Abstract
Pickering emulsions with on–off properties provide significant advantages over simple solid-stabilized emulsions for the development of novel materials, such as oil-displacing agents for enhanced oil recovery and templates for the fabrication of porous materials. However, the irreversible adsorption of particles as emulsion stabilizers endows the Pickering emulsions with kinetically stable property, resulting in a huge challenge to break the stability. Here we fabricated microscale Pickering emulsions, by the use of paramagnetic particles, which possess excellent stability for several months and more interestingly perform complete demulsification under controllable magnetic fields in several minutes. The alternating asymmetrical magnetic field endows oil-in-water droplets ‘‘big’’ N and S poles on the outer particle layers, and attracts the solid particles to the bottom of the vial after the coalescence and the deformation of the droplets, bringing the prevention of re-emulsion and the cyclic utilization. This facile strategy to produce stable Pickering emulsions with a magnetic-response opens a promising avenue for various practical applications including oil recovery, wastewater treatment, and sludge removal.
Highlights
Pickering emulsions with on–off properties provide significant advantages over simple solid-stabilized emulsions for the development of novel materials, such as oil-displacing agents for enhanced oil recovery and templates for the fabrication of porous materials
Preparation of pickering emulsions based on carbonyl iron particles (CIPs)
Compared with the freshly prepared emulsions (Figs. 2f and S1a), the oil droplet size increases largely after 15 days (Figs. 2g and S1b), taking the emulsion with 5 wt% CIPs as an example; interestingly, small oil droplets tend to coalesce to big ones from 15 to 35 days (Figs. 2h and S1c), and the droplet appearance keeps changeless from 35 to 85 days
Summary
Pickering emulsions with on–off properties provide significant advantages over simple solid-stabilized emulsions for the development of novel materials, such as oil-displacing agents for enhanced oil recovery and templates for the fabrication of porous materials. The alternating asymmetrical magnetic field endows oil-in-water droplets ‘‘big’’ N and S poles on the outer particle layers, and attracts the solid particles to the bottom of the vial after the coalescence and the deformation of the droplets, bringing the prevention of re-emulsion and the cyclic utilization This facile strategy to produce stable Pickering emulsions with a magnetic-response opens a promising avenue for various practical applications including oil recovery, wastewater treatment, and sludge removal. The research and technology on switchable emulsions are rarely r eported[6,8], except a complete phase separation triggered by the aid of both magnetic field and stirrer, owning to the missing materials and understanding of the responsive demulsification mechanisms With this in mind, we imposed a controllable magnetic field on a series of Pickering emulsions stabilized by paramagnetic particles. Our results are expected to provide a scientific basis for a rapid, high-efficient, reproducible, and environmentally friendly separation technology
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