Nano‐Modification of the Polyvinyl Alcohol/Organic Acid‐Modified Polyvinylidene Fluoride Thin‐Film Composite Membrane and Its Application in the Nanofiltration Process

Abstract In this study, a novel thin‐film nanocomposite (TFN) membrane is developed consisting of a cross‐linked nano‐modified polyvinyl alcohol (PVA) selective layer on an organic acid‐modified polyvinylidene fluoride (PVDF) membrane. The nano‐modification of the PVA layer is performed via incorporating different amounts of the amine‐functionalized multiwalled carbon nanotubes (MWCNTs‐NH 2 ) into the PVA matrix. The effect of citric acid on the chemical structure and morphology of the PVDF support is also investigated. The performance of the resultant membranes in the nanofiltration (NF) of MgSO 4 and acid yellow‐17 aqueous solutions is also studied. The results indicate that the modification of the support with 0.5 wt% of citric acid increased the water permeance from 1.59 L m −2 h −1 bar −1 (LMH/bar) for PVA/PVDF to 4.49 LMH/bar for the PVA/modified PVDF membrane. Furthermore, the optimum value of MWCNT‐NH 2 (0.6 wt%) increases the permeance of the resultant TFN membrane to 4.94 LMH/bar while maintaining a high rejection. Interestingly, the incorporation of MWCNT‐NH 2 into the PVA layer and citric acid into the PVDF solution results in a membrane with the highest permeance of 6 LMH/bar.