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首页> 外文期刊>Environmental Science & Technology >Enhanced Sorption off Polycyclic Aromatic Hydrocarbons to Tetra-Alkyl Ammonium Modified Smectites via Cation—π Interactions
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Enhanced Sorption off Polycyclic Aromatic Hydrocarbons to Tetra-Alkyl Ammonium Modified Smectites via Cation—π Interactions

机译：通过阳离子-π相互作用增强多环芳烃对四烷基铵改性蒙脱石的吸附作用

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The objective of this study was to characterize molecular sorptive interactions of polycyclic aromatic hydrocarbons (PAHs) by organoclays modified with quaternary ammonium cations. Three PAHs, naphthalene (NAPH), phenanthrene (PHEN), and pyrene (PYR), and three chlorobenzenes, 1,2-dichlorobenzene (DCB), 1,2,4,5-tetrachlorobenzene (TeCB), and pentachlorobenzene (PtCB), were sorbed from aqueous solution to reference montmorillonite clays (SWy-2) exchanged respectively with tetramethyl ammonium (TMA),tetraethyl ammonium (TEA),tetra-n-butyl ammonium (TBA), and hexadecyltrimethyl ammonium (HDTMA) cations. Solute hydrophobicities are compared between PAHs and chlorobenzenes using the solute n-octanol-water partition coefficient, n-hexadecane-water partition coefficient, and polyethylene-water distribution coefficient. The PAHs show several- to more than 10-fold greater sorption than the chlorobenzenes having close hydrophobicities but fewer delocalized π electrons (NAPH/DCB, PHEN/TeCB, and PYR/ PtCB) by TEA-, TBA-, and HDTMA-clays. Furthermore, the PAHs show greater trends of solubility enhancement than the compared chlorobenzenes by TMA, TEA, and TBA in aqueous solution. The enhanced sorption and aqueous solubility of PAHs are best described by cation-π interactions between ammonium cations and PAHs relative to chlorobenzenes that are incapable of such interactions. Cation-π complexation between PAHs and tetra-alkyl ammonium cations in chloroform was verified by ring-current-induced upfield chemical shifts of the alkyl groups of cations in the ~1H NMR spectrum.
机译：这项研究的目的是通过季铵阳离子改性的有机粘土表征多环芳烃（PAHs）的分子吸附相互作用。三个PAH，萘（NAPH），菲（PHEN）和pyr（PYR）以及三个氯苯，1,2-二氯苯（DCB），1,2,4,5-四氯苯（TeCB）和五氯苯（PtCB）将其从水溶液中吸附到分别与四甲基铵（TMA），四乙基铵（TEA），四正丁基铵（TBA）和十六烷基三甲基铵（HDTMA）阳离子交换的参考蒙脱土（SWy-2）。使用溶质的正辛醇-水分配系数，正十六烷-水分配系数和聚乙烯-水分配系数比较了PAH和氯苯之间的溶质疏水性。与具有接近疏水性但氯丁苯的TEA-，TBA-和HDTMA-粘土的离域π电子（NAPH / DCB，PHEN / TeCB和PYR / PtCB）较少的氯苯相比，PAHs的吸附量高出几倍至十倍以上。此外，与水溶液中TMA，TEA和TBA所比较的氯苯相比，PAHs显示出更大的溶解度增强趋势。铵阳离子和PAH之间的阳离子-π相互作用（相对于无法进行这种相互作用的氯苯）可以最好地描述PAH的增强的吸附性和水溶性。通过环电流诱导的〜1H NMR光谱中阳离子烷基的高场化学位移，验证了氯仿中PAHs和四烷基铵阳离子之间的阳离子-π络合。

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