Research output: Contribution to journal › Article › peer-review
Complex hydrogen bonding and thermal behaviour over a wide temperature range of kainite KMg(SO4)Cl⋅2.75H2O. / Borisov, Artem S.; Siidra, Oleg I.; Ugolkov, Valery L.; Kuznetsov, Alexey N.; Firsova, Vera A.; Charkin, Dmitri O.; Platonova, Natalia V.; Pekov, Igor V.
In: Mineralogical Magazine, Vol. 86, No. 1, PII S0026461X21001018, 24.02.2022, p. 37-48.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Complex hydrogen bonding and thermal behaviour over a wide temperature range of kainite KMg(SO4)Cl⋅2.75H2O
AU - Borisov, Artem S.
AU - Siidra, Oleg I.
AU - Ugolkov, Valery L.
AU - Kuznetsov, Alexey N.
AU - Firsova, Vera A.
AU - Charkin, Dmitri O.
AU - Platonova, Natalia V.
AU - Pekov, Igor V.
N1 - Publisher Copyright: Copyright © The Author(s), 2022. Published by Cambridge University Press on behalf of The Mineralogical Society of Great Britain and Ireland.
PY - 2022/2/24
Y1 - 2022/2/24
N2 - Kainite, KMg(SO4)Cl⋅2.75H2O, is one of the most common hydrated sulfate minerals, and it plays an important role as a source of potassium. However, its properties and structure have, to date, been insufficiently studied. In our present work, kainite was investigated using multiple techniques, including single-crystal and powder X-ray diffraction, thermogravimetry, differential scanning calorimetry (DSC), and infrared spectroscopy (IR). The mineral is monoclinic, C2/m, a = 19.6742(2), b = 16.18240(10), c = 9.49140(10) Å, β = 94.8840(10)°, V = 3010.86(5) Å3 and Z = 16. The structure was refined to R1 = 0.0230 for 3080 unique observed reflections with |Fo| ≥ 4σF. The complex hydrogen bonding system for kainite is described for the first time. The structure of kainite contains seven symmetrically independent sites occupied by water molecules, six of which are strongly bonded to Mg2+ cations while the seventh resides in the framework cavities. The acceptors of the hydrogen bonds are either chloride anions, neighbouring water molecules or oxygens atoms of sulfate groups. A bifurcated hydrogen bond was described for one of the water molecules. Based on the analysis of the crystal structure, we have confirmed and propose the correct formula for kainite as KMg(SO4)Cl⋅2.75H2O. The thermal studies of kainite in the temperature range of -150°C to +600°C indicate its stability to 190°C. The decomposition products are K2Mg2(SO4)3, KCl and K2SO4. The thermal expansion was calculated, which for kainite has a character typical for monoclinic crystals and similar to the compressibility tensor described earlier.
AB - Kainite, KMg(SO4)Cl⋅2.75H2O, is one of the most common hydrated sulfate minerals, and it plays an important role as a source of potassium. However, its properties and structure have, to date, been insufficiently studied. In our present work, kainite was investigated using multiple techniques, including single-crystal and powder X-ray diffraction, thermogravimetry, differential scanning calorimetry (DSC), and infrared spectroscopy (IR). The mineral is monoclinic, C2/m, a = 19.6742(2), b = 16.18240(10), c = 9.49140(10) Å, β = 94.8840(10)°, V = 3010.86(5) Å3 and Z = 16. The structure was refined to R1 = 0.0230 for 3080 unique observed reflections with |Fo| ≥ 4σF. The complex hydrogen bonding system for kainite is described for the first time. The structure of kainite contains seven symmetrically independent sites occupied by water molecules, six of which are strongly bonded to Mg2+ cations while the seventh resides in the framework cavities. The acceptors of the hydrogen bonds are either chloride anions, neighbouring water molecules or oxygens atoms of sulfate groups. A bifurcated hydrogen bond was described for one of the water molecules. Based on the analysis of the crystal structure, we have confirmed and propose the correct formula for kainite as KMg(SO4)Cl⋅2.75H2O. The thermal studies of kainite in the temperature range of -150°C to +600°C indicate its stability to 190°C. The decomposition products are K2Mg2(SO4)3, KCl and K2SO4. The thermal expansion was calculated, which for kainite has a character typical for monoclinic crystals and similar to the compressibility tensor described earlier.
KW - bifurcated hydrogen bond
KW - hydrogen bonding
KW - kainite
KW - sulfates
KW - thermal expansion
KW - X-ray diffraction
KW - EVAPORITES
KW - ALKALI
KW - CRYSTAL-STRUCTURE
KW - EPR
KW - LENGTH DISTRIBUTIONS
KW - HYDROLYSIS
KW - IONS
KW - ELECTRON-PARAMAGNETIC-RESONANCE
KW - TOLBACHIK VOLCANO
KW - CHLORIDE
UR - http://www.scopus.com/inward/record.url?scp=85125520874&partnerID=8YFLogxK
U2 - 10.1180/mgm.2021.101
DO - 10.1180/mgm.2021.101
M3 - Article
AN - SCOPUS:85125520874
VL - 86
SP - 37
EP - 48
JO - Mineralogical Magazine
JF - Mineralogical Magazine
SN - 0026-461X
IS - 1
M1 - PII S0026461X21001018
ER -
ID: 94440642