Thermodynamics of Arsenates, Selenites, and Sulfates in the Oxidation Zone of Sulfide Ores. XV. Synthetic Analog of Alfredopetrovite: Composition, Properties, and Stability Limits

The purpose of this work was to synthesize hexahydrate aluminum selenite Al 2 (SeO 3 ) 3 ⋅6H 2 O (analogous to the mineral alfredopetrovite) and study its solubility in water. Al 2 (SeO 3 ) 3 ⋅6H 2 O is synthesized from AlCl 3 and Na 2 SeO 3 solutions at room temperature and atmospheric pressure. The obtained samples were studied using powder diffractometry, infrared and Raman spectroscopy, energy-dispersive X-ray microanalysis, nuclear magnetic resonance spectroscopy, and complex thermal analysis. Solubility was determined by isothermal saturation in ampoules at 25°C. Solubility products were calculated using Geochemist’s Workbench software package (GMB 9.0, SpecE8 program). As a result of the calculation, the average value logKsp[Al 2 (SeO 3 ) 3 ⋅6H 2 O] = –28.3 ± 0.5 was obtained. An Eh–pH diagram is constructed for the Al–Se–H 2 O system, which was used to analyze the stability of alfredopetrovite in near-surface conditions.