Low-temperature Hg0 abatement by ionic liquid based on weak interaction

Abstract Low-temperature gaseous elemental mercury (Hg0) abatement is an objective demand in industrial flue gas treatment. In this work, we proposed a new approach for Hg0 capture via weak interaction of ionic liquids. Ionic liquids with varied anions (1-butyl-3-methylimidazolium thioacetate ([Bmim][ThAc]), 1-butyl-3-methylimidazolium diethyldithiocarbamate ([Bmim][DTCR]), and 1-butyl-3-methylimidazolium ethylxanthate ([Bmim][EX])) were designed and synthesized. The interaction energies between ionic liquids and elemental mercury were proved to be positively related to mercury removal efficiency, revealing that the electrostatic interaction derived physical adsorption from anions is the dominant factor affecting mercury removal performance. [Bmim][ThAc] with the largest anionic electrostatic interaction energy showed the best mercury abatement performance, achieving a Hg0 removal efficiency of over 98% and an adsorption capacity of 10.66 mg/g at 50 oC. The influence of temperature and the results of mercury temperature-programmed desorption (Hg-TPD), X-ray photoelectron spectroscopy (XPS) further confirmed that the ionic liquid combines with elemental mercury through physical adsorption. The work provides a new perspective on designing high-efficiency sorbents for mercury removal at low temperature.