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

Abstract

Gaseous elemental mercury (Hg0) co-existed with high concentration of SO2 is a typical flue gas. Most traditional Hg0 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 Sx2− 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 Hg0 removal performance at low temperature (75 °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 Sx2− was the primary sites for Hg0 oxidation and immobilization (Hg0 + Sx2− → HgS + Sx-12−). Moreover, Cu2+ also acted as the electron acceptor to oxidize Hg0 to Hg2+ which further combined with S2− to form HgS on the surface of the sorbent (Hg0 + 2Cu2+ → 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.