Although mining is essential to life in our modern society, it generates huge amounts of waste that can lead to acid mine drainage (AMD). Most of these mine wastes occur as large piles that are open to the atmosphere so that air and water vapor can circulate through them. This study addresses the reactions and transformations of the minerals that occur in humid air in the pore spaces in the waste piles. The rate of pyrite oxidation in moist air was determined by measuring over time the change in pressure between a sealed chamber containing pyrite plus oxygen and a control. The experiments carried out at 25?C, 96.8% fixed relative humidity, and oxygen partial pressures of 0.21, 0.61, and 1.00 showed that the rate of oxygen consumption is a function of oxygen partial pressure and time. The rates of oxygen consumption fit the expression (dn/dt=(3.31x10^-7)(P^0.5)(t^-0.5) It appears that the rate slows with time because a thin layer of ferrous sulfate + sulfuric acid solution grows on pyrite and retards oxygen transport to the pyrite surface. The transformation of efflorescent sulfate minerals (the reaction products of iron sulfide oxidation) from a pyrrhotite-rich massive sulfide is explained using a systematic analysis of their stoichiometry and thermodynamics. Their stabilities are controlled by oxygen partial pressure, relative humidity, and activity of sulfuric acid and can be visualized using log activity of oxygen-log activity of water and log acitvity of sulfuric acid-log activity of water diagrams developed during this study. Samples from the field site were analyzed in the laboratory to determine mineralogy, equilibrium relative humidity, chemical composition, and acid generation potential. Dissolution experiments showed that fibroferrite-rich samples had the highest acid producing potential, followed by copiapite-rich samples and then halotrichite-rich samples. The most abundant metals in solutions produced by dissolving the salts were magnesium, aluminum, zinc, copper, calcium, and lead. The molar concentrations of the metals varied with mineralogy. However, all of these minerals release metals and acid when they dissolve and therefore represent a significant environmental threat. / Ph. D.

Rare earth elements (REE) exhibit particular and unique properties that render them essential to technological applications. Of particular interest is their involvement in the transition toward global sustainability and their military applications. The magnetic properties of the rare earth elements is of primordial importance to sustainable development. More specifically, terbium and dysprosium are two elements with no known substitutes in critical applications and with no domestic or allied sourcing available. These elements are currently mined by in-situ leaching of ion-absorbed clays, mostly from illegal operations in Myanmar financed by Chinese companies. The demand from both elements, and for the other magnet rare earths is projected to growth at very high rates through 2035 while the world undergoes a transition toward sustainability, and a drastic reduction in greenhouse gases emissions. Our team has been evaluating the potential of acid mine drainage (AMD) as a source of rare earth elements and critical materials (CM). Acid mine drainage is the result of in-situ generation of sulfuric acid due to the weathering of sulfide ores. It is a significant legacy environmental issue and one of the largest pollutants in many mining districts throughout the world. The objective of the present work is to provides a roadmap for the utilization of AMD as a critical material feedstock to preserve the independence of the United States of America with regards to these materials. To that effect, a fundamental economic assessment of REE/CM recovery from AMD using a network sourcing strategy in addition to a robust, flexible feedstock separations and refining facility was undertaken. A techno-economic analysis of the extraction, refining, separation and reduction to metal is presented along with a sensitivity analysis.The results of this analysis show that, with the exception of the minimum price scenario, all operational configurations have positive economic indicators with rates of return varying from 25% to 32% for the contemporary price scenario. This is primarily due to the very high enrichment in terbium and dysprosium of AMD. The optimal configuration was determined to be production of Co, Mn, and all REEs except for mischmetal, which is not recovered. Sensitivity analysis and Monte Carlo Simulation show that capital cost and HCl consumption are the two major factors influencing rate of return, thus indicating opportunities for future technology development and cost optimization. In order to reduce both the capital and operation cost of the facility, alternative ionic liquids extractants based on conventional acidic extractants where synthesized and investigated. The results show that the ionic liquids varied in performance, with [c101][D2EHP] and [c101][EHEHP] performing poorer than their conventional counterparts and [c101][c572] performing better. The performance of [c101][c572] was 13% superior to Cyanex 572, 20% superior to EHEHPA and 27% superior to D2EHPA the current commercially used extractants. Recommendations for further study on [c101][c572] include stripping tests, continuous pilot testing, and techno-economic analysis. The test work revealed that zinc and to a lesser extent calcium were significant deleterious elements in the solvent extraction circuit, and that selective removal would significantly reduce