Raman Spectroscopy in the Hydrometallurgical and Materials Engineering World

The nature of synthetic basic ferric arsenate sulfate (Fe(AsO4)1−x(SO4)x(OH)x) and basic ferric sulfate (FeOHSO4): their crystallographic, molecular and electronic structure with applications in the environment and energy

“…With the view of elucidating/clarifying the various conflicting results surrounding this type of iron arsenate sulfate phase (or phases) we undertook a detailed synthesis, characterization and environmental stability study. [12][13]15,26 From these studies, it was shown unequivocally the two previously described as ''Type 2'' and ''Phase 3'' phases to be the same and have the general formula: Fe(AsO 4 ) 12x (SO 4 ) x (OH) x ? (12x)H 2 O, hence their labeling as BFAS.…”

“…6) showed a diffraction pattern indicative of exsolution. [46][47] Formation of solid solutions at low temperatures, as in the BFAS system [12][13][14] may result in phase segregation due to kinetic/structural factors (e.g. differences in ion size and charge between the sulfate « arsenate and slow ion mobility).…”

“…scorodite, ferric arsenate sub-hydrate, or basic ferric arsenate sulfate, BFAS) 11,14,15 becomes very important because each phase exhibits a distinct arsenic control behavior upon subsequent storage in a waste management facility. Recent characterization studies 10,[13][14][15] on arsenical residues generated in gold or copper processing operations have demonstrated arsenic to be present (immobilized) in a BFS-BFAS type of solid solution system, hence its environmental importance given the well known health risks of water soluble arsenic. 16 In search for inexpensive, safe and high performance electrode materials for new generation Li-ion batteries, among the best cathode materials to date have been Fe-polyanion comounds.…”

“…11 This unknown compound was observed to form under hydrothermal conditions relevant to pressure leaching of refractory gold and copper mineral feedstocks. 11,[12][13][14][15]18,20,[24][25] Of particular interest was the environmental stability (arsenic control) of this intriguing unknown phase. In the original work, 11 it was postulated from the XRD and TEM data that this ''Type 2'' phase may be of a tetragonal or monoclinic nature but structurally distinct to BFS.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part V

“…Gomez et al . carried out vibrational analyses of hydrothermally produced scorodite (FeAsO 4 ‐2H 2 O), ferric arsenate subhydrate (FeAsO 4 ‐0.75H 2 O) and basic ferric arsenate sulfate (Fe[(AsO 4 )‐(SO 4 )(OH)]‐wH 2 O) . Gouadec et al .…”