Speciation of contaminant metals in red mud from Ajka, Hungary

Burke, I. T.; Mayes, W. M.; Peacock, C. L.; Brown, A. P.; Jarvis, A> P.; Gruiz, K.

Abstract

The catastrophic failure of the sludge dam at the Ajkai Timfoldgyar Zrt alumina plant in Hungary on the 4th October 2010 resulted in the release of 700000 m 3 of caustic metalliferous red mud. Red mud leachate is hyperalkaline (pH 13) has elevated concentrations of metals and metalloids such as Al (1000 ppm) As, V, and Mo (4 - 6 ppm) and the red mud itself has elevated concentrations of As, V, Cr, Co, Ni and U (100-1000 ppm). These contaminants persist in water and sediment samples for up to 100 km downstream of the source. The long term effects of the red mud spill on the environment remain largely unknown, especially with respect to the behaviour of the toxic elements present. Here we describe the results of experiments using sequential extraction, electron microscopy and X-ray absorption spectroscopy techniques to characterise the occurrence of metal(loids) within the red mud. SEM and TEM analysis of red mud material sampled from the dyke breach at Ajka was composed primarily of 10- 100 nm haematite particles occurring as 100-700 nm aggregates and 1-4 μm sodium aluminosilicate particles. Transported samples also contain 10-40 μm silt particles, presumably entrained from local soils and sediments. In EDS analysis Cr, Ti, Al, Si, and Mn were associated with aggregates of nano-crystalline (~ 5 nm) haematite. Discrete 2- 10 nm Ce-rich particles were also present. At Ajka, acid dosing and gypsum addition were extensively used to lower pH and precipitate soluble Al, As, V and Mo. Sequential extractions performed on transported red mud deposits determined that 70-90 % As and V are present in residual hard-to-leach phases. The remaining 10-30 %, however, occurred in weak acid / hydroxylamine HCl leached phases, which may represent the presence of freshly precipitated metal(loid) containing phases. XAS analysis of red mud samples and leachate precipitates focused on determining As and V speciation in both the labile and refractory phases present. This baseline information will help in predicting the likely environmental mobility, fate and the long term hazards from metal(loid) contamination associated with the spill.

Citation

Burke, I. T., Mayes, W. M., Peacock, C. L., Brown, A. P., Jarvis, A. P., & Gruiz, K. Speciation of contaminant metals in red mud from Ajka, Hungary. Presented at Goldschmidt 2011 Conference

• Presentation Conference Type: Conference Abstract
• Conference Name: Goldschmidt 2011 Conference
• Acceptance Date: Jan 1, 2011
• Publication Date: Jan 1, 2011
• Print ISSN: 0026-461X
• Publisher: Mineralogical Society
• Volume: 75
• Issue: 3
• Pages: 599 - 599
• Public URL: https://hull-repository.worktribe.com/output/409494