the acid-base consumption of the separation circuit. A process was developed to selectively remove calcium and zinc from AMD-derived feedstock and from REE products. The ammonium chloride leach process offer many advantages, including the possibility of closing the cycle by using carbon dioxide sequestration as a step to regenerate the ammonium chloride in a zero-discharge process. / Doctor of Philosophy / A younger me: - What are these elements in the bottom of the periodic table? My high school chemistry teacher: - "Don't waste time there, these are of no concern." Twenty years later, technological developments and the imperative to transition away from fossil energy to mitigate climate change have brought the rare earth elements, a series of 17 elements with unique properties to the forefront of the conversation. In addition to an organic increase in demand, the recent supply chain consolidation by China is adding a geopolitical risk to the equation. The magnetic properties of the rare earth elements is of primordial importance to sustainable development and to our military technology. More specifically, terbium and dysprosium are two elements with no known substitutes in critical applications and with no domestic or allied sourcing available. These elements are currently mined from illegal operations in Myanmar, with the support of Chinese companies. The demand from both elements, and for the other magnet rare earths is projected to growth at very high rates through 2035 while the world undergoes a transition toward sustainability, and a drastic reduction in greenhouse gases emissions. Given the important of the rare earth elements, and the absence of significant deposits in the united states, with the exception of the Bear Lodge and Elk Creek deposits, the Department of Energy has mandated academic institution of evaluating alternative sources of rare earth elements. Our team has been evaluating the potential of acid mine drainage as a source of rare earth elements and critical materials. Our team has surveyed many acid mine drainage sources and determined that many sites are highly enriched in terbium and dysprosium. Acid mine drainage is a legacy environmental issue related to past problematic mine development techniques. In the problematic mines. these acidic mine waters are permanently generated and if not treated can have severe impacts on water streams in which they flow. The toxicity of the acid mine drainage on the environment is due to its high acidity and significant levels of toxic metals. Acid mine drainage can be recognized by their yellow to red tint. It is treated by reacting it with a neutralization agent, which results in treated water and a sludge. The sludge is dewatered and stored in tailing impoundments. I have designed a process for the economical recovery of rare earth elements and critical materials from acid mine drainage. The cost to build and operate the facility was derived and it was determined that the project could be further enhanced by reducing the plant chemical reagent consumption. One specific category of chemical referred to as extractant, is central to the rare earth separation process. A novel variation on the standard extractants has been evaluated and promises to provide significant savings. While the extractants were investigated, it was noticed that some impurities such as zinc and calcium created issues in the circuit. I then developed a process for their selective removal. The process also provide a net carbon dioxide sequestration potential.

Thirty-six eight-year-old white pine (Pinus strobus L.) trees were used to identify minesoil, plant moisture, and foliar nutrient properties influencing white pine growth on reclaimed mine sites in southwest Virginia. PRESSAll (SAS Views, 1984) was used to determine relationships between soil properties and growth, soil properties and functional environmental factors (plant moisture stress and foliar nutrients), and between functional environmental factors and growth. PRediction Error Sum of Squares (PRESS), Mean Square Error (MSE), and Multiple Correlation Coefficient (R²) were used as criteria for variable selection and model validation. Rooting-volume index, the reciprocal of the electrical conductivity (EC), and extractable P in the soil-sized fraction of the minesoils were the best validated variables, predicting tree heights with the smallest amount of unit error (APRESS of 0.86 m) and accounting for the highest R² ( R² = 53.06%). The depth of the rooting volume had the greatest effect on 2 early growth (R² = 7 .91%), but variation in the last four years of height growth appeared to be a function primarily of rooting volume (R² = 51.40, p < 0.0001). Relationships between soil properties and 2 functional environmental factors varied widely (R² = 0.00-27 .50%). Plant moisture stress was most highly associated with the volume of the soil-sized fraction (R² = 13.6%), foliar phosphorus with soil pH (R² = 22.5%), and foliar cations with anaerobic-mineralizable nitrogen (R² = 0.00-27 .5%). The relationship between functional environmental factors and growth was uniformly weak (R² = 0.00-14.97%). Plant moisture stress was consistently related to overall height and its increment over the last four years, but foliar nutrients were erratically related to growth. No significant relationships between other functional environmental factors and growth were detected. Minesoil indices for individual trees ranged from 47-147 (base age 50). The depth of minesoil for site index 80 (average for Southern Appalachia) was 40 cm. / M. For.

