Efforts to remove aqueous lithium ion using Octolig® and methylated derivatives

Aqueous Li⁺ - containing samples (in DI water or well water) were eluted over Octolig®, a polyethylenediimine covalently attached to a high- surface-area silica gel, and only slight removal, if any, could be claimed. However, when using tetrahydrofuran (THF) as a solvent we quantitatively removed lithium ion with Octolig® or with alkylated Octolig®, demonstrating the efficacy of Octolig® and lack of advantage of a N, N'-dialkylated Octolig®. In addition, the removal of alkali metal ions (lithium, sodium, and potassium) in THF by Octolig® was partially selective: While being quantitative for lithium it was only about 40% for potassium. The study has potential implications for using geothermal brines not only as a heat source, but as a source of lithium as well.