Facile and Novel LiAlO2 Film Electrodes for Energy Efficient Li recovery from Seawater Reverse Osmosis (SWRO) Brine

Abstract

Concentration of Li in seawater is too low at 0.17 ppm despite its high content altogether with a reported 230 billion tons. Hence, seawater is not a practical source to recover Li from; Li is largely extracted by solar drying of salt-lake brines (100-200 ppm of Li). Salt-lake brines are confined to a certain region and not available for most parts of the world. However, seawater reverse osmosis (SWRO) brine is rather a widely available resource due to large adoption of the technique for water desalination. Hence, this study focuses on extraction of Li from concentrated SWRO brine. Li content in the feed can be increased up to 0.85 ppm, which is seemingly a favorable input stream. Electrically switched ion exchange (ESIX) on the other hand is energy efficient and economical in isolating Li, compared to other contemporary techniques such as capacitive deionization and electrodialysis. These approaches are meant to significantly shorten the time consumed in conventional solar drying process. Density functional theory studies have shown novel LiAlO2 type working electrode can be a better electrode to capture Li in ESIX system over widely known LMO and LiFePO4 working electrodes. Thus, this study intends to evaluate qualitatively and quantitatively the suitability of ESIX approach working in two electrodes configuration with LiAlO2 working electrode and activated carbon counter electrode to recover Li from concentrated SWRO brine. The operating system affirmed the recovery of Li with a specific energy consumption of 100Wh/mol and 97% purity, along with recyclability of the working electrode over minimum of 5 cycles without any apparent activity loss.