An internal electrostatic force-driven superoleophilic membrane-magnetic nanoparticles coupling system for superefficient water-in-oil emulsions separation

The inefficient separation of water-in-oil emulsions through conventional techniques and the troublesome membrane fouling of membrane technology call for alternative efficient and antifouling membrane separation approaches to meet the increasing demands for global environmental protection and energy recovery. Here, we demonstrate an internal electrostatic force-driven superoleophilic membrane-magnetic particles coupling system enabling water-in-oil emulsions super-efficiently separated. Specifically, as-prepared magnetic nanoparticles significantly facilitate the separation of water-in-oil emulsions due to their superoleophilic behaviors and electrostatic repulsion forces between the magnetic nanoparticles-encapsulated Pickering emulsions. Furthermore, the magnetic nanoparticles incorporate into the membrane to increase the roughness and superoleophilic ability, distinctly leading to superefficient separation capacity for water-in-oil emulsions. Meanwhile, their separation performances are so stable that remarkably outperform other membrane systems during 10-cycle operation owing to the enhanced antifouling efficacy, under the support of electrostatic repulsion forces caused by the magnetic nanoparticles-modified composite membrane and magnetic nanoparticles-encapsulated Pickering emulsions. Hence, the combination of the electrostatic repulsion forces and interfacial forces render the as-constructed superoleophilic membrane-magnetic nanoparticles coupling system dramatically exhibit a remarkably high separation flux of 8.76 × 104 L m−2 h−1 bar−1 for the water-in-toluene emulsion under the conditions of pH of 10 and sodium dodecyl sulfate surfactant, considerably higher than the existing reports of the state-of-the-art membranes. This study will open up new avenues for superefficient and stable separation of water-in-oil emulsions in actual situations, and this concept will be promising for extending to other oil-in-water emulsions and oily waste water treatment.