Synthesis of ethylene glycol polymerized MIL-125 and their application in arsenic adsorption

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Arsenic in drinking water poses a great threat to human health. While many methods have been examined for arsenic treatment such as coagulation/filtration, reverse osmosis, ion exchange and adsorption, the efficiency of these are relatively low. In this study, water stable titanium metal-organic framework (MIL-125) with and without polymerized ethylene glycol was synthesized and applied to remove arsenic from aqueous solutions. Several methods of characterization had been used to characterize MIL-125 particle and MIL-125 granule including scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR). Both of MIL-125 particles and granule were evaluated in batch experimental systems for their adsorption isotherm, adsorption kinetics, and pH effect. A remarkable arsenic capacity of 189 mg/g for MIL-125 particle and 213 mg/g for MIL-125 granule were achieved at pH=4.7, which were much higher than the capacities of many other adsorbents reported in the literature, generally less than 100 mg/g. At a high arsenic concentration, i.e., 50 parts per million, 60% arsenic could be removed within 5 h at a solid loading of 1.00g/L, and at a concentration of 100 parts per billion, only 10 min was required to reach the EPA standard of 10 ppb maximum contaminant level at the same solid loading. MIL-125 particle and MIL-125 granule were effective for arsenate sorption within a wide pH range of 2 to 10 and the experiment revealed that the adsorption capacity was the highest at pH=2. MIL-125 was first applied as absorbents to remove aquatic arsenic contamination and the result showed that they have tremendous potential in arsenic treatment.