Infrared and infrared emission spectroscopy of nesquehonite Mg(OH)(HCO3)·2H2O–implications for the formula of nesquehonite (original) (raw)
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Journal of Raman Spectroscopy, 2019
Nesquehonite synthesized by mixing MgCl 2 •6H 2 O and Na 2 CO 3 at T 25°C, was thermally treated at various temperatures (170°C, 200°C, 295°C, 350°C, and 390°C), based on thermal analysis study of raw nesquehonite. The mineral phases formed at each temperature were studied by means of Raman microspectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. After thermal treatment of raw nesquehonite above 295°C, its dominant Raman peak at 1,100 cm −1 , which corresponds to the v 1 CO 3 2− antisymmetric stretching vibrations, exhibits broadening and upshift of up to 10 cm −1 , whereas the Raman peaks at 707 cm −1 , at 770 cm −1 , at 1,425 cm −1 , and at 1,710 cm −1 disappear, and new Raman peaks arise at 1,282 cm −1 and at 1,386 cm −1. The latter have been attributed to the decomposition of HCO 3 − , in accordance with the Fourier transform infrared spectroscopy study. According to the differential thermal analysis study, water of crystallization is lost in two steps until 295°C; therefore, the phase studied above this temperature corresponds to Mg (HCO 3)(OH). The Raman peak at 3,550 cm −1 assigned to the existence of OH − , exhibits weakening after thermal treatment. Our results corroborate a Mg (HCO 3)OH•2H 2 O nesquehonite formula.
Journal of Raman Spectroscopy, 2008
Pure nesquehonite (MgCO 3 ·3H 2 O)/Mg(HCO 3 )(OH)·2H 2 O was synthesised and characterised by a combination of thermo-Raman spectroscopy and thermogravimetry with evolved gas analysis. Thermo-Raman spectroscopy shows an intense band at 1098 cm −1 , which shifts to 1105 cm −1 at 450°C, assigned to the n 1 CO 3 2− symmetric stretching mode. Two bands at 1419 and 1509 cm −1 assigned to the n 3 antisymmetric stretching mode shift to 1434 and 1504 cm −1 at 175°C. Two new peaks at 1385 and 1405 cm −1 observed at temperatures higher than 175°C are assigned to the antisymmetric stretching modes of the (HCO 3 ) − units. Throughout all the thermo-Raman spectra, a band at 3550 cm −1 is attributed to the stretching vibration of OH units. Raman bands at 3124, 3295 and 3423 cm −1 are assigned to water stretching vibrations. The intensity of these bands is lost by 175°C. The Raman spectra were in harmony with the thermal analysis data. This research has defined the thermal stability of one of the hydrous carbonates, namely nesquehonite. Thermo-Raman spectroscopy enables the thermal stability of the mineral nesquehonite to be defined, and, further, the changes in the formula of nesquehonite with temperature change can be defined. Indeed, Raman spectroscopy enables the formula of nesquehonite to be better defined as Mg(OH)(HCO 3 )·2H 2 O.
LOW TEMPERATURE SYNTHESIS AND CHARACTERISATION OF NESQUEHONITE
2003
Nesquehonite, Mg(HCO 3 )(OH).2H 2 O or MgCO 3 .3H 2 O, was named after its type locality in Nesquehoning, Pennsylvania, USA. The structure of nesquehonite can be envisaged as infinite chains of corner sharing MgO 6 octahedra along the b-axis. Within these chains CO 3 2groups link 3 MgO 6 octahedra by two common corners and one edge. This structural arrangement causes strong distortion of the octahedra. Chains are interconnected by hydrogen bonds only, whereby each Mg atom is coordinated to two water ligands and one free water molecule is located in between the chains [1, 2].
Journal of Mineralogical and Petrological Sciences, 2021
Neutron diffraction, Raman spectroscopy, and thermal analysis were performed to investigate the composition, structure, and formation conditions of the magnesium carbonate hydrate nesquehonite. The crystal structure of deuterated nesquehonite was analyzed by Rietveld refinement of the time-of-flight neutron powder diffraction pattern. The crystal structure possessed the monoclinic space group P2 1 /n with lattice parameters of a = 7.72100(12) Å, b = 5.37518(7) Å, c = 12.1430(3) Å, β = 90.165(4)°, and V = 503.956(13) Å 3. The refinement with a final crystal structure model of deuterated nesquehonite converged to wRp = 4.22% and Rp = 3.50%. The result of structure refinement showed that two deuterium atoms are coordinated to the O1, O2, and O6 atoms as a water molecule in the nesquehonite. The fact that the three water molecules were included in the structure suggests the structural formula of the nesquehonite obtained in the study should be written as MgCO 3 •3H 2 O not Mg(HCO 3)(OH)•2H 2 O.
