Regenerable sorbents for mercury capture in simulated coal combustion flue gas

•Zero emissions of mercury to the atmosphere from power plants is a global objective.•Regenerable sorbents allow us to recover mercury without producing any toxic waste.•Gold-coated sorbents showed a high mercury retention over several cycles of regeneration.•The presence of acid gases did not poison the gold-coated activated carbon. This work demonstrates that regenerable sorbents containing nano-particles of gold dispersed on an activated carbon are efficient and long-life materials for capturing mercury species from coal combustion flue gases. These sorbents can be used in such a way that the high investment entailed in their preparation will be compensated for by the recovery of all valuable materials. The characteristics of the support and dispersion of gold in the carbon surface influence the efficiency and lifetime of the sorbents. The main factor that determines the retention of mercury and the regeneration of the sorbent is the presence of reactive gases that enhance mercury retention capacity. The capture of mercury is a consequence of two mechanisms: (i) the retention of elemental mercury by amalgamation with gold and (ii) the retention of oxidized mercury on the activated carbon support. These sorbents were specifically designed for retaining the mercury remaining in gas phase after the desulfurization units in coal power plants.