Preparations of organo-vermiculite with large interlayer space by hot solution and ball milling methods: A comparative study

The intercalation of alkylammonium ions into vermiculite (VMT) to improve the interior structure of VMT has evolved into a subject of tremendous interest. The Na+-exchanged vermiculite (Na-VMT) prepared from the VMT in Xinjiang area (China), served as a host for intercalation with cetyl-trimethylammonium (CTA+) to prepare organo-vermiculites (OVMTs) by a typical hot solution method (OVMT (H)) and a novel ball milling method (OVMT (M)) under the optimized conditions confirmed by orthogonal experimental designs. The two methods employed thermal energy and mechanical energy respectively to drive the CTA+ cations into the interlayer space of layers and to carry out the cation exchange reaction. From X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) images and thermogravimetric analysis (TGA) results, the Na-VMTs were structurally modified, and the OVMTs showed remarkably large interlayer spaces, in which alkyl chains built paraffin-type bilayer arrangements nearly perpendicular to silicate layers. However, hot solution and ball milling methods showed different behaviors. The interlayer distance of the OVMT (M) (4.283 nm) was larger than that of the OVMT (H) (4.052 nm), indicating that the tilting angle of alkyl chains in the former was larger than that in the latter. Additionally, the hot solution treatment retained the morphology of the layers and reduced the surface energy of the VMT, whereas the ball milling method caused layers to twist and led to high residual surface energy on the particles, as well as a higher content of organic compounds and lower thermal stability for the product.