Design and properties of polyvinylidene fluoride/poly(styrene-butadiene-styrene)/functionalized multi-walled carbon nanotube nanocomposite membranes

Abstract

In this work, we prepared thin film nanocomposite membranes for water desalination. We synthesized nanocomposite derived from polyvinylidene fluoride (PVDF), poly(styrene-butadiene-styrene) (SBS), and modified multi-walled carbon nanotube (MWCNT). Three nanotube modifications were prepared: carboxylic acid functional MWCNT-COOH, acid chloride functional MWCNT-COCl and thiocyanate-modified MWCNT-SCN. Consequently, three nanocomposite blends with 0.01–1 wt. % nanofiller, PVDF/SBS-MWCNT-COOH, PVDF/SBS-MWCNT-COCl and PVDF/SBS-MWCNT-SCN, were prepared. Functionalization of the nanotube was characterized by Fourier transform infrared spectroscopy. Surface morphology of the membranes was studied by scanning electron microscopy. PVDF/SBS-MWCNT-COOH 0.01–1 nanocomposite tensile strength increased from 10.1 to 13.1 MPa, while PVDF/SBS-MWCNT-SCN 0.01–1 increased from 10.2 to 13.9 MPa. PVDF/SBS-MWCNT-COOH nanocomposite maximum decomposition temperature increased from 516℃ to 559℃ and PVDF/SBS-MWCNT-SCN increased from 551 to 574℃. PVDF/SBS-MWCNT-COOH 0.01–0.1 percent solvent content changed from 1.07% to 1.39% and PVDF/SBS-MWCNT-SCN 0.01–0.1 changed from 1.08% to 2.80%. PVDF/SBS-MWCNT-SCN 0.01–0.1 porosity in water (0.05–0.08) was highest among all membranes. Shrinkage ratio decreased with increasing nanotube content in all membranes. PVDF/SBS-MWCNT-SCN nanocomposite pure water flux (4.7 mLcm−2 min−1), salt rejection (83.9%), and recovery (76.7%) were higher than other membranes prepared.