Ultrafast removal of ppb levels of Hg(II) and volatile Hg(0) using post modified metal organic framework

A novel MOF based adsorbent was prepared by functionalization of MIL 88A with mercapto ethanol to yield MIL88A-SH and evaluated for the removal of Hg(II) in water and Hg(0) in air. The prepared MOFs were characterized by field emission scanning electron microscope (FESEM), Transmission electron microscopy (TEM), Brunauer- Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and zeta X-ray photoelectron microscopy (XPS). The reaction rate was found to be very fast and within 15 min 95.5% Hg(II) was removed. The kinetics data followed pseudo second order model with rate constant values at 1.19 and 2.38 g/μg/min for MIl88A and MIL88A-SH respectively. A very high adsorption capacity in the order 1111.1 mg/g of Hg(II) was found using MIL88A-SH as adsorbent. The uptake was found to be constant in a wide range of pH from 5 to 9. Furthermore, in the presence other interfering metal ions, viz., Cu(II), As(V), Cd(II), Cr(VI), Pb(II), Zn(II), MIL88A-SH demonstrated an excellent adsorption for Hg(II). Around 45.6 mg/g of Hg(0) was found to be adsorbed by MIL88A-SH. XPS, FTIR and XRD studies suggested insitu oxidation Hg(0) to Hg(II) and complexation of Hg(II) with thiol groups during adsorption. Applicability on removal of Hg(II) at ppb levels from drinking water, fast kinetics, wide pH range, a very high sorption capacity, Hg(0) removal, selectivity and recyclability makes MIL88A-SH an efficient adsorbent to tackle mercury contamination.