Adsorption of dinitrophenol herbicides from water by montmorillonites
Adsorption of dinitrophenol herbicides from water by montmorillonites
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DOI：
10.1346/000986002761002630
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发表时间：
2002-02-01
影响因子：
2.2
通讯作者：
Boyd, SA
中科院分区：
文献类型：
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作者：
Sheng, GY;Johnston, CT;Boyd, SA
采用吸附等温线、傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）和分子动力学模拟相结合的方法，研究了两种二硝基苯酚类除草剂4，6-二硝基邻甲酚（DNOC）和4，6-二硝基仲丁基苯酚（地乐酚）在两种蒙脱石粘土（SWy-2和SAz-1）上的吸附行为。粘土受到饱和与各种阳离子，和电荷减少。DNOC的吸附量随pH值的增加而减少，表明DNOC主要以中性吸附形式吸附。DNOC-粘土膜的FTIR光谱表明DNOC分子平行于粘土表面取向。层间阳离子对吸附有很强的影响，这在很大程度上取决于它们的水合能。弱水合阳离子，如K+和Cs+，导致更强的水合阳离子，如Na+或Ca 2+相比，在更大的吸附。较低的水合作用有利于可交换阳离子与DNOC的-NO2基团的直接相互作用，并表明吸附的最佳层间距。在吸附的DNOC的存在下，K-SWy-2的层间距保持在12和12.5埃之间，而不管水的存在。这种d间距允许DNOC分子同时与相对的粘土层相互作用，从而最大限度地减少DNOC与水的接触。粘土的电荷密度也影响吸附通过控制吸附域的大小。因此，低电荷粘土（K-SWy-2）对DNOC的吸附量远高于高电荷粘土（K-SAz-1），锂离子电荷的减少大大增强了K-SAz-1对地乐酚的吸附。空间限制也很明显，从观察到的吸附DNOC，其中含有甲基取代基，是远远大于地乐酚，其中含有一个庞大的异丁基。在地乐酚存在下，K-SAz-1对DNOC的吸附不受影响，而在DNOC存在下，地乐酚的吸附大大降低。
The adsorption of two dinitrophenol herbicides, 4,6-dinitro-o-cresol (DNOC) and 4,6-dinitro-o-sec-butyl phenol (dinoseb), by two reference smectite clays (SWy-2 and SAz-1) was evaluated using a combination of sorption isotherms, Fourier transformation infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and molecular dynamic simulations. Clays were subject to saturation with various cations, and charge reduction. The DNOC adsorption decreased with increasing pH indicating that DNOC was primarily adsorbed as the neutral species, The FTIR spectra of DNOC-clay films showed that DNOC molecules are oriented parallel to the clay surface. Interlayer cations have a strong effect on adsorption depending largely on their hydration energies. Weakly hydrated cations, e.g. K+ and Cs+, resulted in greater sorption compared to more strongly hydrated cations such as Na+ or Ca2+. Lower hydration favors direct interactions of exchangeable cations with -NO2 groups of DNOC and manifests optimal interlayer spacings for adsorption. In the presence of sorbed DNOC, an interlayer spacing for K-SWy-2 of between 12 and 12.5 Angstrom was maintained regardless of the presence of water. This d-spacing allowed DNOC molecules to interact simultaneously with the opposing clay layers thus minimizing contact of DNOC with water. The charge density of clays also affected sorption by controlling the size of adsorption domains. Accordingly, DNOC adsorption by low-cbarge clay (K-SWy-2) was much higher than by high-charge clay (K-SAz-1) and Li-charge reduction greatly enhanced dinoseb adsorption by K-SAz-1. Steric constraints were also evident from the observation that adsorption of DNOC, which contains a methyl substituent, was much greater than dinoseb, which contains a bulkier isobutyl group. Adsorption of DNOC by K-SAz-1 was not affected in the presence of dinoseb, whereas dinoseb adsorption was greatly reduced in the presence of DNOC.