Caesium adsorption on a zeolitic imidazolate framework (ZIF-8) functionalized by ferrocyanide

137Cs is one of the most hazardous radionuclides in nuclear waste owing to its toxicity. Developing an adsorbent for Cs+ with a high capacity and selectivity is a challenging task. A metal-organic framework (MOF) is a material with a high surface area that has been widely applied in wastewater treatment. Exploiting the affinity between ferrocyanide (FC) and Cs+, zeolitic imidazolate framework-8 (ZIF-8) was chemically functionalized with FC, ZIF-8-FC to selectively capture Cs+. After functionalization, ZIF-8-FC has a hollow morphology and small FC related crystals, which might result in better migration of Cs+ inside ZIF-8-FC. This synergistic effect was proven by the Qmax of ZIF-8-FC, 422.42 mg g-1, which is 15.9 times higher than that of ZIF-8. Additionally, ZIF-8-FC retained its good adsorption performance within a pH range of 3-11 and an excellent Cs+ selectivity even in artificial seawater conditions. The structure of ZIF-8-FC after adsorption proves its stability. Furthermore, the thermodynamic adsorption implied that higher temperatures are more favorable for Cs+ uptake. This work demonstrates the remarkable adsorption and selectivity of ZIF-8-FC, which make it a promising candidate for remediation of radioactive Cs+.