Functionalized metal organic framework (MIL-101(Cr)) as selective adsorbent for the mitigation of uranium (VI) from contaminated lake water

Abstract

Metal-organic frameworks (MOFs) received much attention due to their distinct porous structure. Diaminomaleonitrile (DAMN) functionalized chromium (III) terephthalate MOF (MIL-101(Cr)) was developed using a facile method as a promising adsorbent for U removal. The functionalized adsorbent contained abundant amine and cyanide groups onto the coordinatively unsaturated metal binding sites. The DAMN-functionalized MIL-101(Cr) was thoroughly characterized. The adsorbent exhibited maximum Langmuir adsorption capacity of 743 mg/g for U at pH 6 and room temperature. Different coexisting ions, having concentration within 10–50 mg/L, show negligible influence on the U adsorption (86.0–99.3 % removal). The effects of other ions on the U removal were studied in terms of U ionic speciation in the aqueous solution. The surface-grafted −C≡N and –NH2 groups were responsible for the coordinative interactions with the U(VI) ionic moieties. The MIL-101(Cr)_DAMN adsorbent was also subjected to five consecutive adsorption–desorption cycles, with >90.5 % U removal after the 5th cycle. An adsorption-pore diffusion based transport model was used to analyze the adsorption kinetics and estimation of the pore diffusivity. The effectiveness of the developed adsorbent was also demonstrated by a batch kinetic run using U contaminated lake water. In general, this research demonstrates the straightforward design and development of DAMN-functionalized MIL-101(Cr) as an effective adsorbent for the selective uptake of U(VI) from aqueous medium.