SO2 promoted ultrafine nano-sulfur dispersion for efficient and stable removal of gaseous elemental mercury

Development of a low-cost, stable and high-efficiency method is a vital challenge for elemental mercury (Hg-0) decontamination from nonferrous smelting flue gas. The ultrafine size (< 10 nm) and homodisperse nanometer sulfur (Nano-sulfur) was synthesized from alkali desulfurization solution by using a facile method. The as-synthesized Nano-sulfur exhibited excellent Hg-0 removal performance over the bulk sulfur and commercial sublimed sulfur. Sulfur dioxide was surprisingly proved as a promoter for Nano-sulfur to enhance the Hg-0 removal in this study. Nano-sulfur dispersion showed higher than 92% removal efficiency for 119 h under high-concentration SO2 atmosphere. The Hg-0 adsorption capacity and rate of Nano-sulfur reached 242.1 mg/g and 24.6 mu g/(g.min) respectively, which were both higher than other traditional adsorbents like sulfur-containing activated carbon and metal sulfides. S-new was proved as the main active substance to remove Hg-0, which could be continuously generated from Nano-sulfur by the reversible reaction under effect of SO2. The gaseous Hg-0 was largely transformed to colloidal phase (87.47%) and precipitated phase (10.53%) in the HgS form after wet scrubbing. This work offers a new path towards the design of nonferrous smelting flue gas Hg-0 purification method by adding Nano-sulfur dispersion into the wet scrubber of existing air pollution control devices, i.e., flue gas scrubber and wet flue gas desulfurization.