Laboratory Studies of Martian Materials
Coming Soon!
Molecular Dynamics of Alkaline Chemistry in Moisture-Swing Direct Air Capture CO2 Pumps
|
Direct air capture (DAC) and sequestration is one approach being explored for use in removing CO2 from the atmosphere. Moisture-swing (MS) DAC in particular is promising given its potential for increased energy efficiency as compared to other forms. However, more work is needed to refine and optimize the process. The MissionDAC project is a collaboration between NAU and ASU investigating materials that are most likely to excel in capturing CO2 through alkaline anion exchange chemistries.
Quaternary ammonium resins charged balanced with hydroxide and/or carbonate ions are of especial interest and are the focus of my work as part of the research group. I am running classical molecular dynamics simulations to probe the intramolecular interactions occurring between the quaternary ammonium polymer, anions (hydroxide, carbonate, bicarbonate), water, and CO2 under the guidance of Drs. Jennifer Wade and Gerrick Lindberg. The primary goal will be to provide insight into how hydration and molecular structure impacts the free energy of the carbonate-based moisture swing, with the intent of understanding the roles solvation and competitive hydration play in MS alkaline chemistry and why carbonate preferentially hydrolyzes to hydroxide as the system dries. |
Investigating Outer Solar System Materials with Neutron Diffraction
|
Dr. Helen Maynard-Casely (ACNS), Jennifer, and I have recently completed work featuring the solid phases of ethane, propane, and butane using neutron diffraction (with the wonderfully named Wombat instrument). We have recently expanded our studies to include liquids through a collaboration with Drs. Zachary Amato (Queen’s University Belfast, ISIS Neutron and Muon Source), James Hallett (University of Reading), and Oleg Kirichek (ISIS Neutron and Muon Source).
|
|
Experimental Studies Involving Mixtures of Methane, Ethane, Propane, and Nitrogen with Implications for Titan
|
Titan is a cryogenic geochemical laboratory. With global surface temperatures of 89–95 K and a pressure of 1.47 bar, methane (CH4) and ethane (C2H6) are the primary surface liquid constituents and the dominant species that compose the polar lakes and seas on Titan. Atmospheric nitrogen (N2) can dissolve into the liquid, which introduces a layer of complexity to the system due to differences in miscibilities between the methane–nitrogen and ethane–nitrogen systems. It is highly likely that propane (C3H8) is also part of the surface liquid composition, as it is a common by-product of the atmospheric photochemical process and has a low freezing point of 85.5 K.
The geochemistry of these organic materials creates landscapes similar to those seen on Earth. However, the surface conditions plus the parameters for the solid-liquid-vapor equilibria of these exotic mixtures are likely to cause the environment to behave in unfamiliar ways. Thus, I used the Astrophysical Materials Laboratory at Northern Arizona University to experimentally characterize the phase transitions and behaviors of mixtures involving methane, ethane, propane, and nitrogen at conditions relevant to Titan’s surface and considered how the results may be relevant to ongoing cryogenic geochemical processes occurring on Titan. This work was comprised of four primary studies: 1) identifying solid-solid phase transitions of pure ethane and mapping the liquidus and solidus boundaries of the methane–ethane system at low pressures [paper]; 2) considering the effect of nitrogen on the phase behaviors the methane– ethane system between 80–95 K at 1.5 bar [paper]; 3) exploring a ‘freezing-induced outburst’ phenomenon witnessed in the ethane–nitrogen system [paper]; and 4) examining how additions of ≤0.1 propane mole fraction further impacts the behaviors documented in mixtures of methane, ethane, and nitrogen. |
Cooling paths for three different C2H6–N2 mixtures where outbursts occurred. N2 mole fractions were derived at the temperatures shortly before the outbursts occurred (from top to bottom: 0.034, 0.024, 0.013) and the corresponding pictures were taken after each sample had stabilized post-burst. [paper]
|
