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    Beneficiation of rare earth minerals from Bokan Mountain: Dotson Ridge ore

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    Author
    Narantsetseg, Purevbaatar
    Наранцэцэг, Пүрэвбаатар
    Chair
    Ganguli, Rajive
    Ghosh, Tathagata
    Committee
    Akdogan, Guven
    Metadata
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    URI
    http://hdl.handle.net/11122/4908
    Abstract
    The purpose of this research work was to study the beneficiation of rare earth ore of the Bokan Mountain -- Dotson Ridge deposit, located near Ketchikan, Alaska. Rare earth element (REE) composite ore samples from the Bokan Mountain -- Dotson Ridge deposit were tested using gravity concentration, magnetic separation, flotation, and leaching techniques to separate the REE. The composite ore sample was a product of a preliminary x-ray sorting process. Qualitative electron microprobe analysis of the ore showed that most of the REE minerals in the ore were silicate minerals. Since the electron microprobe analysis samples were coated with carbon during sample preparation, the carbon element was inactivated for analysis. Because of this, carbonate compounds of minerals' particles could not be detected. 95% of the REE mineral particles appear to be smaller than about 10 μm in size (about 100 μm² in area). For the gravity concentration, light rare earth elements (LREE) and heavy rare earth elements' (HREE) individual elemental recovery values were in the ranges of 49.6-52.8% and 46.3-48.8%, respectively, at 25% of mass yield. In order to separate a larger amount of the REE, a wet high intensity magnetic separation (WHIMS) test was carried out on tailings of the gravity concentration tests. The HREE individual elemental recovery values ranged from 56.3-63.1% at 37% mass yield, while LREE individual elemental recovery values were in the 57.9% - 59.1% range. For the combined gravity and magnetic separation processes, the net individual elemental recovery values of the LREE and the HREE were in the range of 79.6-80.5% and 76.5-80.9%, respectively. The combined mass yield of the gravity and magnetic separation processes was 3%. Direct leaching tests conducted on the composite ground ore feed yielded high individual elemental recovery values of 90-92% of the LREE. The HREE individual elemental recovery values ranged from 56.5-87.3%. In the leaching, 20% HCl was used in the 1st and 2nd stages with a duration of 2 hrs in each stage at 90°C. The solid percentage of the leach slurry was 20% w/w. The composite ground ore sample was tested in conventional flotation using a 2.0 L capacity Denver cell. In the flotation, 0.05 kg/tonne of Cytec Aero 6493 collector, 0.05 kg/tonne of Cytec Aero Froth 88, and 0.1 kg/tonne of sodium metasilicate as a depressant were used. Pulp pH was set around 9. Results showed individual elemental recovery values in the range of 44.6-50.4% or the LREE. The HREE individual elemental recovery values ranged from 27.9-44.5%. The mass yield of the flotation was 23%. The flotation recoveries reported here are significantly lower than what was achieved previously. For the Leach after flotation process, leaching was conducted on the first concentrate of flotation. Individual elemental recovery values of the LREE and HREE were 94.7-96.5% and 61.1-90.5%, respectively. The concentrate was leached using 20% HCl in both the 1st and 2nd stages, with a duration of 2 hrs in each stage at 90°C. Flotation/Leach process net recoveries of LREE by individual elemental values ranged from 42.2-48.5%. HREE net recoveries by individual elemental values ranged from 17.1-41.4%.
    Description
    Thesis (M.S.) University of Alaska Fairbanks, 2014
    Table of Contents
    Chapter 1 Introduction and Objectives -- Chapter 2 Literature Review -- 2.1 Gravity separation of REE ore -- 2.2 Magnetic separation of REE ore -- 2.3 Froth flotation of REE ore -- 2.4 Leaching of REE -- 2.5 Mineral processing of Bokan Mountain: Dotson Ridge REE ore -- 2.5.1 Mineralogical property -- 2.5.2 Froth flotation -- 2.5.3. Leaching -- 2.5.3.1 Direct leaching -- 2.5.3.2 Leach after flotation -- Chapter 3 Methods and Materials -- 3.1 Materials -- 3.2 Gravity separation tests -- 3.3 Wet high intensity magnetic separation tests -- 3.4 Froth flotation tests -- 3.5 Leaching tests -- 3.5.1 Direct leaching -- 3.5.2 Leach after flotation -- 3.6 Electron microprobe analysis of REE mineralogy -- Chapter 4 Results and Discussion -- 4.1 Gravity separation -- 4.2 Wet high intensity magnetic separation -- 4.3 Froth flotation -- 4.4 Leaching -- 4.4.1 Direct leaching -- 4.4.2 Leach after flotation -- 4.5 Electron microprobe analysis -- 4.5.1 Mineralogy of the ore -- 4.5.2 Mineralogy of flotation concentrate -- Chapter 5 Conclusions and Recommendation -- 5.1 Conclusions -- 5.2 Recommendation for future work -- References -- Appendices.
    Date
    2014-12
    Type
    Thesis
    Collections
    Engineering

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