Electrochemical Lithium Extraction from Canadian Oilfield Brine

This study investigated the electrochemical extraction of lithium from Canadian oilfield brine, an unexplored source containing trace lithium concentrations of approximately 10 mM alongside high levels of competing ions such as Na⁺, K⁺, Ca²⁺, and Mg²⁺ in chlorides. The electrochemical system was in-house built flow cell of working area 25 cm 2 (5cm x 5cm), which has two porous lithium manganese oxide (LMO) electrodes, separated by an anion exchange membrane (AEM). Two Ag/AgCl reference electrodes were incorporated on a cell housing plate to enable precise potential measurements across the LMO working electrodes during the selective lithium intercalation and deintercalation in the electrodes. Initial benchmarking confirmed that the flow cell was functioning as intended. Atomic absorption spectroscopy (AAS) and inductively coupled plasma (ICP) measurements verified lithium extraction and release in the respective brine and recovery chambers over multiple cycles. Key operational parameters investigated in this study were the voltage window, current density, and flow rate, each of which played an important role in determining lithium extraction and recovery efficiency. It was found that flow rate has a strong influence on lithium brine extraction performance. An increase in extraction efficiency from approximately 20% at 10 mL min -1 to nearly 60% at 50 mL min -1 was observed. Similarly, reducing the applied current from 8 mA cm -2 to 1 mA cm -2 increased lithium extraction efficiency from about 45% to 65%, indicating the lithium extraction is limited by both kinetic and concentration polarizations. Li extraction capacity of the LMO electrode was approximately 10 mg/g LMO on average over 18 cycles, and lithium concentration of the recovery solution was reached above 2500mg/L. However, pH fluctuation in the recovery solution and manganese dissolution from the LMO electrodes were detected during cycle tests. Ongoing work will focus on understanding of pH change and mitigating Mn loss to improve electrode durability during extended operation.