Functionalized zeolite imidazolium framework materials for uranium removal performance and mechanism research

Background Zeolite imidazolium framework materials (ZIFs) had been extensively applied for U(VI) removal because of their superior structure, high porosity and large specific surface area. Nevertheless, ZIF-8 tended to accumulate in aqueous solution and it was hard to detach from water, resulting in a decrease in the removal performance. Therefore, it was necessary to conduct thermal modification treatment to solve the above problems. Methods The U(VI) removal capability of ZIF-8 was investigated in this study by subjecting it to various thermal modification temperatures (0 °C, 200 °C, 400 °C, 600 °C). The effect of thermal modification on the removal of U(VI) from ZIF-8 was investigated by a combination of macroscopic and microscopic experiments. Significant findings Macroscopic experiments revealed ZIF-8, ZIF-8-200, and ZIF-8-400 showed excellent removal efficiency, reaching reaction equilibrium rapidly (about 60 min). The adsorption kinetic and isotherm datum were more consistent with proposed second-order kinetic model and Langmuir model, confirming that removal process of U(VI) was mainly a single-molecule chemisorption reaction. The maximum removal amounts of ZIF-8, ZIF-8-200 and ZIF-8-400 were 470.5, 474.6 and 606.0 mg/g, respectively. Microscopic spectroscopic analysis revealed that there was a synergistic effect between the combination bonds in ZIF-8 during the adsorption reaction. Surface complexation and electrostatic interaction were the main mechanisms used by ZIF-8-400 to remove U(VI). This research offered theoretical guidance on the design of high-performance materials and the migration and transformation laws of radionuclides, which had significant theoretical significance for the future treatment of radioactive nuclides or other pollutants.