Role of Cufe2o4 in Elemental Mercury Adsorption and Oxidation on Cufe2o4-Modified Bentonite Used for Coal Gasification

Abstract

The application of active components is essential to improving the quality and efficiency of mineral adsorbents used for mercury removal. In this study, we investigated the role of the CuFe 2 O 4 active component in the removal of elemental mercury (Hg 0 ) from coal gasification on spinel CuFe 2 O 4 -modified bentonite through a combination of experiments and thermodynamic analysis. Meanwhile, the adsorption and oxidation mechanism of CuFe 2 O 4 were established by the density functional theory (DFT). The results showed CuFe 2 O 4 increased the active sites on the surface of bentonite (Ben) and promoted its magnetic properties. Due to the increase in the number of active adsorption sites, the Hg 0 removal ability of CuFe 2 O 4 -modified bentonite was improved significantly. Thermodynamic simulations further confirmed that CuFe 2 O 4 -modified bentonite could promote the conversion of Hg 0 to Hg 2+ more effectively. The adsorption of Hg 0 on the surface of CuFe 2 O 4 (110) had stronger interaction potential due to the atomic orbital hybridization and electron sharing. The Cu-top was identified as the main active adsorption site. The reaction of the surface oxidation of Hg 0 was realized in three steps: (1) Hg 0 -Hg (ads); (2) Hg (ads)-HgO (ads); and (3) HgO desorption, where the HgO generation reaction was a rate-controlling step. The low cost, excellent performance, superior regenerable properties suggest that the CuFe 2 O 4 -modified bentonite is a promising sorbent for mercury removal.

Keywords: CuFe2O4, Density functional theory, Coal, Gasification, bentonite, Elemental mercury