Mercury adsorption on PdAu, PdAg and PdCu alloys

Under specific conditions, sorbent materials such as activated carbon, metal oxides, metal sulfides and pure metals can effectively capture mercury (Hg). Among these materials activated carbon is one of the most widely-used sorbents because of its high removal capacity. Unfortunately, activated carbon can hinder the recycling of particulate matter for concrete manufacturing because it prevents concrete from meeting the freeze-thaw requirements. The use of a sorbent material that can capture Hg efficiently but is also concrete-friendly would allow for the increased sale of waste materials, ultimately oversetting landfill costs. In this work, density functional theory calculations have been used to predict the binding mechanism of Hg on the binary alloys PdAu(111), PdAg(111), PdCu(111) which are potential candidates for concrete-friendly sorbents. Although bulk Pd surfaces are more reactive than bare Au, Ag and Cu surfaces, the addition of small amounts of Au, Ag and Cu alloyed with the Pd acts to increase the overall mercury binding energy. Interestingly, it has been found that the dopant atoms in the PdAu, PdAg and PdCu alloys increase the Hg adsorption most effectively when they remain in sub-surface layers.