Nanoporous asymmetric polyaniline films for filtration of organic solvents

Structure and Conformational Properties of a Short Polyaniline Chain in a Mixture of Water and Ionic Liquid [1-Ethyl-3-methyl-imidazolium][bistriflimide] Investigated by All-Atom Molecular Dynamics Simulations

Development of antifouling membranes for water treatment using conducting polymers and their composites is a fundamental strategy to mitigate the fouling. This manuscript presents an all-atom molecular dynamics simulations of a conducting polymer, polyaniline (PANI), immersed in an ionic liquids (ILs)-water mixtures. We have considered the ionic liquid 1-ethyl-3-methyl imidazolium bistriflimide, [EMIM]+[BIS]-. The two forms of polyaniline, emeraldine base (EB) and emeraldine salt (ES), were considered. Various intra- and intermolecular structural properties of PANI were analyzed, such as polymer chain radius of gyration Rg, radial distribution functions, and torsional angle distributions. The Rg of EB shows an increase, while the Rg of ES shows a decrease with an increase in the IL concentration. The backbone torsional angle probability distributions show a significant trans state for EB, while a combination of trans and gauche states was observed for ES. Similar supportive distributions were seen in the backbone angular distributions. Radial distribution functions between the carbon atoms at ortho and meta positions of the benzene ring on both ES and EB, as well as the amine group attached between two benzene rings, show an enhanced interaction with the ionic liquid compared to water. Anions have a dominant interaction with the polymer chain when compared to cations. The solvent accessible surface area (SASA) calculations were in accordance with the EB and ES structural properties. The SASA values are more favorable for ES than for EB. H-bond analysis shows a decrease in the number of H-bonds with water as the IL concentration increases.

One-Step Electrochemically Prepared Graphene/Polyaniline Conductive Filter Membrane for Permeation Enhancement by Fouling Mitigation

In the electrofiltration process, membrane conductivity plays a decisive role in improving the antifouling performance of the membrane. In this paper, combining the preparation of graphene (Gr) with the fabrication of the Gr layer on the surface of a polyaniline (PANI) membrane, a graphene/PANI (Gr/PANI) conductive membrane was prepared creatively by the one-step electrochemical method. The properties of the as-prepared Gr/PANI membrane were studied systematically. By the tests of Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and atomic force microscopy, it was confirmed that Gr was successfully produced and was combined with the PANI membrane well. Field scanning electron microscopy with energy-dispersive X-ray analysis further confirmed that the top surface and the upper layer pore walls of the membrane were randomly covered by Gr. The antifouling performance of the prepared membrane was evaluated by studying the permeation flux of the yeast suspension, compared with the ones with no electric field: the total permeation flux at 1 V direct current (dc) increased by 109%; besides, under 1 V dc, the average flux of the Gr/PANI membrane was approximately 1.4 times that of the PANI membrane. This approach may provide a promising strategy for the combination of Gr with conductive polymers to produce separation membranes.

Polyethylene Battery Separator as a Porous Support for Thin Film Composite Organic Solvent Nanofiltration Membranes

Organic solvent nanofiltration (OSN) has made significant advances recently, and it is now possible to fabricate thin film composite (TFC) membranes with a selective layer thickness below 10 nm that gives ultrafast solvent permeance. However, such high permeance is inadvertently limited by the support membrane beneath the selective layer, and thus there is an urgent need to develop a suitable support to maximize TFC performance. In this work, we employed a commercially available polyethylene (PE) battery separator as a porous support to fabricate high performance TFC OSN membranes. To deposit a uniform polyamide selective layer onto the porous support via interfacial polymerization, the PE support was hydrophilized with O₂ plasma and the reaction efficiency was optimized using a surfactant. Owing to the high surface porosity of the PE support and the high permselectivity of the PA layer, the PE-supported TFC membrane outperformed the previously reported OSN membranes and its performance exceeded the current performance upper bound. A solvent activation step dramatically improved the solvent permeance by 5-fold while maintaining nanoseparation properties. In addition to the superior OSN performance, the commercial availability of the PE support and simplified TFC fabrication protocol would make the PE-supported OSN membranes commercially attractive.

Nanopapers for organic solvent nanofiltration

The production of nanopapers from nanocellulose suspensions by a papermaking-process and their utilization as organic solvent nanofiltration membranes is demonstrated.