Date of Award
Doctor of Philosophy
Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic organic compounds manufactured for their heat, water, and stain-resistant properties. PFAS can be found ubiquitously in the environment because they are widely used in everyday consumer products such as fast-food wrappers, non-stick cookware, stain-resistant products, cosmetics, aqueous film-forming foams, etc. As a result, PFAS are commonly detected in surface water, wastewater, and biosolids from wastewater treatment plants (WWTPs). These are the direct sources of PFAS contamination in drinking water supplies, which are substantial sources of human exposure. Among these PFAS chemicals, two major groups are perfluoroalkyl carboxylic acids (PFCAs) and their precursors, fluorotelomer alcohols (FTOHs). Even though studies have been conducted nationwide to evaluate the degree of these PFAS in the environment, research is lacking in our region. To fill the knowledge gap, we aimed to investigate the occurrence and transport of PFCAs and FTOHs in wastewater and biosolids. Furthermore, it is crucial to have a simple, fast, green, and reliable detection technique that can monitor the trace amount of PFCAs and FTOHs in water and biosolid matrices. In this study, we developed and validated a simple, low-cost, no clean-up, and sensitive method for the determination of PFCAs and FTOHs in water by applying 'green chemistry' based extraction named stir bar sorptive extraction (SBSE) coupled with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Three commonly detected FTOHs (6:2 FTOH, 8:2 FTOH, and 10:2 FTOH) were selected as the model compounds to develop an enhanced SBSE-TD-GC-MS for the analysis of FTOHs in water. Factors such as extraction time, stirring speed, solvent composition, salt addition, and pH were investigated to achieve optimal extraction efficiency. This "green chemistry" based extraction provided good sensitivity and precision with low method limits of detection ranging from 2.16 ng/L to 16.7 ng/L and with an extraction recovery ranging 55% to 111%. The developed methods were tested on tap water, brackish water, and wastewater influent and effluent. In two wastewater samples, 6:2 FTOH and 8:2 FTOH were detected at 78.0 and 34.8 ng/L, respectively. This optimized SBSE-TD-GC-MS method stands as a valuable alternative to investigate FTOHs in water matrices. In addition, we developed an enhanced SBSE-TD-GC-MS for the analysis of PFCAs in water. Our study provides a comprehensive evaluation of the method's linearity, recovery, sensitivity, repeatability, and spiked recovery across diverse water matrices. The method demonstrates linearity with coefficients of determination (RÂ²) spanning from 0.9892 to 0.9988. Sensitivity metrics showed low limits of detection (LOD) in the low ng/L (ppt) range for all analytes, achieving LODs between 21.2 ng/L to 74.0 ng/L. The recoveries for the method varied from 47-97%, suggesting an efficient extraction process. Additionally, the methodâ??s robustness across various water matrices (tap water, wastewater influent, and effluent) reflected by the spiked recovery experiment underscored the methodâ??s efficiency in real-world applications. In comparison with traditional PFCAs analysis methods, our optimized SBSE technique requires only a minimum sample volume of 1 mL and minimal solvent usage, enhancing eco-friendliness and reducing potential contamination and handling errors. Repeatability assessments at two concentration levels produced %RSD (Relative Standard Deviation) values at 14% or less for any target PFCA compounds, indicating good precision. These attributes showcase the developed method's capability to serve as a precise, eco-friendly, and reliable tool for the analysis of PFCAs across diverse water matrices. This study also presents a comprehensive exploration into the presence and transport behavior of FTOHs and PFCAs in biosolid samples collected from wastewater treatment plants (WWTPs) in El Paso, Texas. We optimized an ultrasonic extraction method for efficient recovery of FTOHs and PFCAs compounds from biosolids followed by SBSE-TD-GC-MS analysis. The results showed specific concentrations of FTOHs compounds in biosolid samples from the different WWTPs. 6:2 FTOH was not detected in any of the samples, while 8:2 FTOH was found in three WWTPs at varying concentrations: 100.30 ng/g in WWTP-1, 62.87 ng/g in WWTP-2, and 56.41 ng/g in WWTP-4. Additionally, 10:2 FTOH was detected in WWTP-1 at a concentration of 68.07 ng/g. Interestingly, despite the sensitive analytical approach employed, none of the targeted PFCAs were detected in any of the biosolid samples. These findings provide important insights into the distribution and prevalence of specific FTOHs in biosolids from WWTPs, that highlight the inherent variability in their occurrence. Through the development and validation of a cost-effective, environmentally friendly, and sensitive analytical method, this dissertation represents a reliable alternative analytical technique for monitoring PFCAs and FTOHs in aquatic matrices and contributes valuable data to the ongoing efforts to monitor and manage emerging contaminants in wastewater treatment systems.
Recieved from ProQuest
Habib, Ahsan, "Green Analytical Methods For The Determination Of Perfluorocarboxylic Acids (pfcas) And Fluorotelomer Alcohols (ftohs) In Water" (2023). Open Access Theses & Dissertations. 3975.