Collaborative Research: ERASE-PFAS: Thermal Regeneration of PFAS-laden Granular Activated Carbon presents an Opportunity to Break the Forever PFAS Cycle

全氟和多氟烷基物质(PFAS)是近二十年来作为优先污染物出现的含氟有机化学品，由于它们在环境中积累时的持久性、稳定性和毒性日益受到关注。饮用水中全氟辛烷磺酸的检测引起了人们对其对人类健康影响的严重关切。传统的水处理氧化剂(如氯、臭氧和过氧化氢)很难降解和破坏，因为它们具有很强的C-F共价键和C-F键极化，从而对化学攻击造成空间位阻。颗粒活性碳(GAC)滤床吸附已成为去除受污染饮用水水源中全氟辛烷磺酸的最有效和最具成本效益的方法。然而，含有全氟辛烷磺酸的废GAC滤床需要处理或再生，以实现其再利用。该项目的总体目标是调查热再生作为一种有效和成本效益高的过程的可行性，以便能够重复使用装满全氟辛烷磺酸的颗粒炭滤床，同时催化降解和破坏吸附的全氟辛烷磺酸污染物。为了推进这一目标，首席调查员(PI)建议测试一种假设，即活性碳石墨化表面上丰富的高活性电子将催化从废GAC滤床中吸附的PFAS分子的热分解和随后的降解。这项研究的成功完成将使社会受益，因为它将产生新的基础知识，以促进利用GAC作为一种有效和具有成本效益的吸附剂来处理受全氟辛烷磺酸污染的饮用水水源。还将通过教育和培训实现对社会的其他好处，包括指导缅因州大学的一名毕业生和一名本科生，以及里诺州内华达大学的一名毕业生和一名本科生。颗粒活性碳(GAC)已在现场和规模上被证明是去除饮用水来源(包括经过处理的地表水和地下水)中全氟辛烷磺酸污染物的最有效和最具成本效益的吸附剂。热再生是废旧全氟辛烷磺酸GAC床再生的既定程序。然而，对废GAC滤床在热再生过程中全氟辛烷磺酸的降解、转化和破坏机理的基本了解仍然难以捉摸。该项目的目的是促进对在相关工艺和现场条件下装填了全氟辛烷磺酸的颗粒炭床热再生过程中全氟辛烷磺酸的降解、转化和破坏的基本理解。这项研究的具体目标是：1)调查热再生对商用和表征良好的GAC PFAS候选吸附剂的物理化学性质的影响；2)评估升温速度、再生温度、气体气氛和再生剂对PFAS降解/转化和GAC再生效率的影响；3)评估GAC孔结构和表面化学对PFAS热解离程度和速率的影响；以及4)表征和揭示富含PFAS的GAC床热再生过程中吸附的PFAS的解吸、分解和矿化途径。该项目的成功完成有可能通过产生基础知识和性能数据产生变革性的影响，以推动实施GAC吸附，作为一种有效、成本效益高和可持续的处理全氟辛烷磺酸污染饮用水水源的过程。为实现该项目的教育和推广目标，首席调查员计划将这项研究的结果纳入缅因州大学和里诺市内华达大学现有的本科/研究生课程。此外，PIs建议利用各自机构现有的计划，举办一个“女童子军”外展计划，向K-3年级的学生传授环境工程和水处理的基本概念。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Per- and polyfluoroalkyl substances (PFAS) are fluorinated organic chemicals that have emerged as priority pollutants during the last two decades due to increasing concerns about their persistence, stability, and toxicity as they accumulate in the environment. The detection of PFAS in drinking water has raised significant concerns about their impact on human health. PFAS are difficult to degrade and destroy using conventional water treatment oxidants (e.g., chlorine, ozone, and hydrogen peroxide) due to their strong C-F covalent bonds and C-F bond polarization which causes steric hindrance to chemical attack. Sorption onto granular activated carbon (GAC) filter beds has emerged as the most efficient and cost-effective process from removing PFAS from contaminated drinking water sources. However, spent PFAS-laden GAC filter beds need to be disposed of or regenerated to enable their reuse. The overarching goal of this project is to investigate the viability of thermal regeneration as an efficient and cost-effective process to enable the reuse of PFAS-laden GAC filter beds while catalyzing the degradation and destruction of the sorbed PFAS contaminants. To advance this goal, the Principal Investigators (PIs) propose to test the hypothesis that the abundance of highly mobile electrons on the graphitic surface of activated carbon will catalyze the thermolysis and subsequent degradation of sorbed PFAS molecules from spent GAC filter beds. The successful completion of this research will benefit society through the generation of new fundamental knowledge to advance the utilization of GAC as an efficient and cost-effective sorbent for the treatment of PFAS contaminated drinking water sources. Additional benefits to society will be accomplished through education and training including the mentoring of one graduate and one undergraduate student at the University of Maine and one graduate and one undergraduate student at the University of Nevada, Reno.Granular activated carbon (GAC) has been demonstrated in the field and at scale to be the most efficient and cost-effective sorbent from removing PFAS contaminants from drinking water sources including pretreated surface water and groundwater. Thermal regeneration is an established process for the regeneration of spent PFAS-laden GAC beds. However, a fundamental understanding of the mechanisms of PFAS degradation, transformations, and destruction during the thermal regeneration of spent GAC filter beds has remained elusive. The goal of this project is to advance the fundamental understanding of PFAS degradation, transformations, and destruction during the thermal regeneration of PFAS-laden GAC beds under relevant process and field conditions. The specific objectives of the research are to: 1) Investigate the effect of thermal regeneration on the physicochemical properties of commercially available and well-characterized GAC PFAS sorbent candidates; 2) Evaluate the impacts of heating rate, regeneration temperature, gaseous atmosphere, and reactivation agents on PFAS degradation/transformations and GAC regeneration efficiency; 3) Assess the impact of GAC pore structure and surface chemistry on the extent and rate of PFAS thermolysis; and 4) Characterize and unravel the desorption, decomposition, and mineralization pathways of sorbed PFAS during the thermal regeneration of PFAS-laden GAC beds. The successful completion of this project has the potential for transformative impact through the generation of fundamental knowledge and performance data to advance the implementation of GAC sorption as an efficient, cost-effective, and sustainable process for the treatment of PFAS contaminated drinking water sources. To implement the educational and outreach goals of this project, the Principal Investigators (PIs) plan to integrate the findings from this research into existing undergraduate/graduate courses at the University of Maine and the University of Nevada, Reno. In addition, the PIs propose to leverage existing programs at their respective institutions to host a “Girls Scouts” outreach program to teach basic concepts of environmental engineering and water treatment to K-3 grade students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.