Removal of redox sensitive selenium from mine waters: Towards the trapping of the escapist element


Mr Dipti PMohapatra, Mr Deepak MKirpalani

Selenium, a redox sensitive element, has emerged as a major concern in Canada’s mining industry, particularly in areas with rich alluvial soils or in selenium-bearing geologic formations. In mines, selenium exists as a sulfur-substituting element in pyrite (FeS2) minerals. The mobilization of selenate in water, a highly toxic Se species, occurs as selenopyrite (FeSe2) is oxidized by the presence of nitrate (NO3) and the nitrate is “denitrified’. Removal technologies are essential as selenium-rich mine waters cannot be recycled into process operations and impact aquatic life and wild life habitats when discharged. As a result, existing water treatment technologies such as ion exchange, membrane separation and film bioreactors among others, have been adapted to remove selenium. National Research Council of Canada (NRC) has pioneered the development of advanced processes for mine water treatment to address the removal of redox sensitive elements. New cavitation technologies were applied towards the improvement of selenium removal rates, thereby reducing its uninhibited transport to trap selenium from mine waters. In this work, the fate and transport of mobilized selenium, which undergoes an advection-diffusion transport process, only retarded by chemical/biological reduction to immobile species or competitive adsorption to surfaces was examined for existing as well as new and upcoming technologies.
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