增强TMA改性膨润土吸附性能的方法研究

Methods of increasing the adsorption capacity of TMA-bentonites

本研究报道一种增强有机膨润土硅氧烷表面暴露量的新方法:首先将膨润土层间无机阳离子用Li+交换,然后将Li+部分被有机阳离子四甲基铵(TMA)交换(交换量分别为20%和60%CEC);接下来通过180℃热处理12h将Li+迁移进入膨润土片层内,以降低膨润土电荷密度.由于TMA的柱撑作用,该方法可有效减少常规减电荷方法导致的膨润土层结构塌陷,因此该方法所制备的减电荷有机膨润土具有更大的比表面积及更好的HOCs吸附性能.其中TMA交换量为20%CEC的有机膨润土,其比表面积几乎是传统减电荷方法制得有机膨润土比表面积的2倍(236m2/g vs 131m2/g),进而增强对硝基苯的吸附能力.

A new method that can increase the exposure of siloxane surface was developed in this work. First the inorganic cations on bentonite were exchanged with Li＋, and then a part of the Li＋ were further exchanged with tetramethylammonium cation （TMA）, i.e., 20%or 60%of the bentonite＆#39;s cation exchange capacity. After that the samples were heated under 180℃ for 10h to make sure that most of the Li＋were transferred to bentonite sheets. By this way, the layer charge of bentonites can be effectively reduced while the layers of bentonite can be preserved by pre-exchanged TMA. The resulting organic bentonite showed larger specific surface areas and better adsorption capacity than those synthesized using traditional method （i.e., first reducing the charge density and then exchanging TMA）. For example, in the case of organic bentonite with 20%CEC TMA, the one synthesized using new method has almost twice the specific surface areas as the one synthesized using traditional method （236 vs 131m2/g）, and the adsorption capacity of nitrobenzene also significantly increased.