Novel Functionalized Cellulose Microspheres for Efficient Separation of Lithium Ion and Its Isotopes: Synthesis and Adsorption Performance

The adsorption of lithium ions(Li(+)) and the separation of lithium isotopes have attracted interests due to their important role in energy storage and nuclear energy, respectively. However, it is still challenging to separate the Li(+) and its isotopes with high efficiency and selectivity. A novel cellulose-based microsphere containing crown ethers groups (named as MCM-g-AB15C5) was successfully synthesized by pre-irradiation-induced emulsion grafting of glycidyl methacrylate (GMA) and followed by the chemical reaction between the epoxy group of grafted polymer and 4′-aminobenzo-15-crown-5 (AB15C5). By using MCM-g-AB15C5 as adsorbent, the effects of solvent, metal ions, and adsorption temperature on the adsorption uptake of Li(+) and separation factor of (6)Li/(7)Li were investigated in detail. Solvent with low polarity, high adsorption temperature in acetonitrile could improve the uptake of Li(+) and separation factor of lithium isotopes. The MCM-g-AB15C5 exhibited the strongest adsorption affinity to Li(+) with a separation factor of 1.022 ± 0.002 for (6)Li/(7)Li in acetonitrile. The adsorption isotherms in acetonitrile is fitted well with the Langmuir model with an ultrahigh adsorption capacity up to 12.9 mg·g(−1), indicating the unexpected complexation ratio of 1:2 between MCM-g-AB15C5 and Li(+). The thermodynamics study confirmed the adsorption process is the endothermic, spontaneous, and chemisorption adsorption. As-prepared novel cellulose-based adsorbents are promising materials for the efficient and selective separation of Li(+) and its isotopes.