Solubility of Scandium Cesium Double Sulfate CsSc(SO4)2 in Sulfuric Acid Solutions

Abstract

Cesium sulfatoscandate CsSc(SO4)2 (space group P, a = b = 5.0971(1) Å, c = 8.6924(5) Å, V = 195.580(2) Å3, Z = 1) has been crystallized from aqueous solutions in layered hexagonal prisms sized up to 50 µm and up to 2–5 µm thick. Its water solubility is 0.0104 mol/L at 25 ± 1°С. A way to reduce the solubility of scandium as CsSc(SO4)2 is to increase acidity to 3.5–5.5 М H2SO4 and add Cs2SO4. Experimental evidence is supported by calculations that took into account changes in the ionic strength of the solution and the influence of the simultaneous presence of Cs+ andions. The results will be useful for those who will study the behavior of rare-metal compounds having similar properties and their separation.