Metal-organic frameworks HKUST-1 for liquid-phase adsorption of uranium

This paper reports on the efficient adsorption for uranium by metal-organic frameworks (MOFs) HKUST-1 from aqueous solution. The structure of the prepared HKUST-1 was characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption/desorption analysis. The influences of different experimental parameters were studied, such as initial solution pH, adsorbent dosage, adsorption time, temperature and various concentrations of uranium uptake. The thermodynamic parameters including Gibbs free energy (Delta G(0)), standard enthalpy change (Delta H-0) and standard entropy change (Delta S-0) for the process were calculated using the Langmuir constants. The results showed that the equilibrium data fitted well to Langmuir model in the studied range of uranium concentration (10 mg/L-800 mg/L) and temperature (298 K-318 K), and the HKUST-1 exhibited the highest uptake for uranium at 318 K, at the initial solution pH value of 6 and at the initial uranium concentration of 800 mg/L. The thermodynamics of uranium/HKUST-1 system indicated the spontaneous and endothermic nature of the process. And the kinetics of the adsorption process followed the pseudo-second-order kinetics model. (C) 2013 Elsevier B.V. All rights reserved.