American Mineralogist, 2016
A series of 1:1 silicate clays of the lizardite-nepouite series (Si 2 Mg 3-x Ni x O 5 (OH 4) with x = 0, 0.5, 1, 1.5, 2, 2.5, and 3) was synthesized at 220°C during 7 days from coprecipitated gels in hydrothermal conditions. A clear relationship was evidenced between the d(06-33) and the Ni/Mg ratio of the synthesized samples following a Vegard's law and suggested a rather random distribution of octahedral cations. For the first time, infrared spectra of this series were given in both near and mid infrared spectral regions (250-7500 cm-1). Notably, the bands due to the OH stretching vibrations and those of their first overtones in the lizardite-nepouite series were attributed. The combination bands observed in the near infrared region for both end-members could be attributed thanks to combinations of two or three mid infrared features. Some of the observed combination bands are clearly linked to combination of different vibrational groups. Infrared spectroscopy is simple to use and is a powerful tool to study the crystal-chemistry of garnierites. More broadly, the improvement of band attributions especially in near infrared contributes to develop the infrared analyses in field geology and remote sensing.
Infrared and infrared emission spectroscopy of the zinc carbonate mineral smithsonite
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2008
The mineral nesquehonite Mg(OH)(HCO 3 )·2H 2 O has been analysed by a combination of infrared (IR) and infrared emission spectroscopy (IES). Both techniques show OH vibrations, both stretching and deformation modes. IES proves the OH units are stable up to 450 • C. The strong IR band at 934 cm −1 is evidence for MgOH deformation modes supporting the concept of HCO 3 − units in the molecular structure. Infrared bands at 1027, 1052 and 1098 cm −1 are attributed to the symmetric stretching modes of HCO 3 − and CO 3 2− units. Infrared bands at 1419, 1439, 1511, and 1528 cm −1 are assigned to the antisymmetric stretching modes of CO 3 2− and HCO 3 − units. IES supported by thermoanalytical results defines the thermal stability of nesquehonite. IES defines the changes in the molecular structure of nesquehonite with temperature. The results of IR and IES supports the concept that the formula of nesquehonite is better defined as Mg(OH)(HCO 3 )·2H 2 O.
Bulletin of the Geological Society of Greece
Nesquehonite, a hydrous carbonate with promising uses such as building raw material and treatment of wastewaters, was synthesized under low pressure conditions by reaction of gaseous CO2 with Mg chloride solution and it was studied by means of X-Ray Diffraction, optical and scanning/transmission electron microscopy, and FTIR and Raman spectroscopic methods. Synthesized nesquehonite forms elongated fibers, exhibiting transparent to translucent diaphaneity and vitreous luster. It is characterized by high crystallinity. IR and Raman spectroscopy indicated the presence of OHand HCO3 - in the crystal structure of nesquehonite. The nesquehonite synthesis described herein constitutes a potential permanent storage of CO2 emissions.
Journal of Hazardous Materials, 2010
In order to gauge the appropriateness of CO 2 reaction with Mg chloride solutions as a process for storing carbon dioxide, the thermal behaviour and structural stability of its solid product, nesquehonite (MgCO 3 ·3H 2 O), were investigated in situ using real-time laboratory parallel-beam X-ray powder diffraction. The results suggest that the nesquehonite structure remains substantially unaffected up to 373 K, with the exception of a markedly anisotropic thermal expansion acting mainly along the c axis. In the 371-390 K range, the loss of one water molecule results in the nucleation of a phase of probable composition MgCO 3 ·2H 2 O, which is characterized by significant structural disorder. At higher temperatures (423-483 K), both magnesite and MgO·2MgCO 3 coexist. Finally, at 603 K, periclase nucleation starts and the disappearance of carbonate phases is completed at 683 K. Consequently, the structural stability of nesquehonite at high temperatures suggests that it will remain stable under the temperature conditions that prevail at the Earth's surface. These results will help (a) to set constraints on the temperature conditions under which nesquehonite may be safely stored and (b) to develop CO 2 sequestration via the synthesis of nesquehonite for industrial application.