![]() ![]() Influence of magnetic field on Pickering emulsion stabilized by Fe 3O 4 particles. used dynamic strain amplitude scanning to measure the linear viscoelasticity of Pickering emulsions and obtained that the elastic modulus of emulsions is directly related to the elasticity of the network structure formed by solid particles and droplets. The influence of magnetic field on emulsions is shown in Figure 1. It was found that magnetic field would strengthen the three-dimensional network in Pickering emulsions and intensify droplet aggregation. used silane-modified Fe 3O 4 nanoparticles to stabilize butyl butyrate–water system and dodecane–water system to form Pickering emulsion. Zhou used Fe 3O 4 nanoparticles to stabilize polar and nonpolar oil-aqueous Pickering emulsions and discovered that droplet size increased with the increase of initial oil-phase volume fraction and decreased with the increase of solid concentration, which was believed to be influenced by agglomeration of nanoparticles. 1.2 Pickering emulsion stabilized by Fe 3O 4 nanoparticlesįe 3O 4 particle is amphiphilic and so it is easy to form Pickering emulsion, and nanoscale Fe 3O 4 particle is paramagnetic. pointed out that when solid content in emulsions was greater than a certain value, particles entered into continuous phase and interlinked to prevent droplet merger and settlement. proposed the three-dimensional viscos-elastic particles network mechanism, in which the interaction between particles formed a three-dimensional network structure and increased the viscosity of continuous phase and reduced the migration rate of emulsion droplets. Mechanical barrier refers to the formation of a dense particles’ membrane outside the dispersed phase to prevent droplet aggregation, and the adsorption of solid particles interface enhances stereo-hindrance effect and increases emulsion stability. Studies have shown that the stabilizing mechanism of Pickering emulsions mainly consists of mechanical barrier and three-dimensional viscos-elastic particles network structure moreover, the stabilizing mechanism can be capillary forces on the oil–water interface for nonspherical solid particles. Adsorption is the strongest when θ OW is 90° for the particles with a radius bigger than 10 nm, Δ G remove is far greater than the thermal motion energy of themselves, and therefore, adsorption of nanoparticles on the oil/water interface is almost irreversible. In equation ( 1), Δ G remove is the energy required to remove the particle from the interface, J γ OW is the interfacial tension of oil–water interface, N/m R is the radius of solid particles, m θ OW is the contact angle of particles. (1) Δ G remove = π R 2 γ OW ( 1 ± cos θ OW ) 2 Researches and engineering practice have proved that Pickering emulsions have extremely high stability as adsorption of solid particles under partial wetting conditions is very strong the free energy of adsorption can be calculated by equation ( 1). At present, fabrication methods to form Pickering emulsions mainly include rotor–stator homogenization, high-pressure homogenization, ultrasonic emulsification, membrane emulsification, and microfluidic technology ultrasonic dispersion method is used in this research. In addition, this kind of emulsion has fluidity, magnetism, as well as low preparation cost and consequently can be considered as an alternative to magnetic fluid for viscous drag reduction of magnetic liquids. In terms of industrial applications, crude oil Pickering emulsion stabilized by Fe 3O 4 nanoparticles can be used in crude oil emulsifying transportation due to its high stability and ability of demulsification under strong magnetic field. Fe 3O 4 nanoparticles endow the emulsion with magnetic-responsive functionality. Particles are the key component in the formation of Pickering emulsions, and properties of particles are strongly influenced by their fabrication. During these producing processes, solid particles easily adhere to crude oil under the condition of high temperature and high pressure as a result, the Pickering emulsions are formed. It can also be found in the petroleum industry, such as the process of Pickering foam flooding, oil production by magnetic fluid, and low salinity water flooding. Although no product based on Pickering emulsions is commercialized yet, because of their special properties, Pickering emulsions can be widely used in pharmacy, agriculture, food, catalyst, and other fields. The emulsion stabilized by solid particles instead of surfactants is called Pickering emulsion, which mainly consists of spherical particles (SiO 2, Fe 3O 4, etc.), flaky solids (montmorillonite, kaolin, etc.), graphene oxide, and other particles. ![]()
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