First Production of High Purity 99.9% Scandium Oxide

Fra researchgate.net 2011

Metallurgical processes for scandium recovery from various resources
(Weiwei Wang, Yoko Pranolo, Chu Yong Cheng)

- Metallurgical processes for scandium recovery from various resources are reviewed. Scandium is mainlyrecovered as by-product from residues, tailings and waste liquors in the production of other metals such asrare earths, uranium, titanium, tungsten, aluminium, nickel, tantalum and niobium.

- Scandium is the 31st abundant element in the Earth's crust, with an average crustal abundance of 22 ppm (Hedrick, 2010b)

- Ores with the scandium content range of 0.002–0.005% can be considered as resources of scandium and deserve exploitation (Xu and Li, 1996)

- America, Australia, China, Kazakhstan, Madagascar, Norway, Russia and Ukraine are the countries with main scandium resources (Hedrick, 2010a; Munnoch and Worstall, 2003). In America, scandium resources are mainly found in uranium, tantalum, aluminium and zirconium ores; in Australia in nickel laterite ores; in China in iron, tin and tungsten ores; in Kazakhstan in uranium ores; in Madagascar and Norway in pegmatite rocks; and in Russia and Ukraine in iron ores.


Recovery of scandium from titanium and zirconium ores
- Some titanium minerals such as ilmenite (FeTiO2) and rutile (TiO2) contain significant amounts of scandium. For example, the magneto-vana-ilmenite ore (an ilmenite with high content of vanadium) in Panzhihua, China, contains 0.002–0.004% Sc2O3 (Chen, 1990). Australia, Canada, India, Norway and South Africa are the main producers of titanium minerals.

- Ilmenite is often further beneficiated to produce synthetic rutile and titaniferous slag. The scandium was enriched in the slag, for example, a significant amount of 128 ppm was included (Mao et al., 1996). The scandium in the tailings was combined with high contents of impurities (40% SiO2, 16% FeO, 15% CaO, 14% MgO, 5.3% TiO2 and 5.8% Al2O3). For the production of titanium dioxide or titanium metal, titanium feed materials are first fused in the chlorination step to produce a vaporous titanium tetrachloride (Baptiste, 1959). The scandium is concentrated principally in the residue or in the dust as scandium chloride, making the recovery of scandium feasible. It was reported that the dust contains a high level of scandium of at least 132 ppm (Xu and Li, 1996). About 90% of the scandium was leached from the ilmenite slag with a process shown in Fig. 4 (Maoet al.,1996). The process included grinding the slag, roasting with Na2CO3 in the temperature range of 900–1000 °C, and leaching with 30% HCl at 80 °C at a solid to liquid ratio (S/L) of 1:2. Over 94% scandium was extracted from the leach liquor using 30% HDEHP in kerosene at an A/O ratio of 20:1 with only about 2.2% iron co-extraction. The extracted iron was removed by scrubbing with 5 M HCl and the scandium was stripped with 2 M NaOH. The obtained Sc(OH)3 precipitate was dissolved with HCl and the scandium was precipitated with oxalic acid. A scandium oxide product of 99% purity was obtained after calcining the oxalate precipitate at 800 °C.