Volatilization of elemental mercury from fresh blast furnace sludge mixed with basic oxygen furnace sludge under different temperatures

Abstract

Blast furnace sludge (BFS) is a waste with elevated mercury (Hg) content due to enrichment during the production process of pig iron. To investigate the volatilization potential of Hg, fresh samples of BFS mixed with basic oxygen furnace sludge (BOFS; a residue of gas purification from steel making, processed simultaneously in the cleaning devices of BFS and hence mixed with BFS) were studied in sealed column experiments at different temperatures (15, 25, and 35 °C) for four weeks (total Hg: 0.178 mg kg⁻¹). The systems were regularly flushed with ambient air (every 24 h for the first 100 h, followed by every 72 h) for 20 min at a flow rate of 0.25 ± 0.03 L min⁻¹ and elemental Hg vapor was trapped on gold coated sand. Volatilization was 0.276 ± 0.065 ng (_m: 0.284 ng) at 15 °C, 5.55 ± 2.83 ng (_m: 5.09 ng) at 25 °C, and 2.37 ± 0.514 ng (_m: 2.34 ng) at 35 °C. Surprisingly, Hg fluxes were lower at 35 than 25 °C. For all temperature variants, an elevated Hg flux was observed within the first 100 h followed by a decrease of volatilization thereafter. However, the background level of ambient air was not achieved at the end of the experiments indicating that BFS mixed with BOFS still possessed Hg volatilization potential.