1992-07-01

Chemical Resistance of Electrodialysis Membranes for their Utilisation in a Water Recycling System 921402

Electrodialysis (ED) is an electrically driven process that operates at ambiant temperature and pressure. It is of interest for removing ionized molecules, and reconcentrating them, specially at medium and low concentration. It is always used in association with other membrane technologies and/or pretreatment.
It is of high interest to simulate the contact of ED membranes with candidate stabilizing or cleaning agents in a water recycling system.
We selected among a large and representative range of commercial anionic and cationic membranes, 20 different ED membranes and tested them regarding their resistance to 5 chemical agents.
The samples were immerged in the solution (480 h / 60 °C), and a physical characterisation was performed: dimensional stability, measure of electrical resistance, determination of exchange capabilities.
Four membranes presented acceptable performances after contact with hydrogen peroxyde (300 ppm) regarding electrical resistance.
An original functional test was elaborated to measure the permselectivity of the membrane (determination of the apparent transport number from zero-current membrane potential measurements).
Regarding this test, only two membranes remained selective to ions after contact with hydrogen peroxyde (an anionic exchange membrane with quaternary ammonium groups on a polyethylene matrix, and a cationic exchange membrane based on a perfluorinated copolymer with sulfonic implants).
We conclude that electrodialysis membranes must be selected carefully when used with oxidizing compounds in a same system.

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