Effect of organic modification on the thermal transformations of abentonite during sintering up to 1250 degrees C

摘要

X-ray diffraction (XRD) and thermal analysis techniques were used to study the thermal transformations of raw (Maghnia bentonite) and modified bentonite (algae extract (ulvans) within clay). XRD data showed that the basal spacing (d (001)) was gradually decreased from12.80 (6.90A degrees (2oee integral)) at room temperature to about 9.97 (8.86A degrees (2oee integral)) and 10.08 (8.74A degrees (2oee integral)) after calcination at 200, 400 and 600A degrees C for raw and modified bentonites, respectively. Such behaviour was assigned to the loss of physisorbed water molecules (200A degrees C) and to the occurrence of a distorted octahedral metal (complex for modified bentonite) in the clay. Calcinations above 800A degrees C gave rise to a complete distortion of this crystal lattice, leading to the disappearance of d (001) XRD peak due to the dehydroxylation of bentonites. The occurrence of cordierite was enhanced at lower temperature (1100A degrees C instead of 1250A degrees C) in the modified bentonite.