Elemental Mercury Capture from Flue Gas by a Supported Ionic Liquid Phase Adsorbent

As promising-functional materials, ionic liquids have been widely used in flue gas purification and separation. Previous studies reported that ionic liquid based mixtures can be used for mercury removal due to their high economic efficiency and environmental friendliness. In comparison with ionic liquid based mixtures, a supported ionic liquid phase (SILP) adsorbent shows significantly improved mercury removal performance because of its greatly enhanced, gas/liquid interfacial area. In this study, a novel supported task-specific ionic liquid phase adsorbent [C(4)mim][FeCl4]-SiO2 was prepared for high efficiency elemental mercury capture from flue gas. The Hg-0 removal performance was investigated in a bench-scale fixed bed reactor, and the reaction mechanism was proposed based on the temperature programmed desorption (TPD) test. The results showed that Hg-0 removal was mainly due to the oxidation by [C(4)mim] [FeCl4]. The addition of [C(4)mim] [FeCl4] on SiO2 in a certain composition range enhanced the Hg-0 removal performance, and the optimized ionic liquid loading is 30%. The Hg-0 removal by the adsorbent was favored at higher temperatures. TPD results showed that the mercury compound formed on the adsorbent was HgCl2. The Hg-0 removal mechanism involves combined physisorption and chemisorption, which consists of Hg-0 oxidation to HgCl2 by the ionic liquid and physical adsorption of HgCl2 on the porous adsorbent.