Binding of vapour-phase mercury (Hg0) on chemically treated bauxite residues (red mud)

Abstract

Environmental context. Mercury (Hg) is a toxic, persistent pollutant that accumulates in the food chain. Atmospheric Hg is a global problem with many sources of emissions, of which anthropogenic sources are estimated to account for approximately one-third. Stationary combustion (coal combustion, municipal waste incinerators, etc.) are the largest worldwide sources of anthropogenic Hg emissions, and great effort has been taken to develop control technologies for capture of mercury from these sources. In the present study, Hg capture using bauxite residue (red mud) – a waste product from the aluminium industry – is evaluated and compared with other, more conventional sorbent materials. Abstract. The development and testing of novel control technologies and advanced adsorbent materials continue to be active areas of research. In the present study, Hg capture using adsorbent material derived from the bauxite residue (red mud) from two North American refineries was studied. The red mud, seawater-neutralised red mud, and acid-treated red mud were evaluated for their mercury adsorption capacity and compared with other, more conventional sorbent materials. Two different seawater-neutralised red mud (Bauxsol) samples were treated with HCl and HBr in an effort to increase the mercury sorption capacity. In all cases, the acid treatment resulted in a significant increase in the total surface area and an increase in the total pore volume. The fixed-bed mercury capture experimental results showed that the HBr activation treatment was very effective at increasing the mercury capture performance of both Bauxsol samples whereas the HCl treatment had no effect on the mercury capture performance. Entrained-flow experiments revealed that the Br-Bauxsol was not effective for in-flight mercury capture. This indicates that the mechanism of mercury capture is likely mass-transfer-limited in the entrained-flow experiments.