Adsorption of Gas-Phase Mercury and Arsenic Using Ionic Liquid Based Adsorbents

Mercury and arsenic are toxic contaminants produced in coal combustion. To control the release of these toxic substances, gas-phase mercury and arsenic can be adsorbed from the flue gas produced by coal combustion. In this study, a nano-engineered ionic liquid based silica adsorbent was developed to remove elemental mercury and arsenic (III) in the gas-phase. Laboratory-scale fixed-bed adsorption trials have demonstrated that the room temperature ionic liquid (RTIL) methylpolyoxyethylene(15) octadecanammonium chloride (MEC) coated on silica substrate and 1-butyl-3-methyl-imidazolium chloride ([bmim]Cl) coated on 3-mercaptopropyltrimethoxysilane (MPTS) silica can remove mercury in simulated flue gas at 160˚C; the total mercury capacities were 17-58 mg/g. The effectiveness of these materials for gas-phase arsenic capture was tested in fixed-bed tests at 160°C using arsenic oxide (As₂O₃) vapor as a representative arsenic species. Arsenic (III) removal efficiencies ranged from 60 to 85%; the total arsenic capacities ranged from 5 mg/g to 11 mg/g. Additional work on the mechanism of interaction is in progress. Ionic liquid based silica adsorbents are promising adsorbents for simultaneous warm-gas mercury and arsenic capture from flue gas.