Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Indiana University-Purdue University Indianapolis (IUPUI) / Improvised explosive devices (IEDs) are a global threat due to their destructive potential, the easy access to raw materials, and online instructions to manufacture them. These circumstances have led to an increase in the number of IEDs using potassium chlorate as an oxidizer. The standard methods to detect chlorate are mainly designed for laboratory-only testing. Thus, field instrumentation capable of detecting oxidizers from explosives fuel-oxidizers is critical for crime scene investigation and counterterrorism efforts (described in Chapter 1). We developed a paper-based sensor for the in-field detection of chlorate (described in Chapter 2). The sensor is low-cost, disposable, portable, and inexpensive to fabricate, and its flexibility features allow for surface sampling without sample destruction. The sensor has an electrodeposited molybdate sensing layer, as chlorate was reported to have a catalytic effect on the molybdate reduction. The chlorate detection relies on monitoring the change in redox activity of the molybdate sensing layer using different electroanalytical techniques. We effectively demonstrated the analytical performance of the sensor (Chapter 3), obtaining a limit of detection of 1.2 mM and a limit of quantification of 4.10 mM. We evaluated the selectivity of the sensor by testing other oxidizers, such as perchlorate and nitrate, which did not present any electrochemical activity with the molybdate sensing layer. Additionally, we performed an interferent study with sugar, commonly used as fuel in IEDs, and other common white household powders such as baking soda, flour, and corn starch and neither a false positive nor a false negative result was observed (Chapter 3). As bromate has been reported to have a stronger catalytic effect than chlorate on the redox activity of molybdate, the quantification of bromate was also explored, and a bromate sensor was developed using the findings of the chlorate sensor (Chapter 4). The reaction mechanism involved in the molybdate reduction was explored and discussed in Chapter 5. The capability of the sensor in detecting chlorate from combusted samples and post-blast samples was successfully demonstrated in Chapter 6, as well as the design of encased prototypes to allow for an in-field presumptive test, storage, and transport for in-laboratory confirmatory tests and compared the performance of the sensor to the available commercial tests.

Alkaline fly ash has been studied as a liming agent within coal refuse fills to reclaim acid-forming refuse. Previous studies focused on bulk blending ash with acid-forming (pyritic) refuse. A better representation of field conditions is a "pancake layer" of ash above the refuse. A column study was initiated to evaluate the leachate chemistry from acid-forming refuse-ash bulk blends vs. ash over refuse layers. An acidic and an alkaline ash were blended with, or layered over, acid-forming refuse and sandstone and packed into columns which were leached with deionized water twice a week for 24 weeks under unsaturated conditions. Leachates were analyzed for pH, electrical conductivity, and a suite of elements with a focus on the oxyanions of As, Cr, Mo, and Se. A sequential extraction procedure revealed a significant portion of the elements in the residual fraction for the refuse/spoil substrates and in metal-oxide bound fractions for the ashes prior to leaching, and a general trend for a greater proportion of oxyanion elements to be associated with metal oxide fractions after leaching. Bulk-blended treatments maintained higher leachate pH than corresponding layered treatments. The acidic ash and refuse pancaked treatments exhibited relatively high initial concentrations of most elements analyzed. Pancake layers of ash over refuse are an inadequate co-disposal method to prevent and mitigate acid mine drainage. Blending alkaline ash with refuse to acid-base accounting specifications should improve leachate quality overall, but there may be water quality concerns for loss of Se and other soluble ions during initial leaching events. / Master of Science

<p> </p> <p><em>Improvised explosive devices (IEDs) are a global threat due to their destructive potential, the easy access to raw materials, and online instructions to manufacture them. These circumstances have led to an increase in the number of IEDs using potassium chlorate as an oxidizer. The standard methods to detect chlorate are mainly designed for laboratory-only testing. Thus, field instrumentation capable of detecting oxidizers from explosives fuel-oxidizers is critical for crime scene investigation and counterterrorism efforts (described in Chapter 1). We developed a paper-based sensor for the in-field detection of chlorate (described in Chapter 2). The sensor is low-cost, disposable, portable, and inexpensive to fabricate, and its flexibility features allow for surface sampling without sample destruction. The sensor has an electrodeposited molybdate sensing layer, as chlorate was reported to have a catalytic effect on the molybdate reduction. The chlorate detection relies on monitoring the change in redox activity of the molybdate sensing layer using different electroanalytical techniques. We effectively demonstrated the analytical performance of the sensor (Chapter 3), obtaining a limit of detection of 1.2 mM and a limit of quantification of 4.10 mM. We evaluated the selectivity of the sensor by testing other oxidizers, such as perchlorate and nitrate, which did not present any electrochemical activity with the molybdate sensing layer.</em></p> <p><em>Additionally, we performed an interferent study with sugar, commonly used as fuel in IEDs, and other common white household powders such as baking soda, flour, and corn starch and neither a false positive nor a false negative result was observed (Chapter 3). As bromate has been reported to have a stronger catalytic effect than chlorate on the redox activity of molybdate, the quantification of bromate was also explored, and a bromate sensor was developed using the findings of the chlorate sensor (Chapter 4). The reaction mechanism involved in the molybdate</em></p> <p><em>reduction was explored and discussed in Chapter 5. The capability of the sensor in detecting chlorate from combusted samples and post-blast samples was successfully demonstrated in Chapter 6, as well as the design of encased prototypes to allow for an in-field presumptive test, storage, and transport for in-laboratory confirmatory tests and compared the performance of the sensor to the available commercial tests.</em></p>

