Recovery of Rare Earth Elements from Bauxite Residue: A Comparative Economic Analysis
Remya P. Narayanan
Rare earth (RE) elements, are important in many applications such as lighting phosphors, lasers, rechargeable batteries, motors in automobiles, wind turbines, appliances, computers, and hard drives. Despite their common name, REs are not particularly rare, as their concentration in the earth's (150-220 parts per million (ppm)) is comparable to other elements such as zinc (70 ppm) which are not considered to be rare at all. Importantly, REs occur together in ores and since the chemical and physical properties are same, separation is very challenging. During the past 15 years, China has provided the vast majority of the world’s RE supply. This essential monopoly of Chinese RE producers became problematic in 2010 when export quota limited the availability of the RE elements. The resulting price spikes for REs exposed the non-sustainable nature of the RE supply chain lead to several approaches to limit price and availability fluctuations of these important elements, including stockpiling, replacement of REs in applications, recovery of REs from end-of-life materials. In view of this there’s a growing interest in recovering and recycling REs from secondary resources. Bauxite residue or “Red mud” is a potential source for rare earth elements. The highly alkaline waste is stored in holding ponds and is produced at a rate of 120 million tons/year and 2.7 billion tons is already stockpiled. The composition of REEs in the red mud varies with its place of origin. Owing to its large volume and environmental impact, there’s a need for an effective method for the remediation of red mud. But the number of reports available on the recovery of REEs from red mud is limited. Herein, an attempt has been made to compare the economics of the various reported processes using ASPEN PLUS and ASPEN Process Economic Analyzer.