Enhanced bioweathering of coal for rare earth element extraction and concentration

Thesis (M.S.) University of Alaska Fairbanks, 2019Rare earth elements (REEs) are a group of seventeen elements that include scandium, yttrium, and fifteen of the lanthanide series elements, which are used in a variety of consumer goods and for defense purposes. Acquiring a domestic profitable source of REEs is a critical national need as most of the global supply comes from one country, China. To counter this problem, the US is actively looking at alternative sources of REEs by implementing unconventional methods of extraction. Coal is one of the alternative sources of REEs. Alaskan coal from Wishbone Hill and Healy are known to contain REEs up to 286 ppm and 524 ppm, respectively, while having concentrations as high as 950 ppm on ash basis in some density fractions. Microbial leaching or bioleaching is a novel method that can be used for extraction of REEs from coal as microbes are known to affect earth's surface over geologic time by playing critical roles in weathering of minerals. A certain species of bacteria, Shewanella oneidensis MR-1, was used to separate the REEs from Wishbone Hill and Healy coal samples. The experiments were performed for various density fractions of both coals by varying solids percentage, temperature, size of coal, and bacterial concentration, and recovery of REEs for these conditions was recorded. Highest individual recovery of neodymium, 75.3%, was obtained for Wishbone Hill 1.3 floats, while a maximum of 98.4% total REE recovery was obtained for Healy 1.3 sinks. Healy coal has the higher total recovery of REEs in comparison to Wishbone Hill coal. Bioleaching process was also compared to the acid leaching process. Healy coal responded better to bioleaching than the acid leaching process. The Wishbone Hill coal had comparable recoveries of bioleaching with acid leaching, although they were always less than acid leaching.University of Alaska Fairbanks: Department of Mining and Geological Engineering and Department of Labo

Study on MRI evaluation of various etiologies of seizures

Introduction: Epilepsy describes a condition in which a person has unprovoked, recurrent seizures due to a chronic, underlying process. Several studies have estimated the prevalence of epilepsy ranging from 5-30 persons per 1000 population. Most of the patients suffering from epilepsy have good control on seizures with the use of antiepileptic medications, however most of the patients with intractable epilepsy have seizures that are focal and can be potentially treated. Objectives of our study: The objective of our study to find out the role of MRI in evaluating the aetiologies of seizures in subjects with seizure disorder. Methodology: We included a total of 150 subjects after taking voluntary consent from the study subjects based on inclusion and exclusion criteria. A detailed proforma was recorded which included subject’s socio demographic data, medical history, personal history, past-history, family history and general physical examination, blood pressure measurement, systemic examination etc. The points noted were duration of illness, type of seizures, and any associated illness. Detailed clinical and neurological examination were done to find out any neurological deficit. Based on the history and examination, a clinic etiological diagnosis was made. Follow up of subjects were done until the completion of treatment (maximum 6 months).&nbsp

Self-Organized Wrinkling in Thin Polymer Films under Solvent–Nonsolvent Solutions : Patterning Strategy for Microfluidic Applications

Self-organized wrinkling instabilities in thin polymer films have instigated a field of versatile surface patterning and have spurred several research efforts in developing micro- and nanopatterned templates for a wide range of applications. Here, we report for the first time a distinct class of wrinkles in a thin polymer (polystyrene, PS) film coated on a substrate under a mixture of organic solvent and aqueous nonsolvent. The solvent (dimethyl formamide, DMF) softens and swells the polymer and paves the way for wetting of the hydrophilic substrate (≥46 mJ/m2) by the solvent–nonsolvent (S-NS) mixture, leading to wrinkle formation. It is investigated that selective delamination-induced wrinkling is a generic phenomenon and takes place in various polymers as well as different combinations of solvent–nonsolvent mixtures. The surface energy of the substrate and the composition of the solvent–nonsolvent mixture play a critical role as wrinkling is not observed on substrates with lower surface energy (<46 mJ/m2). An isotropically distributed yet disordered self-organized wrinkle network of hollow buried channels is formed, and it is illustrated that these can be exploited to generate a mesh of microwires and harnessed to form highly directional patterns using electron beam lithography, which can turn the new leaf for nano- and microfluidic device fabrication platforms

Bio-weathering Using Shewanella oneidensis MR-1 Enhances Selective Recovery of Rare Earth Elements from Alaskan Coal Mines

Coal mines in Alaska with high rare earth elements (REEs) levels (286-524 mg/kg) serve as an alternative domestic source for REEs. Existing leaching/separation technologies fail to selectively recover REEs from the feedstock and require downstream multiple purification stages that increase the overall operational cost. This study aims at bio-weathering coal from two Alaskan coal mines (Wishbone Hill and Healy) at three density fractions (1.3 float, and 1.3 and 1.5 sink) using Shewanella oneidensis MR-1 for achieving higher selective REEs recovery in one-step process. Optimizing the bio-weathering process by varying solids percentages (5.7 to14.3% w/v), particle size (-14 to -200 M), incubation temperatures (30 to 34 °C), and inoculum dosing (0.2 to 1% v/v) resulted in highest recovery of Neodymium (75.3%) and total REEs (98.4%) from 1.3 float Wishbone Hill and 1.3 sink Healy coal, respectively. When compared to the chemical leaching process, bio-weathering enhanced selective recovery of REEs including Scandium, Yttrium, Ytterbium, Terbium, Erbium, and Lutetium from Healy coal at low density, and Yttrium from Wishbone Hill coal at high density. The results indicate the future scope for developing cost-effective selective REEs recovery processes that may address the global critical minerals supply chain risk