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    Synthesis, characterization and thermochemistry of synthetic Pb–As, Pb–Cu and Pb–Zn jarosites

    Forray, F.L. and Smith, A.M.L. and Navrotsky, A. and Wright, K. and Hudson-Edwards, Karen A. and Dubbin, W.E. (2014) Synthesis, characterization and thermochemistry of synthetic Pb–As, Pb–Cu and Pb–Zn jarosites. Geochimica et Cosmochimica Acta 127 , pp. 107-119. ISSN 0016-7037.

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    Abstract

    The enthalpy of formation from the elements of well characterized Pb-As, Pb-Cu, and Pb-Zn synthetic jarosites, corresponding to chemical formulas (H3O)0.68±0.03Pb0.32±0.002Fe2.86±0.14(SO4)1.69±0.08(AsO4)0.31±0.02(OH)5.59±0.28(H2O)0.41±0.02, (H3O)0.67±0.03Pb0.33±0.02Fe2.71±0.14Cu0.25±0.01(SO4)2±0.00(OH)5.96±0.30(H2O)0.04±0.002 and (H3O)0.57±0.03Pb0.43±0.02Fe2.70±0.14Zn0.21±0.01(SO4)2±0.00(OH)5.95±0.30(H2O)0.05±0.002, was measured by high temperature oxide melt solution calorimetry and gave ΔH°f = -3691.2 ± 8.6 kJ/mol, ΔH°f = -3653.6 ± 8.2 kJ/mol, and ΔH°f = -3669.4 ± 8.4 kJ/mol, respectively. Using estimated entropies, the standard Gibbs free energy of formation from elements at 298 K ΔG°f of the three compounds were calculated to be -3164.8 ± 9.1 kJ/mol, -3131.4 ± 8.7 kJ/mol, and -3153.6 ± 8.9 kJ/mol, respectively. Based on these free energies, their logKsp values are -13.94 ± 1.89, -4.38 ± 1.81 and -3.75 ± 1.80, respectively. For this compounds, a log10{Pb2+} - pH diagram is presented. The diagram shows that the formation of Pb-As jarosite may decrease aqueous arsenic and lead concentrations to meet drinking water standards. The new thermodynamic data confirm that transformation of Pb-As jarosite to plumbojarosite is thermodynamically possible.

    Metadata

    Item Type: Article
    Additional Information: “NOTICE: this is the author’s version of a work that was accepted for publication in Geochimica et Cosmochimica Acta. 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 Geochimica et Cosmochimica Acta, vol. 127, Feb 2014, DOI:10.1016/j.gca.2013.10.043
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: Karen Hudson Edwards
    Date Deposited: 16 Jan 2014 09:01
    Last Modified: 11 Apr 2014 11:31
    URI: http://eprints.bbk.ac.uk/id/eprint/8978

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