Engineering >> 2023, Volume 23, Issue 4 doi: 10.1016/j.eng.2022.02.017
Research Materials for Molecular Separations
Membrane Contact Demulsification: A Superhydrophobic ZIF-8@rGO Membrane for Water-in-Oil Emulsion Separation
a State Key Laboratory of Chemical Resource Engineering, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
b State Key Laboratory of Chemistry and Utilization of Carbon-Based Energy Resources, College of Chemistry, Xinjiang University, Urumqi 830046, China
c Institute of Physical Chemistry and Electrochemistry, Leibniz Universität Hannover, Hannover D-30167, Germany
d Guangdong Engineering Technology Research Center of Advanced Insulating Coating, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, ChinaReceived：2021-10-15 Revised：2021-12-18 Accepted： 2022-02-14 Available online：2023-02-21
Achieving a water–oil interface imbalance has been identified as a critical factor in the demulsification of water-in-oil emulsions. However, conventional demulsifying membranes generally break the interface balance by depending on a relatively high transmembrane pressure. Here, we present a "contact demulsification" concept to naturally and quickly achieve disruption of the water–oil interface balance. For this purpose, a novel demulsifying membrane with a high flux of the organic component has been developed via the simple vacuum assembly of zeolitic imidazolate framework-8 (ZIF-8)@reduced graphene oxide (rGO) microspheres (ZGS) on a polytetrafluoroethylene (PTFE) support, followed by immobilization processing in a polydimethylsiloxane (PDMS) crosslinking solution. Due to the micro-nano hierarchies of the ZGS, the prepared ZIF-8@rGO@PDMS/PTFE (ZGPP) membranes feature a unique superhydrophobic surface, which results in a water–oil interface imbalance when a surfactant-stabilized water-in-oil emulsion comes into contact with the membrane surface. Under a low transmembrane pressure of 0.15 bar (15 kPa), such membranes show an excellent separation efficiency (~99.57%) and a high flux of 2254 L·m–2·h–1, even for surfactant-stabilized nanoscale water-in-toluene emulsions (with an average droplet size of 57 nm). This "contact demulsification" concept paves the way for developing next-generation demulsifying membranes for water-in-oil emulsion separation.