Laponite and hybrid surfactant/laponite particles processed as spheres by spray-drying

Abstract

Laponite elementary disc crystals dispersed in water in the presence or absence of non-ionic Brij58 surfactant have been used as nanobuilding blocks to form laponite and laponite/surfactant spherical particles by spray-drying. The size distribution of the spherical spray-dried particles ranges from 70 to 1000 nm (average size about 220 nm). Although raw laponite (RL) was almost totally exfoliated in water, the spray-dried spherical particles were found partially delaminated and stable when spread into water. Based on a full characterization by several techniques such as dynamic light scattering, scanning and transmission electron microscopies, X-ray diffraction, thermal analyses, nitrogen volumetric sorption and solid-state multi-nuclear NMR studies, a mechanism has been proposed to explain the formation of the spherical micron size particles: a face-to-face and edge-to-edge stacking of the elementary disc crystals leads to the formation of few-layer laponite platelets that aggregate within the restricted volume of water droplets during the drying stage. In the presence of Brij58, elementary disc crystals are covered by surfactant molecules adsorbed on their surface. As a consequence, surfactant molecules fill the interlayer space to form spherical Brij58/laponite nanocomposite particles. These spray-dried laponite and Brij58/laponite spherical particles present a high potential for sorption applications.