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

Ferenc Lázár Forray, A. M.L. Smith, A. Navrotsky, K. Wright, K. A. Hudson-Edwards, W. E. Dubbin

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

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±8.6kJ/mol, δH°f=-3653.6±8.2kJ/mol, and δH°f=-3669.4±8.4kJ/mol, respectively. Using estimated entropies, the standard Gibbs free energy of formation from elements at 298K δG°f of the three compounds were calculated to be -3164.8±9.1, -3131.4±8.7, and -3153.6±8.9kJ/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.

Original languageEnglish (US)
Pages (from-to)107-119
Number of pages13
JournalGeochimica et Cosmochimica Acta
Volume127
DOIs
StatePublished - Feb 15 2014
Externally publishedYes

ASJC Scopus subject areas

  • Geochemistry and Petrology

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