MENVSC / Department of Ecology and Resource Management

This study was conducted to determine how the structure and surface chemistry of bulk CaCO3 differs from that of nanometer-sized CaCO3 and then to determine rate, extent and mechanisms of As adsorption on various synthetic CaCO3 materials. Additionally, we sought to devise a chemical CaCO3 precipitate that approximates biogenic CaCO3. The bulk CaCO3 precipitation was performed by using a solution that was highly oversaturated so that large CaCO3 precipitates rapidly form. Two different methods were employed for the synthesis of nanometer size CaCO3 i) an in situ deposition technique and ii) an interfacial reaction (water in oil emulsion). Mineral characterization of all CaCO3 precipitates was done with Nitrogen Porosimetry (Brunauer Emmett Teller method), particle size analysis, X-ray diffraction and Fourier Transform Infrared/ Fourier Transform Raman spectroscopy. The principal objective of the research was to assess the overall reactivity of As(III) and As(V) with different synthetic CaCO3 minerals. This was accomplished by i) running adsorption isotherms (varying As concentration), ii) measuring pH envelopes (varying pH at a fixed concentration) and iii) kinetic experiments (varying reaction time). Also, electrophoretic mobility experiments were performed in the presence of As(III) and As(V), and these studies revealed that As(III) forms stronger inner-sphere complexes with CaCO3 than As(V). Also, it was found that nanometer-sized CaCO3 prepared via deposition formed stronger inner-sphere complexes with As oxyanions (q = 5.26 µmol/m2) compared to either nano-sized CaCO3 from interfacial reactions (q = 4.51 µmol/m2) or bulk CaCO3 (q = 4.39 µmol/m2).<p> The PEG-based nano CaCO3 prepared by an in-situ deposition technique presents a novel and readily available synthesis route that can be used as proxy for the biogenic CaCO3 known to be present in many different environmental conditions. The results of this study suggest that CaCO3 can be used as a sorbent for As in groundwater.

This study was conducted to determine how the structure and surface chemistry of bulk CaCO3 differs from that of nanometer-sized CaCO3 and then to determine rate, extent and mechanisms of As adsorption on various synthetic CaCO3 materials. Additionally, we sought to devise a chemical CaCO3 precipitate that approximates biogenic CaCO3. The bulk CaCO3 precipitation was performed by using a solution that was highly oversaturated so that large CaCO3 precipitates rapidly form. Two different methods were employed for the synthesis of nanometer size CaCO3 i) an in situ deposition technique and ii) an interfacial reaction (water in oil emulsion). Mineral characterization of all CaCO3 precipitates was done with Nitrogen Porosimetry (Brunauer Emmett Teller method), particle size analysis, X-ray diffraction and Fourier Transform Infrared/ Fourier Transform Raman spectroscopy. The principal objective of the research was to assess the overall reactivity of As(III) and As(V) with different synthetic CaCO3 minerals. This was accomplished by i) running adsorption isotherms (varying As concentration), ii) measuring pH envelopes (varying pH at a fixed concentration) and iii) kinetic experiments (varying reaction time). Also, electrophoretic mobility experiments were performed in the presence of As(III) and As(V), and these studies revealed that As(III) forms stronger inner-sphere complexes with CaCO3 than As(V). Also, it was found that nanometer-sized CaCO3 prepared via deposition formed stronger inner-sphere complexes with As oxyanions (q = 5.26 µmol/m2) compared to either nano-sized CaCO3 from interfacial reactions (q = 4.51 µmol/m2) or bulk CaCO3 (q = 4.39 µmol/m2).<p> The PEG-based nano CaCO3 prepared by an in-situ deposition technique presents a novel and readily available synthesis route that can be used as proxy for the biogenic CaCO3 known to be present in many different environmental conditions. The results of this study suggest that CaCO3 can be used as a sorbent for As in groundwater.