Carbon materials loaded with maghemite as regenerable sorbents for gaseous Hg0 removal

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 387; p. 124151
• Main Authors: Antuña-Nieto, Cristina, Rodríguez, Elena, López-Antón, María Antonia, García, Roberto, Martínez-Tarazona, María Rosa
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2020
• Subjects: Carbon foam; Maghemite-loaded support; Mercury; Regenerable sorbent; Regenerable sorbent; Mercury; Maghemite-loaded support; Carbon foam
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2020.124151

[Display omitted] •γ-Fe2O3-loaded carbon supports are effective regenerable Hg capture sorbents.•Carbon foam-Fe sorbents are better at Hg0 removal than activated carbon-Fe sorbents.•Elemental mercury (Hg0) is efficiently retained via adsorption/oxidation.•The presence of O2 in the gas stream enhances sorbent regenerability. In a scenario where mercury emission regulations are becoming increasingly stringent, the use of regenerable sorbents is an attractive economic and ecological alternative for the elimination of gaseous mercury. This study attempts to develop cost-effective regenerable sorbents made up of carbon supports loaded with maghemite and evaluate their application for mercury capture in CO2 enriched atmospheres. To achieve this goal, an activated carbon (AC) and a carbon foam (CF) were impregnated with different concentrations of an iron salt and then subjected to thermal treatment to obtain the maghemite oxide. The Hg removal capacity of the prepared sorbents was evaluated at a laboratory-scale at 80 °C under different gas atmospheres. It was found that the characteristics of the carbon support as well as the iron concentration influence the distribution and morphology of the deposited maghemite particles. The CF-derived sorbents exhibited a better Hg0 removal performance than the AC-derived sorbents due to the presence of areas with a high concentration of iron oxide particles on the carbon support, which led to stronger interactions between the Hg and sorbent. The adsorption mechanism seems to occur via an adsorption/oxidation process involving the oxygen lattice of the metal oxide. Consequently, the sorbents lose their Hg retention capacity as the lattice oxygen is consumed. However, the deactivation can be counteracted by adding O2 to the gas stream to regenerate the sorbents. Carbon foams loaded with maghemite possess interesting properties which make them suitable for application at industrial scale. These include their low-cost, design versatility, and easy in-batch producibility. Hence, CF-derived sorbents are a versatile option for Hg capture in regenerable columns, capable of competing with the one-use sorbents, typically injected into flue gas.