Journal of Hazardous Materials, Vol.244, 495-500, 2013
A novel oxidative method for the absorption of Hg-0 from flue gas of coal fired power plants using task specific ionic liquid scrubber
A simple continuous process is described for the removal of mercury from gas streams (such as flue gas of a coal fired power stations) using imidazolium based Task Specific Ionic Liquids [TSILs] with the general structure ([RMIM][XI2-]) where X = Cl, Br or I. The latter are formed by blending dialkylimidazolium halide salts with iodine. When applied in a gas/liquid scrubber, these salts were shown to absorb >99% of elemental mercury originally present in a gas stream in concentration of 75-400 ppb. The mercury abatement is attained by oxidating the mercury to HgI2 which is bound as a stable IL complex ([RMIM+][XHgI2-]. The novel absorption system exhibits a remarkable mercury concentration factor of seven orders of magnitude. The final solution obtained contains up to 50% (w/w) mercury in the IL. Upon exposure to sodium formate, directly added to the saturated IL at 45 degrees C, reduced metallic mercury swiftly precipitated from the solution and could be quantitatively separated and collected. The free IL could be fully recycled. (c) 2012 Elsevier B.V. All rights reserved.
Keywords:Mercury;Mercury abatement;Flue gas;Ionic liquid;Task specific ionic liquid;Liquid scrubber;Iodine