Pore structure design of NFES PTFE membrane for membrane emulsification

In this research, a novel poly(tetrafluoroethylene) (PTFE) membrane with regular geometric pore structure fabricated by near-field electrospinning (NFES) method was firstly utilized in the preparation of water-in-oil (W/O) emulsion through membrane emulsification process. Effects of NFES PTFE membranes’ pore aspect ratio (length-width ratio of rectangle pore structure) on the water-in-oil droplet size, droplet size distribution, and uniformity of water-in-oil emulsion was investigated respectively. Results showed that the increase of pore aspect ratio would bring about a smaller water-in-oil droplet size. The average water-in-oil droplet size decreased from 234.9 nm (M-1) to 167.8 nm (M-4) when the pore aspect ratio increased from 1 to 4. Compared with conventional mechanical agitation, the water-in-oil emulsion formed by membrane emulsification process showed not only more uniform water-in-oil droplet size, but also higher long-term stability (remained homogeneous after 30 days). In addition to showing the excellent membrane emulsification performance in harsh environment, the NFES PTFE membrane also exhibited excellent water-in-oil emulsion separation performance. Compared with other NFES PTFE membranes, M-1 membrane showed the highest oil flux (33.4 L m-2 h-1, -0.02 MPa) and water rejection rate (94.4%) in the separation of water-in-oil emulsion formed by membrane emulsification process.