High-temperature study of basic ferric sulfate, FeOHSO4

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.

In Situ High-Temperature X-ray Powder Diffraction and Infrared Spectroscopic Study of Melanterite, FeSO4·7H2O

“…Similar results were obtained by combining X-ray diffraction and infrared analyses in Safiullin et al [22]. FeOHSO 4 was also observed after X-ray refinement of a synthetic FeSO 4 •7H 2 O sample heated at 300 • C for 24 h [23] and at 280 • C for 7 days [24].…”

“…The three-step dehydration process entails the formation of FeOHSO 4 as also observed in synthetic samples [21,23,24]. However, our structural analysis provides further details on the stability of the FeOHSO 4 phase, which in fact resulted to be the predominant product of the entire decomposition process, as it was refined in the patterns collected from 100 to 475 • C (Figure 7).…”

“…Rietveld refinements were carried out for all collected patterns, providing agreement factors in the range 1.57 ≤ R (%) ≤ 2.75 and 1.98 ≤ R wp (%) ≤ 3.74. The crystal structure data for the phases present in the high temperature patterns were taken from: Wildner and Giester [32] for szomolnokite; Ventruti et al [24] for FeOHSO 4 ; Miura et al [33] for the mikasaite and Blake et al [34] for hematite.…”

“…In particular, we provide quantitative phase analysis based on Rietveld refinements, thus contributing to detail the full decomposition process. This work is part of an ongoing research activity focused to the advance in the knowledge on the thermal stability of natural iron-bearing hydrous sulfates of our group [24,26].…”

Dissolution, Solubility, and Stability of the Basic Ferric Sulfate-Arsenates [Fe(SO4)x(AsO4)y(OH)z·nH2O] at 25–45°C and pH 2–10

“…Even though the XRD measurement indicated that no other phases than the basic ferric sulfate-arsenates existed, their presence in a small amount under the detection limit could not be excluded (Figure 1). e FeSAsOH structure is constructed from layered Fe-O 6 octahedra that are cross-linked by AsO 4 and SO 4 tetrahedra (Figure 7) [4,9,18]. For the dissolution of the basic ferric sulfate-arsenate [FeSAsOH-1] at pH ≥2, the gradual decrease in solution pH indicated an OH − depleting.…”