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Characterization of Products of Incomplete Combustion From the Incineration of Neat PFOA and PFOS Solutions in a Pilot-Scale Combustor
Citation:
Krug, J., W. Roberson, E. Shields, W. Linak, N. Weber, J. Mattila, R. Burnette, M. Allen, AND W. Preston. Characterization of Products of Incomplete Combustion From the Incineration of Neat PFOA and PFOS Solutions in a Pilot-Scale Combustor. 18th International Congress Combustion By-Products and Their Health Effects, Durham, NC, May 19 - 22, 2024.
Impact/Purpose:
Perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonic acid (PFOS) are two legacy per- and polyfluoroalkyl substance (PFAS). PFAS have been widely used in the past and commonly measured at various concentrations in many wastes and environmental media. Thermal treatment techniques such as incineration are a common method of waste disposal and destruction of contaminants in environmental media. However, the uniquely strong carbon-fluorine bonds that give PFAS many of their desirable properties also result in additional challenges for incineration systems to fully mineralize PFAS to CO2 and HF. PFAS may have an increased propensity to form fluorinated organic products of incomplete combustion (PICs) in incineration environments. In this research, we use a pilot-scale combustor previously used to characterize the destruction of complex mixtures of several commercial aqueous film forming foams (AFFFs) to characterize PICs from the incineration of neat single component aqueous solutions of PFOA and PFOS. Experiments involved the atomization of these solutions at post-flame furnace locations exhibiting peak temperatures of ~850 and ~750°C and the characterization of samples collected downstream by multiple methods including chemical ionization mass spectroscopy (CIMS) and other test method (OTM) -50 with subsequent gas chromatography/mass spectroscopy (GC/MS) analysis. CIMS results found emissions of several perfluoro carboxylic acids (PFCAs) from both PFOA and PFOS as well as differences in PICs generated at 850 and 750°C. OTM-50 results indicated that perfluoroalkanes and 1H-perfluorocarbons are important families of PICs from these species. Additionally, OTM-50 confirmed the presence of small fluorocarbons such as C2F6 and CHF3 which have their own challenges as PICs. The intent is to better understand how temperature affects PIC formation from individual PFAS and inform mechanistic studies that are developing complex reaction sets describing PFAS destruction.
Description:
Perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonic acid (PFOS) are two legacy per- and polyfluoroalkyl substance (PFAS). PFAS have been widely used in the past and commonly measured at various concentrations in many wastes and environmental media. Thermal treatment techniques such as incineration are a common method of waste disposal and destruction of contaminants in environmental media. However, the uniquely strong carbon-fluorine bonds that give PFAS many of their desirable properties also result in additional challenges for incineration systems to fully mineralize PFAS to CO2 and HF. PFAS may have an increased propensity to form fluorinated organic products of incomplete combustion (PICs) in incineration environments. In this research, we use a pilot-scale combustor previously used to characterize the destruction of complex mixtures of several commercial aqueous film forming foams (AFFFs) to characterize PICs from the incineration of neat single component aqueous solutions of PFOA and PFOS. Experiments involved the atomization of these solutions at post-flame furnace locations exhibiting peak temperatures of ~850 and ~750°C and the characterization of samples collected downstream by multiple methods including real-time Fourier transform infrared (FTIR) spectroscopy, chemical ionization mass spectroscopy (CIMS) and extractive other test method (OTM) -50 with subsequent gas chromatography/mass spectroscopy (GC/MS) analysis. CIMS results found emissions of several perfluoro carboxylic acids (PFCAs) from both PFOA and PFOS as well as differences in PICs generated at 850 and 750°C. OTM-50 results indicated that perfluoroalkanes and 1H-perfluorocarbons are important families of PICs from these species. Additionally, both FTIR and OTM-50 confirmed the presence of small fluorocarbons such as C2F6 and CHF3 which have their own challenges as PICs. The intent is to better understand how temperature affects PIC formation from individual PFAS and inform mechanistic studies that are developing complex reaction sets describing PFAS destruction.
