The swelling of HDTMA smectites as influenced by their preparation and layer charges
The swelling of HDTMA smectites as influenced by their preparation and layer charges
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DOI：
10.1016/j.clay.2003.07.007
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发表时间：
2004-04
影响因子：
5.6
通讯作者：
P. Slade;W. Gates
中科院分区：
文献类型：
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作者：
P. Slade;W. Gates
溴化十六烷基三甲基铵（HDTMA）的水溶液和乙醇溶液与不同电荷的层状硅酸盐反应。所得插层的层间距随电荷而变化，并与插层HDTMA形成一致：当层电荷时，单层的平躺分子，在每单位晶胞的基础上，是<0.5 e-;双层的平躺分子的电荷之间的0.5和1.0 e-和倾斜的石蜡状排列的电荷大于1.0 e-。使用水溶液进行的插层反应允许盐分子与HDTMA阳离子共吸附。当用乙醇进行插层反应时，盐分子的共吸附似乎不会发生。用乙醇浸提从在水性介质中产生的插层中除去盐分子。对于电荷>0.5 e-的蒙脱石和蛭石，来自水性介质的盐分子的插入导致比在乙醇中形成或用乙醇浸出的插入物更大的层间距。甲苯吸附等温线表明，甲苯从水的插层吸收增加时，它是由一个高度带电的蒙脱石形成。当插层物含有HDTMA盐分子时，甲苯从水中的吸收也增加。层间距表明，HDTMA插层硅酸盐溶胀在纯甲苯的存在下，因此从溶液中的吸附也伴随着层间膨胀。理想情况下，含有BTEX污染物的反应性屏障应该使用最高电荷的粘土生产，并且应该与水性HDTMA反应。洗涤是没有必要的。
Both aqueous and ethanolic solutions of hexadecyltrimethylammonium (HDTMA) bromide have been reacted with layer silicates of different charge. Layer spacings of the resulting intercalates vary with charge and are consistent with the intercalated HDTMA forming: monolayers of flat-lying molecules when layer charges, on a per unit cell basis, are <0.5 e−; bilayers of flat-lying molecules for charges between 0.5 and 1.0 e−and tilted paraffin-like arrangements for charges greater than 1.0 e−. Intercalation reactions carried out using aqueous solutions allow salt molecules to be coadsorbed with HDTMA cations. Coadsorption of salt molecules appears not to occur when intercalation reactions are carried out with ethanol. Leaching with ethanol removes salt molecules from intercalates produced in an aqueous medium. For smectites with charges >0.5 e−, and for vermiculites, the intercalation of salt molecules from an aqueous medium leads to greater layer spacings than for intercalates formed in ethanol or leached with ethanol. Toluene sorption isotherms show that toluene uptake from water by an intercalate is increased when it is formed from a highly charged smectite. Toluene uptake from water also increases when the intercalate contains HDTMA salt molecules. Layer spacings show that HDTMA intercalated layer silicates swell in the presence of neat toluene, and thus sorption from solution is also accompanied by interlayer expansion. Reactive barriers to contain BTEX pollutants ideally should be produced using a clay of the highest charge available, and should have been reacted with aqueous HDTMA. Washing is not necessary.