Method and corresponding device for testing through pore diameters and pore diameter distribution of ultra-filtration membranes

Abstract

The invention discloses a method for testing through pore diameters and pore diameter distribution of ultra-filtration membranes. The method includes placing the membranes in pure water, ultrasonically wetting the membranes, then taking the membranes out of the pure water, placing the membranes in a membrane pool, starting to test wet curves, then testing dry curves, recording gas permeability flow of the membranes under different inlet gas pressures, stopping inletting gas when the dry / wet curves coincide with one another and completing pore diameter tests; measuring apparent contact angles theta <*> of the membranes by the aid of optical processes and recording change of the apparent contact angles over the time to obtain equilibrium contact angles theta <e>; acquiring the average pore diameters of the membranes according to Laplace's equations; computing the pore diameter distribution of the membranes according to gas flow corresponding to the dry / wet curves of every two corresponding adjacent points. The method has the advantages that the water is used as wetting liquid, the water and the ultra-filtration membranes are good in compatibility, drying treatment on the membranes can be omitted in pore diameter measurement procedures, and accordingly pore structures of the membranes can be prevented from being destroyed; the method is particularly applicable to ultra-filtrationgrade pore diameters ranging from 20 nm to 50 nm, is simple and is high in practicality, and measurement data acquired by the aid of the method are high in accuracy.

Description

technical field [0001] The invention relates to the technical field of porous membrane structure measurement and characterization, in particular to a method for testing membrane through-hole diameter and pore size distribution and a corresponding testing device. Background technique [0002] The pore size is an important indicator of the performance of the porous membrane, which directly affects the application performance of the membrane. Among them, the membrane holes include not only through holes as effective holes, but also invalid holes such as rotary holes, blind holes, dead holes, and spherical cells. For porous membranes, only through-holes can determine the separation effect of the membrane, so the strict definition of pore size should be the diameter of the pore throat that runs through the channels on both sides of the membrane. Due to the existence of ineffective pores, the average pore size and pore size distribution calculated according to the general definit...

AI Technical Summary

Problems solved by technology

Although the nitrogen adsorption-desorption method is suitable for the analysis of the full pore size of mesoporous materials with a pore size of 2nm to 50nm, it cannot identify through-holes and is not suitable for the pore size analysis of separation membranes.

Similarly, the mercury porosimeter cannot identify through-holes. In addition, the test pressure is too high, and the membrane pore structure with insufficient rigidity is easy to compress, deform or collapse.

The gas-liquid displacement method is different from the above-mentioned pore size analysis method. It can measure the through-hole and pore size distribution of the membrane. There are the following problems in the operation process: 1. In order to improve the wetting effect, perfluoropolyether or fluorocarbon surfactant with low surface tension is used Wet the sample, prone to swelling of the membrane sample structure or peeling off of the membrane surface

2. The membrane sample needs to be dried before infiltration. The drying treatment will affect the membrane pore structure to varying degrees, causing the measurement results to deviate from the actual value.

[0004] According to the measurement principle of the above method, electron microscope method, mercury porosimetry and nitrogen desorption adsorption method cannot distinguish through holes and invalid holes

The gas-liquid displacement method using the low surface tension immersion liquid will affect the operability of the pore size test and the accuracy of the test results due to the compatibility of the membrane and the immersion liquid and the drying treatment of the sample.

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