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http://www.dodsbir.net/sitis/display_topic.asp?Bookmark=4282… http://www.dodsbir.net/sitis/display_topic.asp?Bookmark=4282… http://www.dodsbir.net/sitis/display_topic.asp?Bookmark=4282… OSD STTR 12.B Topic Descriptions OSD12-T01 TITLE: Advanced Separation Technologies for Extraction of Rare Earth Elements (REE) TECHNOLOGY AREAS: Materials/Processes OBJECTIVE: The objective of this research is to conduct fundamental surface chemistry measurements and demonstrate the use of these data to laboratory and small scale froth flotation systems so that more effective recovery can be achieved than with existing methods. DESCRIPTION: A critical step in the extraction of elements from ore, especially rare earth elements that are found in complex minerals, is separation. Froth flotation is a highly versatile method for physically separating particles based on differences in the ability of air bubbles to selectively adhere to specific mineral surfaces in a mineral/water slurry. The particles with attached air bubbles are then carried to the surface and removed, while the particles that remain are completely wetted stay in the liquid phase. Froth flotation is an attractive approach, but its effectiveness is limited for the rare earth minerals as they occur as phosphates, carbonates, fluorides, silicates and oxides with gangue minerals, which often share physical properties. By providing another tool for separation, increased understanding of localized surface chemistries in complex rare earth minerals could enable affordable processes that improve grades, recoveries, capital costs and operating costs for separation of rare earth elements from their ores. The techniques used to characterize surface chemistry in flotation relate to methods to make selective minerals hydrophobic by adjusting the surface charge so that ionic collectors may be adsorbed. In the case of non-sulfide minerals this is complicated by the fact that the waste materials are also non-sulfide, so very small differences in surface chemistry properties are observed. Finding chemical methods to selectively adsorb collectors onto the desired minerals requires additional fundamental understanding of the surface ions (potential determining ions) and charges (electrochemical potentials) encountered. The work, coupled with the development of a fundamental understanding can lead to greatly improved processes for concentration by froth flotation. PHASE I: In the phase I effort, the investigators need to explore the fundamental surface chemistry measurements (zeta potential, contact angle, micro-flotation tests) on pure rare earth mineral samples to evaluate various alternatives chemistries for selective froth flotation. Pure mineral samples need to be acquired, crushed, ground, screened, and analyzed using chemical and X-ray diffraction techniques. The surface chemistry measurements will be made as a function of collector type, pH, feed rate, particle size, mineral composition (phosphate, carbonate, fluoride, oxide, silicate), surface modification chemicals, etc. Attention will also be paid to the principal gangue minerals that occur in these ore bodies. Models are to be developed to describe and understand the surface chemistry and relate this to separation efficiency. Process environmental impact will also be a factor of evaluation. PHASE II: In the phase II effort, the investigators shall evaluate and validate the process models, modify the process models and analyze and characterize the efficiency and the environmental impact of the separation methodology using real crushed ores using standard large scale laboratory flotation equipment. Modification of the models, as necessary, based on the test results, will be conducted and retested to determine the range of their applicability. This will demonstrate the effect of this increased understanding on the grades and recoveries obtained by determining (1) the Ratio of Concentration and (2) the Percent REE Recovered. This then could be compared to conventional methods in order to demonstrate increased value and/or reduced operating costs as a function of ore type and original concentration. Separation variability as a function of REE ore composition should be assessed. If viable, scalability will be evaluated and preliminary drawings of pilot plant floth floatation system will be planned. PHASE III: Working with industry, a pilot plant sized floth floatation system is constructed and various crushed commercial ores will feed to determine separation efficiency based on (1) the Ratio of Concentration and (2) the Percent REE Recovered. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The modeling of surface chemistries for froth floatation will lead to greater separation efficiencies and benefit the domestic mineral extractive companies specializing in rare earth recovery and production. More secure, domestic REE sources would be of great strategic importance to the Department of Defense for many applications where REE are utilized. REFERENCES: 1. Q. Min, Y.Y. Duan, X.F. Peng, A.S. Mujumdar, C. Hsu, “Froth Flotation of Mineral Particles: Mechanism”, Drying Technology, v. 26 (8), 985-995 (2008). 