Schwertmannite, a ferric oxyhydroxysulfate mineral typically found under acidic, high sulfate and iron aqueous conditions, such as acid mine drainage environments, was studied using analytical high resolution transmission electron microscopy (HRTEM). HRTEM offers advantages over bulk techniques such as powder x-ray diffraction and pair distribution function (PDF) analysis of synchrotron data, in its ability to discern multiple phases within poorly crystalline nanominerals. Based on extensive HRTEM observations of both natural and synthetic schwertmannite samples, the authors suggest that schwertmannite should not be described as a single phase mineral with a repeating unit cell, but as a polyphasic nanomineral with crystalline areas spanning less than a few nanometers within an amorphous matrix. The few visible lattice fringes observable in both natural and synthetic schwertmannite agree well with d-spacings of goethite (and jarosite in natural samples) implying that the transformation from schwertmannite to these phases occurs as a gradual structural reordering at the nanoscale. In the synthetic study, the complete transformation from schwertmannite to goethite nanorods and nanoparticles within 24 hours at 75°C was observed, indicating a low energetic barrier to schwertmannite's phase transformation. We also found that amorphous silica can be intimately entrained within natural schwertmannite, and that high concentrations of arsenic can be held in close association of nanocrystalline regions of the mineral. / Ph. D.

Drainage ditches, or grassed waterways, collect nutrient-laden runoff from agricultural fields and transport it to nearby waterbodies. The high nitrogen and phosphorus content in this water leads to negative effects, such as eutrophication in the receiving waters. In-ditch bioreactors are a simple, inexpensive treatment technology that could potentially remove nitrogen and phosphorus from agricultural runoff. In-ditch bioreactors are intended to reduce flow rate and stimulate denitrification and sedimentation. Using experimental ditch segments and simulated runoff, this study evaluated nutrient removal in 1) vegetated ditches, 2) vegetated ditches with woodchip bioreactors and 3) vegetated ditches with combination woodchip and biochar bioreactors. Biochar was added in an effort to increase phosphorus removal. Inlet and outlet concentrations of nitrate, ammonium and phosphate were measured for each of the three treatments in triplicate. There were no statistically significant differences between treatments on load removed for any of the three nutrients of interest. Issues in measuring outlet flow rate made drawing definitive conclusions on nutrient load reductions difficult. Further experimentation using adjusted outlet flow measuring methods and bioreactor design would help establish whether in-ditch bioreactors are suitable for use as a nutrient removal technology in agricultural grassed waterways. / Master of Science / Drainage ditches, or grassed waterways, are located at the edge of agricultural fields where runoff migrates naturally. These ditches help to direct runoff from the field to receiving waterbodies while reducing erosion. Agricultural runoff often contains high levels of nitrogen and phosphorus from fertilizer added to promote crop growth. When runoff with a high nutrient content reaches a waterbody, it reduces the quality of the water for the plants and animals that live in it and for human recreation or consumption. In-ditch bioreactors are a simple, inexpensive treatment technology that could potentially remove nitrogen and phosphorus from agricultural runoff. In-ditch bioreactors have the potential to remove nitrogen from the water by creating optimal conditions for the microorganisms that transform nitrogen in the water to nitrogen in the air. Phosphorus removal has the potential to be enhanced by in-ditch bioreactors that reduce flow and allow for phosphorus to settle out of the water. In addition, settling of phosphorus may be increased by adding a material, such as biochar, that phosphorus can attach to. Using experimental ditch segments and simulated runoff, this study looked at nutrient removal in 1) vegetated ditches, 2) vegetated ditches with woodchip bioreactors installed and 3) a vegetated ditch with combination woodchip and biochar bioreactors installed. Concentrations of two nitrogen compounds and one phosphorus compound were measured before and after passing through each ditch. There were no significant differences between any of the three ditch types on how much of each compound they could remove. These results are inconclusive due to inaccuracies in measuring flow rate at the outlet of the ditches. Further experimentation using improved flow measuring techniques and bioreactor designs would likely help establish whether in-ditch bioreactors are suitable for use as a nutrient removal technology.

