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SynopsisFor the purpose of preparing the monovalent cation permselective membrane for electrodialysis, the membrane having -SO,Cl groups reacted with the polyethyleneimine to form a cationic polyelectrolyte layer on the membrane surface by using the acid-amide bonding. Reaction conditions, i.e., reaction temperature, concentration of the polyethyleneimine solution and the addition of tertiary amines to the polyethyleneimine solution, were all examined in detail. As a result, all the different kinds of polyethyleneimines were effective in obtaining the monovalent cation permselective membrane if the correct reaction conditions were selected. The durability of the monovalent cation permselectivity was evaluated in a continuous electrodialytic concentration of sea water. The monovalent cation permselectivity decreased gradually during the electrodialysis in the cation exchange membrane with the polyethyleneimine layer. Therefore, the cation exchange membrane with the cationic polyelectrolyte layer was further treated with crosslinking reagents, i.e., formaldehyde-hydrochloric acid, epichlorohydrin, etc. or other alkylating reagents. The monovalent cation permselectivity of the treated membranes was almost constant for t w o months. The crosslinking reaction of polyethyleneimine was more effective than alkylation in maintaining the high permselectivity constantly.

In order to give the monovalent cation permselectivity to the cation exchange membrane permanently, polyethyleneimine layer was formed on the membrane surface by acid-amide bond between polyethyleneimine and the -SQCl groups of a styrene-divinylbenzene copolymer membrane. After the reaction, the -SQCl groups remaining in the inner part of the membrane were hydrolyzed by immersing the membrane into an aqueous sodium hydroxide solution.The resultant cation exchange membranes were evaluated by electrodialysis of sea water from the point of view of the monovalent cation permselectivity, electric resistance of the membrane, current efficiency, and transport number of sodium ions calculated by membrane potential in connection with reduced viscosity of the various commercial polyethyleneimines, ATR-IR measurements on the membrane surface suggested that the acid-amide bond was stable for severe hydrolysis reaction. ZUSAMMENFASSUNG: Um bei Kationen-Austauschmembranen eine dauerhafte Selektivitlt fur die Durchlbsigkeit von einwertigen Kationen zu erzielen, wurde eine Polyethylenimin-Schicht auf der Membranoberfllche durch Saureamidbindung zwischen Polyethylenimin und den -SQCl-Gruppen einer Styrol-co-Divinylbenzol-Membran erzeugt. Nach der Reaktion wurden die im Inneren der Membran verbleibenden -SQCl-Gruppen durch Tauchen in wurige Natronlauge hydrolysiert . Die so gewonnenen Kationen-Austauschmembranen wurden mittels Elektrodialyse von Seewasser hinsichtlich ihrer Selektivitlt fur die Durchlksigkeit von einwertigen Kationen, ihres elektrischen Widerstandes, ihrer Stromleistung und ihrer Uberfiih-* Part IX, submitted to J. Membrane Sci. 0 1989 HUthig & Wepf Verlag, Base1 OOO3-3146/89/$03.00T. Sata and R. Izuo rungszahlen fur Natrium-Ionen untersucht. ATR-IR-Messungen auf der Membranoberflache belegen, da8 die Shreamidbindung gegenllber starker Hydrolyseeinwirkung stabil war.

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