The ability of resisting deformation has also been enhanced. As shown in Figure 3(b), the interaction between particles and particles and between particles forms a stable three-dimensional network structure, which increases the viscosity of the continuous phase, prevents the aggregation of the droplets, and inhibits the delamination of the emulsion. (2) Three-dimensional viscoelastic particle network mechanism : This theory was proposed by Lagaly et al. (a) Mechanical barrier mechanism and (b) three-dimensional viscoelastic particle network mechanism. Stability mechanism of Pickering emulsion. Schematic diagram of classical (surfactant based) emulsion and Pickering emulsion are shown in Figure 1. Pickering emulsion can be classified into oil-in-water (O/W) and water-in-oil (W/O) types as well as surfactant stabilized emulsion. Granular solid particles include silicon dioxide, zinc oxide, iron oxide, titanium silicate, metal sulfate, polystyrene, Janus microspheres, starch nanocrystals, and so on. Flake solid particles mainly include kaolin, clay, synthetic lithium saponite, montmorillonite, graphene oxide (GO), and so on. Solid particles can be divided into flakes and granular. The droplet size of Pickering emulsion is generally in micron order, and the smaller the size, the better the emulsification ability. Pickering emulsion is prepared by homogenizing or ultrasonic emulsification of aqueous phase (some containing electrolytes), oil phase (strong polarity, medium polarity, weak polarity, or non-polarity), and solid emulsifiers. 2 Pickering emulsion and its stability 2.1 Formation of Pickering emulsion In this article, the formation, stability mechanism, influencing factors, and application progress of Pickering emulsion in oil and gas field will be introduced. Pickering emulsion has also attracted more and more attention in petroleum industry, such as drilling, enhanced oil recovery (EOR), sand control, and petroleum wastewater treatment. Therefore, Pickering emulsion has been widely studied and applied in the fields of food, fine chemical synthesis, medicine, cosmetics, and so on. In addition, compared with common emulsion, Pickering emulsion has the advantages of better stability, less emulsifier, recyclability, and environmental friendliness.
The biggest difference between Pickering emulsion and common emulsion is that emulsifier is solid particles. Later, people called this emulsion system as Pickering emulsion, and the solid particles which can emulsify and stabilize were called Pickering particles. Pickering first found in 1907 that solid particles could be adsorbed on the surface of oil droplets to form a stable emulsion. Pickering emulsion is a special one, which uses ultrafine solid particles as an emulsifier. Emulsion is a dispersion system in which one liquid is dispersed in the form of liquid beads in another immiscible liquid.
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