X-ray Absorption Spectroscopy Study of Solvation and Ion-Pairing in Aqueous Gallium Bromide Solutions at Supercritical Conditions

Cécile da Silva (1) , Olivier Proux (2) , Jean-Louis Hazemann (1) , Julianne James-Smith (3) , Denis Testemale (1) , T. Yamaguchi (4)

1 NEEL - MRS - Matériaux, Rayonnements, Structure
2 équipe FAME
3 NEEL - CRG - CRG & Grands instruments
4 Advanced Materials Institute and Department of Chemistry

X-Ray Absorption Spectroscopy measurements have been performed both at the Ga and Br K-edges on aqueous GaBr3 solutions. The isobaric experiments have been recorded at 30 MPa from ambient temperature to 670 K for two GaBr3 concentrations (0.017 and 0.17 mol/dm3). At room temperature, Ga3+ and Br- ions are fully solvated, surrounded by water O atoms at 1.97 Å (Ga-O) and 3.37 Å (Br-O). When the temperature is elevated, Ga3+ cations precipitate as gallium oxy-hydroxide colloids while Br- anions remain solvated. With a further increase in temperature, the gallium solid precipitates remarkably re-dissolved (25% and 50% for 0.017 and 0.17 mol/dm3 respectively), due to the formation of (n=2, 3 or 4) tetrahedral complexes.

Mots clés: X-ray Absorption Spectroscopy; EXAFS; XANES; hydrothermalism; supercritical fluids

Domaines: Chimie-Physique [physics.chem-ph]

Cécile da Silva, Olivier Proux, Jean-Louis Hazemann, Julianne James-Smith, Denis Testemale, et al.. X-ray Absorption Spectroscopy Study of Solvation and Ion-Pairing in Aqueous Gallium Bromide Solutions at Supercritical Conditions. Journal of Molecular Liquids, 2008, 147, pp.83-95. ⟨10.1016/j.molliq.2008.06.022⟩. ⟨insu-00709767⟩