Synthesis and characterizations of hydroxy-aluminum cross-linked montmorillonite

Cross-linked montmorillonite was prepared by reacting homoionic sodium form of bentonite (Na-M) from Istenmezeje (Hungary) with high molecular weight polyhydroxy-aluminum complex. The complex was prepared by controlled hydrolysis of alumina macrocation. The intercalated clay (Na-Al-M) was thermally treated to convert the hydroxy cations to oxide pillars. The pillared products were characterized by X-ray powder diffraction (XRD), Fourie transform infrared spectroscopy (FTIR), thermogravimetry (TG), differential thermal analysis (DTA) and thermal analysis-mass spectrometry (TA-MS) methods. The specific surface area as well as pore size and pore structure distribution of samples were measured by nitrogen, water and carbon tetrachloride adsorption, and the heat of immersion was also determined. The pillared products were characterized by d(001) reflections of 19 Angstrom, which is stable even at 500 degrees C. The interaction of polymer alumina caused several changes in the obtained FTIR spectra due to the formation of different new bonds. The rate of dehydroxylation of the pillared product is very moderate, the water release occurred in different temperature ranges according to TA-MS results. Dehydration starts at interfaces and at the wall of pores, occurring nearly with uniform rate at 250-500 degrees C. DTA curve indicates the formation of a new phase at 950 degrees C. The obtained surface area of the pillared product by nitrogen adsorption becomes larger (208 m(2) g(-1)) with respect to the non pillared clay, which decreases less than 10% upto 700 degrees C. The pillared sample has a definite pore structure, the quantity of micropores (0-40 Angstrom) decreased with increasing of macropores (>1000 Angstrom). The obtained domestic pillared montmorillonite possesses a high degree of thermal stability and may be used as adsorbent.