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首页> 外文期刊>Environmental Science & Technology >Effects of Monovalent Cations on the Competitive Adsorption of Perfluoroalkyl Acids by Kaolinite: Experimental Studies and Modeling
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Effects of Monovalent Cations on the Competitive Adsorption of Perfluoroalkyl Acids by Kaolinite: Experimental Studies and Modeling

机译：一价阳离子对高岭石竞争性吸附全氟烷基酸的影响：实验研究和建模

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摘要

Our hypothesis that longer-chained perfluoroalkyl acids (PFAAs) out-compete shorter-chained PFAAs during adsorption was tested in this study, wherein the adsorption interactions of six frequently detected PFAAs with kaolinite clay were modeled and examined experimentally using various suspension compositions. Competitive adsorption of PFAAs on the kaolinite surface was observed for the first time, and longer-chained PFAAs outcompeted those with a shorter chain. The electrostatic repulsion between adsorbed PFAA molecules is a primary inhibitory factor in PFAA adsorption. An increase in aqueous sodium or hydrogen ion concentration weakened electrostatic repulsions and changed the adsorption free energy. Therefore, the adsorption of a shorter-chained PFAA with weaker hydrophobicity could occur at high sodium or hydrogen ion concentrations. The experimental and modeling data suggest that the adsorption of shorter-chained PFAAs (≦4 perfluorinated carbons) in freshwater with a typical ionic strength of 10~(-2.5) is not thermodynamically favorable. Furthermore, by measuring the electrokineac potential of kaolinite suspension in the presence of PFAAs, we found that the kaolinite surface became more negatively charged because of the adsorption of PFAAs. This observation indicates that the adsorbed PFAA molecules were within the electrical double layer of the kaolinite surface and that they contributed to the potential at the slipping plane. The possible alignments of adsorbed PFAA molecules on the kaolinite surface were then proposed.
机译：我们的假设是在吸附过程中长链全氟烷基酸（PFAAs）竞争于短链PFAA的竞争，在此假设中，使用各种悬浮液成分对六种常见的PFAA与高岭石粘土的吸附相互作用进行了建模和实验研究。首次观察到PFAA在高岭土表面上的竞争性吸附，长链PFAA的竞争性优于短链PFAA。吸附的PFAA分子之间的静电排斥是PFAA吸附的主要抑制因素。钠或氢离子水溶液浓度的增加会削弱静电排斥力，并改变吸附自由能。因此，在较高的钠或氢离子浓度下，可能会发生疏水性较弱的短链PFAA的吸附。实验和模型数据表明，典型离子强度为10〜（-2.5）的淡水中短链PFAAs（≤4个全氟化碳）的吸附在热力学上并不理想。此外，通过测量在PFAA存在下高岭石悬浮液的电动势，我们发现由于PFAAs的吸附，高岭石表面带更多的负电荷。该观察结果表明，所吸附的PFAA分子在高岭石表面的双电层内，并且它们有助于在滑移面上产生电势。然后提出了在高岭石表面上吸附的PFAA分子的可能排列。

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  • 来源
    《Environmental Science & Technology》 |2011年第23期|p.10028-10035|共8页
  • 作者

    Feng Xiao; Xiangru Zhang; Lee Penn; John S. Gulliver; Matt F. Simcik;

  • 作者单位

    Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States,Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota 55455,United States;

    Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China;

    Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States;

    Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States;

    Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota 55455,United States;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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