Benchtop 19F NMR spectroscopy as a practical tool for testing of remedial technologies for the degradation of perfluorooctanoic acid, a persistent organic pollutant

The development of effective remedial technologies for the destruction of environmental pollutants requires the ability to clearly monitor degradation processes. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for understanding reaction progress; however, practical considerations often restrict the application of NMR spectroscopy as a tool to better understand the degradation of environmental pollutants. Chief among these restrictions is the limited access smaller environmental research labs and remediation companies have to suitable NMR facilities. Benchtop NMR spectroscopy is a low-cost and user-friendly approach to acquire much of the same information as conventional nuclear magnetic resonance (NMR) spectroscopy, albeit with reduced sensitivity and resolution. This paper explores the practical application of benchtop NMR spectroscopy to understand the degradation of perfluorooctanoic acid using sodium persulfate, a common reagent for the destruction of groundwater contaminants. It is found that Benchtop 19F NMR spectroscopy is able to monitor the complete degradation of perfluorooctanoic acid into fluoride; however, the observation of intermediate degradation products formed, which can be observed using a conventional NMR spectrometer, cannot be readily distinguished from the parent compound when measurements are performed using the benchtop instrument. Under certain reaction conditions, the formation of fluorinated structures that are resistant to further degradation is readily observed. Overall, it is shown that benchtop 19F NMR spectroscopy has potential as a quick and reliable tool to assist in the development of remedial technologies for the degradation of fluorinated contaminants

Nuclear Magnetic Resonance Spectroscopy Analysis of Anaerobic Microbial Metabolic Response to Benzalkonium Chloride Disinfectant

Quaternary ammonium compounds (QACs) are disinfection agents used in industrial cleaning processes that are known to interfere with the proper functioning of anaerobic waste digestion directly impacting the quality and quantity of the biogas produced (i.e., CO2 and CH4). While the impact of these contaminants on waste digestors are well known, the impact these compounds have on the metabolic profile of an anaerobic digestor is less understood. This paper describes the use nuclear magnetic resonance (NMR) spectroscopy as a non-targeted tool to monitor variations in the metabolic profile of anaerobic bioreactor microcosms simulating the treatment of food production wastewater exposed to benzalkonium chloride (BAC), a key QAC. Using NMR, the variation in the metabolic profile of these wastewater microcosms is compared to variations in the quality and quantity of the biogas produced. A clear development of propionic, isobutyric, isovaleric, and other volatile fatty acids (VFAs) is observed indicating a disruption to the overall ability of the system to convert fatty acids to methane. The ability of NMR to successfully identify the overall metabolic profile, the occurrence of the individual VFAs, and the occurrence of BAC itself in one analysis helps to provide valuable information on the metabolic pathways involved in the disruption of these anaerobic processes