Textural effects in powdered montmorillonite induced by freeze-drying and ultrasound pretreatment

Powder XRD patterns of freeze-dried and/or ultrasound treated montmorillonite show significant differences in the intensity ratio of 001 and 020 reflections. Combined SEM, argon adsorption at 87 K and particle size distribution analyses allow for interpretation of this effect in terms of the modification of textural properties of the materials resulting from the change of the clay particles morphology. Both the freeze-drying and the sonication lead to the disruption of clay agglomerates into finer, more prone to mutual self orientation particles. Sonication, even mild, constitutes a more efficient means of clay disintegration and induces larger textural ordering. Textural properties of the sonicated clay depend on the method of drying. Conventionally dried material shows stronger self ordering than the freeze-dried sample, due to the occurrence of sedimentation, which enhances horizontal orientation of platy clay particles.