Kinetics of Dimethyl Methylphosphonate Adsorption and Decomposition on Zirconium Hydroxide Using Variable Temperature...

Area of Science:

• Materials Science
• Chemical Kinetics
• Spectroscopy

Background:

• Dimethyl methylphosphonate (DMMP) is a key simulant for organophosphorus chemical warfare agents (CWAs).
• Accurate kinetic data for DMMP decomposition is crucial for effective sequestration strategies.
• Existing methods for monitoring DMMP decomposition kinetics can be inaccurate due to spectral interferences.

Purpose of the Study:

• To quantitatively describe DMMP decomposition kinetics on amorphous zirconium hydroxide (ZH) under ambient conditions.
• To develop a more accurate method for tracking DMMP adsorption and decomposition.
• To provide insights relevant for CWA sequestration and decontamination material development.

Main Methods:

• Investigated DMMP adsorption and decomposition on ZH using variable-temperature in situ attenuated total reflection (ATR) infrared spectroscopy.
• Employed density functional theory (DFT) simulations to assign specific vibrational modes.
• Utilized ρ(PCH3) vibrational modes as an alternative to P-O modes for kinetic analysis.

Main Results:

• Demonstrated that conventional monitoring of P-O modes is confounded by C-O modes from methoxy species.
• Successfully assigned and utilized ρ(PCH3) modes to accurately track DMMP decomposition kinetics.
• Obtained time-dependent IR spectra at various temperatures to monitor decomposition products.

Conclusions:

• The ρ(PCH3) vibrational modes provide a reliable method for quantifying DMMP adsorption and decomposition kinetics.
• This approach overcomes limitations of previous methods, offering improved accuracy for sequestration applications.
• Tracking PCH3 bands is valuable for assessing the surface kinetics of CWAs and simulants on decontamination materials.