Design and preparation of polytetrafluoroethylene/carbon (PTFE/C) composite membrane‐equivalent foam for gravity‐driven emulsion separation

Abstract

AbstractHerein, the concept of a membrane‐equivalent foam (MEF) with equivalent characteristics to a separated multilayer membrane is proposed and elaborated to mitigate the conflict between efficiency and selectivity in emulsion separation. Porous polytetrafluoroethylene/carbon (PTFE/C) composite MEF with a two‐level microporous structure (bubble pores and ice‐templated pores) was prepared successfully, derived from a PTFE/glutaraldehyde crosslinked polyvinyl alcohol (PVAG) composite foam green body. The PVAG‐based in situ carbon was analyzed as composed mainly of amorphous carbon. The bubble pores were observed to be interconnected by ice‐templated pores. The porosity of the porous PTFE/C composite MEF reached a remarkable value of 73.35%. Corresponding to m(PTFE)/m(PVA) values of 14/1, 12/1, 10/1 and 8/1, the average pore sizes of the bubble pores were 32.99, 44.31, 47.33 and 48.01 μm, and the average sizes of the ice‐templated pores were about 2.24, 2.77, 3.02 and 3.47 μm, respectively. Meanwhile, the porous PTFE/C composite MEF exhibited near superhydrophobicity in air and superhydrophobicity under oil. In gravity‐driven water−oil emulsion separation tests, the oil flux was up to 3541 L h−1 m−2 and the separation efficiency reached more than 99.52%. After 20 cycles of testing, the oil flux and separation efficiency remained stable. The membrane‐equivalent thickness of the samples from PTFE/C‐m1 to PTFE/C‐m4 were below 3.47, 4.26, 0.58 and 0.30 nm, respectively, which is about 10−7–10−6 times lower than the height of porous PTFE/C composite MEF. It is reasonable to believe that porous PTFE/C composite MEF could effectively mitigate the ‘trade‐off’ effect. © 2023 Society of Industrial Chemistry.