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A Exam Summary Document ADAPTATIONS OF URANIUM HYDROMETALLURGY: CASE STUDIES IN COPPER IN SITU LEACHING AND SUPERCRITICAL EXTRACTION OF RARE EARTH ELEMENTS A Dissertation Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Laura Katherine Sinclair May 2018 © 2018 Laura Katherine Sinclair ADAPTATIONS OF URANIUM HYDROMETALLURGY: CASE STUDIES IN COPPER IN SITU LEACHING AND SUPERCRITICAL EXTRACTION OF RARE EARTH ELEMENTS Laura Katherine Sinclair, Ph. D. Cornell University 2018 ABSTRACT In this work, two uranium hydrometallurgical processes were adapted for other metals: in situ leaching was adapted to copper and supercritical extraction was adapted to rare earth elements. In situ leaching offers a way to extract copper from the subsurface without costly fragmentation. Applicability of in situ leaching is limited to deposits where sufficient permeability and leachable copper mineralogy exists. A computational copper in situ leaching model was developed to forecast recovered solution composition. This requires incorporating chemical reaction kinetics, mass transfer, and hydrology. These phenomena act over a range of length scales from centimeters up to hundreds of meters. Laboratory-scale leaching of ore provided data which was used to develop a list of geochemical reactions and associated rate laws. The risk of short-circuiting was treated probabilistically through geostatistical analysis of hydrophysical flow profiles, fracture spacing from Florence Copper's drill core database, and pumping tests. The geochemical reaction set and the geostatistical characteristics of hydraulic conductivity were brought together in a MATLAB model with a plugin to link to Geochemist's Workbench for computing chemical reaction pathways. Results highlighted the importance of large- scale flow patterns in copper recovery. The second part of this work pertains to rare earth element separation with supercritical carbon dioxide. Rare earth nitrates can be complexed with tributyl phosphate, thus forming a metal-ligand complex which is soluble in supercritical CO2. Rare earth elements were recovered from roasted and sodium hydroxide digested bastnäsite concentrate using supercritical carbon dioxide extraction with nitric acid/tributyl phosphate adducts. A range of tributyl phosphate/nitric acid adduct compositions were tested. A drop in recovery at higher acidities may indicate condensation of aqueous droplets which create an equilibrium limitation. To investigate the role of water, neodymium and holmium nitrate were extracted into supercritical CO2 with varying amounts of tributyl phosphate and water. Absorption spectroscopy was used to measure supercritical metal and water concentrations. It was found that holmium is preferentially extracted over neodymium. The results indicated that supercritical CO2 can be used to extract and separate rare earth elements from primary materials. BIOGRAPHICAL SKETCH Laura Sinclair was born in Toronto, Canada. She showed an early interest in both science and art, but ultimately chose to pursue an engineering career. After obtaining her bachelor’s degree in Chemical Engineering from the University of Toronto, she worked as a process engineer primarily focused on precious metal and copper hydrometallurgy. After taking a year off for a tri-continental bicycle trip, she began her graduate work at Cornell University. iii ACKNOWLEDGEMENTS I would like to thank Jeff, for always asking questions that pushed me to learn, John for providing an invaluable perspective, Larry for his direction and focus, and Don for his mathematical insight. A special thanks to Bob and his colleagues for teaching me so many cool new skills and introducing me to the beautiful state of Idaho. Polly and Bailey, thank you for everything you do for our group. I would like to thank Lou Derry and his whole group for letting me use his lab and all the loaned equipment and software. Thank you to Jared for all his help with statistics. To all the amazing students that I’ve met at Cornell (especially Arna), this experience would not have been the same without you! Lastly, to my family and Joey, for always believing in me and encouraging me to pursue my passions. TABLE OF CONTENTS Part I – In Situ Leaching of Copper ................................................................................. 1 CHAPTER 1 ................................................................................................................................... 2 1.1 In Situ Leaching ............................................................................................................... 2 1.1.1 Background ................................................................................................................... 2 1.1.2 Recovery Challenges .................................................................................................... 4 1.1.3 Containment.................................................................................................................. 5 1.1.4 Restoration .................................................................................................................... 5 1.2 The Florence Deposit ....................................................................................................... 6 1.2.1 Geology ........................................................................................................................ 7 1.2.2 Hydrology ..................................................................................................................... 8 1.2.3 History .......................................................................................................................... 9 1.3 Goal and Scope................................................................................................................. 9 CHAPTER 2 ................................................................................................................................. 12 2.1 Ground Ore Leach Tests ................................................................................................ 12 2.1.1 Samples ....................................................................................................................... 12 2.1.2 Procedure .................................................................................................................... 12 2.1.3 Results ........................................................................................................................ 14 iv 2.2 Box Leaching Tests ........................................................................................................ 14 2.2.1 Samples ....................................................................................................................... 14 2.2.2 Procedure .................................................................................................................... 14 2.2.3 Results ........................................................................................................................ 16 2.3 Geochemical Interpretation ............................................................................................ 16 2.3.1 Reaction Set ................................................................................................................ 16 2.3.2 Acid Consumption ...................................................................................................... 20 2.3.3 Kinetics ....................................................................................................................... 20 CHAPTER 3 ................................................................................................................................. 25 3.1 Goal and Scope............................................................................................................... 25 3.2 Series Leach Test ........................................................................................................... 25 3.2.1 Samples ....................................................................................................................... 25 3.2.2 Procedure .................................................................................................................... 25 3.2.3 Results ........................................................................................................................ 27 3.3 Comparison with Geochemical Model ........................................................................... 28 3.4 Petrographic Examination of Tails ................................................................................. 30 CHAPTER 4 ................................................................................................................................. 34 4.1 Goal and Scope............................................................................................................... 34 4.2 Available Data ................................................................................................................ 36 4.2.1 Flow Profiles............................................................................................................... 36 4.2.2 Fracture Intensity ........................................................................................................ 37 4.2.3 Pumping Tests ............................................................................................................ 39 4.2.3.1 Single Well Pumping Tests ................................................................................
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