On the Pickering emulsions stabilized by calcium carbonate particles with various morphologies

Cubic, spherical and rod-like calcium carbonate particles were prepared by precipitation method and were used as stabilizers for the formation of Pickering emulsions. The calcium carbonate particles were characterized with SEM, XRD and Zeta sizer. The type of Pickering emulsions was inferred by a diluting method. The size and the stability of the droplets of Pickering emulsions were observed by an optical microscope. The results showed that the zeta potentials of cubic, spherical and rod-like calcium carbonate particles were -23.2 mV, 16.5 mV and 1.2 mV, respectively. The Pickering emulsions stabilized by calcium carbonate particles were of oil-in-water type. With the increase of the amount of water, the droplets of Pickering emulsions became larger. When using the mixture of two oppositely charged calcium carbonate particles as stabilizers, the droplets of Pickering emulsions preferentially adsorbed positively charged ones. When used the mixture of two kinds of cubic calcium carbonate particles with different sizes as stabilizers, the droplets of Pickering emulsions preferentially adsorbed the smaller ones. The selective adsorption of particles at the oil-water interfaces of Pickering emulsions was attributed to the electrostatic interaction between the particles and droplets, and had potential applications in separation process and in synthesis of new materials.