Studies on ion‐exchange membranes. XXXII. Heterogeneity in ion‐exchange membranes

Abstract

SynopsisTwelve kinds of cation-exchange membranes were treated with hydrogen peroxide. Some of them (Selemion CMV, Nepton CR-61, Scrion C-100, SAM-1) were completely destroyed. Heterogeneity is believed to be present in that part of their chemical structures that is decomposable by the treatment. The other membranes were converted into porous membranes by the decomposition of the resinous part. Water permeabilities and electric resistances of the porous membranes were examined to evaluate the pore radius. It was concluded that the "paste method" membranes have a heterogeneity or localized distribution of the resinous part under 50 mr. The "paste method" membranes seemed to resemble the "graft method" membranes in chemical structure and to be much different from the mosaic-type membranes such as Permaplex and MC-3142. These results were also supported by extraction of the membranes with appropriate solvents and observation by electron microscopy.

Irreversible thermodynamics and overall mass transport in ion-exchange membrane electrodialysis

“…Mizutani et al investigated micro-structure of cationexchange membranes by converting them into porous inert membranes having no ion-exchange component by the treatment with hydrogen peroxide, and determined apparent pore size, tortuosity factor, number of pores and pore size distribution in the porous membranes [22]. Characteristics of the membranes and micro-structure of porous membranes observed in this study are listed in Table 1.…”

Transport Properties of Cation Exchange Membranes in the Presence of Ether Compounds in Electrodialysis

“…On the other hand, the weight increase of a strongly basic anion exchange resin, Amberlite IRA-400, Cl Ϫ form, immersed in diethylene glycol was 286% under the same conditions (13), and the weight increase in the anion exchange membrane (ion exchange capacity of 2.25 meq/g Cl Ϫ form dry membrane) with diethylene glycol was 51% (13). The fact that the weight increase in the cation exchange membrane was almost the same as that of the anion exchange membrane is thought to be due to the existence of inert polymers such as poly(vinyl chloride) and others and of a microdomain of the sulfonated styrene-divinylbenzene copolymer in the membrane (14), as well as to a different temperature of impregnation (for 48 h at 45°C). The glycols are thought to be impregnated for following reasons, complex formation of the glycols with sodium ions ion-exchanged with sulfonic acid groups, impregnation in the interface between the inert polymers and the copolymer, and hydrophobic interaction of the glycols with the membrane matrix.…”

Synthesis, characterization and properties of polystyrene incorporated calcium tungstate membrane and studies of its physicochemical and transport behavior

“…In order to determine the water concentration, void porosity and swelling of the inorganic-organic composite membrane, different samples prepared with different quantity of polystyrene were immerged in distilled water as well as in 1 M NaCl solution for 24 h [21,22]; their surfaces were wiped with filter paper and then the wet membranes were weighed. The thickness of the samples was measured by means of a micrometer screw gauge and membrane density for wet membrane was determined by dividing the wet membrane weight by its volume.…”