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Beneficiation of rare earth minerals from Bokan Mountain: Dotson Ridge ore
Get PDFThesis (M.S.) University of Alaska Fairbanks, 2014The 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%.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
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Phase equilibria and thermodynamic evaluation of the Fe-Ti-V-O system in air
Get PDFThesis (PhD)--University of Pretoria, 2018.In this study, the iron-titanium-vanadium-oxygen (Fe-Ti-V-O) system in equilibrium with air was
studied experimentally by high-temperature equilibration, quenching, scanning electron microscope
and microprobe analysis coupled with critical assessment and thermodynamic evaluation. The thermodynamic
evaluation was performed with FactSage 7.0. The purpose of the study was to develop
a set of Gibbs equations for all compounds and solutions of the Fe-Ti-V-O system in equilibrium
with air, using the well-known calculation of phase diagram (CALPHAD) technique. The study was
categorically divided into three separate investigations. The lower order Fe-V-O and Ti-V-O systems
in equilibrium with air were st experimentally investigated and thermodynamically assessed. This
was then followed by an experimental investigation and thermodynamic assessment of the Fe-Ti-V-O
system in equilibrium with air.
The Fe-V-O and Ti-V-O systems in equilibrium with air were studied experimentally in temperatures
ranging from 700 C to 1500 C. The measured concentration of Fe in the V-O slag is 35
weight % at 1400 C, and the measured V concentration in the hematite phase reached a maximum
of 4.4 weight % at 1350 C. A signi cant amount of precipitation was observed for Fe-V-O samples
quenched at 1400 C, causing calculated standard deviations of Fe and V to be more than 1 weight
%. The measured concentration of Ti in the V-O slag is less than 6 weight % at 1500 C, and the
measured V concentration in the rutile phase reached a maximum of 15 weight % at 1400 C.
The solubility of V2O5(s) in the hematite and rutile phases was described with the compound
energy formalism. The properties of the liquid phase were described with both the modi ed quasichemical
model and the associate species model. A set of self-consistent thermodynamic parameters
was estimated within acceptable error limits. The calculated phase diagrams of Fe-V-O and Ti-V-O
in equilibrium with air are presented and compared to experimental observations and other literature
data.
Before experiments in the Fe-Ti-V-O system in equilibrium with air were conducted, the Fe-Ti-O
system in equilibrium with air was critically assessed and thermodynamically evaluated. This was due
to the slag phase and solid solutions of the Fe-Ti-O system that were previously thermodynamically
evaluated only under reducing conditions. However, limited data were available in literature, hence
assumptions were required for the evaluation. Nevertheless, an improved phase diagram of the
Fe-Ti-O system in equilibrium with air was calculated.
Thereafter, isothermal planes were calculated from optimized binary parameters to estimate a
range of plausible starting compositions for experiments of the Fe-Ti-V-O system in equilibrium with
air. The Gibbs phase rule was carefully applied to avoid redundant experiments. The Fe-Ti-V-O
system in equilibrium with air was studied experimentally, ranging from 1000 C to 1400 C.
The properties of the liquid phase were successfully described with the quasichemical model by
optimizing parameters only related to the Fe-Ti-O system. The model for the rutile solid solution
was extended to describe the solubility of Fe2O3(s) and V2O5(s) simultaneously. The model for the
hematite solid solution was similarly extended to describe the solubility of TiO2(s) and V2O5(s) simultaneously.
The ferropseudobrookite solid solution was modelled with a simple polynomial model
to include a small solubility region of V2O5(s). A nal set of self-consistent thermodynamic parameters
was estimated within acceptable error limits. Calculated isothermal projections at 1000 C,
1100 C, 1200 C, 1300 C, and 1400 C are presented and compared to experimental observations.Materials Science and Metallurgical EngineeringPhD (Metallurgical Engineering)Unrestricte
Recovery of rare earth elements from Alaskan coal and coal combustion products
Get PDFThesis (M.S.) University of Alaska Fairbanks, 2016Owing to the monopolistic supply and rapid demand growth of Rare Earth Elements (REEs), cost effective and eco-friendly technologies for extraction of REEs from coal and coal byproducts are being widely explored. Physical separation tests, like magnetic separation, float-sink and froth flotation, were conducted at a laboratory scale, for identification and characterization of REEs in two Alaskan coal samples. The studies revealed that the samples are enriched in critical REEs, and have elevated REE concentrations as compared to average world coal estimates. The selected coal samples from Healy and Wishbone Hill regions were found to possess an overall concentration of 524 ppm and 286 ppm, respectively, of REEs in coal on ash basis and some density fractions have total REE concentrations as high as 857 ppm. Based on the characterization studies, detailed investigations were conducted to enrich the REEs and produce a concentrate for downstream extraction. A three-factor three-level Box-Behnken design for modeling and optimization of froth flotation revealed that the optimum flotation conditions for maximum REE Enrichment in the froth fraction was independent of collector dosage for both coal samples. The response variable was maximized at 4.2% solids and 32.7 ppm of frother dosage for Healy Coal sample and 10% solids and 37.9 ppm of frother dosage for Wishbone Hill Coal sample. A processing flowsheet for REE enrichment in clean coal is proposed, which aims at concentrating REEs in lower density fractions by a combination of dense medium separation and froth flotation processes. The overall REE recovery of the process is calculated to be 76% for Healy and 60% for Wishbone Hill with clean coal fractions enriched in REE concentrations above the cut-off value required for the commercial exploitation. The coals are bound to possess the potential to be used as a REE resource under favorable socio-economic and geo-political scenarios
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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