TY - JOUR
T1 - Synthesis, characterization and thermochemistry of synthetic Pb-As, Pb-Cu and Pb-Zn jarosites
AU - Forray, Ferenc Lázár
AU - Smith, A. M.L.
AU - Navrotsky, A.
AU - Wright, K.
AU - Hudson-Edwards, K. A.
AU - Dubbin, W. E.
N1 - Funding Information:
This work was funded through U.S. Department of Energy (Grant DEFG02-97ER14749) to A. Navrotsky and through the UK Engineering and Physical Sciences Research Council (EPSRC) studentship award (No. 309778) to A.M.L. Smith. We thank A.S. Wills for the GSAS refinement of the original synthetic plumbojarosite, C. Jones and A. Ball for help with SEM analysis and photography, G. Jones and V. Din for assistance with geochemical analysis, and I. Wood for expert help with the XRD analysis.
PY - 2014/2/15
Y1 - 2014/2/15
N2 - 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.
AB - 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.
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U2 - 10.1016/j.gca.2013.10.043
DO - 10.1016/j.gca.2013.10.043
M3 - Article
AN - SCOPUS:84891356930
SN - 0016-7037
VL - 127
SP - 107
EP - 119
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -