High pervaporation dehydration performance of the composite membrane with an ultrathin alginate/poly(acrylic acid)-Fe₃O₄ active layer

Poly(acrylic acid)-Fe₃O₄ nanoparticles (PAA-Fe ₃O₄) with a size of 50 nm were synthesized by a one-pot method and then blended with sodium alginate matrix to prepare an ultrathin hybrid active layer of composite membrane for pervaporation dehydration of ethanol solution. The in situ modification of Fe₃O₄ nanoparticles by PAA improved the nanoparticle dispersion in the membrane. PAA-Fe₃O₄ nanoparticles not only interfered the ordered packing of polymer chains, but also enhanced the membrane structure stability and the diffusion selectivity. Compared with the membrane blended with Fe ₃O₄ nanoparticles, the membrane blended with PAA-Fe ₃O₄ nanoparticles displayed a much higher separation factor. When the PAA-Fe₃O₄ nanoparticle content was 8 wt %, the hybrid membrane acquired the optimal pervaporation performance with a separation factor of 1044 and a permeation flux of 1634 g/m² h for 90 wt % ethanol aqueous solution at 350 K. Furthermore, the hybrid membrane possessed good long-term operation stability.