Abstract:

The effects of OH-/Al3+ ratio within the range of 1.0-2.5, on physico-chemical properties of Al-pillared clays obtained from Hancili (Turkey) bentonites and the change of these properties with the calcination temperature were examined. Characterization studies were performed by use of XRF, XRD, FTIR, SEM and N2-adsorption/desorption analysis. Basal spacing and multi point BET surface area values of Al-pillared clays obtained from Hancili White Bentonite (HWB) increased from 1.69 nm and 149 m2g-1 to 1.83 nm and 198 m2g-1 by the increase of OH-/Al3+ ratio from 1.0 to 2.0 similar to the ones obtained from Hancili Green Bentonite (HGB). Decreases in these values were observed with temperature; however, even after calcination at 700ºC, they were higher than those of natural bentonite clays. HWB host resulted in samples with higher surface area values with the gained thermal stability. Calcium content of the products (determined by XRF) decreased to zero level with increasing OH-/Al3+ ratio and a corresponding decrease of Si/Al ratio. Presence of peaks at 1550 cm-1 corresponding to Brønsted acid site and at 1450 cm-1 corresponding to Lewis acid sites confirmed the existence of both physical and chemical acid sites in the synthesized samples.

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