Preparation of Li2CO3 from high Mg2+/Li+ brines based on selective-electrodialysis with feed and bleed mode

Abstract Extracting lithium from brines is challenging due to the high Mg2+/Li+ ratio and low Li+ concentration. In this paper, a selective electrodialysis process (S-ED) with feed and bleed mode was developed to extract Li+ continuously from brines. Take the system performance including the recovery ratio of Li+ (RLi), leakage ratio of Mg2+ (LMg), migration rate (Mr), specific energy consumption (ESEC), current efficiency (η) and separation coefficient of Li+ and Mg2+ (FLi-Mg) as evaluation parameters, the typical factors such as applied voltage, supplementary feed flow rate, and linear flow velocity were investigated. In addition, the Li+ extraction parameters of different feed solution species in the S-ED process were compared under optimization operating conditions and Li2CO3 was obtained from Li-rich solution by precipitation reaction. The results showed that the increase of voltage could promote RLi, but the excessive voltage caused a decrease in FLi-Mg. The increase of the linear flow velocity could increase Mr but hardly affected FLi-Mg and ESEC. The increase in the supplementary feed flow increased FLi-Mg. For different feeding solutions, it was found that extracting Li+ from bittern had good economic value and high purity Li2CO3 was obtained after S-ED. Compared with the traditional process, the S-ED process with the “feed and bleed” mode proposed in this article has the advantages of simple operation, continuity, and environmental friendliness. It is a promising technology that can continuously enrich Li+ from brines.