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ZIF-8, a sort of zeolitic imidazolate frameworks (ZIFs), had showed superior adsorptive property of typical radionuclide U(VI), but it reminded uncertain how the performance of ZIF-8 would be affected by adding humic acid (HA). HA could significantly change the surface charge of ZIFs and the transport of U(VI) in natural settings, which affected the eradication of U(VI) in aquatic ecology. Thus the impact of HA for the U(VI) removal by ZIF-8 as well as its mechanism had been analyzed by batch experiments and spectral analyses. It was demonstrated that the addition of HA increased the maximum removal capacity towards U(VI) from 781.2 mg g -1 to 1398.5 mg g -1 . Moreover, removal property in acidic solution was improved, and the influence of background ions on ZIF-8 was reduced. The detailed mechanism was further explored by microscopic spectral analysis. The zeta potential showed that HA enhanced the electronegativity of ZIF-8 thus enhancing the electrostatic interaction with positive ions. Moreover, FT-IR and XPS further indicated that HA enhanced the removal capacity by affecting the surface complexation phenomena and strong chemical interactions between U(VI) and ZIF-8. Also, investigations indicated that the incorporation of HA improved the removal efficiency for U(VI), which had far-reaching significance for the application of ZIF-8 in practical environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

• ZIF-8 was fabricated by stirring at room temperature. • Enhancing the adsorption performance of ZIF-8 through thermal modification. • Surface complexation and electrostatic interaction were main removal mechanisms. • U(VI) formed coordination complexes with the N atoms of ZIF-8-400. 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. 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. 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. [Display omitted] [ABSTRACT FROM AUTHOR]