Cabanzo Olarte, Andrea C.

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    Microscopic mass transfer of 2,4,6-Trinitrotoluene (TNT) through sand by scannig electron microscopy measurements
    (2006) Cabanzo Olarte, Andrea C.; Castro Rosario, Miguel E.; College of Arts and Sciencies - Sciences; Hernández-Rivera, Samuel P.; Briano-Peralta, Julio G.; Department of Chemistry; Muñoz, Miguel
    Scanning electron microscopes (SEMs) are widely used to provide three-dimensional information about the morphology and distribution of components on the surfaces of soil specimens. The transport of 2,4,6- Trinitrotoluene in soils has been found to be influenced by a number of environmental factors, such as, temperature and water content. In this work, we used a scanning electron microscope coupled with energy-dispersed X-ray (EDS) to study and describe the distribution of TNT on soil surfaces as a function of time. X-ray dot mapping was used to analyze carbon and nitrogen on surface of mixing TNT/sand on microscopic scale by comparing scanning electron microscope image of the same areas of soil samples after four days. The images obtained from SEM showed differences in the morphology and spatial distribution of the explosive on sand after sample preparation. On the other hand, EDS measurements showed a decrease in the nitrogen fluorescence signal as well as in the carbon fluorescence signal, demonstrating the movement of TNT during the time. The kinetics of surface sublimation and the kinetics of TNT through the sand were studied. According to experimental results, two theoretical models incorporate parametric equations to explain nonlinear sublimation rate of TNT on sand and diffusion rate of solid TNT through to sand surface.
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    Synthesis, characterization and mild detemplation of novel cobalt rich SBE type nanoporous materials
    (2012) Cabanzo Olarte, Andrea C.; Hernández Maldonado, Arturo J.; College of Arts and Sciences - Sciences; Briano Peralta, Julio G.; Hernández Rivera, Samuel P.; Meléndez, Enrique; Department of Chemistry; Acevedo, Aldo
    The optimization of the synthesis, extended characterization and evaluation of the adsorption properties of cobalt-rich SBE type aluminophosphates (CoAPO-SBE) were investigated. According to X-ray diffraction (XRD), scanning electron microscopy (SEM) and porosimetry analyses, a longer gel aging time results in crystals with less faulting. We employed a vacuum assisted thermal process to avoid destruction of the periodic framework, since the porous properties of the framework could only be evaluated upon removal of the structure- directing agent (SDA) species (i.e., detemplation); this approach resulted in micropore surface areas of ca. 600 m2/g. Coupled thermal gravimetric and Fourier transformed infrared spectroscopy (TGA/FTIR) analyses suggested that the decomposition of the SDA takes place in a multi-step fashion, with products that included ammonia, carbon monoxide, carbon dioxide and water. In situ high temperature XRD tests indicated that the detemplated open framework is also highly unstable to oxidative and high temperature conditions probably due to the large content of transition metal centers (Co/Al ~ 1). Attempted detemplation of CoAPO-SBE materials by UV- ozone followed by vacuum assisted thermal process was also performed. The complete process itself appears to be more efficient and less harmful to the SBE framework, but will require further investigation. We found, however, that it is possible to effectively functionalize these materials using coupled vacuum assisted partial detemplation and solid-state ion exchange (PD/SSIE) at mild temperatures. CoAPO-SBE was detemplated and Na+ or Li+ species were introduced by SSIE in an attempt to modify its surface properties while preserving the framework’s structural and textural properties. The resulting porous materials were also tested for equilibrium adsorption of CO2. The best CO2 loading capacities were observed in the sodium-SBE variants at 25 ºC for both low and high partial pressure ranges. Furthermore, this adsorbent material exhibited good selectivity toward CO2 over CH4 or N2. Structural refinement of the CoAPO-SBE before and after CO2 adsorption process was also explored.