β-diketone-based mesoporous ionogel for high-efficiency lithium adsorption

The β-diketone-based ionic liquids (ILs) possesses outstanding advantage of high Li/Na selectivity and capacity over a wide pH range. By immobilizing ILs in the interconnected 3D pore structure, ionogels have received considerable attention due to their fast ion diffusion efficiency and excellent structural stability. Here we first present a novel functionalized IL featuring tetrabutylphosphonium ([P4444]+) as the cation and deprotonated thenoyltrifluoroacetone ([TTA]−) as the anion. Then the β-diketone-based ILs are used to form functionalized mesoporous silica-based ionogels (MSI). The prepared functionalized MSI adsorbents feature a mesoporous structure and a large specific surface area of 1631.9 m2·g−1. ILs are effectively immobilized within the 3D network of mesoporous silica, thereby preventing the loss of extractants. It is found that the adsorbent could effectively extract Li over a wide range of pH, and even under acidic conditions. A high removal efficiency of 98.32 % is achieved, with a Li adsorption capacity of 3.44 mg·g−1, which is much higher than other MSI adsorbent in literatures. Additionally, high selectivity of 1052 for SFLi/Na and 886 for SFLi/K, as well as fast kinetic with an equilibrium time of less than 20 min are also realized. In the pre-treated oilfield brine with mass ratio of Na/Li at 390 and K/Li at 26, the adsorbent demonstrates an outstanding adsorption capacity of 3.25 mg·g−1. Finally, good separation performance is observed in the column-based experiment. The prepared β-diketone-based MSI adsorbent is expected to be applied in extracting Li from brine solutions.