Grantee Research Project Results

2024 Progress Report: Enhanced detection and removal of GenX from water supplies

EPA Grant Number: SU840578
Title: Enhanced detection and removal of GenX from water supplies
Investigators: Tong, YuYe J , Chen, Dejun
Institution: Georgetown University
EPA Project Officer: Cunniff, Sydney
Phase: I
Project Period: August 1, 2023 through July 31, 2024 (Extended to July 31, 2025)
Project Period Covered by this Report: August 1, 2023 through July 31,2024
Project Amount: $25,000
RFA: 19th Annual P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet Request for Applications (RFA) (2022) RFA Text |  Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources

Objective:

The widespread use of per- and polyfluoroalkyl substances (PFAS) has led to significant environmental and public health concerns. Perfluorooctanoic acid (PFOA) is one of the most ubiquitous PFAS in the environment, and has been shown to disrupt kidney function, induce metabolic syndrome, disrupt the thyroid, and cause pregnancy complications (Blake and Fenton, 2020). In attempts to provide a safer option for industrial use, Gen-X was introduced as an alternative for PFOA. However, despite that toxicological studies on the effects of Gen-X in humans are still lacking, preliminary research has shown that Gen-X has similar effects as PFOA such as metabolism impacts and DNA damage (Chappell et al., 2020).

Our research addresses the limitations of current detection methods and enhances Gen-X degradation in water. By enhancing detection accuracy, researchers can identify contaminated sites more effectively, while improving removal techniques supports wastewater treatment plants in better managing Gen-X contamination. Through the proposed methods, public health and environmental integrity can continue to be safeguarded. The main objective of the project was to achieve a 99% or higher degradation of Gen-X in water by optimizing parameters such as UV radiation, sodium sulfite amount, stirring of solution, and sonification in a photocatalytic system.

Progress Summary:

Optimization of detection of Gen-X was conducted following EPA method 1633, employing a HPLC-TQ (High Performance Liquid Chromatograph - Triple Quadrupole) mass spectrometer. The highest mass signal of m/z=169 from Gen-X fragmentation in electrospray ionization (ESI) appeared with 350 °C for ESI drying gas, 400 °C for ESI sheath gas, and 4000 V for capillary voltage. Therefore, it was picked as the quantification ions for the best sensitivity of detection. The other two transitions (m/z 285 → 169 and 285 → 185) were utilized as identification and confirmations at the same retention time. The instrument detection limit was identified as 8.8 ppt, lower than the maximum contamination level (MCL) at 10 ppt from EPA regulation.

A photochemical reactor (253.7 nm) was used to conduct degradation reactions of the sample. A quartz beaker was filled with a solution of 500 mL of DI water, 20mM dissolved sodium sulfide (Na2SO3, Sigma Aldrich), and 1.0 M sodium hydroxide until the solution reached a pH close to 10. To our best knowledge, most literature on the topic of Gen-X degradation reported initial concentration values in the range of hundreds of ppm. However, the majority of contaminated surface water are under 2 ppb. Our experimental design chose this as a starting concentration in order to target the direct treatment of Gen-X in surface water with applicable, low concentrations.

In photocatalytic degradation, sulfite has been found to be a great substance for reducing PFAS in studies with advanced reduction processes (ARPs); when sulfite gets hit by light, it forms solvated electrons (eaq), which helps break down PFAS effectively (Ren et al., 2021). UV light excites the electrons in the catalyst to a higher energy state. These energized electrons then participate in redox reactions with the target pollutant, in this case, Gen-X, leading to its degradation. Sonication can improve the efficiency of photocatalytic degradation by facilitating the contact between the catalyst and the pollutant, increasing reaction rates, and promoting the generation of reactive species (Camargo-Perea et al., 2020). Employing these ideas into one photocatalytic degradation experiment resulted in 99.2% degradation of GenX which with the use of an optimized solid-phase extraction, quantified to a final Gen-X concentration of 9.5 ppt.

Our system's degradation potential on other PFAS chemicals was explored as well but with varied results. The percentage of degradation for 6:2 fluorotelomer sulfonic acid and perfluorobutanoic acid were generally good at 94.8% and 98.3% respectively. It implies that the method can effectively degrade fluorotelomer sulfonic acid and short-chain polyfluoroalkyl carboxylic acids (PFCAs). However, the performance for hydrogen-substituted PFCA or long-chain PFCA are really poor, the degradation rate ranging from 48~85%.

Future Activities:

The UV/sulfite-sonication treatment has demonstrated substantial success in degrading Gen-X in our phase I study, in which 99.2% degradation of Gen-X was observed within 90 minutes from the starting 2 ppb concentration. Our finding proves that Gen-X can be effectively degraded even at very low concentrations to ppt levels that are under regulatory limits. The significant removal of

Gen-X in aqueous solution can be used for the purification of aqueous solvent to reduce background from the impurity of Gen-X. Also, it can be used for the direct treatment of environmental samples with Gen-X contamination at very low-concentration level, in order to meet the criteria of EPA regulations. However, this batch process has limitations when considered for large-scale surface water treatment. Further improvements are required to make this approach practical, cost-effective, and environmentally sustainable for field applications.

Phase II will have significant implications for Gen-X pollution control, offering an innovative, cost-effective, and potentially sustainable approach to Gen-X degradation directly in surface water. By developing a continuous-flow treatment device and optimizing chemical usage, this research aims to make Gen-X treatment feasible at a large scale, bridging a critical gap in PFAS remediation technology. Furthermore, the identification of degradation by-products and fluoride recovery will ensure that the treatment is not only effective but also safe for the environment. This study will address key challenges in the current treatment process, providing a foundation for practical implementation.

References:

Blake, B. E.; Fenton, S. E. Early Life Exposure to Per- and Polyfluoroalkyl Substances (PFAS)and Latent Health Outcomes: A Review Including the Placenta as a Target Tissue and Possible Driver of Peri- and Postnatal Effects. Toxicology 2020, 443, 152565. https://doi.org/10.1016/j.tox.2020.152565.

Camargo-Perea, A. L.; Rubio-Clemente, A.; Peñuela, G. A. Use of Ultrasound as an Advanced Oxidation Process for the Degradation of Emerging Pollutants in Water. Water 2020, 12 (4), 1068. https://doi.org/10.3390/w12041068.

Chappell, G. A.; Thompson, C. M.; Wolf, J. C.; Cullen, J. M.; Klaunig, J. E.; Haws, L. C. Assessment of the Mode of Action Underlying the Effects of GenX in Mouse Liver and Implications for Assessing Human Health Risks. Toxicol. Pathol. 2020, 48 (3), 494-508. https://doi.org/10.1177/0192623320905803.

Ren, Z.; Bergmann, U.; Leiviskä, T. Reductive Degradation of Perfluorooctanoic Acid in Complex Water Matrices by Using the UV/Sulfite Process. Water Res. 2021, 205, 117676. https://doi.org/10.1016/j.watres.2021.117676.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this project

Supplemental Keywords:

PFAS; Gen-X; Photocatalytic Degradation; Method Optimization; Safe and Sustainable Water Resources