TY - JOUR
T1 - Speciation of iron and sulfate in acid waters
T2 - Aqueous clusters to mineral precipitates
AU - Majzlan, Juraj
AU - Myneni, Satish Chandra Babu
PY - 2005/1/1
Y1 - 2005/1/1
N2 - Acid mine drainage (AMD) contaminates surface water bodies, groundwater, soils, and sediments at innumerable locations around the world. AMD usually originates by weathering of pyrite (FeS2) and is rich in Fe and sulfate. In this study, we investigated speciation of FeII, Fe III, and SO4 in acid waters by Fourier transform infrared and X-ray absorption spectroscopy. The molalities of sulfate (15 mmol/kg) and iron (10, 20, and 50 mmol/kg), and pH (1, 2, and 3) were chosen to mimic the concentration of ions in AMD waters. Sulfate and FeII either associate in outer-sphere complexes or do not associate at all. In contrast, sulfate interacts strongly with FeIII. The predominating species in FeIII-SO4 solutions are hydrogen-bonded complexes; innersphere complexes account only for 10 ± 10% of the total sulfate. Our results show that the mode of interaction between FeIII and sulfate is similar in aqueous phase and in nanocrystalline precipitate schwertmannite (~FeO(OH)3/4(SO4)1/8). Because of this similarity, schwertmannite should be the phase that controls solubility and availability of FeIII, SO4, and indirectly also other components in the AMD solutions.
AB - Acid mine drainage (AMD) contaminates surface water bodies, groundwater, soils, and sediments at innumerable locations around the world. AMD usually originates by weathering of pyrite (FeS2) and is rich in Fe and sulfate. In this study, we investigated speciation of FeII, Fe III, and SO4 in acid waters by Fourier transform infrared and X-ray absorption spectroscopy. The molalities of sulfate (15 mmol/kg) and iron (10, 20, and 50 mmol/kg), and pH (1, 2, and 3) were chosen to mimic the concentration of ions in AMD waters. Sulfate and FeII either associate in outer-sphere complexes or do not associate at all. In contrast, sulfate interacts strongly with FeIII. The predominating species in FeIII-SO4 solutions are hydrogen-bonded complexes; innersphere complexes account only for 10 ± 10% of the total sulfate. Our results show that the mode of interaction between FeIII and sulfate is similar in aqueous phase and in nanocrystalline precipitate schwertmannite (~FeO(OH)3/4(SO4)1/8). Because of this similarity, schwertmannite should be the phase that controls solubility and availability of FeIII, SO4, and indirectly also other components in the AMD solutions.
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U2 - 10.1021/es049664p
DO - 10.1021/es049664p
M3 - Article
C2 - 15667094
AN - SCOPUS:11244347113
SN - 0013-936X
VL - 39
SP - 188
EP - 194
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 1
ER -