Low temperature synthesis and characterisation of lecontite, (NH4)Na(SO4)·2H20

Abstract

Lecontite, (NH 4 )Na(SO 4 ).2H 2 O, was synthesised at room temperature in high purity compared to earlier work with a minor impurity of mascagnite, (NH 4 ) 2 SO 4 . Rietveld refinement of the XRD results confirmed the crystal structure and unit cell dimensions as published earlier. Raman and Infrared spectroscopy, in conjunction with factor group analysis, resulted in a complex pattern of overlapping sulphate, NH and OH modes. The NH modes υ 1 was observed around 2880 cm -1 , υ 2 around 1700 cmoverlapping with water OH-bending modes, υ 3 around 3300 cm -1 overlapping with water OH-stretching modes around 3023, 3185 and 3422 cm -1 , and υ 4 around 1432, 1447 and 1462 cm -1 . The sulphate group in the crystal structure displays a decrease in symmetry from T d as evidenced by the activation of the ν 1 mode at 982 cm -1 and the ν 2 mode around 452 cm -1 in the Infrared spectrum. The υ 3 mode shows clear splitting in the infrared spectra with a strong band at 1064 cm -1 accompanied by two shoulders at 1107 and 1139 cm -1 . The Raman spectra show three weak bands at 1068, 1109 and 1135 cm -1 with a shoulder at 1155 cm -1 . Similar splitting was observed for the υ 4 mode around 611 and 632 cm -1 in the Infrared and Raman spectra, respectively.

Mineralogical and Spectroscopic Study of Nesquehonite Synthesized by Reaction of Gaseous Co2 With Mg Chloride Solution

“…9) is ascribed to the antisymmetric stretching of the HCO3 - (Hales et al, 2008;Frost and Palmer, 2011). Nesquehonite has a chemical composition of MgCO3*3H2O (Kloprogge et al, 2003;Dong et al, 2009;Stephan and McGillavry, 1972), but has been described also as Mg(OH)(HCO3)*2H2O (Hales et al, 2008;Hales et al, 2008;Frost and Palmer, 2011). Our IR and Raman results showed the presence of OH -and HCO3 -in the crystal structure of nesquehonite.…”

“…8) showed the symmetric stretching (v1) and the bending (v2) modes of CO3 2-at 1097.94 cm -1 and at 853.61 cm -1 , respectively. The three bands at 1520, 1466.06, 1420.06 cm -1 are ascribed to the split v3 antisymmetric stretching mode (Kloprogge et al, 2003;Coleyshaw et al, 2003;Morgan et al, 2015).The stretching of the O-H and the H2O molecule gives rise to broad bands in the region between 2500-4000 cm -1 (Ferrini et al, 2008;Kloprogge et al, 2003). The bands at 3326.33, 3455.14, 3564.25 cm -1 can be ascribed to OH-stretching modes of water in the crystal structure of the nesquehonite (Hopkinson et al, 2012;Hopkinson et al, 2008).…”

“…Nesquehonite is a magnesium carbonate mineral with proposed chemical formula either MgCO3*3H2O (Kloprogge et al, 2003;Dong et al, 2009;Stephan and McGillavry, 1972) or Mg(OH)(HCO3)*2H2O (Hales et al, 2008;Hales et al, 2008;Frost and Palmer, 2011), named after a location in Pennsylvania, USA, where found for first time. It is crystallized in the monoclinic crystal structure in space group P21/n, Z = 4 and it has unit cell parameters of a = 7.70Å, b = 5.37Å, c = 12.12 Å and β= 90 o , 45ˊas described by Stephan and MacGillavry (1972) and by Giester et al (2000).…”

Thermo‐Raman spectroscopy of synthetic nesquehonite — implication for the geosequestration of greenhouse gases

“…Synthetic nesquehonite used in this thermal stability study was synthesised by a wet chemical precipitation method similar to that published by Kloprogge et al 46 . Other synthesis methods have been used 47 -50 but are similar.…”

“…The literature contains a number of methods for the synthesis of pure nesquehonite. 5,46,50,51 Various authors 5,50,52 -53 have discussed the effects of temperature and partial pressure of carbon dioxide (pCO 2 ) on the stability of the synthetic nesquehonite.…”