Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments
MetadataShow full item record
NOTICE: this is the author’s version of a work that was accepted for publication in Chemical Geology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Chemical Geology, Volume 229, Issue 4, 30 May 2006, Pages 344–361, http://dx.doi.org/10.1016/j.chemgeo.2005.11.006
Lead- and Pb-As-jarosites are minerals common to acidic, sulphate-rich environments, including weathering zones of sulphide ore deposits and acid rock or acid mine drainage (ARD/AMD) sites, and often form on or near galena. The structures of these jarosites are based on linear tetrahedral-octahedral-tetrahedral (T-O-T) sheets, comprised of slightly distorted FeO6 octahedra and SO4 2- (-AsO4 3- in Pb-As-jarosites) tetrahedra. To better understand the dissolution mechanisms and products of the break down of Pb- and Pb-As-jarosite, preliminary batch dissolution experiments were conducted on synthetic Pb- and Pb-As-jarosite at pH 2 and 20 C, to mimic environments affected by ARD/AMD, and at pH 8 and 20 C, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)2). All four dissolutions are incongruent. Dissolution of Pb-jarosite at pH 2 yields aqueous Pb, Fe and SO4 2-. The pH 8 Pb-jarosite dissolution yields aqueous Pb, SO4 2- and poorly crystalline Fe(OH)3, which does not appear to resorb Pb or SO4 2-, possibly due to the low solution pH (3.44-3.54) at the end of the experiment. The pH 2 and 8 dissolutions of Pb-As-jarosite result in the formation of secondary compounds (poorly crystalline PbSO4 for pH 2 dissolution; poorly crystalline PbSO4 and Fe(OH)3 for pH 8 dissolution), which may act as dissolution inhibitors after 250 to 300 h of dissolution. In the pH 2 dissolution, aqueous Fe, SO4 2- and AsO4 3- also form, and in the pH 8 dissolution, Fe(OH)3 precipitates then subsequently resorbs aqueous AsO4 3-. The dissolutions probably proceed by preferred dissolution of the A- and T-sites, which contain Pb, and SO4 2-and AsO4 3-, respectively, rather than Fe, which is sterically remote, within the T-O-T Pb- and Pb-As-jarosite structures.These data provide the foundation necessary for further, more detailed investigations into the dissolution of Pb- and Pb-As-jarosites.
Showing items related by title, author, creator and subject.
Dissolution of jarosite [KFe3(SO4)2(OH)6] at pH 2 and 8: Insights from batch experiments and computational modellingWright, Kathleen; Smith, A.; Hudson-Edwards, K.; Dubbin, W. (2006)Jarosite [KFe3(SO4)2(OH)6] is a mineral that is common in acidic, sulphate-rich environments, such as acid sulphate soils derived from pyrite-bearing sediments, weathering zones of sulphide ore deposits and acid mine or ...
Simultaneous Release of Fe and As during the Reductive Dissolution of Pb-As Jarosite by Shewanella putrefaciens CN32Smeaton, C.; Walshe, G.; Smith, A.; Hudson-Edwards, K.; Dubbin, W.; Wright, Kathleen; Beale, A.; Fryer, B.; Weisener, C. (2012)Jarosites are produced during metallurgical processing, on oxidized sulfide deposits, and in acid mine drainage environments. Despite the environmental relevance of jarosites, few studies have examined their biogeochemical ...
McGinnity, Justin (2001)Studies were conducted into the mechanism and kinetics of the dissolution of synthetic zinc sulfide and zinc concentrate in aqueous solutions containing sulfur dioxide.Experiments at ambient temperature established that ...