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

全氟烷基和多氟烷基物质（PFAS）是氟化有机化学品，在过去二十年中，由于人们越来越关注其在环境中积累时的持久性，稳定性和毒性，因此已成为优先污染物。饮用水中PFAS的检测引起了人们对其对人类健康影响的严重关注。PFAS难以使用常规水处理氧化剂（例如，氯、臭氧和过氧化氢），这是由于它们的强C-F共价键和C-F键极化，这导致对化学侵蚀的空间位阻。吸附到颗粒活性炭（GAC）滤床已成为最有效和最具成本效益的过程中去除PFAS从受污染的饮用水源。然而，用过的载有PFAS的GAC滤床需要被处置或再生以使其能够再利用。该项目的总体目标是研究热再生作为一种高效且具有成本效益的工艺的可行性，以使负载PFAS的GAC滤床能够重复使用，同时催化吸附的PFAS污染物的降解和破坏。为了推进这一目标，主要研究者（PI）建议测试以下假设：活性炭石墨表面上丰富的高移动的电子将催化从用过的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通过产生新的基础知识来促进GAC作为一种高效且具有成本效益的吸附剂用于处理PFAS污染的饮用水源，从而造福社会。对社会的额外好处将通过教育和培训来实现，包括指导缅因州大学的一名研究生和一名本科生以及内华达州大学的一名研究生和一名本科生，里诺。颗粒活性炭（GAC）已在现场和规模上被证明是最有效和最具成本效益的，有效的吸附剂去除饮用水源中的PFAS污染物，包括预处理的地表水和地下水。热再生是用于再生用过的负载PFAS的GAC床的既定工艺。然而，PFAS的降解，转化和破坏的机制，在用过的GAC滤床的热再生过程中的基本理解仍然难以捉摸。本项目的目标是推进PFAS降解，转化和破坏过程中的PFAS负载GAC床在相关工艺和现场条件下的热再生的基本理解。本研究的具体目标是：1）考察热再生对商业上可获得的和充分表征的GAC PFAS吸附剂候选物的物理化学性质的影响; 2）评估加热速率、再生温度、气态气氛和再活化剂对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热再生的程度和速率的影响;以及4）表征并阐明在PFAS负载的GAC床的热再生期间吸附的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来推动GAC吸附的实施，使其成为一种高效、经济和可持续的PFAS污染饮用水源处理工艺。为了实现本项目的教育和推广目标，主要研究者（PI）计划将本研究的结果整合到缅因州大学和里诺内华达州大学的现有本科生/研究生课程中。此外，PI建议利用各自机构的现有计划，举办一个“女童军”外展计划，向K-3年级的学生教授环境工程和水处理的基本概念。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值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.