Description:
OBJECTIVE: The objective of this project is to design an electrode/electrolyte system for the electrolytic reduction of rare-earth and scarce metals directly from refined feedstocks. This project also supports the goals of the Materials Genome Initiative (MGI) in the area of Integrated Computational Materials Engineering (ICME). DESCRIPTION: The rare-earth elements find uses in hundreds of high tech applications, including cellular telephones, laptop computers, iPods, critical military applications, and green technologies. These reactive metals have a natural abundance that is similar to that of copper. Their high costs and relative scarcity are due to the high cost of their separation, concentration, and extraction from the ores. Current methods involve the leaching of the rare-earth elements from the ore, solvent ion-exchange reactions to concentrate the elements, followed by roasting. From this concentrated state, reduction using an adaptation of the Kroll process, that is the formation of halide gasses from the oxides followed by reduction using an alkali metal, is typical. The environmental issues behind the mining of rare-earth elements are also a concern. For typical extraction processing technologies, every ton of rare-earth metal produced results in as much as 9 kg of fluorine and 15 kg of possibly radioactive dust residues. The electrolytic extraction of metals from the native ore chemistries is entering production for a number of systems. The process offers the advantage of scientific simplicity, though a number of technological issues loom important in using the process in production. Among these are the stability of the electrodes, the chemistry of the electrolyte, and the delivery of electrical power. To minimize costs and maximize utility, the use of a non-consumable anode is extremely important. Such an electrode must be capable of maintaining integrity at high temperatures in molten oxides and/or sulfides, and resistant to attack by high-activity oxygen in these conditions. Many prospective commercial operations use carbon as an anode, but it is consumed in the process to form gaseous CO2. This adds to the costs, and the environmental impact of the process. The objective of this project is to design and develop an anode material, with the associated electrolyte system, for electrolytic reduction of reactive rare-earth elements that has both the high temperature structural and chemical stability. Phase I: The successful phase I project will identify the conditions necessary for a successful electrode/electrolyte system. The investigators will then identify a group of electrode and electrolyte system chemistries, and show through thermokinetic models and simulations that the selected systems have a high likelihood of performing acceptably in the design. Phase II: The successful phase II project will perform validations of the preliminary electrode/electrolyte designs, and down-select a design for detail design work. The detail design work will require the development of thermokinetic data to predict system behavior in service, and the validation of the data and models prior to final design. Phase III: Mining operations, and materials recyclers, will implement this new technology system to reduce the costs and environmental impact of any new processing operations they might introduce. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The materials system developed in this project can play an important role in reducing the overall environmental impact and total cost of producing metal from ore systems. This we anticipate will increase the availability of these scarce materials, and reduce the overall costs for obtaining them. This will make significant changes in the ways that we can use these scarce materials in new designs.
