coagulating bath, forming hollow membrane filaments through phase inversion in the coagulating bath, and winding the hollow membrane filaments for later use; and (3) preparing a hollow fiber nanofiltration composite membrane, namely soaking the wound membrane filaments with pure water, then soaking the membrane filaments in a water phase solution of polyamine, and carrying out polymerization reaction on an oil phase containing a polyacyl chloride monomer and a water phase monomer on the surface of the membrane on a coating machine to form a compact separation skin layer so as to finally obtain the nanofiltration membrane. Poly(N-vinylcaprolactam) gel is introduced in the preparation of the base membrane, so that the pore structure of the ultrafiltration base membrane can be adjusted through temperature, and the surface pore diameter of the base membrane and the interfacial polymerization reaction rate in the preparation process of the composite nanofiltration membrane can be adjusted and controlled while the water-phase temperature is realized.

Description

technical field [0001] The invention relates to a water filtration membrane, in particular to a preparation method of a nanofiltration membrane. Background technique [0002] Nanofiltration membrane is a new type of pressure-driven separation membrane whose separation scale is between ultrafiltration membrane and reverse osmosis membrane. Low, large flux and other advantages, widely used in food processing, purification of pharmaceutical intermediates and water treatment and other fields. It is usually divided into asymmetric nanofiltration membrane and composite nanofiltration membrane. The methods include phase inversion method, interfacial polymerization method, coating method, layer-by-layer self-assembly method, etc. At present, most commercial nanofiltration membranes are polyamide composite membrane structures. It is formed by interfacial polymerization of polyamines and polyacyl chlorides on a porous support layer. This type of composite membrane has good water per...

AI Technical Summary

Problems solved by technology

[0003] However, the currently prepared nanofiltration membranes generally have a fixed flux and rejection rate, which cannot meet the special needs of different application scenarios or regions. Therefore, it is urgent to develop a nanofiltration membrane with adjustable flux and rejection rate to meet market demand.

[0004] At present, the nanofiltration membrane with adjustable flux / rejection rate is mainly prepared in the following ways: 1. The interfacial polymerization process is affected by regulating the surface pore size and surface porosity of the porous support layer. The advantage of this method is that the formed nanofiltration membrane is stable. The disadvantage is that if you want to obtain a nanofiltration membrane with a specific flux and rejection rate, you must select the base membrane according to your needs. The requirements for the base membrane are high and the universality is poor.

2. By changing the concentration of the water phase and the oil phase, the reaction rate of interfacial polymerization is affected, and the thickness and compactness of the separation layer are adjusted. The advantage of this method is that the operation process is simple, but the adjustable range of flux and rejection rate is low. The accuracy is poor. Once the interfacial polymerization process is completed, the flux and rejection rate of the prepared nanofiltration membranes have been finalized, and only different batches of nanofiltration membranes can be prepared to meet the needs.