Synthesis and Study of UiO-66-(COOH)₂ on Adsorption and Separation Properties of Lithium Isotopes

Metal-Organic Framework Material UiO-66-(COOH)₂ was synthesized from zirconium tetrachloride and pyromellitic acid by hydrothermal method, and first performed experimental study on the adsorption and separation of lithium isotopes. The morphology, aperture and thermal stability of UiO-66-(COOH)₂ were confirmed by X-ray diffraction analysis(XRD),scanning electron microscope (SEM), automatic specific surface area analysis (BET) and thermogravimetric analysis (TG). The effects of different conditions (time, temperature, concentration of lithium ions) on adsorption properties and separation in the static adsorption experiments were discussed. The concentration of Li and the isotope abundance of ⁶Li/⁷Li were determined separately using inductively coupled plasma optical emission spectrometer (ICP-OES) and multi-channel receiving inductively coupled plasma mass spectrometer (MC-ICP-MS). The results demonstrated that UiO-66-(COOH)₂ achieves lithium adsorption and the separation of lithium-7, performs static adsorption of 0.05 mol/L Li₂CO₃ at 10 mL, per 0.05 g of UiO-66-(COOH)₂ at 293 K, Li₂CO₃ solution for 4 hours. The maximum adsorption quantity (Q) was 9.53 mg/g, and the separation factor S(⁷Li/⁶Li) was 1.019 54. The results provide a new method for the separation of ⁷Li.