Study On The Preparation And Application Of Pickering Emulsions

As a thermodynamic stability and dynamic instability system, solid-stabilized emulsion is stabilized by solid particles as emulsifier instead of traditional surfactants, which is often called Pickering emulsion. Pickering emulsion has important applications in many frontiers, which was widespread concerned by researchers in and abroad. In this paper, the stable behaviors of Pickering emulsions stabilized by single and mixed particles were investigated separately. The application of Pickering emulsions was discussed in the fields of drug deliver and new pesticide preparation.Using alcohol-water as co-solvent, ammonia as catalyst, SiO₂ particles were prepared by hydrolysis of TEOS. CaCO₃ particles were prepared by a precipitation method. The CaCO₃/SiO₂ particles were prepared with a layer by layer method by coating SiO₂ particles on the surface of CaCO₃ particles. The nano-SiO₂ particles were spherical with an average diameter of 110 nm. The CaCO₃ particles were cubic with an average diameter of 2μm. The size of CaCO₃ increased with the increasing of the reaction concentration and temperature. The sickness of SiO₂ in the composite CaCO₃/SiO₂ particles increased with the increasing of coating times.The octanol-in-water Pickering emulsions stabilized by SiO₂ were prepared, and the effect of the acidity of the continuous phase on the formation and stability of the emulsions were investigated. The result showed that the stabilization time and the average drop size of the emulsions increased with the increasing of the concentration of the hydrochloric acid in the continuous phase, while the stabilization time decreased with the increasing of the sodium hydroxide concentration. The influence of the acidity of the continuous phase on the stability of the Pickering emulsions could be ascribed to the changing of the electric charge density and the flocculation behavior of the nano-silica particles.The olive oil-in-water Pickering emulsions stabilized by CaCO₃ particles were prepared. The factors of CaCO₃ size, concentration, oil-water ratio and electrolyte concentration of continuous phase to the drop size and stabilization time of the emulsions were investigated. The result showed that the drop size of the emulsions increased with the increasing of the CaCO₃ particle size and the volume ratio of oil to water, while decreased with the increasing of the amount of CaCO₃ particles and the concentration of carbonate concentration. The stability of the emulsions decreased with the increase of the volume ratio of oil to water and the concentration of sodium carbonate, while increased with the increase of the amount of CaCO₃ particles.The olive oil-in-water Pickering emulsions were prepared using the mixed particles of SiO₂ and CaCO₃ as emulsifiers. The effect of the SiO₂ content in the mixed particles on the stability and the drop size of the Pickering emulsions were investigated. The result showed that the Pickering emulsions were of oil-in-water type. With the increase of the SiO₂ content in the mixed particles, the stability and the drop size of the Pickering emulsions decreased. Bigger SiO₂ particles had more efficient influence on the stability of the emulsions, while smaller ones had more efficient influence on the drop size of the emulsions. The effect of the SiO₂ particles on the emulsions was attributed to their adsorptive behavior at oil-water interfaces of the Pickering emulsions.On the basic of stable Pickering emulsions were prepared, and the application of Pickering emulsions was investigated in fields of drug release and preparation of pesticide microcapsule. The result showed that the ethyl acetate dissolved in the dispersed phase of the emulsions stabilized by CaCO₃ particles showed a certain degree of controlled release behavior and the water-based pesticide prepared by emulsions stabilized by solid particles as emulsifier have well stability. The pesticide microcapsules were obtained use Pickering emulsions as templates.