Laboratory experiments were carried out to evaluate the effectiveness of antibacterial substances and antibiotics against Thiobacillus ferrooxidans, the organisms responsible for bacterial mediated acidic mine drainage. Twenty two antibiotics (obtained from Lilly and Co.) and two antibacterial substances were added to: bacterial culture ATCC 19859 grown in 9K medium. Appropriate controls were maintained. Inhibition of iron oxidizing bacteria was recorded in terms of changes in Eh of the medium treated with the compound. Seven antibiotics (A38533A:, A38533B, 197506, 13780, 171541, chloramphenicol and cephalexin) and the two antibacterial substances [N-serve(nitrapyrin) and Dicyandiamide] effectively inhibited the oxidation of Fe²⁻ ions in the medium. The kinetics of Fe²⁻ oxidation with the addition of antibiotics and the antibacterial substances was studied. N-serve [2-chloro-6-(trichloromethyl) pyridine], used as a nitrification inhibitor in agriculture, was highly effective at concentrations greater than 0.1 ml/l. Iron oxidation levels were reduced to levels close to that in uninoculated controls (abiotic oxidation). The use of N-serve to inhibit acid mine drainage (AMD) causing bacteria seems to be both economical and environmentally safe. / Master of Science

Several recent studies have shown that acid mine drainage (AMD) may be a promising source of rare earth elements (REEs), which are essential feedstocks for many high tech applications and defense products. AMD is a longstanding environmental challenge and is currently the primary pollutant of water in the Appalachian coal mining region. Acid generated during the coal mining process tends to leach several transition metals from the surrounding rock strata. While iron, aluminum, and manganese have traditionally been noted as the predominant metals in AMD, recent studies have also shown that REEs are also present, albeit in trace concentrations, often less than 5 μg/L. The recovery of REEs from AMD can be both an economic and environmental advantage; however, the low REE concentrations and high contamination from other metals makes the concentration and purification of REEs quite difficult. This research seeks to develop and optimize a process capable of producing mixed rare earth concentrates with purities exceeding 90% from an AMD feedstock. Parallel efforts by other members of the research team showed that a solid preconcentrate, nominally 0.1 to 2% REE, can be readily produced from AMD; however, that pre-concentration process cannot provide the further enrichment needed to generate high purity oxides suitable for downstream markets. In this project, solvent extraction was investigated as secondary process used to further enrich the low grade preconcentrate to a purity exceeding 90%. Initially, laboratory-scale batch solvent extraction tests were performed on synthetic REE solutions to determine the influence of various process parameters (e.g. pH, extractant dosage, diluent type, and feedstock concentration). Next, the separation of REEs from major AMD gangue elements was investigated using synthetic leachate solutions with concentrations similar to those expected from the pre-concentrate samples. This process showed that the grade targets could easily be met when combining optimal parameters from each step. From this preliminary work with synthetic solutions, an optimal SX process was developed and validated using a real leachate generated from a pre-concentrate sample. By integrating leachate preparation, solvent extraction, scrubbing, stripping, and oxalic acid precipitation, an oxide containing 90.5% rare earth oxides was generated. Details on the process development, experimental optimization, and opportunities for process improvement are described. / Master of Science / Rare earth elements (REEs) are essential for many modern industries, high-tech applications, and defense products. The U.S. consumes approximately 11% of the global REE demand; however, the US supply chain is heavily reliant on imported Chinese feedstocks. This lack of a domestic supply chain exposes the US to both price and supply volatility, which are prevalent in the international markets. This supply issue is further compounded by a lack of suitable domestic feedstocks. REEs are rarely concentrated into mineable ore deposits, and in some cases the extraction and processing of conventional REEs deposits entails considerable environmental risk. As a result of these challenges, numerous federal agencies and private companies have recently sought to identify promising alternative resources. One potential alternative resource is acid mine drainage (AMD), which is a common environmental challenge associated with coal and hard rock mining. Prior studies have shown that acid mine drainage contains REEs; however, other metals, such as iron, aluminum, and manganese, preclude REE recovery using conventional processing techniques. As such, the goal of this research is to develop and optimize a process capable of recovering and concentrating REEs from an AMD feedstock. The research conducted in this thesis predominantly included laboratory testing using synthetic AMD samples. The complexity of the synthetic AMD progressively increased from very simple, single element solutions to complex multi-component mixtures. Through this research, data and information from these controlled experiments was used to design a multi-step solvent extraction process capable of producing final REE products exceeding 90% purity. In the last stage of the research, the final process was validated using actual AMD recovered from an operating mine site. The validation test showed that the process was effective in meeting its initial objectives: the grade of the final rare earth oxide was determined to be 90.5%. This laboratory-scale experimental work represents the first step of process needed to develop and deploy a commercial technology capable of producing REE products from AMD feedstocks.

