Synthesis of Hybrid PVDF–PTFE Membrane Using Nonhazardous Solvent for Ethanol–Water Separation through Membrane Distillation

Abstract

This work was focussed on synthesizing a polyvinylidene fluoride (PVDF)–polytetrafluoroethylene (PTFE) hybrid flat sheet membrane using a nonhazardous solvent dimethyl sulfoxide (DMSO) for ethanol–water separation via vacuum membrane distillation (VMD). The base polymer (PVDF) concentrations were varied from 12 wt% to 16 wt% and the copolymer (PTFE) loading were ranged from 1 wt% to 2 wt% (e.g., 1.0 wt%, 1.5 wt%, and 2.0 wt%). The morphological characteristics, porosity, and contact angle (CA) were examined for the synthesized membranes. An increased CA was observed when PTFE loading was increased in the dope solution. The addition of PTFE to the dope solution efficiently diminished the formation of micro voids and increased the hydrophobicity of the membrane with improved characteristics. Membrane pore size, porosity, and thickness increased significantly from 0.17 µm to 0.21 µm, 48.37% to 67.79%, and 79.31 µm to 107.62 µm, respectively, within the studied range. A pure PVDF membrane CA of 88° was increased to 117.3° for 2 wt% loaded PTFE in PVDF. The synthesis of PVDF–PTFE hybrid membranes that used DMSO as a solvent and distilled water as a nonsolvent in a coagulation bath appears to be viable for membrane preparation via phase inversion to provide a reliable and sustainable separation process with a safer environment. The performance of the synthesized membrane was studied for flux and the separation factor. The maximum ethanol flux and separation factor obtained were 11 kg/m2/h and 7.0, respectively. This work suggests that the PVDF–PTFE hybrid flat sheet membranes could be used for ethanol separation in VMD.