2012
Crystal structure, thermodynamic properties, and paragenesis of bukovskyite, Fe-2(AsO4)(SO4)(OH)center dot 9H(2)O
MAJZLAN, Juraj; Biljana LAZIC; Thomas ARMBRUSTER; Michel B JOHNSON; Mary Anne WHITE et al.Základní údaje
Originální název
Crystal structure, thermodynamic properties, and paragenesis of bukovskyite, Fe-2(AsO4)(SO4)(OH)center dot 9H(2)O
Autoři
MAJZLAN, Juraj; Biljana LAZIC; Thomas ARMBRUSTER; Michel B JOHNSON; Mary Anne WHITE; Robert Allan FISHER; Jakub PLÁŠIL; Jan LOUN; Radek ŠKODA a Milan NOVÁK
Vydání
JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES, SENDAI, JAPAN ASSOC MINERALOGICAL SCIENCES, 2012, 1345-6296
Další údaje
Jazyk
angličtina
Typ výsledku
Článek v odborném periodiku
Obor
10500 1.5. Earth and related environmental sciences
Stát vydavatele
Japonsko
Utajení
není předmětem státního či obchodního tajemství
Impakt faktor
Impact factor: 0.589
Označené pro přenos do RIV
Ano
Kód RIV
RIV/00216224:14310/12:00064415
Organizační jednotka
Přírodovědecká fakulta
UT WoS
Klíčová slova anglicky
Bukovskyite; Crystal structure; Thermodynamics; Paragenesis
Změněno: 9. 4. 2013 18:34, Ing. Andrea Mikešková
Anotace
V originále
Bukovskyite is a relatively rare secondary ferric arsenate-sulfate. At the type locality near the municipality of Kutna Hora (Czech Republic), it is the main secondary mineral in the medieval dumps, where it occurs in enormous amounts and forms nodules of prodigious dimensions. We investigated the mineral bukovskyite and the type locality in detail to understand the abundance of the mineral at this locality. The crystal structure of bukovskyite was solved for bukovskyite crystals from Grossvoigtsberg (Germany) and found to be of the space group P (I) over bar with a final R factor of 5.08% from 2403 reflections. The lattice parameters at room temperature are a = 7.549(1) angstrom, b = 10.305(1) angstrom, c = 10.914(2) angstrom, alpha = 115.136(3)degrees, beta = 99.798(3)degrees, and gamma = 92.864(3)degrees. The structure consists of octahedral-tetrahedral Fe-arsenate chains. Sulfate tetrahedra are bonded to the chains and free H2O molecules via a complicated network of hydrogen bonds. Calorimetric measurements (acid-solution calorimetry at T = 298.15 K and relaxation calorimetry yielded heat capacities from T = 0.4 K to 300 K) gave an enthalpy of formation of -4742.4 +/- 3.8 kJ.mol(-1) and standard entropy of 615.2 +/- 6.9 J.mol(-l).K-1. A combination of these values gives a Gibbs free energy of formation of -3968.9 +/- 4.3 kJ.mol(-1) and aqueous solubility product (log K) of -30.627. Bukovskyite is metastable with respect to scorodite; if scorodite is not considered in the thermodynamic calculations, a stability field of bukovskyite appears at low pH and high sulfate and arsenate activity. Field observations showed that bukovskyite occurs in dumps where the space between the rock fragments is filled by clays. Bukovskyite crystallizes from Fe-As-S-rich gels that replace Si-Al gels. The exact mechanisms that control the entire process are not clear but will be the subject of further studies.
Návaznosti
| MSM0021622412, záměr |
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| MUNI/A/1060/2009, interní kód MU |
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