A field study was conducted at a residence in Chesapeake, Virginia to determine the effect of setback distances from a drainage ditch on the disposal of septic tank effluent. The study was done from September 1979 to August 1981. The soil used is the Tomotley series belonging to the fine-loamy, mixed, thermic family of Typic Ochraquults. Four prototype trenches were installed at 1.5, 3, 6 and 21 m from the edge of a drainage ditch which was 1.5 m deep. The trenches were pressure dosed equally with 2.4 to 4 cm per day. Replicated nests of sampling wells at depths 90, 150 and 300 cm were placed with distance from the trenches. Continuous stage recorders were positioned 4.5, 29.1 and 60 m from the ditch to monitor water table behavior. Groundwater analysis included fecal coliforms, the NH₄, NO₃, NO₂, Na, Ca, Mg, Cl and PO₄ ions, pH and EC. Ammonium concentrations in the soil beneath the trenches indicated nonuniform effluent infiltration yet more uniform than with conventional gravity flow distribution. High sodium absorption ratios of the septic tank effluent ranging from 18 to 45 did not significantly reduce infiltration rates as no ponding of effluent in the trenches was observed. The existing land surface was sloped greater than the water table gradient resulting in decreasing unsaturated depths with closeness to the ditch. The mean distances between the trench bottom and the water table were 64 cm at 3 m, 80.1 at 6 m and 90.4 cm at 21 m. The accumulation of fecal coliforms, NH₄, P, Cl and total salts (EC) in the groundwaters at 120 to 150 cm depth was inversely proportional to the mean distances from the trench bottoms to the water table. The lack of denitrification occurring underneath the trench with the most extensive unsaturated zone suggests NO₃ may accumulate under disposal systems that have mean unsaturated depths of ≥ 90 cm. Effluent movement was mainly lateral and in the upper zone of the water table with limited vertical movement below the water table surface. An equation applying D-F theory to infinitely deep soil was developed to describe flow for the given drainage system and for the inclusion of standard size drain fields. The current practical setback distance of 21 m is considered counterproductive for effluent treatment for some situations. / Ph. D.

A system of detention basins is an effective device for control of, storm flood both in terms of quantity and quality. The feasibility of designing detention basins for flood control by use of abandoned spaces near highway interchange and between highway embankments is investigated. Three algorithms are examined for routing inflow hydrographs through interconnected basins under various hydraulic and. hydrologic conditions. The programs solve for both the time dependent flow quantities and the extent of pollutant removal in the system for given inflows and pollutant trap efficiencies of the individual basins. The first algorithm is the extended version of the classical single reservoir routing and involves solution of a system of simultaneous nonlinear equations. The other two algorithms employ the so-called linearized or simplified versions of the continuity equation. The algorithms can take care of various possible combinations of inflow, type of connections between basins, and the boundary conditions at the outlet(s). Results from the three algorithms are comparatively analysed and the one which does not require excessively small time step for solution convergence is selected. The Kuo method employing the standard approximation for the mass conservation equations as in classical single reservoir routing is found favorable with respect to the time step required for convergence and hence is selected for application to design examples. Various basin arrangements are included to show the routing results with respect to quantity and quality for different combinations of storm inflows and outlet structure types. Interconnection between basins is found desirable both in terms of quantity and quality control of effluent. / M.S.

