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阳离子型和两性离子型PFAS的吸附和解吸附行为

已有 2567 次阅读 2019-10-21 11:50 |系统分类:论文交流

Environ. Sci. Technol.53, 11818-11827, 2019


Sorption and Desorption Mechanisms of Cationic and Zwitterionic Per- and Polyfluoroalkyl Substances in Natural Soils: Thermodynamics and Hysteresis

Link: https://pubs.acs.org/doi/10.1021/acs.est.9b05379


摘要:Per- and polyfluoroalkyl substances (PFAS) 是全球关注的有机污染物。本研究第一次得出了对阳离子型和两性离子型PFAS的土壤吸附常数,对吸附和解吸附的机理进行了系统的研究。


Abstract.

Sorption linearity and reversibility are implicit in models for the fate and transport of per- and polyfluoroalkyl substances (PFAS). In this study, however, we found that the sorption of cationic and zwitterionic PFAS in natural soils was highly nonlinear. The nonlinearity was so severe that it led to a variation in the coefficient of sorption by several orders of magnitude over the experimental concentration range. This implies a considerable increase in sorption as concentration falls in the natural environment. Sorption of cationic PFAS correlated strongly with the soil organic matter (SOM) content and was reversible in all soils. Sorption of zwitterionic PFAS, on the other hand, displayed concentration-dependent hysteresis in soils with a low SOM content. The irreversibility, which was associated with neither SOM, pore deformation, nor surface complexation, was likely caused by the entrapment of molecules in porous structures within inorganic components of soil aggregates. Furthermore, electrostatic interactions with negatively charged soil constituents and the hydrophobic effect were found to be major sorption driving forces for cationic/zwitterionic PFAS at low and high concentrations, respectively. The maximum electrostatic potential of PFAS ions, computed using density functional theory, was found to be a useful predictor of the sorption of ionic PFAS species.



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