Study on lithium extraction from brines based on LiMn₂O₄/Li_1-xMn₂O₄ by electrochemical method

Highlights: •A recovery system with LiMn₂O₄/Li_1-xMn₂O₄ as electrodes was used to extract lithium. •The influence sequence of coexisting ions on lithium extraction was Mg²⁺ > Na⁺ > Ca²⁺ > K⁺. •The values of α_Li-Na, α_Li-Mg and α_Li-Ca were more than 300, 70 and 110, respectively. •The specific energy consumption was between 18 and 19 W h·mol⁻¹. -- Abstract: Lithium rechargeable batteries have been used for lithium extraction in recent years. Here, we report on a highly selective lithium recovery system that consists of a LiMn₂O₄ positive electrode, a Li_1-xMn₂O₄ negative electrode and a monovalent selective anion-exchange membrane. The effect of potential, temperature and coexisting ions on lithium extraction were investigated in this paper, and the lithium recovery system was applied to extract lithium from brine and concentrated seawater. The extraction capacity of Li⁺ reached 34.31 mg· (1 g LiMn₂O₄) ⁻¹ at 1.2 V. With higher reaction rate and lower energy consumption, 25 °C (room temperature) was considered as the appropriate temperature. The system still remained high selective for Li⁺ even in the presence of impurity ions (K⁺, Na⁺, Mg²⁺, Ca²⁺). With simulated brine and concentrated seawater as source solutions, the concentrations of Na⁺, Mg²⁺ and Ca²⁺ were reduced more than 300, 70 and 100 times, consuming 18–19 W h per mole of lithium recovered. And the electrodes still had high separation coefficients of Li⁺ and Meⁿ⁺ (Na⁺, Mg²⁺, Ca²⁺) after five cycles although a slight drop was existing.