Theses and Dissertations at Montana State University (MSU)
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Item Biorecovery of rare earth elements and critical minerals via Gluconobacter oxydans(Montana State University - Bozeman, College of Engineering, 2024) Kessler, Kendall Rhea; Co-chairs, Graduate Committee: Ross Carlson and Ryan AndersonThe depletion of high-grade ore deposits, accumulation of electronic waste, and the geopolitical challenges in sourcing critical materials have emphasized the need for sustainable metal recovery methods and recycling efforts in the United States. Conventional metal recovery approaches, including pyrometallurgy and hydrometallurgy, are not only environmentally unsustainable but also inadequate for the retrieval of metals from low-grade deposits. Biorecovery, defined by microorganism-mediated metal recovery, provides an advantageous alternative to traditional recovery methods due to increased sustainability, lower operational costs, and high efficiencies observed for the recovery of low-grade feedstocks. This study investigates the potential of bioleaching as an eco-friendly alternative in the recycling of two distinct waste feedstocks: magnetic swarf and lithium-ion batteries (LIBs). Cultivation of Gluconobacter oxydans was investigated under varying growth medium compositions, wherein increased concentrations of yeast extract were substituted for KH 2PO 4, to determine the subsequent impact on the base metal and rare earth element recovery through the application of the cell-free biolixiviant. This substitution resulted in increased growth yields and enhanced recovery with respect to magnetic swarf, whereas negligible improvement was observed for LIBs. Biorecovery has also been demonstrated for the recovery of metals from ore, where yields are a function of comminution and concentration efficiencies. Typical compressive comminution practices account for the largest proportion of energy expenditures in a mining process. Transcritical CO 2 (tCO 2) comminution, wherein ore is fractured through overcoming a rock's tensile strength, was examined to determine whether physical differences in particle generation were present as compared to traditional fracture techniques. An ore deposit in British Columbia, rich in a nickel-iron alloy mineral phase called awaruite, was examined through scanning electron microscopy, backscatter electron imaging, and energy dispersive spectroscopy to determine the impact of comminution method on awaruite recovery. Image processing was used to investigate shape factors for the individual particles. Preliminary evidence indicates despite a lack of distinct particle differences, tCO 2 comminution resulted in increased liberation and recovery of awaruite ore. Abiotic leaching studies were conducted to determine whether the method of comminution impacted leaching efficiencies. Although samples could not be quantitatively measured, initial qualitative results indicate tCO 2 comminution provides increased yields.Item The implementation of municipal composting in the state of Montana(Montana State University - Bozeman, 1994) Jones, Brian Stanley; Chairperson, Graduate Committee: Kenneth L. BruwelheideItem Montana's future in recycling : a geographic study of factors contributing to the viability of recycling municipal solid waste(Montana State University - Bozeman, College of Letters & Science, 1999) Livingston, JuliannItem Feasibility of reclaimed asphalt pavement as aggregate in Portland cement concrete pavement(Montana State University - Bozeman, College of Engineering, 2011) Bermel, Bethany Noel; Chairperson, Graduate Committee: Michael BerryEach year, the US highway industry produces over 100 million tons of reclaimed asphalt pavement (RAP) through the rehabilitation and construction of the nation's roads. Using RAP as aggregate in Portland cement concrete pavement (PCCP) is one attractive application for a further use of this recyclable material. Earlier research has demonstrated the feasibility of creating concrete with RAP aggregate; however, prior studies focus on mechanical properties of the material. This research project will further distinguish the properties of this material and draw conclusions on the concrete's aptness for use as a pavement in Montana. This thesis encompasses the development of candidate RAP in PCCP mixtures that will subsequently move forward for a more thorough evaluation of their material properties. The mixing experiment and preliminary testing phases of this project provided information to draw a number of conclusions about the appropriateness of RAP aggregate in PCCP, including: (1) using conventional practices, PCCP containing RAP aggregate (20 percent fine and 45 percent coarse) can achieve compressive strengths in excess of 3,000-psi; (2) as the RAP replacement rate is increased, the compressive strength of the concrete decreases; (3) fine RAP aggregate appears to have a more detrimental effect on the concrete than coarse aggregate; (4) concretes with a relatively high RAP replacement rate (50 percent fine and 100 percent coarse) may be suitable for transportation applications; (5) at high RAP replacement rates, there appears to be a benefit (relative to concrete strength) in using increased replacements of both fine and coarse RAP, rather than singly replacing just one aggregate gradation; and (6) concrete containing RAP displays increased flexural strengths as compared to traditional PCCP. This material research was performed using a Design of Experiments (DOE) method. The suitability of this statistical method as a mix design development tool was characterized through several important findings, which include: (1) the DOE method was effective in distinguishing mixture behaviors; (2) mix design optimization is readily accomplished using the statistical model generated from the DOE data; and (3) variability in the concrete mixing and testing processes has a significant effect on the capabilities of the statistical model.