Exposed carboxyl functionalized MIL-101 derivatives for rapid and efficient extraction of heavy metals from aqueous solution

Exploring efficient adsorbent for heavy metals remediation from wastewater and contaminated soil is a pursuing issue. Robust functionalized metal-organic frameworks (MOFs) represent one of burgeoning scavengers because of their tunable structural topology, designable functionalities and extraordinary affinity for heavy metal ions. In this present work, we report a facile and versatile strategy to synthesize a series of carboxyl-functionalized MIL-101(Fe) derivatives by microwaving a solution of organic ligands with varying carboxyl number and Fe3+ ions. The resulting MIL-101(Fe) derivatives were characterized using various techniques including scanning electron microscope (SEM), powder X-ray diffraction, Fourier transformed infrared, Brunauer-Emmett-Teller specific surface area and X-ray photoelectron spectroscopy. The intrinsically carboxyl-rich characteristic and large sur-face area of MIL-101-(COOH)(2) afford fast adsorption kinetics (< 15 min) and high saturation capacity (467.6 mg/g) for Pb(II). Strikingly, it can efficiently capture Pb(II) possessing impressive adsorption efficiencies (> 90%) over a wide pH range of 4.5-11.0. Moreover, the resulting MIL-101-(COOH)(2) simultaneously exhibited high affinity toward different types of heavy metal ions, including borderline Lewis acid (Pb(II), Cu(II) and Ni (II)), soft Lewis acid (Cd(II) and Hg(II)) and hard Lewis acid (Eu(III) and Cr(III)). Such impressive treatment for Pb(II)-contaminated lead-acid battery industrial wastewater (more than 96.7%) can be attributed to the coordination arising from abundant carboxyl groups in the pores of MIL architecture with target heavy metal ions. Significantly, these findings validate the exceptional potential of carboxyl-functionalized MIL-101(Fe) derivatives in the application of heavy metal ions remediation.