Temporally explicit life cycle assessment as an environmental performance decision making tool in rare earth project development

Strategies and options for the sustainable recovery of rare earth elements from electrical and electronic waste

Monazite (REPO4; RE = La to Gd) and xenotime (REPO4; RE = Tb to Lu & Y) materials have been proposed as host matrices for the immobilization of actinides. Aqueous alteration of monazite and xenotim...

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Synthesis, Crystal Structure, and Enthalpies of Formation of Churchite-type REPO4·2H2O (RE = Gd to Lu) Materials

BACKGROUND
Critical raw materials (CRM) are crucial to Europe's economy and essential to maintaining and improving our quality of life due to their usage for production of many devices. Red mud is generated from alumina production where bauxite is digested in hot sodium hydroxide solution during the Bayer process. Red mud can contain considerate amounts of CRM such as rare earth elements (REEs). In the present study, purification of CRM from perturbing, co-extracted elements such as Fe and Al from red mud hydrochloric acid leachates was evaluated.

RESULTS
A first purification was achieved by removing Fe (>87%) from the acidic leachate using precipitation with NaOH. REEs as well as Al were hardly removed by precipitation (21%, and 33%, resp.). A second purification was achieved using liquid/liquid extraction (LLE) with di-(2-ethylhexyl)phosphoric acid (D2EHPA). Here, four explanatory variables (i.e. LLE organic/aqueous ratio, D2EHPA concentration in kerosene, stripping acid organic/aqueous ratio, HCl concentration) were studied. Finally, the optimal extraction conditions maximizing the economic potential (total metal extracted × economic value of the respective metal) of CRM were determined using a design of experiment approach.

CONCLUSION
The experimentally determined economic potential extracted corresponded well to the prediction (88%; to the predictions, maximum recovery of 17.18 ± 0.59 US $ t−1). Ultimately, more than > 40% of the overall REEs (>62% of the leachable REEs) in red mud could be purified using LLE, whereas Al was successfully rejected from the concentrate (~5% of the overall Al present).

Red mud as secondary source for critical raw materials – Purification of rare earth elements by liquid/liquid extraction

Rare earth elements (REEs) are important raw materials for green technologies. However, REE mining and production uses techniques that are often not environmentally sustainable. Life cycle assessment (LCA) is a well-recognized method for evaluating the environmental impacts of products and technologies. This article provides an overview of the environmental impacts based on published LCA results of primary REE production. Existing major REE deposits (Bayan Obo in China, Mountain Pass in the United States, Mount Weld in Australia, ion-adsorption deposits in several Chinese southern provinces) and currently possible production routes are compared. Alternative minerals, such as eudialyte, are also discussed. The article shows which environmental effects can be minimized by technology optimization and environmental safety strategies. Additionally, some of the environmental impacts discussed, may be difficult to mitigate, as they depend on the mineral type. Activities along the complex process chain of REEs production that have particularly high environmental impacts are identified.

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Environmental impacts of rare earth production

This chapter gives an overview of the major and minor ore minerals of the rare earths, and of the related major ore deposits. As most of the rare earths are mined in China, the impression may arise that ore deposits of these metals occur in few other places on Earth. However, nothing is less true. The extensive overview of the ore deposits of the rare earths in this chapter is especially meant to indicate that deposits occur in quite a variety of countries, and that the apparent dominance of China is economically (and politically) powered.

J. H. L. Voncken

Papers

The Ore Minerals and Major Ore Deposits of the Rare Earths