Study On The Preparation And Application Of Pickering Emulsions

As a thermodynamic and dynamic stability system, solid-stabilized emulsions are stabilized by solid particles as emulsifiers instead of traditional chemical surfactants, which are often called Pickering emulsions. Because of low cost, non-toxic and environmental, Pickering emulsions play an important role in food, pharmaceutical and cosmetics et al. In this paper, Pickering emulsions stabilized by single and composite particles were prepared, the factors influenced the stability of Pickering emulsions were discussed, and the application in separation process of Pickering emulsions was investigated.Using St?ber method, SiO₂ particles were prepared by hydrolysis reaction of tetraethoxysilane (TEOS). ZnO and MgO particles were prepared by direct precipitation method. SiO₂/ZnO composite particles were prepared with a layer by layer method by coating ZnO on the surface of SiO₂ particles. SEM showed that SiO₂ particles were dispersed well and spherical with an average diameter of 300 nm, ZnO particles were needle-like morphology with an average size of 20 nm, MgO particles had both spherical and dubic crystal structure with an average diameter of 100 nm, ZnO were uneven distributed on the surface of SiO₂ and different components composite particles could be prepared by changing the concentration of zinc salt solution and the drops of liquid speed. FTIR showed that a large number of hydroxyl groups on the surface of SiO₂, ZnO, SiO₂/ZnO and MgO. XRD confirmed MgO had a high degree of crystallization.The oil-in-water Pickering emulsions stabilized by SiO₂, ZnO, SiO₂/ZnO and MgO particles as emulsifiers were prepared, and the factors of solid particles type, component content of composite particles, oil-water ratio, electrolyte in continuous phase and surfactants on the formation and stability of the emulsions were investigated. The results showed that the emulsions stabilized by SiO₂/ZnO and MgO were very stable, but by SiO₂ and ZnO were not while chloroform as oil phase. The stability of Pickering emulsions stabilized by MgO decreased when oil-water ratio increased, but no phase inversion occurred. The stability decreased when electrolyte concentration was high, and Na2CO3 was stronger than NaCl. The droplets became smaller and much more stable when surfactants were added in the emulsions stabilized by MgO particles as emulsifier and chloroform as oil, and joined solid particles to the chloroform in water emulsions stabilized by surfactants, the size and the stability of the droplets were increased.The static and dynamic separation of methyl violet based on the chloroform-styrene in water emulsions stabilized by SiO₂/ZnO particles. The results showed that Pickering emulsions tended to separation saturation with in 30 min, but temperature had little influence, the separation efficiency could be improved by increasing the amount of emulsions and the concentration of methyl violet on the static separation, and the droplets changed little before and after separation. The penetration time extended and the separation ability of methyl violet increased when increasing the amount of the emulsions, decreasing the concentration of methyl violet and flow rate, and the droplets changed depression, flat and so on.The static and dynamic separation of aniline was carried out with Pickering emulsions as separation media. The results showed that Pickering emulsions reached to the maximum capacity, with increasing the amount of emulsions and the extraction stages, the static extraction efficiency increased, increasing MgO particles, the extraction efficiency raised first and then decreased, and the static extraction efficiency of single-stage was 70%, while that of three-stages exceeded 98%. The dynamic extraction behavior of aniline from aqueous solution was similar to that of adsorption procedure in fixed bed, with the increase of the volume amount of Pickering emulsions, the decrease of inlet rate and initial aniline concentration, the dynamic extraction efficiency increased, the penetration time was prolonged and the droplets had large deformation.