2. S. Farrokhpay, “The Significance of Froth Stability in Mineral Flotation – A Review”, Advances in Colloid and Interface Science, v. 166 (1-2) 1-7 (2011). 3. N. Barbian, E. Ventura-Medina, J.J. Cilliers, “Dynamic Froth Stability in Froth Flotation”, v. 16(11), 1111-1116 (2003). KEYWORDS: froth floatation, surface chemistry, rare earth separation, ore separation, recovery, hydrophilic, hydrophobic, wetting, air bubbles OSD12-T02 TITLE: Novel Primary Processing of Scarce Element Ores TECHNOLOGY AREAS: Materials/Processes OBJECTIVE: The objective of this project is to develop and demonstrate at a relevant laboratory scale a novel, efficient, and environmentally friendly approach to the extraction, concentration, and separation of rare-earth elements from common ore stocks. This project 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. Using concentrated sulfuric acid leaching with high temperature calcination techniques, producing one ton of calcined rare earth ore generates: up to 12,000 m3 of waste gas containing ore dust concentrate, hydrofluoric acid, sulfur dioxide, and sulfuric acid; along with approximately 75 m3 of acidic wastewater; plus up to one ton of radioactive wet waste residue. Many ores contain Thorium, a radioactive element; so that the ore dust effluents, and residuals, are radioactive and contain many toxic heavy metals. Without special treatments, these waste products pose the threat of contaminating local water supplies and producing far-field environmental damage. The disposal of tailings, the components of the ore left behind after rare-earth extraction, also contributes to the problem. Most operations simply place tailings in large land impoundments for storage. These also present long-term environmental challenges without special treatment. A novel means of separation and fractionation of the multiple species in the ores, and concentrating these elements into separate streams using less-aggressive techniques environmentally, could enable the increased availability of these elements for engineering applications. Over the past decade, a number of liquid-liquid ion extraction processes for rare-earth elements have become available. These, however, involve the use of toxic organic compounds that require sophisticated handling technologies to work safely in an industrial scale extraction process. Novel chemistries for the extraction, concentration, and separation of these elements that a processing plant can implement in an environmentally benign manner would improve the availability, decrease the costs of extraction, and decrease the environmental impact of the extraction operations. The objective of this project is to develop and demonstrate a more environmentally benign technique for the extraction, concentration, and separation of rare-earth elements from ores. PHASE I: The successful phase I project will develop and define concept chemistries, along with basic engineering evaluations of the relative suitabilities of the approaches and outlines of the likely relative environmental impacts. PHASE II: The successful phase II project will down-select a concept extraction system from the phase I effort and perform detailed chemical engineering design on the proposed process. The investigators will show through combinations of modeling, simulation, and relevant experiments that the final design is suitable for insertion into a mining/extraction process. PHASE III: Mining operations require the concentration, and separation of the relevant elements from the ores prior to subsequent purification and processing to final form. An efficient controllable process which is either environmentally benign, or can be easily controlled for minimal environmental impact, will decrease dramatically the overall costs associated with the extraction and enable mining and ore processing for deposits which are not currently profitable for exploitation. 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 rare-earth compounds 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. REFERENCES: 1. C.K.Gupta, and N.Krishnamurthy, Extractive Metallurgy of Rare Earths, CRC Press, 2005. 2. House of Commons, Science and Technology Committee, Strategically important metals: Fifth Report of Session 2010–12, The Stationery Office Limited, London, UK, 2011. 3. “New opportunities for metals extraction and waste treatment by electrochemical processing in molten salts”,Donald R. Sadoway, Journal of Materials Research 10 (1995) 487-492. 4. “Emerging molten salt technologies for metals production”, Derek J. Fray, Journal of the Minerals, Metals and Materials Society 53 (2001) 27-31. 5. “The direct electrorefining of copper matte”, Douglas J. McKay, Journal of the Minerals, Metals and Materials Society 45 (1993) 44-48. KEYWORDS: MGI; ICME; rare-earths; extractive metallurgy; electrolysis; environmental impact. OSD12-T03 TITLE: Novel Electrolytic Extraction Processes for Scarce Elements TECHNOLOGY AREAS: Materials/Processes 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. Read more at http://www.stockhouse.com/bullboards/messagedetail.aspx?p=0&… |
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