Efficient Targeted Recovery of Lithium Using Fluorine-Rich Supramolecular Nano-Container Crosslinked Hydrogel

Fluorine is a non-metallic chemical element with the chemical symbol F and atomic number 9. Fluorine compounds refer to organic or inorganic compounds containing fluorine. The uses of fluorine compounds include fluorine pesticides, fluorine pharmaceuticals, fluorine dyes, fluorine containing aromatic intermediates, and fluorine containing surfactants. Many fluorine compounds have important uses. For example, polytetrafluoroethylene can be used as a component of artificial joints for long-term use in the human body; the mixed emulsion of perfluorinated naphthalene and perfluorotripropylamine can be used as a fluorocarbon blood substitute; Perfluorocyclobutane can be used as a food foaming agent, etc.

Lithium is an important resource for the development of new energy. Therefore, the efficient extraction and recycling of lithium resources has become a hot frontier. The existing technologies for recovering lithium from solution generally face problems such as low recovery rate, poor selectivity, environmental pollution, and high cost. The efficient recovery of lithium still faces enormous challenges. Therefore, the development of Li⁺ targeted adsorption materials with both high adsorption capacity and high selectivity has important theoretical and practical value.

Recently, researchers have introduced Li-F interactions with specific recognition into polymers and constructed fluorine-rich supramolecular nano-container crosslinked hydrogel (FCH), achieving efficient targeted recovery of lithium from lithium containing wastewater. This material is prepared by polymerization of supramolecular nanosheets containing fluorinated monomers, acrylic acid, and a small amount of chemical crosslinking agents. It has excellent lithium adsorption capacity (Qm Li⁺=122.3 mg/g) and can be reused.

The experimental results show that the maximum adsorption capacity of FCH for Li⁺ can reach 122 mg/g; When other coexisting interfering metal ions (Na⁺, K⁺, Ni²⁺, Mn²⁺, Co²⁺, Fe²⁺, etc.) exist, FCH can selectively adsorb Li⁺. Taking actual wastewater as an example, the separation coefficient of Li⁺/Na⁺ reached 153.72. At the same time, researchers and others simulated the actual adsorption and recovery devices in industrial waste metal resources, and constructed an artificial simulation device to treat complex lithium containing wastewater from different sources, evaluating the feasibility of FCH recovery of Li⁺ under the actual water quality background. In addition, due to the introduction of covalent and non-covalent dual intermediate forces, FCH is endowed with good mechanical strength and formability, improving its stability and recycling ability in practical complex lithium-containing wastewater environments. By utilizing a series of experimental characterization and theoretical calculations, it was preliminarily elucidated that the adsorption mechanism of FCH for Li⁺ is mainly through the combination of fluorine and Li⁺.

Reference

1. Fluorine-Rich Supramolecular Nano-Container Crosslinked Hydrogel for Lithium Extraction with Super-High Capacity and Extreme Selectivity
   Angew. Chem. Int. Ed., 2023