Preparation and characterization of encapsulated solid particles, composed of partially hydrolysed aluminium and zirconium oxochlorides

Abstract

Partially hydrolysed aluminium oxochlorides (ACH) and aluminium–zirconium–glycine oxochlorides (AZG) have been encapsulated using lipophilic carboxylic acids from H₂O–silicone solvent systems. The encapsulated materials (E-materials) precipitate out of solution in the form of spherical beads. Their particle size varies with agitation conditions. Distributions from a few tenths to a few hundreds of micrometres are easily produced.

ESCA sputtering experiments and elemental analysis indicate that the beads are composed of a water-soluble ACH or AZG inner core that is surrounded by a thin lipophilic shell a few angstroms in thickness. We believe that the encapsulant is held around the core via, hydrogen bonding and coulombic interactions. Atomic absorption spectrometry was used to measure the release rates of ACH and AZG from the E-materials in ethanol–water systems. The release rates are affected by the amount of H₂O in the mixed solvents, the type of encapsulant, and the particle size of the beads.