SYNTHESIS AND CHARACTERIZATIONS OF HYDROXYALUMINUM CROSS-LINKED MONTMORILLONITE

Cross-linked montmorillonite was prepared by reacting homoionic sodium form of bentonite (Na-M) from Istenmezeje (Hungary) with high molecul ar weight polyhydroxy-aluminum complex. The complex was prepared by co ntrolled hydrolysis of alumina macrocation. The intercalated clay (Na- Al-M) was thermally treated to convert the hydroxy cations to oxide pi llars. The pillared products were characterized by X-ray powder diffra ction (XRD), Fourie transform infrared spectroscopy (FTIR), thermograv imetry (TG), differential thermal analysis (DTA) and thermal analysis- mass spectrometry (TA-MS) methods. The specific surface area as well a s pore size and pore structure distribution of samples were measured b y nitrogen, water and carbon tetrachloride adsorption, and the heat of immersion was also determined. The pillared products were characteriz ed by d(001) reflections of 19 Angstrom, which is stable even at 500 d egrees 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 c urve indicates the formation of a new phase at 950 degrees C. The obta ined surface area of the pillared product by nitrogen adsorption becom es larger (208 m(2) g(-1)) with respect to the non pillared clay, whic h 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.