Ship-in-a-bottle CMPO in MIL-101(Cr) for selective uranium recovery from aqueous streams through adsorption

• Published in: Journal of hazardous materials Vol. 335; pp. 1 - 9
• Main Authors: De Decker, Jeroen, Folens, Karel, De Clercq, Jeriffa, Meledina, Maria, Van Tendeloo, Gustaaf, Du Laing, Gijs, Van Der Voort, Pascal
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 05.08.2017
• Subjects: Adsorption; Environmental chemistry; Metal-organic frameworks; Uranium; Environmental chemistry; Uranium; Adsorption; Metal-organic frameworks
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2017.04.029

•Highly stable metal-organic framework, MIL-101(Cr), for uses in aqueous, acidic adsorption.•Uranium recovery from low concentration acidic solutions.•One-step ship-around-the-bottle synthetic approach to incorporate CMPO in MIL-101(Cr).•Highly selective U(VI) adsorbent in competition with a high variety of metals, incl. rare earths and transition metals.•Regenerable and reusable adsorbent via 0.1M nitric acid stripping. Mesoporous MIL-101(Cr) is used as host for a ship-in-a-bottle type adsorbent for selective U(VI) recovery from aqueous environments. The acid-resistant cage-type MOF is built in-situ around N,N-Diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO), a sterically demanding ligand with high U(VI) affinity. This one-step procedure yields an adsorbent which is an ideal compromise between homogeneous and heterogeneous systems, where the ligand can act freely within the pores of MIL-101, without leaching, while the adsorbent is easy separable and reusable. The adsorbent was characterized by XRD, FTIR spectroscopy, nitrogen adsorption, XRF, ADF-STEM and EDX, to confirm and quantify the successful encapsulation of the CMPO in MIL-101, and the preservation of the host. Adsorption experiments with a central focus on U(VI) recovery were performed. Very high selectivity for U(VI) was observed, while competitive metal adsorption (rare earths, transition metals...) was almost negligible. The adsorption capacity was calculated at 5.32mg U/g (pH 3) and 27.99mg U/g (pH 4), by fitting equilibrium data to the Langmuir model. Adsorption kinetics correlated to the pseudo-second-order model, where more than 95% of maximum uptake is achieved within 375min. The adsorbed U(VI) is easily recovered by desorption in 0.1M HNO3. Three adsorption/desorption cycles were performed.