In the following group of metals - lanthanum, lanthanide, yttrium, and scandium - scandium is the scarcest and commercially attractive. The use of scandium, primarily in aluminum alloys, can improve the mechanical strength, heat resistance, and service life of gas turbine engines in aircraft and spacecraft production. Innovative scandium-based scientific and technical solutions are strategically important to the aerospace industry. Therefore numerous efforts are focused primarily on developing an effective method of scandium extraction.
The key raw material for scandium extraction is the aluminum industry waste from the bauxite processing using Bayer method, i.e. red sludge, which has a scandium content of 80 - 120 grams per ton. The amount of red sludge accumulated at Russian plants is several hundred million tons, and this accumulation goes on. Similar “impoundments” exist in all countries of the world where aluminum is produced.
Global SO conducted the research work on the following topic: “Extraction of scandium and other REEs from solid man-made wastes,” and developed a process sequence for extracting scandium from red mud, including the following basic stages:
- preliminary enrichment of feedstock using non-chemical methods (dry or wet magnetic separation, crushing followed by vibration and cavitation classification, etc.),
- chemical leaching of red mud (acid or alkaline one) to convert scandium to the liquid phase,
- extraction or sorption concentration of scandium to produce a crude concentrate,
- extraction treatment of scandium from impurities of iron, aluminum, silicon and other metals, with simultaneous concentration of scandium in solutions,
- extraction of scandium from the solution to obtain the product in the form of an oxide.
A lab unit for chemical leaching of red sludge was developed, optimal conditions and operating modes were selected allowing to transfer up to 50% of the target product into the liquid phase and to concentrate it by 2 orders of magnitude relative to iron and by 2-4 times relative to aluminum.
Studies of the processes of extraction and sorption concentration of leaching solutions were carried out. The possibility of increasing the concentration of the target product by 3-5 times was shown, including the use of sorbents based on carbon nanomaterials produced by our plant.