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THE COMPOSITION, CHEMICAL PROPERTIES, AND PROCESSING OF THE UNIQUE
NIOBIUM-RARE EARTH ORES OF THE TOMTOR DEPOSIT
V.I. Kuzmin and V.N. Kuzmina
Institute of Chemistry and Chemical Technology SB RAS (Krasnoyarsk, Russia); [email protected],
A.V. Tolstov
Institute of Geology and Mineralogy SB RAS (Novosibirsk, Russia)
ABSTRACT
The complex niobium-rare earth pyrochlore-monazite-crandallite ores of the Tomtor deposit should be
considered as a new type of rare metal materials. The major valuable components of the ore are niobium,
rare earth elements, yttrium, and scandium; associated components are titanium, vanadium, aluminum, and
phosphorus. The ore composition is represented by mixture of minerals of the crandallite group (florencite,
goyazite, gorceixite) in amounts ranging from 5 % to 50 %. The major and associated minerals compose up
to 75 % of the ore volume. The ores are commonly sideritized (up to 15 % FeO). More than 80% of the ore
volume is represented by grain-size material with a size of less than 40 μm. Because of the irregular
distribution of the rare earth metals and niobium according to grain-size, the extremely finely dispersed
nature of the minerals, and their close interpenetration to each other, ore processing by gravitation and
flotation is not successful.
The processes for treatment of the Tomtor ores use direct alkaline-acid leaching to open the ore and the
extraction of REE and Sc was studied. The alkaline-acid leaching of the ore yields a niobium-titanium
concentrate containing up to 25% Nb2O5 and 20% TiO2. A problem in the first stage of alkaline leaching is
the high aluminum content, which increases the activity of sodium hydroxide, and alkaline-earth metals,
which are bound to phosphorus. In addition the trisodium phosphate so obtained is contaminated with
much vanadium, purification from which is a difficult problem.
Ore processing using alkaline-nitrate and alkaline-chloride leaching were proposed and investigated. The
first variant was used to obtain rare earth and scandium materials and a niobium-titanium concentrate,
which can be a stock material for businesses that use chlorination for the processing of ores and
concentrates. The second variant is a complex advanced ore processing scheme with electrochemical
regeneration of the waste chloride solutions obtaining sodium hydroxide, hydrochloric acid, and
chloridizing agents. Moreover trisodium phosphate is used for purification of the waste mother liquors
from metal cations. The complex salt, NaAlCl4, is proposed as the chloridizing agent for the decomposition
of the niobium-titanium concentrate.
KEYWORDS
Tomtor supergene complex ore, chemical processing, niobium, rare earths, titanium, alkaline pre-leach,
nitrate leaching, chloride leaching