Chemical Sciences: (5) Environmental Chemistry, (i) Transport and transformation in multiphase environments
Abstract
In Situ Spectroscopy and Kinetic Characterization of the Photodegradation of Chemical Warfare Agent Simulants at Kaolinite and Kaolinite/Iron-Oxide Composite Surfaces Mineral dust is believed to contribute more than half of the atmospheric aerosol burden, with emission estimates ranging from 1000 to 3000 Mt/yr, and dust load estimates ranging from 8 to 35 Mt/yr. Through direct (e.g., light scattering, inhalation, etc.) and indirect (e.g., chemical reactions with other aerosols) effects, these aerosol particles are believed to have a wide-ranging impact on climate, human health, etc., although the specific influences are not always well understood. Mineral dust particles can participate in a wide range of chemical and photochemical reactions, including reactions with chemical warfare agents (CWA). When released, CWA are present in liquid as well as aerosolized and gas-phase forms, with the latter two able to interact with aerosolized mineral dust. The goal of this project is to characterize the photodegradation of gas-phase and aerosolized CWA simulants with some of the most abundant minerals, kaolinite and kaolinite/iron-oxide composites. In situ kinetic diffuse reflectance infrared Fourier transform spectroscopy (k-DRIFTS), transmission FTIR, kinetic Raman spectroscopy, and GCMS will be used to determine the decomposition pathways and kinetics of the CWA simulants. THz-Raman spectroscopy will be used to identify any potential impact of the photodegradation process on the structural properties of the samples. To achieve this goal, the following objectives will be pursued: Objective #1: Verify the functionality of the experimental photodegradation setup. Baseline photodegradation measurements of gas-phase DMMP over UV-irradiated titania powder will be performed and the results compared with those reported in the literature. Objective #2: Determine the photodegradation pathway and kinetics for the interaction of gas-phase CWA simulants with kaolinite and kaolinite/iron-oxide composites. Once the experimental system functionality has been verified, it will be used to identify the photodegradation products and kinetics from the interaction of gas-phase diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP), and dimethyl methylphosphonate (DMMP) with kaolinite and kaolinite/iron-oxide composite surfaces. Objective #3: Determine the photodegradation pathway and kinetics for the interaction of aerosolized CWA simulants with kaolinite and kaolinite/iron-oxide composites. Once the interaction with gas-phase simulants has been determined, the system will be used to identify the photodegradation products and kinetics from the interaction of aerosolized DIMP, DEMP, and DMMP with kaolinite and kaolinite/iron-oxide. A successful completion of this proposed work will determine: ¥ The photodegradation properties of kaolinite and kaolinite/iron-oxide composites with respect to three different sarin simulants. ¥ Identify decomposition pathways and kinetics of the photodegradation process. ¥ Identify differences of the interaction with gas-phase vs. aerosolized CWA simulants. This information could be of use to the atmospheric chemistry community as well as the chem-bio defense community, helping to better understand the interaction of chemical warfare agent with mineral dust and decontamination of surfaces.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 09, 2023
- Source ID
- W911NF2310058
Entities
People
- Hergen Eilers
Organizations
- Army Contracting Command
- United States Army
- Washington State University