短链烷基季铵盐改性蒙脱石结构及性质研究

Study on structure and properties of montmorillonite modified by short alkyl quaternary ammonium salts

利用阳离子交换反应制备了短链烷基季铵盐(四乙基氯化铵和四丁基氯化铵)改性钠基蒙脱石,通过傅里叶红外光谱(FT-IR)、X-射线衍射(XRD)和热重分析(TG)进行了实验表征,同时采用蒙特卡洛分子模拟方法,对季铵盐阳离子插层蒙脱石的层间结构进行了模拟探究.结果表明:短链季铵盐离子插层,未改变蒙脱石原有的硅铝酸盐片层结构,但使蒙脱石由亲水性向疏水性转变,同时,插层季铵盐的热稳定性得到有效提高.季铵盐离子主要以单层排列的形式有规律地分布在蒙脱石层间,制备过程中季铵盐添加量变化对蒙脱石层间距的变化影响较小.分子模拟计算的d001值与X-射线衍射实验很好地吻合,计算结合能在分子层次上揭示了季铵盐离子种类和添加量变化对蒙脱石层间距影响及其原因.

The short alkyl chain quaternary ammonium salts(tetraethyl ammonium chloride and tetrabutyl ammonium chloride)intercalated sodium montmorillonite were prepared by cation exchange reaction and characterized by fourier transform infrared(FT-IR),X-ray diffraction(XRD)and thermogravimetric analysis(TG).Further,the Monte Carlo simulations were carried on investigating the interlayer structure of the modified montmorillonite.The experimental and theoretical results showed that the intercalation of the quaternary ammonium cations did not change the original lamellar structure of montmorillonite,but changed montmorillonite from hydrophilic to hydrophobic,and improved the thermal stability of the quaternary ammonium cations.The quaternary ammonium cations are regularly distributed in a single layer between the layers of montmorillonite.The change of the dosage of quaternary ammonium salts used in preparation has little effect on the variation of the spacing of montmorillonite layer.The d001 values of the spacing calculated by the simulations are in good agreement with those from the X-ray diffraction.The calculated binding energy explored the influence of different types and dosages of quaternary ammonium salts on the spacing of montmorillonite at the molecular level.