Physico chemical adsorption and aggregative structures of the organic cation [C18mim]+ in the interlayer of montmorillonite

An organic cation [C(18)mim](+) formed from [C(18)mim]Br, one type of ionic liquids, can go into the interlayer of sodium montmorillonite (MMT) through the ion-exchanging reaction. The adsorption state, the adsorption amount, and the aggregative structure of [C(18)mim](+) in the interlayer of MMT have been investigated by thermogravimetric analysis (TGA), wide-angle X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results indicated that there is a maximum chemical adsorption of [C(18)mim](+) in the interlayer of MMT, but the total amount of adsorbed [C(18)mim](+) in the interlayer of MMT increases with the physical adsorption of [C(18)mim](+). With the increasing amount of adsorbed [C(18)mim](+) in the interlayer of MMT, the aggregative structures of [C(18)mim](+) become more ordered, leading to an obvious increase of the interlayer distance of MMT.