Mineralogical characterization of arsenic in uranium mine tailings precipitated from iron-rich hydrometallurgical solutions.
Arsenic-rich uranium mine tailings from the Rabbit Lake in-pit tailings management facility (RLITMF) in northern Saskatchewan, Canada, were investigated to determine the mineralogy and long-term stability of secondary arsenic precipitates formed from iron-rich hydrometallurgical solutions. Total arsenic and iron concentrations in six iron-rich samples of the mine tailings ranged from 56 to 6,000 microg/g and from 12 600 to 30 200 microg/g, respectively (Fe/As molar ratios of 5.3-303). On the basis of stability field diagrams generated from pH, Eh, and temperature measurements on tailings samples (mean values of 9.79, +162 mV, and 2.8 degrees C, respectively), it was concluded that arsenic and iron in the tailings were stable as As5+ and Fe3+. Synchrotron-based X-ray absorption spectroscopic studies of tailings samples, fresh mill precipitates, and reference compounds showed that the arsenic in iron-rich areas of the tailings existed as the stable As5+ and was adsorbed to 2-line ferrihydrite through inner-sphere bidentate linkages. Furthermore, under the conditions in the RLITMF, the 2-line ferrihydrite did not undergo any measurable conversion to more crystalline goethite or hematite, even in tailings discharged to the RLITMF 10 yr prior to sampling.
Moldovan
Brett J
BJ
Cameco Corporation, 2121 11th Street West, Saskatoon, Saskatchewan, Canada S7M 1J3.
Jiang
D T
DT
Hendry
M Jim
MJ
D001151:Arsenic / Q000737:chemistry*; D001682:Biological Availability; D011232:Chemical Precipitation; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D008906:Mining; D013057:Spectrum Analysis; D014865:Waste Disposal, Fluid; D014867:Water / Q000737:chemistry
D014867:Water; D007501:Iron; D001151:Arsenic