PVDF-CaAlg nanofiltration membranes with dual thin-film-composite (TFC) structure and high permeation flux for dye removal

Novel polyvinylidene fluoride-calcium alginate (PVDF-CaAlg) nanofiltration (NF) membranes were prepared by impregnating electrospun PVDF substrates with sodium alginate solution and crosslinking with CaCl 2 solution. The NF membranes were characterized via field emission scanning electron microscopy (FESEM) equipped with an energy-dispersive spectrometry (EDS), attenuated total reflectance Fourier transform infrared spectra (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The results show that the prepared PVDF-CaAlg NF membranes exhibit dual thin-film-composite (TFC) structure and superior surface hydrophilicity. The highest pure water flux can achieve 63.8 L·m −2 ·h −1 ·bar −1 accompanied with a 98.5% rejection rate for methyl blue (MB), which is superior to many polymeric NF membranes. The prepared PVDF-CaAlg NF membranes exhibit much higher rejections for seven typical dyes, and the rejection slightly rises with the increase of impregnating time. In the long-term filtration process, the permeation flux for dye solution remains stable. PVDF-CaAlg NF membranes show good anti-fouling performance to BSA protein and lactobacillus.