Fabrication of hierarchical porous ZIF-8 for enhanced adsorption of uranium

Abstract

The adsorption and separation of uranium are critical for the treatment of nuclear wastewater. Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles have been widely employed in wastewater treatment due to their large specific surface area, thermal stability, and chemical stability. However, the small pore size (<2 nm) of ZIF-8, which is predominantly microporous, increases reaction resistance and reduces the separation efficiency of metal ions in aqueous solutions. To address these limitations, this study proposes a hierarchical porous ZIF-8 (HpZIF-8) structure containing both micropores and mesopores. HpZIF-8 was synthesized using polydiallyldimethylammonium chloride (PDDA) as a template to guide the formation of the microporous ZIF-8 framework. Nitrogen adsorption-desorption isotherms confirmed that HpZIF-8 exhibits dual microporous and mesoporous characteristics. The equilibrium adsorption capacity of HpZIF-8 for uranium was 297.7 mg/g, significantly exceeding that of conventional ZIF-8 nanoparticles. Additionally, the adsorption rate of uranium by HpZIF-8 was 46.52 mg/g·min, 1.67 times higher than that of ZIF-8 (27.92 mg/g·min). HpZIF-8 demonstrates superior adsorption capacity, attributed to its unique hierarchical porous structure. This study highlights the potential of HpZIF-8 for rapid uranium capture in contaminated environments, providing a promising approach for the application of metal-organic frameworks in environmental remediation.