The influence of pH on organovermiculite structure stability

Abstract

There is a large amount of research and application studies in the topic of organically modified vermiculites and their properties. In this work, the stability of two organovermiculites, one modified with hexadecyltrimethylammonium (HDTMA+) and the other modified with hexadecylpyridinium (HDP+) ions, was investigated at pH values from 1 to 14 at laboratory temperature. The organovermiculites in the pH range of 4–10 were stable. In addition, the HDTMA+-vermiculite was stable in strong alkaline media and under extreme acidic conditions as well. However, HDP+-vermiculite underwent significant decomposition when exposed to strong acidic or alkaline conditions (pH 1, 2 and 12, 14). The prepared and tested materials were investigated using X-ray diffraction (XRD) method, Fourier transform infrared (FTIR) spectrometry, total organic carbon content (TOC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The leaching of structural cations was determined as well.