Enhanced adsorption of rubidium ion by a phenol@MIL-101(Cr) composite material

A novel composite adsorbent, phenol@MIL-101(Cr), was prepared using MIL-101(Cr) functionalized with different amount of phenol via an impregnation technique. These new composite adsorbents were characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and N-2 adsorption and the results showed that the phenol was immobilized in the MIL-101(Cr) structure. The adsorption performance of the composite for rubidium ions from aqueous solutions was evaluited by batch tests and using a fixed-bed breakthrough column at room temperature (25 degrees C). The phenol@MIL-101(Cr) exhibited high Rb+ uptake capacities, which are superior to all those previously reported in the literature. This excellent capacity is attributed to the exchange of acidic protons between the phenol groups and the rubidium ions. The saturated adsorbents were easily regenerated by washing with an ammonium nitrate solution. After regeneration, more than 90% of the rubidium ion capacity was maintained. Based on these results, MIL-101(Cr) modified by phenol should be a promising adsorbent for the separation and purification of rubidium ions from salt lakes. (C) 2017 Elsevier Inc. All rights reserved.