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

Abstract

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 (d001) was gradually decreased from ∼12.80 Å (6.90° (2θ)) at room temperature to about 9.97 Å (8.86° (2θ)) and 10.08 Å (8.74° (2θ)) after calcination at 200, 400 and 600°C for raw and modified bentonites, respectively. Such behaviour was assigned to the loss of physisorbed water molecules (200°C) and to the occurrence of a distorted octahedral metal (complex for modified bentonite) in the clay. Calcinations above 800°C gave rise to a complete distortion of this crystal lattice, leading to the disappearance of d001 XRD peak due to the dehydroxylation of bentonites. The occurrence of cordierite was enhanced at lower temperature (1100°C instead of 1250°C) in the modified bentonite.