Membrane chemical exchange for lithium isotope enrichment(Ⅱ): Multistage cascade process

摘要

A novel multistage cascade membrane chemical exchange (MCE)process was introduced to separate lithium isotope using solvent resistant polyethylene vinyl alcohol (EVAL) hollow fiber membranes. A MCE pilot with 10 pieces 4-inch membrane modules was designed and commissioned using an azo chelating agents (HA system) as the organic phase. Li-7 was enriched from a natural abundance of 92.47 %-92.92 %. The height of transfer unit (HTU) of the current EVAL module was estimated to be about 1.2 m. We estimated a total length of membrane modules in a multistage MCE to enrich Li-7 from natural abundance to 99.95 % about 279.6 m. EVAL membrane showed mechanical and lithium flux stability in a simulated experiment for over 700 h. For the first time, MCE was demonstrated experimentally as a successful technology for the enrichment of Li-7.