Cheap, Novel Process to Obtain Scandium from Red Mud with High Selectivity

Red mud, an extremely alkaline by-product formed during aluminum extraction from bauxite, is a serious environmental concern. One disaster that particularly stands out is the Ajka alumina plant accident in West Hungary: In 2010, the dam of one of the red mud reservoirs collapsed, leading to loss of life in the entire Marcal river. The toxic waste eventually reached the Danube, Europe’s second largest river, spurring countries located down the river to improvise countermeasures. Red mud contains a number of Rare Earth (RE) elements and trying to extract those is a smart way to mitigate the environmental threat it poses. Of all the RE elements, Scandium in particular has a high demand in the market; its high strength alloys are used in the aerospace and car industries. Constituting less than 1% by composition of red mud, the current extraction procedure – solvent extraction – is not very cost-effective due to the high cost of reagents.

A novel process invented in collaboration with the Center for Resource Recovery and Recycling (CR3) at WPI takes a different approach by selectively obtaining Scandium without extracting the more abundant Iron. The strategies used have improved separation selectivity and minimized reagent use at each step. What makes this process unique and marketable is its high selectivity, which leads to significant benefits in the cost profile. After the Scandium separation from red mud, a roasting step produces Scandium oxide, which is the common commercial form in which Scandium is traded in. If the entire process flowsheet is thought of as a black box, the input is highly alkaline red mud, and the output is Scandium oxide and an acidic by-product which when put back into the holding ponds, neutralizes the red mud, thereby remediating the dangers of red mud to the environment.