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Solubility of Platinum and Rhodium in Lime–Alumina–Silica Melts at 1700 K

2001; Wiley; Volume: 84; Issue: 5 Linguagem: Inglês

10.1111/j.1151-2916.2001.tb00796.x

1551-2916

Pierre Dablé, M. Allibert, J.C. Poignet, J. Amossé,

Minerals Flotation and Separation Techniques

Three oxide melts of composition 10‐20‐70, 30‐13‐57, and 40‐20‐40 (wt%) in the ternary system CaO–Al 2 O 3 –SiO 2 were equilibrated at 1700 K in platinum or platinum–rhodium boats, under oxygen partial pressures ( P O2 ) ranging from 10 −13 to 1 atm, and fixed by various gaseous mixtures (H 2 /H 2 O, CO/CO 2 , and Ar/O 2 ). The melts were analyzed for platinum and rhodium content after quenching. The complex dependence of solubility of these elements with P O2 was explained by their speciation. Chronopotentiometric measurements confirmed the passivation of the metallic boats. For increased P O2 , this speciation followed the series Pt, PtO, PtO 2 or RhO for the solid phases covering the metallic boats and Pt 0 , Pt 2+ , Pt 4+ , Pt 6+ or Rh 0 , Rh 2+ , Rh 3+ , Rh 4+ in solution in the oxide melt. The predominance diagrams were determined for the three compositions in the ternary system.