Influence of small amounts of water and ethanol on Na+-montmorillonite solid-state modification by inorganic and organic intercalants

Abstract The possibility of solid-state solvent-free modification of Na+-montmorillonite by transition metal salts (NiCl2•6H2O, CoCl2, FeCl3•6H2O) and quaternary ammonium salts (cetyltrimethylammonium bromide, dioctadecyldimethylammonium chloride, alkylbenzyldimethylammonium chloride) was investigated in the presence of water or ethanol. The introduction of water or ethanol was necessary for the effective modification, small amounts (4–8 mmol per 2 g clay) were sufficient, as was the crystallohydrate water in the case of FeCl3•6H2O. Solid-state intercalation produces metal cation- and organo-modified montmorillonites (M-Mt and O-Mt), which were studied by wide-angle X-ray diffraction (WAXD), wavelength dispersive X-ray fluorescence analysis (WDXRF) and thermal analysis (TGA). On mechanochemical interaction during grinding Na+ and Ca2+ were exchanged for intercalant cations, the residual amount of initial cations in the rinsed modified montmorillonite did not exceed 0.1–0.2%, measured by WDXRF, and NaCl was produced as a distinct WAXD phase in quantities consistent with WDXRF, from 3.0% to a theoretical maximum of 5.6%. M-Mt were identical in structure and composition to ones obtained by solution modification. For O-Mt, the intercalation and modification proceeded to a larger extent compared to solution-modified and commercial equivalents, and with a substantially higher basal spacing (by 2–3 nm) and modifier content. The products were obtained as fine powders that did not require subsequent dispersion and fractional separation.