Precipitation Stripping of Rare-Earth Carbonate Powders from Rare-Earth-Loaded Carboxylate Solutions Using Carbon Dioxide and Water

Abstract

This paper describes a chemical processing route of a rare-earth oxide precursor, in which rare-earth carbonate powders are prepared directly from disperse systems of rare-earth-loaded carboxylate solutions and water, using carbon dioxide gas as a precipitant. This synthetic route of rare-earth carbonate is a combined process of the stripping and precipitation stages in a conventional solvent extraction. Tertiary carboxylate solutions of lanthanum and yttrium gave precipitates of lanthanum carbonate and yttrium carbonate, when contacted with both water and pure carbon dioxide gas at 10−80 °C and 0.1−3.0 MPa for 2 h. The rates of carbonate precipitation in a batch autoclave were sensitive to processing parameters such as carbon dioxide pressure, temperature, and organic-phase composition. The particle size distributions of the carbonate powders were markedly dependent on the operating temperature: the mean particle size of yttrium carbonate drastically decreased from 41 μm at 80 °C to 7.2 μm at 10 °C.