Mine influenced waters (MIW) pose a broad range of potential environmental impacts, which often also carry financial and social consequences. MIWs are often high in solids content, and can have highly acidic or alkaline pH and high contents of metals or other problematic constituents (e.g., traces of chemicals used in minerals processing or water treatment). Acid mine drainage (AMD) is a common type of MIW characterized by low pH. Release of untreated MIWs like AMD to surface waters, for example, can lead to problems such as a sedimentation and siltation, undesirable changes in pH and/or precipitation of metals and salts, and addition of particular stressors for various aquatic organisms. As such, these waters are frequently captured and treated on-site in systems requiring extensive piping. Polyethylene (PE) pipes are popular in mining, including MIW, applications because they are chemically inert, and have relatively low costs, low density, and high flexibility. However, PE material is susceptible to abrasion. To combat this problem and offer a single pipe option for a variety of mining applications, Gerodur MPM Kunststoffverarbeitung GmbH and Co. KG.(Gerodur) has developed a novel liner for PE pipes. The liner is made of a rubber-like material that is resistant to mechanical abrasion by slurries or high-solids waters, but its susceptibility to mineral scale buildup has not been specifically evaluated. In order to evaluate scale buildup on the lined PE versus traditional PE pipe material, two studies were undertaken and are reported in this thesis. A short-term field study was conducted in the Reiche Zeche underground mine in Freiberg, Germany – an inactive lead-zinc mine. Water quality varies considerably between different zones in this mine, but is characterized by very high dissolved solids, which is typical for AMD. For this study, the pipe materials were exposed to waters in six locations for three weeks; and were then analyzed for weight gain and scale composition. Results showed that there was only a marginal difference in the scale build up when comparing the two piping materials. In a follow-up study in the laboratory, the two pipe materials were exposed over a total of 16 weeks to three idealized AMD water qualities: an untreated AMD made to simulate the most extreme condition observed in the field study, the same AMD following passive treatment (i.e., neutral pH), and the same AMD following active treatment (i.e., slightly basic pH). Exposure was done in pipe-loop apparatuses such that samples could be subjected to different flow and sedimentation conditions (i.e., gentle mixing only on the sides of the water reservoir, gentle mixing and sedimentation on the bottom of the reservoir, and constant flow and possible sedimentation within the pipe-loop tubing itself). Results of this study indicated that factors such as water chemistry and flow velocity had significant effect on the quantity and chemistry of scale. However, there was very little difference in propensity for scale build up between the two materials. This liner was designed in an effort to resist mechanical abrasion. Because scale build up is not exacerbated by the liner, it may provide a means for uniform applications across mines with contiguous abrasive and scale prone waters. That is, it could eliminate the need to have various specialized piping materials on a site to handle these problems individually, streamlining the pumping and piping network installation and operation. / Master of Science / Mine influenced waters (MIW) are a potential danger to the environment, and a company’s financial and social standings. MIW’s come in many different varieties, and can contain harmful contaminants from the mine site. One of the most common MIW’s is characterized by low pH, and is commonly referred to as Acid Mine Drainage (AMD). In addition to the problematic pH, AMD can have excessive dissolved solids such as metals, salts, and sediment. Polyethylene (PE) pipes are popular in mining applications because they do not react to most chemicals, and have low costs, low density, and high flexibility. However, PE material is susceptible to losing wall thickness through abrasion caused by slurries and solids in water. Gerodur MPM Kunststoffverarbeitung GmbH and Co. KG.(Gerodur) has developed a liner for PE pipes to address the abrasion problem. The liner is made of a rubber-like material that is resistant to mechanical abrasion, but its susceptibility to mineral scale buildup has not been specifically evaluated. To study the differences between the new liner versus traditional PE pipe, two studies were completed and are reported in this thesis. The first was a short field study conducted in an underground mine in Freiberg, Germany. Though the water throughout the mine varies, it generally has high dissolved solids as seen in most AMD. In the mine, traditional and lined pipes were exposed to waters in six different locations for three weeks, and weight gain and scale composition were tested. Results showed very little difference in both quantity, and content of scale. To further test the material, a longer lab study was conducted. The two materials were exposed for 16 weeks to three different simulated waters. One simulated untreated AMD, AMD treated to a neutral pH, and finally AMD treated to a basic pH. Results showed that the water chemistry and flow did have an effect on the quantity and chemistry of the scale. It also supported that there was very little difference in the scale on the two materials when exposed to the same water conditions. Because the material did not make scale worse, it can be applied to waters with high abrasion and scaling potential. This could be an asset to the mining community because it eliminates the need for v multiple pipe materials. It simplifies the mining process by allowing one pipe material to be applied uniformly across a mine site.