Preparation of sepiolite@ZIF-8 mesoporous material for enhanced adsorption of uranium

The development of high-performance uranium adsorbents exhibiting exceptional adsorption capacity and selectivity remains a critical challenge in environmental remediation and nuclear waste management. In this study, we report a facile room-temperature synthesis of mesoporous two-dimensional (2D) hybrid materials via the integration of sepiolite and zeolitic imidazolate framework-8 (ZIF-8), designated as Sep@ZIF-8. Sepiolite serves as a structural template, inducing mesoporosity through steric hindrance effects that modulate pore architecture and enhance surface accessibility. The optimized Sep@ZIF-8(24) composite demonstrates a remarkable equilibrium uranium adsorption capacity of 367.6 mg/g at pH 4.0, representing a 1.35-fold enhancement compared to pristine ZIF-8. Kinetically, Sep@ZIF-8(24) exhibits superior performance with an initial adsorption rate of 72.12 mg/(g·min) within the first 5 min, substantially surpassing that of unmodified ZIF-8. This accelerated uranium uptake is attributed to the reduced mass transfer resistance afforded by the mesoporous structure and enlarged pore dimensions, facilitating rapid uranyl ion diffusion to active binding sites. The exceptional adsorption kinetics and capacity of Sep@ZIF-8 underscore its significant potential for rapid uranium capture from contaminated aqueous environments, with broad implications for the design of advanced mixed-MOF materials in environmental and energy-related applications.