Lithium Extraction from Wairakei Geothermal Fluid using Electrodialysis

Abstract

Fluid sourced from the Wairakei geothermal power station was treated at small laboratory scale by electrodialysis. The fluid was first desilicated using electrocoagulation with aluminium electrodes. The influence which the voltage, current, temperature of fluid and acidification had on lithium extraction was explored. It was determined that the power supplied to the system determined the extraction rate; whilst, also severely degrading the membranes. Acid dosing was found to be essential to the electrodialysis process, due to the alkalinity of geothermal desilicated brine. The greatest extraction rates were obtained at ~ pH 2 and the highest extraction rate achieved was 0.28 mg/hour.cm2 of active membrane using a three membrane stack in the laboratory electrodialysis unit. It was determined that the process had sufficient potential to be taken into the pilot plant stage. However large scale field pilot plant experiments are required to produce an understanding of the economic viability.