High-efficiency technology for lithium isotope separation using an ionic-liquid impregnated organic membrane

摘要

The tritium needed as a fuel for fusion reactors is produced by the neutron capture reaction of lithium-6 (~6Li) in tritium breeding materials. New lithium isotope separation technique using ionic-liquid impregnated organic membranes (lonic-Liquid-i-OMs) have been developed. Lithium ions are able to move by electrodialysis through certain Ionic-Liquid-i-OMs between the cathode and the anode in lithium solutions. In this report, the effects of protection cover and membrane thickness on the durability of membrane and the efficiency of isotope separation were evaluated. In order to improve the durability of the lonic-Liquid-i-OM, we developed highly-durable lonic-Liquid-i-OM. Both surfaces of the Ionic-Liquid-i-OM were covered by a nafion 324 overcoat or a cation exchange membrane (SELEMION™ CMD) to prevent the outflow of the ionic liquid. It was observed that the durability of the Ionic-Liquid-i-OM was improved by a nafion 324 overcoat. On the other hand, the organic membrane selected was 1, 2 or 3 mm highly-porous Teflon film, in order to efficiently impregnate the ionic liquid. The ~6Li isotope separation factor by electrodialysis using highly-porous Teflon film of 3 mm thickness was larger than using that of 1 or 2 mm thickness.