TY - JOUR

T1 - Thermal behavior of ferric selenite hydrates (Fe 2(SeO 3) 3·3H 2O, Fe 2(SeO 3) 3·5H 2O) and the water content in the natural ferric selenite mandarinoite

AU - Holzheid , Astrid

AU - Charykova, Marina V.

AU - Krivovichev, Vladimir G.

AU - Ledwig , Brenan

AU - Fokina, Elena L.

AU - Poroshina, Ksenia L.

AU - Platonova, Natalia V.

AU - Gurzhiy, Vladislav V.

N1 - Holzheid A., Charykova M.V., Krivovichev V.G., Ledwig B., Fokina E.L., Poroshina K.L., Platonova N.V., Gurzhiy V.V. Thermal behavior of ferric selenite hydrates (Fe2(SeO3)3•3H2O, Fe2(SeO3)3•5H2O) and the water content in the natural ferric selenite mandarinoite. Chemie der Erde. 2018. Vol. 78(2). P. 228-240.

PY - 2018/5/1

Y1 - 2018/5/1

N2 - Any progress in our understanding of low-temperature mineral assemblages and of quantitative physico-chemical modeling of stability conditions of mineral phases, especially those containing toxic elements like selenium, strongly depends on the knowledge of structural and thermodynamic properties of coexisting mineral phases. Interrelation of crystal chemistry/structure and thermodynamic properties of selenium-containing minerals is not systematically studied so far and thus any essential generalization might be difficult, inaccurate or even impossible and erroneous. Disagreement even exists regarding the crystal chemistry of some natural and synthetic selenium-containing phases. Hence, a systematic study was performed by synthesizing ferric selenite hydrates and subsequent thermal analysis to examine the thermal stability of synthetic analogues of the natural hydrous ferric selenite mandarinoite and its dehydration and dissociation to unravel controversial issues regarding the crystal chemistry. Dehydration of synthesized analogues of mandarinoite starts at 56–87 °C and ends at 226–237 °C. The dehydration happens in two stages and two possible schemes of dehydration exist: (a) mandarinoite loses three molecules of water in the first stage of the dehydration (up to 180 °C) and the remaining two molecules of water will be lost in the second stage (>180 °C) or (b) four molecules of water will be lost in the first stage up to 180 °C and the last molecule of water will be lost at a temperature above 180 °C. Based on XRD measurements and thermal analyses we were able to deduce Fe 2(SeO 3) 3·(6-x)H 2O (x = 0.0–1.0) as formula of the hydrous ferric selenite mandarinoite. The total amount of water apparently affects the crystallinity, and possibly the stability of crystals: the less the x value, the higher crystallinity could be expected.

AB - Any progress in our understanding of low-temperature mineral assemblages and of quantitative physico-chemical modeling of stability conditions of mineral phases, especially those containing toxic elements like selenium, strongly depends on the knowledge of structural and thermodynamic properties of coexisting mineral phases. Interrelation of crystal chemistry/structure and thermodynamic properties of selenium-containing minerals is not systematically studied so far and thus any essential generalization might be difficult, inaccurate or even impossible and erroneous. Disagreement even exists regarding the crystal chemistry of some natural and synthetic selenium-containing phases. Hence, a systematic study was performed by synthesizing ferric selenite hydrates and subsequent thermal analysis to examine the thermal stability of synthetic analogues of the natural hydrous ferric selenite mandarinoite and its dehydration and dissociation to unravel controversial issues regarding the crystal chemistry. Dehydration of synthesized analogues of mandarinoite starts at 56–87 °C and ends at 226–237 °C. The dehydration happens in two stages and two possible schemes of dehydration exist: (a) mandarinoite loses three molecules of water in the first stage of the dehydration (up to 180 °C) and the remaining two molecules of water will be lost in the second stage (>180 °C) or (b) four molecules of water will be lost in the first stage up to 180 °C and the last molecule of water will be lost at a temperature above 180 °C. Based on XRD measurements and thermal analyses we were able to deduce Fe 2(SeO 3) 3·(6-x)H 2O (x = 0.0–1.0) as formula of the hydrous ferric selenite mandarinoite. The total amount of water apparently affects the crystallinity, and possibly the stability of crystals: the less the x value, the higher crystallinity could be expected.

KW - Differential scanning calorimetry

KW - Ferric selenite hydrates

KW - Mandarinoite

KW - Selenites

KW - Thermogravimetry

KW - SULFATES

KW - ARSENATES

KW - CRYSTAL-STRUCTURE

KW - STABILITY

KW - SULFIDE ORES

KW - FEATURES

KW - Therrnogravimetry

KW - THERMODYNAMICS

KW - DEHYDRATION

KW - OXIDATION ZONE

UR - http://www.scopus.com/inward/record.url?scp=85041622310&partnerID=8YFLogxK

UR - http://www.mendeley.com/research/thermal-behavior-ferric-selenite-hydrates-fe2seo333h2o-fe2seo335h2o-water-content-natural-ferric-sel

U2 - 10.1016/j.chemer.2018.01.002

DO - 10.1016/j.chemer.2018.01.002

M3 - Article

VL - 78

SP - 228

EP - 240

JO - Geochemistry

JF - Geochemistry

SN - 0009-2819

IS - 2

ER -