Center for Natural Resources, Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA.
Department of Civil, Environmental and Ocean Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
Environ Pollut. 2023 Apr 1;322:121160. doi: 10.1016/j.envpol.2023.121160. Epub 2023 Jan 27.
The need for the efficient remediation of soils impacted by per- and polyfluoroalkyl substances (PFAS) is substantially growing because of the notable upsurge in societal and regulatory awareness of this class of chemicals. To remediate PFAS-contaminated soils using mobilization approaches, the choice of appropriate techniques highly depends on the soil's composition, particularly the clay content, which significantly affects the soil's permeability. Here, we investigated the PFAS mobilization efficiency from soils with different clay contents by using two techniques: electrokinetic (EK) remediation and hydraulic flushing. Artificial kaolinite was added to a loamy sand soil to prepare four soil blends with clay contents of 5, 25, 50, and 75%, each contaminated with perfluorooctanoic acid (PFOA) and perfulorooctanesulfonic acid (PFOA) at 10,000 μg/kg. EK remediation was conducted by applying a low voltage (30 V) with a current of 100 mA, and hydraulic flushing was carried out by applying a hydraulic gradient (HG) with a slope of 6.7%. Results show that, with a 14-day treatment duration, the EK-mobilization efficiency was enhanced substantially with the increase of clay content (removal of PFOS increased from 20% at 5% clay to 80% at 75% clay), most likely due to the increase of electroosmotic flow due to the higher content of particles having a zeta potential (i.e., clay). For HG, increasing the clay content significantly suppressed the mobilization of PFAS (removal of PFOS decreased from 40% at 5% clay to 10% at 75% clay) due to a notable decrease in the soil's permeability. Based on the results, applying hydraulic flushing and washing techniques for mobilizing PFAS would be appropriate when treating permeable soils with a maximum clay content of about 25%; otherwise, other suitable mobilization techniques such as EKs should be considered.
由于社会和监管对这类化学物质的认识显著提高，需要有效地修复受全氟和多氟烷基物质（PFAS）影响的土壤，这一需求正在大幅增长。为了使用调动方法修复 PFAS 污染的土壤，选择合适的技术在很大程度上取决于土壤的组成，特别是粘土含量，这会显著影响土壤的渗透性。在这里，我们通过两种技术研究了不同粘土含量土壤中 PFAS 的调动效率：电动修复（EK）和水力冲洗。向壤土砂中添加人工高岭土，制备了 4 种粘土含量分别为 5%、25%、50%和 75%的土壤混合物，每种混合物均受到 10000μg/kg 的全氟辛酸（PFOA）和全氟辛烷磺酸（PFOS）的污染。EK 修复通过施加 30V 的低电压和 100mA 的电流进行，水力冲洗通过施加 6.7%的水力梯度（HG）进行。结果表明，在 14 天的处理时间内，随着粘土含量的增加，EK 调动效率显著提高（PFOS 的去除率从 5%粘土时的 20%增加到 75%粘土时的 80%），这很可能是由于具有 ζ 电位的颗粒（即粘土）的电渗流增加所致。对于 HG，由于土壤渗透性显著降低，增加粘土含量会显著抑制 PFAS 的调动（PFOS 的去除率从 5%粘土时的 40%降低到 75%粘土时的 10%）。根据结果，在处理最大粘土含量约为 25%的渗透性土壤时，应采用水力冲洗和洗涤技术来调动 PFAS；否则，应考虑其他合适的调动技术，如 EK。
