Preparation of Mono-Valent Cation Selective Cation-Exchange Membranes for Electrodialysis of Seawater by Electron-Beam-Induced Graft Polymerization

Abstract

Glycidyl methacrylate (GMA) and divinyl benzene (DVB) were cografted onto a high-density polyethylene (HDPE) film with a thickness of 35 μm by electron-beam-induced graft polymerization. First, one surface of the resultant GMA/DVB-cografted film reacted with trimethylammonium chloride to convert the epoxy group of the cograft chain into trimethylammonium group capable of selectively permeating mono-valent cations. Second, the remaining epoxy group across the entire film was converted into a sulfonic acid group by a reaction with sodium 3-mercapto-1-propanesulfonate. Electrodialysis of a mixture of 0.5 mol/L NaCl and 0.05 mol/L MgCl₂ using a pair of the resultant mono-valent cation selective cation-exchange membrane and a commercially available anion-exchange membrane exhibited a permselectivity coefficient of 0.56.