Abstract
We report in this paper a new crystal-chemical study of synthetic basic ferric sulfate FeOHSO4. The structure solution performed by the Endeavour program, from new X-ray powder diffraction (XRPD) data, indicated that the correct space group of the monoclinic polytype of FeOHSO4 is C2/c. Selected Area Electron Diffraction (SAED) patterns are also consistent with this structure solution. The arrangement of Fe and S atoms, based on linear chains of Fe3+ octahedra cross-linked by SO4 tetrahedra, corresponds to that of the order/disorder (OD) family. The positions of the hydrogen atoms were located based on DFT calculations. IR and Raman spectra are presented and discussed according to this new structure model. The decomposition of FeOHSO4 during heating was further investigated by means of variable temperature XRPD, thermogravimetry, and differential thermal analysis as well as IR and Raman spectroscopies.
Highlights
The basic iron hydroxyl sulfate, FeOHSO4, has attracted in the last decades significant attention in many research fields such as environmental science, catalysis, electrochemistry, mineralogy, and soil science (Cheng and Demopoulos 2004; Fleming 2010; Xu et al 2010; Reddy et al 2009)
Paktunc et al (2013) indicated that a residue from pressure oxidation (POX) hydrothermal gold extraction was in the form of an iron hydroxy sulfate with a 5.42 wt % AsO4 content, and proposed it precipitated in a triclinic (I1) space group based on Transmission Electron Microscopy (TEM)-Selected Area Electron Diffraction (SAED) investigation
We investigate the decomposition of F eOHSO4 during thermal treatment using a combination of in situ techniques
Summary
The basic iron hydroxyl sulfate, FeOHSO4, has attracted in the last decades significant attention in many research fields such as environmental science, catalysis, electrochemistry, mineralogy, and soil science (Cheng and Demopoulos 2004; Fleming 2010; Xu et al 2010; Reddy et al 2009). Paktunc et al (2013) indicated that a residue from POX hydrothermal gold extraction was in the form of an iron hydroxy sulfate with a 5.42 wt % AsO4 content, and proposed it precipitated in a triclinic (I1) space group based on TEM-SAED investigation. It is worth noting that Transmission Electron Microscopy (TEM) may be used for sub-micron-sized samples to obtain an approximate structure model (e.g., Li and Sun 2017). If a sufficient amount of sample is available, structure refinement is better suited via powder X-ray diffraction because of the detrimental effects of dynamical scattering on electron diffraction intensities (e.g., Gemmi et al 2010). Good results have been obtained applying dynamical theory to electron diffraction structure refinement (e.g., Palatinus et al 2017)
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