Effects of applied voltages on Lithium-6 enrichment by electrodialysis with lithium ionic conductor

Abstract

Enrichment of Lithium-6 (6Li) is one of the necessary conditions to produce tritium as a fuel of fusion reactors by the neutron capture reactions. In previous studies, we have established the Li extraction technique using a fast ionic conductor Li0.29La0.57TiO3 (LLT) —Lithium Separation Method by Ionic Conductor (LiSMIC). LiSMIC can also be applied to the enrichment of 6Li, because 6Li has a lighter mass than 7Li and has a different extraction speed. In the LiSMIC, applied voltage gives a electrical driving force which may enhance the difference in the motions of 6Li and 7Li. In this work, we explore effects of applied voltage on the 6Li enrichment from a 3 mol/L LiOH solution when a LLT plate with 16 cm2 electrode area and 0.5 mm thickness was employed. We examined the Li extraction speed and 6Li enrichment when square and sine wave voltage profiles of maximally 5 V with 1 Hz frequency were applied, then compared them with the case of 5 V DC voltage. We found that the 1 Hz square wave voltage achieved the highest 6Li enrichment, ∼1.08, until 40% of Li was extracted from the source solution of 400 ml. Instead, the Li extraction speed for square wave was lower than the DC voltage case owing to the reduction of the application. In the DC voltage case, a high separation factor ∼1.06 was obtained at early stage of the electrodialysis but it gradually decreased. The sine wave case was in between. These results indicate that carefully choosing the applied voltage will accelerate the 6Li enrichment process.