Effects of grinding montmorillonite and illite on their modification by dioctadecyl dimethyl ammonium chloride and adsorption of perchlorate

Montmorillonite (Mt) and illite (lit) were ground for different times under wet condition and sequentially subjected to organic modification by dioctadecyl dimethyl ammonium chloride (DDAC). The influence of the grinding time on the obtained products in terms of DDAC loading and ClO4- adsorption were evaluated. Multiple techniques were used to characterize the changes in structure and morphology before and after mechanical or organic modification. Compared with Ilt, Mt showed a stronger resistance to mechanical treatment due to its swelling property. Silicon nuclear magnetic resonance (Si-29 NMR) spectra and X-ray diffraction (XRD) patterns of samples ground for 30 min indicate the disintegration of Ilt and exfoliation of Mt, resulting in increase of ClO4- uptake by 147% for ont and 13% for OMt. Three stages in the grinding Mt can be proposed, including the separation of large particles into small particles, exfoliation of small particles, and disintegration of exfoliated single layers. In contrast, two stages are involved in the grinding Ilt, which are the destruction/exfoliation of large particles and further disintegration of small exfoliated layers.