Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States.
Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States.
Environ Sci Technol. 2023 Nov 7;57(44):17154-17165. doi: 10.1021/acs.est.3c05140. Epub 2023 Oct 19.
While foam fractionation (FF) process has emerged as a promising technology for removal of per- and polyfluoroalkyl substances (PFASs) from contaminated groundwater, management of the resulting foam concentrates with elevated concentrations of PFASs (e.g., >1 g/L) remains a challenge. Here, we applied hydrothermal alkaline treatment (HALT) to two foam concentrates derived from FF field demonstration projects that treated aqueous film-forming foam (AFFF)-impacted groundwater. Results showed >90% degradation and defluorination within 90 min of treatment (350 °C, 1 M NaOH) of all 62 PFASs (including cations, anions, and zwitterions) identified in foam concentrates. Observed rate constants for degradation of individual perfluoroalkyl sulfonates (PFSAs, CF-SO), the most recalcitrant class of PFASs, in both foam concentrates were similar to values measured previously in other aqueous matrices, indicating that elevated initial PFAS concentrations (e.g., PFHxS = 0.55 g/L), dissolved organic carbon (DOC; up to 4.5 g/L), and salt levels (e.g., up to 325 mg/L chloride) do not significantly affect PFAS reaction kinetics. DOC was partially mineralized by treatment, but a fraction (∼15%) was recalcitrant. Spectroscopic characterization revealed molecular features of the HALT-recalcitrant DOC fraction, and nontarget high-resolution mass spectrometry tentatively identified 129 nonfluorinated HALT-recalcitrant molecules. Analysis of process energy requirements shows that treating PFAS-contaminated foam concentrates with HALT would add minimally (<5%) to the overall energy requirements of an integrated FF-HALT treatment train.
虽然泡沫分离（FF）工艺已成为从受污染地下水中去除全氟和多氟烷基物质（PFAS）的有前途的技术，但管理由此产生的泡沫浓缩物中 PFAS 浓度升高（例如，>1 g/L）仍然是一个挑战。在这里，我们将水热碱性处理（HALT）应用于从 FF 现场示范项目中得出的两个泡沫浓缩物，这些浓缩物处理了受水性成膜泡沫（AFFF）影响的地下水。结果表明，在 350°C 和 1 M NaOH 下处理 90 分钟内，可将泡沫浓缩物中鉴定出的所有 62 种 PFAS（包括阳离子、阴离子和两性离子）的降解和除氟率提高 90%以上。在这两种泡沫浓缩物中，观察到的个别全氟烷基磺酸盐（PFSAs，CF-SO）的降解速率常数与以前在其他水性基质中测量的值相似，表明初始 PFAS 浓度升高（例如，PFHxS = 0.55 g/L）、溶解有机碳（DOC；高达 4.5 g/L）和盐度（例如，高达 325 mg/L 氯化物）不会显著影响 PFAS 反应动力学。DOC 经处理部分矿化，但一部分（约 15%）具有抗降解性。光谱特征揭示了 HALT-抗降解 DOC 部分的分子特征，非靶向高分辨率质谱法暂定鉴定出 129 种非氟化 HALT-抗降解分子。对工艺能源需求的分析表明，用 HALT 处理受 PFAS 污染的泡沫浓缩物只会对集成 FF-HALT 处理线的总能源需求增加最小（<5%）。
