Schwertmannite precipitated from acid mine drainage: phase transformation, sulphate release and surface properties

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title = "Schwertmannite precipitated from acid mine drainage: phase transformation, sulphate release and surface properties",
abstract = "Schwertmannite precipitated from acid mine drainage at the Kristineberg Zn-Cu mine in northern Sweden has been characterised regarding elemental composition, phase transformation as a function of pH and time. SO42- release and speciation of SO42- associated with the solid. The elemental analysis gave the composition FeSOS(OH)(5.02)(-SO4)(1.49) . 0.5H(2)O where approximately 1/3 of the SO42- is adsorbed to the surface. The conversion of schwertmannite to goethite at pH 9 was complete within 187 days; at pH 6. the conversion was still incomplete after 514 days. Lower pH and relatively high SO42- concentration decreased the conversion even further. Also temperature was shown to be an important parameter for this process and low temperature (+4 degreesC) effectively stopped the transformation at pH 3. The release of SO42- was linear with pH and X-ray photoelectron spectroscopy measurements confirming that the surface bound SO42- was released before bulk SO42-. Zeta potential measurements indicate a pH(IEP) of 7.2 for the schwertmannite sample. Prior to conversion into goethite, the SO42- associated with schwertmannite was indicated by attenuated total reflectance FTIR spectroscopy to be present both as bulk and surface species. Furthermore: the speciation of surface SO42- was shown to vary with pH and two predominating species were detected. As pH increases. SO42- is increasingly Coordinated in an outer sphere mode whereas a stronger. possibly inner sphere, complex dominates. at low pH. (C) 2004 Elsevier Ltd. All rights reserved.",
author = "J. Jonsson and Per Persson and S. Sjoberg and L. Lovgren",
note = "1",
year = "2005",
doi = "10.1016/j.apgeochem.2004.04.008",
language = "English",
volume = "20",
pages = "179--191",
journal = "Applied Geochemistry",
issn = "0883-2927",
publisher = "Elsevier",