A Raman spectroscopic study of bukovskýite Fe₂(AsO₄)(SO₄)(OH)· 7H₂O, a mineral phase with a significant role in arsenic migration

Abstract

The Raman spectrum of bukovskýite [Fe 3+ 2 (OH)(SO 4 )(AsO 4 )· 7H 2 O] has been studied and compared with that of an amorphous gel containing specifically Fe, As and S, which is understood to be an intermediate product in the formation of bukovskýite. The observed bands are assigned to the stretching and bending vibrations of (SO 4 ) 2− and (AsO 4 ) 3− units, stretching and bending vibrations and vibrational modes of hydrogen-bonded water molecules, stretching and bending vibrations of hydrogen-bonded (OH) − ions and Fe 3+ -(O,OH) units. The approximate range of O-H· · ·O hydrogen bond lengths was inferred from the Raman spectra. Raman spectra of crystalline bukovskýite and of the amorphous gel differ in that the bukovskýite spectrum is more complex, the observed bands are sharp and the degenerate bands of (SO 4 ) 2− and (AsO 4 ) 3− are split and more intense. Lower wavenumbers of δ H 2 O bending vibrations in the spectrum of the amorphous gel may indicate the presence of weaker hydrogen bonds compared to those in bukovskýite.

Recently formed arsenates from an abandoned mine in Radzimowice (SW Poland) and the conditions of their formation

“…The bending vibrations of the arsenate groups are present at 472 cm -1 (ν 4 ). The position of the absorption bands is close to the position recorded for the holotypic material from Kaňk near Kutna Hora (Novák et al 1967;Loun et al 2011).…”

Effect of Al content on the structure of Al‐substituted goethite: a micro‐Raman spectroscopic study

“…The Raman technique is being increasingly employed in our understanding of related minerals and investigating corrosion product films on the metal surface because this technique can provide quick identification of compounds present in surface films as thin as 5 nm, and water or/and hydroxyls give a weak Raman spectra. [24,25,33,[35][36][37][38][39][40][41][42][43][44][45][46][47][48] Thibeau et al [24] investigated the possible corrosion products of iron by using Raman spectroscopy. Faria et al [25,26] tried to differentiate heated goethite and natural goethite by using Raman spectroscopy and obtained the Raman spectra of hematite, magnetite, wustite, maghematite, goethite, and lepidocrocite.…”

“…With the remarkable development of Raman instrumentation, it is possible to obtain good quality spectra in spite of very poor laser power varying from few microwatt to milliwatt. The Raman technique is being increasingly employed in our understanding of related minerals and investigating corrosion product films on the metal surface because this technique can provide quick identification of compounds present in surface films as thin as 5 nm, and water or/and hydroxyls give a weak Raman spectra . Thibeau et al .…”

Mineralogy and Origin of Vein Wolframite Mineralization from the Pohled Quarry, Havlíčkův Brod Ore District, Czech Republic: Interaction of Magmatic and Basinal Fluids

“…The Raman spectrum suggests the presence of water in the crystal structure. Bands in the region between 3300 and 3400 cm −1 are assigned to the ν OH stretching vibrations of hydrogen-bonded hydroxyls and hydrogen-bonded water molecules [73]. The chondrite-normalized REE patterns (Figure 10d) show first increase from La to Sm and then decrease towards Yb with a more pronounced zig-zag shape of patterns at heavy REE.…”