The particles comprise a silica-based core and an at least a discontinuous layer of an oxide, hydroxide or hydrated oxide
of zirconium, whose isoelectric point is greater than that of the core.
Avalon's Hydrometallurgical Plant will produce four (4) saleable products in hydrated oxide
form - a total rare earth oxide, a zirconium oxide, a niobium oxide and a tantalum oxide.
Rare earth, or lanthanide, elements are characterized by: large atomic radii; a diversity of allowable electronic configurations; formation of multiple oxidation states, typically +3 and +4 with occasional +2 valence state; (1) reactivity with water to form neutral oxides; formation of stable, insoluble oxides of mixed valence states (19); complex coordination chemistry (20,21); instability of lower valence salts in alkaline conditions with a tendency to hydrolyze and precipitate as the hydrated oxide
(22); and an extremely low reduction potential.
Individual fractions are given in diagrams: (a) fraction I--exchanged, (b) fraction II--carbonate, (c) fraction III--connected with hydrated oxides
of manganese and iron, (d) fraction IV--organic, e) fraction V--the residual
A mixed light and heavy rare earth precipitate as hydrated oxides