Fabrication Of Polymer-magnetic Nanoparticle Hybrid Membranes For Pervaporation Process

Polymer-inorganic membranes have become the hotspot in the development ofadvanced membrane materials, because they integrate the advantages of polymericmembranes and inorganic membranes, and meanwhile overcome their disadvantages.To prepare the hybrid membrane with high separation performance, it is vital to tailorthe polymer-inorganic interfaces and construct continuous channels within membrane.In this study, pervaporation dehydration of ethanol aqueous solution was chosen asthe investigation object. Magnetic particles were incorporated into polymer matrix byblending or in-situ method to prepare hybrid membranes. The hybrid membranesexhibited excellent pervaporation performance due to the ability of magnetic particlesin tuning physicochemical characteristics and microstructural morphologies of themembranes.Poly(acrylic acid) in-situ modified Fe3O4nanoparticles (PAA-Fe3O4) with a size of50nm were blended into sodium alginate (SA) matrix to prepare an ultrathin hybridactive layer of composite membrane. The in-situ modifcation of Fe3O4nanoparticlesby PAA improved the nanoparticle dispersion in the membrane. The interactionbetween PAA-Fe3O4nanoparticles and SA matrix not only interfered the orderedpacking of polymer chains to increase the quantity of free volume cavities in themembrane, but also confned the size of free-volume cavities to create the selectiveinterfaces between nanoparticles and polymer. Effects of modification by PAA andPAA-Fe3O4content on membrane pervaporation performance were investigated.When PAA-Fe3O4content was8wt.%, the hybrid membrane acquired optimizedperformance with a permeation fux of1634g/m2h and a separation factor of1044,which was higher than the performance of hybrid membrane incorporated withpristine Fe3O4at the same content.In nature, geomagnetic field drives Fe3O4nanoparticles to be aligned pearl-likeinside the magnetotactic bacteria. Inspired by that, Fe3O4nanoparticles were in-situsynthesized in the confined space of chitosan (CS) networks in the external magneticfield. On one hand, in-situ synthesized Fe3O4nanoparticles interacted strongly withCS, which decreased the crystallinity of adjacent CS matrix, thus favoring theproduction of free-volume cavities. On the other hand, induced by the external magnetic field (the direction of magnetic field lines was perpendicular to themembrane surface), Fe3O4nanoparticles were aligned in the direction of magneticfield, which constructed channels at the continuous interface region betweennanoparticles and polymer, thus facilitating transmembrane water diffusion. Effects ofFeCl24H2O content and the magnetic filed on membrane pervaporation performancewere investigated. When FeCl24H2O content was8wt.%, the hybrid membrane in themagnetic field possessed the optimized performance with a flux of1042g/m2h and aseparation factor of674. The external magnetic filed enhanced the permeation fluxwith a little sacrifice of separation factor of the hybrid membrane.Carbon nanotubes (CNT) surface-loaded with Fe3O4(Fe3O4@CNT complex) wereblending into SA matrix to prepare hybrid membranes. Fe3O4loaded at the surface ofCNT improved the dispersion of CNT, and one-dimensional CNT in turn facilitatedthe ordered arrangement of Fe3O4. The introduction of Fe3O4@CNT not onlydecreased the crystallinity of adjacent SA matrix and favored the production offree-volume cavities, but also constructed the channels for water diffusion andenhanced the rigidity of polymer chain. Effects of Fe3O4@CNT, pristine Fe3O4andCNT contents on membrane pervaporation performance were investigated. WhenFe3O4@CNT content was2wt.%, the hybrid membrane acquired the optimizedperformance with a permeation flux of2211g/m2h and a separation factor of1870.That performance was higher than those of the hybrid membranes incorporated withpristine Fe3O4or CNT, owing to the synergistic effect of Fe3O4and CNT.