STUDIES OF ORGANOPHILIC CLAYS - THE DISTRIBUTION OF QUATERNARY AMMONIUM-COMPOUNDS ON CLAY SURFACES AND THE ROLE OF IMPURITIES

Wyoming bentonite (predominantly Na+ form) was shown to contain quartz as a major impurity, together with a number of minor impurities. Air refinement of the clay gave some separation by particle size, but impurity phases persisted in both the coarse (7.3-188 mu m) and fine (1.9-9.8 mu m) fractions. Exchange of the clay with a long-chain alkyl-quaternary ammonium salt, R(2)NMe(2) . Cl(R = C-18, 64%;C-16, 31%;C-14, 4%;C-12, 1%), by a ''dry'' process gave a partially exchanged material (68-78%) with surface-sorbed quaternary ammonium ion pairs as demonstrated using X-ray photoelectron spectroscopy. The surface-sorbed material was somewhat labile to washing. Despite a relatively high paramagnetic gram susceptibility, good quality Si-29 MAS NMR spectra were obtained from the materials. The origin of the paramagnetism is iron present in a small amount as structural Fe-II and to a larger extent as Fe-III, the distribution of which is more ambiguous. The surface-sorbed quaternary ammonium species induces a measurable shielding of the Si-29 nuclei of both clay and quartz particles which is considered to arise from an anisotopic magnetic susceptibility effect