Gaseous mercury capture using supported CuSx on layered double hydroxides from SO2-rich flue gas

Gaseous elemental mercury (Hg-0) co-existed with high concentration of SO2 is a typical flue gas. Most traditional Hg-0 sorbents are restricted to practical application owing to low reaction rate, small mercury capacity, and especially, poor resistance to SO2. The CuSx/layered double hydroxides (LDH) composite was prepared via the anion-exchange between poly-sulfur ions S-x(2-) and LDH. Metallic Cu2+ modification guarantee the exposure of more sulfur active sites due to the regulatory effect of metal ions. CuSx/LDH exhibited excellent Hg-0 removal performance at low temperature (75 degrees C) with SO2 concentration of 500-2000 ppm. The porous structure and large surface area were beneficial for gas transfer through its interior structure and surface. Surface S-x(2-) was the primary sites for Hg-0 oxidation and immobilization (Hg-0 + S-x(2-) -> HgS + Sx-12-). Moreover, Cu2+ also acted as the electron acceptor to oxidize Hg-0 to Hg2+ which further combined with S2- to form HgS on the surface of the sorbent (Hg-0 + 2Cu(2+) -> Hg2+ +2Cu(+), Hg2++S2- -> HgS). Such a composite was a promising material for practical applications to various flue gas conditions, especially for SO2-rich flue gas.