Low-temperature heat capacity of pentlandite

Berezovskii, G. A.; Drebushchak, V. A.; Кравченко, Т. А.

doi:10.2138/am-2001-1020

Cited by 9 publications

(9 citation statements)

References 4 publications

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“…(2)). The thermodynamic data for millerite are from Wagman et al (1982), and for pentlandite were estimated using the standard entropy and heat capacity from Berezovskii et al (2001) and the standard Gibbs free energy of formation from Klein and Bach (2009). Equilibrium constants for reactions describing the dissolution of millerite and pentlandite are compiled in Table A5.…”

Section: Geological Implicationsmentioning

confidence: 99%

The stability of aqueous nickel(II) chloride complexes in hydrothermal solutions: Results of UV–Visible spectroscopic experiments

Liu

Migdisov

Williams‐Jones

2012

Geochimica et Cosmochimica Acta

124

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Section: Geological Implicationsmentioning

confidence: 99%

The stability of aqueous nickel(II) chloride complexes in hydrothermal solutions: Results of UV–Visible spectroscopic experiments

Liu

Migdisov

Williams‐Jones

2012

Geochimica et Cosmochimica Acta

124

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“…Consequently, these data must be considered preliminary. Berezovskii et al (2001) conducted low-temperature heat capacity measurements for synthetic pentlandite (Fe 4Á60 Ni 4Á54 S 8 ) and reported a standard entropy (S8) of 474Á9 J/mol per K and H 298Á15 À H 0 of 762Á80 kJ/mol. Using these data, we calculated a standard enthalpy of formation (iH8 f ) of À847Á0 kJ/mol for stoichiometric pentlandite (Fe 4Á5 Ni 4Á5 S 8 ), using standard enthalpies of formation for troilite (FeS) and millerite (NiS) from Robie & Hemingway (1995).…”

Section: Thermodynamic Calculationsmentioning

confidence: 99%

Fe-Ni-Co-O-S Phase Relations in Peridotite-Seawater Interactions

Klein

Bach

2009

Journal of Petrology

224

160

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Serpentinization of abyssal peridotites is known to produce extremely reducing conditions as a result of dihydrogen (H 2 ,aq) release upon oxidation of ferrous iron in primary phases to ferric iron in secondary minerals by H 2 O. We have compiled and evaluated thermodynamic data for Fe^Ni^Co^O^S phases and computed phase relations in fO 2 ,g^fS 2 ,g and aH 2 ,aq^aH 2 S,aq diagrams for temperatures between 150 and 4008C at 50 MPa. We use the relations and compositions of Fe^Ni^Co^O^S phases to trace changes in oxygen and sulfur fugacities during progressive serpentinization and steatitization of peridotites from the Mid-Atlantic Ridge in the 15820 0 N Fracture Zone area (Ocean Drilling Program Leg 209). Petrographic observations suggest a systematic change from awar-uite^magnetite^pentlandite and heazlewoodite^magnetite^pentlandite assemblages forming in the early stages of serpentinization to millerite^pyrite^polydymite-dominated assemblages in steatized rocks. Awaruite is observed in all brucite-bearing partly serpentinized rocks. Apparently, buffering of silica activities to low values by the presence of brucite facilitates the formation of large amounts of hydrogen, which leads to the formation of awaruite. Associated with the prominent desulfurization of pentlandite, sulfide is removed from the rock during the initial stage of serpentinization. In contrast, steatitization indicates increased silica activities and that highsulfur-fugacity sulfides, such as polydymite and pyrite^vaesite solid solution, form as the reducing capacity of the peridotite is exhausted and H 2 activities drop. Under these conditions, sulfides will not desulfurize but precipitate and the sulfur content of the rock increases. The co-evolution of fO 2 ,g^fS 2 ,g in the system follows an isopotential of H 2 S,aq, indicating that H 2 S in vent fluids is buffered. In contrast, H 2 in vent fluids is not buffered by Fe^Ni^Co^O^S phases, which merely monitor the evolution of H 2 activities in the fluids in the course of progressive rock alteration.The co-occurrence of pentlan-dite^awaruite^magnetite indicates H 2 ,aq activities in the interacting fluids near the stability limit of water. The presence of a hydrogen gas phase would add to the catalyzing capacity of awaruite and would facilitate the abiotic formation of organic compounds.

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“…Therefore, pentlandite's free energy of formation (−813 kJ/mol, at 25°C) proposed by Warner et al (1996), along with its standard enthalpy of formation (−837.37 kJ/mol, at 25°C) (Waldner and Sitte, 2008), were used to estimate the entropy of formation for nickel sulfide. Afterwards, using these values, both the enthalpy and entropy of formation were determined at 50°C with the help of the Cp data proposed by Berezovskii et al (2001), and fitted to the following equation:…”

Section: Leaching Thermodynamicsmentioning

confidence: 99%

“…It must be stressed that the Berezovskii et al (2001) data only covered the 6-34°C range and that the Cp equation was then assumed to be valid up to 50°C, i.e., Eq. (1) was extended to that temperature.…”

Section: Leaching Thermodynamicsmentioning

confidence: 99%

High-temperature bioleaching of nickel sulfides: thermodynamic and kinetic implications

et al. 2010

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a b s t r a c tThe effect of temperature on nickel sulfide bioleaching was studied in the presence of mesophile (Acidithiobacillus ferrooxidans) and moderate thermophile (Sulfobacillus thermosulfidooxidans) strains and the results were discussed in terms of sulfide dissolution thermodynamics (Eh-pH diagrams) and kinetics (cyclic voltammetry). It was observed that in the pH range 1.8-2.0 the highest nickel dissolution was achieved which reached 50% for mesophiles and over 80% for moderate thermophiles. External ferrous iron addition had no effect on the metal dissolution at 34°C, but adversely affected nickel leaching at higher temperatures. The best outcomes were accomplished with low FeSO 4 additions (2.5 g/L) at 50°C. Pyrrhotite dissolution avoided the need for external iron addition, providing Fe 2+ concentrations as high as 7 g/L during bioleaching, which supports bacterial growth. Eh-pH diagrams for pentlandite and pyrrhotite show a negligible effect of temperature on the stability field of each sulfide whilst cyclic voltammetry indicated that temperature has the strongest influence on pyrrhotite oxidation. The latter along with a rapid increase in solution potential (Eh) explains the higher and faster extraction observed with S. thermosulfidooxidans.

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Low-temperature heat capacity of pentlandite

Cited by 9 publications

References 4 publications

The stability of aqueous nickel(II) chloride complexes in hydrothermal solutions: Results of UV–Visible spectroscopic experiments

The stability of aqueous nickel(II) chloride complexes in hydrothermal solutions: Results of UV–Visible spectroscopic experiments

Fe-Ni-Co-O-S Phase Relations in Peridotite-Seawater Interactions

High-temperature bioleaching of nickel sulfides: thermodynamic and kinetic implications

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