Selective extraction of lithium from salt lake brine with a high Mg/Li ratio using an N,N-dioctyl-2-methoxyacetamide-FeCl3-sulfonated kerosene extraction system

Abstract

The selective extraction of lithium from salt lake brines has attracted widespread attention with the rapid increase in demand for lithium. Since Mg²⁺ and Li⁺ are chemically similar, this poses a huge challenge to the selective extraction of Li⁺ from salt lake brines with a high Mg/Li ratio. This paper reports a new amide extractant, N,N-dioctyl-2-methoxyacetamide, and constructs an N,N-dioctyl-2-methoxyacetamide-FeCl₃-sulfonated kerosene extraction system. The effects of operating conditions on the Li⁺ extraction performance are investigated. Under the optimal operating conditions by three-stage countercurrent extraction, the extraction rate for Li⁺ could reach 97.5%, and the separation factor of Li/Mg reaches 1225. After washing the impurity ions in the organic phase with an HCl + LiCl mixed solution, HCl is used for back extraction, achieving a 95% back extraction rate of Li⁺. During the five extraction cycles, the extraction efficiency of Li⁺ remained above 70%, indicating that the extraction system has good stability and reusability. In addition, the extraction system operates at low acidity, which can effectively avoid the formation of phase interfaces and does not produce emulsification. This work provides a new way to selectively recover lithium from high Mg/Li ratio salt lake brines.