Uncovering Mechanisms of PFAS Adsorption by Granular Activated Carbon to Support PFAS Remediation

摘要 (环境科学及工程)研究计划4 项目4是拟议中的两个环境科学和工程研究项目之一 北卡罗来纳州立大学(北卡罗来纳州立大学)领导的“全氟辛烷磺酸环境与健康影响中心” 州)。拟议中心的主要目标是提供高度相关的数据和信息，以帮助 超级基金研究计划(SRP)解决了全氟烷基物质和多氟烷基物质日益增长的问题 全美范围内(PFAS)污染，包括饮用水水源的污染。考虑使用全氟辛烷磺酸 新出现的关注的污染物，以及对受PFAS影响的场地的补救是一个关键和及时的公众 健康挑战。颗粒活性碳(GAC)吸附是目前应用最广泛的PFAS修复方法 技术虽然关于GAC对有机污染物的吸附已知很多，但预测GAC 来自实验室数据或基础污染物和GAC属性的有效性仍然是重要的 挑战。我们的长期目标是开发预测有机微污染物吸附的模型， 在GAC处理系统中，包括全氟辛烷磺酸。改进现有模型的一个关键障碍是可访问性 GAC颗粒内部的吸附位置尚不清楚。当前模型的一个重要假设是 在吸附平衡时，污染物在颗粒内均匀分布。但是，直接 对吸附污染物的观察表明，吸附可以优先发生在外部吸附剂附近 浮出水面。这一区别很重要，因为它可以解释为什么全氟辛烷磺酸的吸附容量随着 降低GAC颗粒大小以及为什么实验室实验高估了PAS的去除效果 广汽集团。因此，我们的首要假设是，对全氟辛烷磺酸(以及许多其他有机物质)的吸附 污染物)优先出现在靠近GAC外表面的壳层区域。壳层吸附 假设将通过(目标1)观察和描述吸附时颗粒内PFAS的分布来评估 平衡和(目标2)定量和描述全氟辛烷磺酸的吸附/解吸动力学。使用创新的 同位素显微镜等方法，我们将开始打开广汽仍然代表的“黑匣子” 直接观察颗粒内PFAS的分布。我们将使用来自直接观测的信息在 结合吸附平衡和动力学实验的结果来解释我们的壳层数据 吸附模型。我们预计模型参数将具有物理意义，并且可以从 基本的脱硫剂和脱硫剂性能。该项目的成果将支持有效的开发 用于去除全氟辛烷磺酸的吸着剂，用于全氟辛烷磺酸修复的(成本)高效的GAC处理系统的设计，以及 对废GAC的管理选择进行评估。

ABSTRACT (Environmental Science and Engineering) Research Project 4 Project 4 is one of two Environmental Science and Engineering (ESE) Research Projects for the proposed “Center for Environmental and Health Effects of PFAS” being led by North Carolina State University (NC State). The primary goal of the proposed Center is to provide highly relevant data and information to help the Superfund Research Program (SRP) address the growing problem of per- and polyfluoroalkyl substance (PFAS) contamination across the US, including contamination of drinking water sources. PFAS are considered contaminants of emerging concern, and remediation of PFAS-impacted sites is a critical and timely public health challenge. Granular activated carbon (GAC) adsorption is the most widely employed PFAS remediation technology. Although much is known about sorption of organic contaminants by GAC, predicting GAC effectiveness from laboratory data or from fundamental pollutant and GAC properties remains a significant challenge. Our long-term objective is to develop models that predict sorption of organic micropollutants, including PFAS, in GAC treatment systems. A critical barrier to improving existing models is that accessibility of sorption sites inside of GAC particles is not known. An important assumption of current models is that contaminants are uniformly distributed inside of GAC particles at sorption equilibrium. However, direct observations of sorbed contaminants suggest that sorption can occur preferentially near the external sorbent surface. This distinction is significant because it can explain why PFAS sorption capacity increases with decreasing GAC particle size and why laboratory experiments overestimate PFAS removal effectiveness of GAC. Our overarching hypothesis is, therefore, that sorption of PFAS (as well as many other organic pollutants) occurs preferentially in a shell region near the external GAC surface. The shell adsorption hypothesis will be evaluated by (Aim 1) observing and describing intraparticle PFAS distributions at sorption equilibrium and (Aim 2) quantifying and describing PFAS adsorption/desorption kinetics. Using innovative approaches, such as isotope microscopy, we will begin to open the “black box” that GAC still represents and directly observe intraparticle PFAS distributions. We will use information from direct observations in conjunction with results from sorption equilibrium and kinetic experiments to explain our data with a shell adsorption model. We expect that model parameters will be physically meaningful and can be predicted from fundamental sorbent and sorbate properties. Results of this project will support the development of effective sorbents for PFAS removal, the design of (cost-)effective GAC treatment systems for PFAS remediation, and the evaluation of management options for spent GAC.