Raman and infrared spectroscopic characterization of the phosphate mineral paravauxite Fe2+Al2(PO4)2(OH)2⋅8H2O

Abstract

We have undertaken a vibrational spectroscopic study of paravauxite the Siglo XX mine, Bustillo Province, northern of Potosí department, Bolivia. This mine is important source for rare and unusual secondary phosphate minerals and is the type locality for a number of rare phosphates such as vauxite, sigloite, metavauxite and for jeanbandyite. The chemical formula of the studied sample was determined as Fe(2+)(0.9)5, Al(0.07)Σ1.02 (Al)2.09 (PO4)1:97 (OH)1.98 · 7.90(H2O). The Raman spectrum is dominated by an intense Raman band at 1020 cm(-1) assigned to the PO4(3-) ν1 symmetric stretching mode. Low intensity Raman bands found at 1058, 1115 and 1148 cm(-1) are assigned to the PO4(3-) ν3 antisymmetric stretching vibrations. Raman bands of paravauxite at 537, 570, 609 and 643 cm(-1) are assigned to the ν4 PO4(3-) bending modes whilst the Raman bands at 393 and 420 cm(-1) are due to the ν2 PO4(3-) bending modes. The Raman spectral profile of paravauxite in the hydroxyl stretching region is broad with component bands resolved at 3086, 3215, 3315, 3421, 3505 and 3648 cm(-1). Vibrational spectroscopy enables the assessment of the molecular structure of paravauxite to be undertaken.

On the complex H-bonding network in paravauxite, Fe2+Al2(PO4)2(OH)2·8H2O: A single-crystal neutron diffraction study

“…0 0 2 ) S 0 . 9 9 8 Al(1)Al(2) Al 2.005 P (P 1.998 Si 0.002 ) S2 O 8 (OH) 2 ·8H 2 O, which is close to that reported by Frost et al (2013) for a paravauxite from the same locality: F e (Fe 2 + 0 . 9 5 Mn 2 + 0 .…”

“…2, Table 4). Frost et al (2013) reported the Raman and IR spectra for a paravauxite from the same locality as that used in this study. The Raman spectrum was dominated by an intense Raman band at 1020 cm À1 , assigned to the n 1 symmetrical stretching mode of the PO 4 3À group.…”

Application of Gettering Process on the Improvement of the Structural and Mineralogical Properties of Tunisian Phosphate Rock

“…This range is assigned to the vibration of ʋ2 and ʋ4 PO 4 3-bending modes. It was reported by S. Elgharbi and H. Lefires when they work about Tunisian phosphate rock that the Raman bands at 582, 591 and 607 cm -1 are assigned to ʋ4 PO 4 3-and the bands at 431 and 435 cm -1 are due to the ʋ2 PO 4 3- [12,13]. Then, the work reported by Karampasa about calcium phosphate confirmed very well the results above [29].…”

“…The chemical composition was determined by energy disersive X-ray EDX analysis. For the TEM sample preparation, we employed the ultrasound vibration method [13]. The samples were immersed in ethanol solution and ultrasound vibration was applied to separate precipitates from the phosphate.…”

A novel method for synthesis of nano-γ-Al2O3: study of adsorption behavior of chromium, nickel, cadmium and lead ions

“…In this work, Cu radiation (kCu = 1.5405 Å ) was used and the sample was scanned in a 2h range of 8-108.5°at a scanning rate of 0.015°/S. The crystalline size was determined from the characteristic peak at 2h = 67.1667°(corresponding to the 440 plane) using Scherrer formula (Frost et al 2013), crystalline size, nm = K k/W cos h, where K is the shape factor = 0.9, k = wavelength of the X-ray used (1.5405) and W = (Wb -Ws, width of peak at half-height at 2h = 33.5833) the difference of broadened profile width of the experimental sample and the standard width of reference Al 2 O 3 sample. The mean crystalline size was obtained to be 11.5 nm.…”