Abstract
Per- and polyfluoroalkyl substances (PFAS) have become global environmental contaminants due to being notoriously difficult to degrade, and it has become increasingly important to employ suitable PFAS alternatives, especially in aqueous film-forming foams (AFFF). Trimethylsiloxane (TriSil) surfactants are potential fluorine–free replacements for PFAS in fire suppression technologies. Yet because these compounds may be more susceptible to high-temperature decomposition, it is necessary to assess the potential environmental impact of their thermal degradation products. Our study analyzes the high-temperature degradation of a truncated trimethylsiloxane (TriSil-1n) surfactant based on quantum mechanical methods. The degradation chemistry of TriSil-1n was studied through radical formation and propagation initiated from two prominent pathways (unimolecular and bimolecular reactions) at both 298 K and 1200 K, a relevant temperature in flames and thermal incinerators. Regardless of the pathway taken and temperature, all radical intermediates stemmed from the polyethylene glycol chain and primarily formed stable polydimethylsiloxanes (PDMS) and small organics such as ethylene, formaldehyde, and acetaldehyde, among other products. The major degradation products of TriSil-1n resulting from high-temperature thermal degradation as predicted by this study would be relatively less harmful to the environment compared to PFAS incineration/combustion products from previous research, supporting the replacement of PFAS with TriSil surfactants.
| Original language | English |
|---|---|
| Article number | 136351 |
| Journal | Chemosphere |
| Volume | 308 |
| DOIs | |
| State | Published - Dec 2022 |
| Externally published | Yes |
Funding
The use of trade, product or firm names in this report is for descriptive purposes only and does not imply endorsement by the U.S. Government. The tests described and the resulting data presented herein were obtained from research conducted under the Installations and Operational Environments Program of the United States Army Corps of Engineers by the USAERDC under the work supported by (OUSD (R&E)) through the Applied Research for the Advancement of Science and Technology Priorities (ARAP) program. Permission was granted by the Chief of Engineers to publish this information. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. Authors also acknowledge grant of computer time from the DOD High Performance Computing Modernization Program at ERDC, Vicksburg MS. The work performed by MM and SV was supported by funding provided by U.S. Army Corps of Engineers (Cooperative agreement # W912HZ-20-2-0067 ). MM and SV also gratefully acknowledge allocated computational resources from High Performance Computing facility at Colorado School of Mines . The use of trade, product or firm names in this report is for descriptive purposes only and does not imply endorsement by the U.S. Government. The tests described and the resulting data presented herein were obtained from research conducted under the Installations and Operational Environments Program of the United States Army Corps of Engineers by the USAERDC under the work supported by (OUSD (R&E)) through the Applied Research for the Advancement of Science and Technology Priorities (ARAP) program. Permission was granted by the Chief of Engineers to publish this information. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. Authors also acknowledge grant of computer time from the DOD High Performance Computing Modernization Program at ERDC, Vicksburg MS.The work performed by MM and SV was supported by funding provided by U.S. Army Corps of Engineers (Cooperative agreement #W912HZ-20-2-0067). MM and SV also gratefully acknowledge allocated computational resources from High Performance Computing facility at Colorado School of Mines.
Keywords
- DFT
- Fire suppression
- High-temperature degradation
- Mechanism
- Trimethylsiloxane