Development of Gold Nanoparticle-Doped Activated Carbon Sorbent for Elemental Mercury

The control of mercury (Hg) from coal-fired power plants by adsorption in solid sorbents is an attractive way to reduce Hg emissions. In this study, a commercial activated carbon (Norit RB3) was impregnated with gold nanoparticles for the retention of Hg in the gas phase, with the intention to explore their potential to be regenerated in future investigations. The activated carbon (RB3) was impregnated with different gold contents using polyvinyl alcohol (PVA) and tetrakis(hydroxymethyl)phosphonium chloride (THPC) to compare the performance of these two methods. Gold particles of ∼5 nm were obtained in the carbonaceous support for low gold contents (0.1%). With comparative purposes of the sorbent behavior, the Hg0 retention capacity was evaluated in a lab-scale device in an O2 + N2 atmosphere. Although the Hg retention capacities of these sorbents were similar by the two methods, a higher efficiency was achieved with THPC, being in some cases 80%. The results showed that the use of THPC is a promising means for dropping gold (0.1%) to make carbonaceous sorbents for use in Hg capture.