Uranium (VI) adsorption by copper and copper/iron bimetallic central MOFs

Two metal-organic framework materials Cu-BTC and Cu/Fe-BTC were designed and synthesized with Cu ion and Cu/Fe double metal ions as the metallic centers and 1,3,5-benzenetricarboxylic acid (BTC) as the ligand, respectively. And used for the adsorption of U(VI) in aqueous environment. The stability, structure, size, and porosity of the materials were investigated by TGA/DSC, XPS, SEM-EDS, XRD and BET analyses. The results illustrated both the two MOFs had good chemical stability and thermal stability. The optimum pH for Cu-BTC was 3.0. At pH = 3.0, the maximum adsorption capacity for U(VI) determined using the Langmuir equation was 617 mg g−1. The optimum pH value for Cu/Fe-BTC was 7.0, and at pH = 7.0, the maximum adsorption capacity was determined (Langmuir equation) to be 354 mg g−1. The thermodynamic parameters revealed that the adsorption processes for the two materials were both spontaneous and endothermic. Additionally, Cu/Fe-BTC exhibited excellent renewable adsorption properties, and it could be regenerated by simply washing with NaCO3 solution (0.1 M).