Preparation method of hydrophilic and hydrophobic double-layer polyvinylidene fluoride membrane

Abstract

The invention discloses a preparation method of a hydrophilic and hydrophobic double-layer polyvinylidene fluoride membrane. By preparing macromolecule cast film liquor with low critical dissolving temperature and a hydrophilic modification macromolecule solution, spin hollow fiber membranes are extruded out at the same time in suitable spinning nozzles, and the hydrophilic and hydrophobic double-layer hollow fiber membrane with a structure easy to regulate and control is obtained. During membrane preparation, the process of phase separation includes a thermally induced split-phase mechanism of a hydrophobic layer based on the low critical dissolving temperature and a non-solvent induced phase separation mechanism of a hydrophilic layer. According to the hydrophilic and hydrophobic double-layer membrane structure, boundaries of the hydrophilic layer and the hydrophobic layer are tightly combined, layering does not exist, and the membrane has the advantages of being high in porosity andthin in hydrophobic layer; during membrane distillation, the steam mass transfer distance in the membrane is reduced, mass transfer resistance is reduced, the permeating flux of the membrane is increased, meanwhile, temperature difference polarization and heat transfer loss are reduced, and application prospects are broad.

Description

technical field [0001] The invention belongs to the technical field of polymer membrane separation, and in particular relates to a method for preparing a hydrophilic-hydrophobic double-layer polyvinylidene fluoride membrane. Background technique [0002] Membrane distillation (MD) is a membrane separation process in which the vapor pressure difference on both sides of a hydrophobic microporous membrane is the driving force for mass transfer. At present, direct contact membrane distillation (DCMD) is the most widely studied, and its transfer process involves two aspects of mass transfer and heat transfer. Reducing the film thickness can reduce the mass transfer resistance and increase the permeation flux of the membrane, but the thinner the film thickness, the greater the transmembrane heat transfer loss. In order to solve the contradiction between mass transfer and heat transfer in DCMD process, the use of hydrophilic / hydrophobic bilayer membrane is an effective way. The h...

AI Technical Summary

Problems solved by technology

Reducing the film thickness can reduce the mass transfer resistance and increase the permeation flux of the membrane, but the thinner the film thickness, the greater the transmembrane heat transfer loss