Rahul Shevate

Graphene oxide doped ionic liquid ultrathin composite membranes for efficient CO2 capture

Advanced membrane systems with high flux and sufficient selectivity are required for industrial gas separation processes. In order to achieve high flux and high selectivity, the membrane material should be as thin as possible and it should have selective sieving channels and long term stability. This could be achieved by designing a three component material consisting of a blend of an ionic liquid and graphene oxide covered by a highly permeable low selective polymeric coating. By using a simple dip coating technique, we prepared high flux and CO2 selective ultrathin graphene oxide (GO)/ionic liquid membranes on a porous ultrafiltration support. The ultrathin composite membranes derived from GO/ionic liquid complex displays remarkable combinations of permeability (CO2 flux: 37 GPU) and selectivity (CO2/N2 selectivity: 130) that surpass the upper bound of ionic liquid membranes for CO2/N2 separation. Moreover, the membranes were stable when tested for 120 hours.

Nanostructured double hydrophobic poly(styrene-b-methyl methacrylate) block copolymer membrane manufactured via a phase inversion technique

In this paper, we demonstrate the formation of nanostructured double hydrophobic poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymer membranes via a state-of-the-art phase inversion technique. The nanostructured membrane morphologies are tuned by different solvent and block copolymer compositions. The membrane morphology has been investigated using FESEM, AFM and TEM. Morphological investigation shows the formation of both cylindrical and lamellar structures on the top surface of the block copolymer membranes. The PS-b-PMMA, with an equal block length (PS160 K-b-PMMA160 K), exhibits both cylindrical and lamellar structures on the top layer of the asymmetric membrane. All membranes fabricated from PS160 K-b-PMMA160 K show incomplete pore formation in both cylindrical and lamellar morphologies during the phase inversion process. However, the PS-b-PMMA (PS135 K-b-PMMA19.5 K) block copolymer, with a short PMMA block, allowed us to produce open pore structures with ordered hexagonal cylindrical pores during the phase inversion process. The resulting PS-b-PMMA nanostructured block copolymer membranes have pure water flux from 105–820 L m−2 h− bar− and 95% retention of PEG50 K.

Polybenzimidazole-based mixed membranes with exceptionally high water vapor permeability and selectivity

Polybenzimidazole (PBI), a thermally and chemically stable polymer, is commonly used to fabricate membranes for applications like hydrogen recovery at temperatures of more than 300 °C, fuel cells working in a highly acidic environment, and nanofiltration in aggressive solvents. This report shows for the first time the use of PBI dense membranes for water vapor/gas separation applications. They showed an excellent selectivity and high water vapor permeability. The incorporation of inorganic hydrophilic titanium-based nano-fillers into the PBI matrix further increased the water vapor permeability and water vapor/N2 selectivity. The most selective mixed matrix membrane with 0.5 wt% loading of TiO2 nanotubes yielded a water vapor permeability of 6.8 × 104 barrer and a H2O/N2 selectivity of 3.9 × 106. The most permeable membrane with 1 wt% loading of carboxylated TiO2 nanoparticles had a water vapor permeability of 7.1 × 104 barrer and a H2O/N2 selectivity of 3.1 × 106. The performance of these membranes in terms of water vapor transport and selectivity is among the highest reported ones. The remarkable ability of PBI to efficiently permeate water versus other gases opens the possibility to fabricate membranes for the dehumidification of streams in harsh environments. This includes the removal of water from high temperature reaction mixtures to shift the equilibrium towards products.

Embedding 1D Conducting Channels into 3D Isoporous Polymer Films for High-Performance Humidity Sensing

Isoporous block copolymer (BCP) films have received exponential interest as highly selective membranes, stemming from their unique morphological features, but their applications in functional devices remain to be realized. Now single-walled carbon nanotubes (CNTs) were efficiently incorporated into isoporous block copolymer films for chemiresistive sensing at room temperature. Leveraging the efficient charge extraction ability of CNTs together with nanochannel arrays aligned perpendicular to the surface of the films, an ultrafast response time of 0.3 s was achieved for humidity detection with a sensor response of about 800 on changing humidity from 10 % to 95 %. Furthermore, the sensor also responds to various organic vapors, underscoring its promising detection capability.

CO2-Philic Thin Film Composite Membranes: Synthesis and Characterization of PAN-r-PEGMA Copolymer

In this work, we report the successful fabrication of CO2-philic polymer composite membranes using a polyacrylonitrile-r-poly(ethylene glycol) methyl ether methacrylate (PAN-r-PEGMA) copolymer. The series of PAN-r-PEGMA copolymers with various amounts of PEG content was synthesized by free radical polymerization in presence of AIBN initiator and the obtained copolymers were used for the fabrication of composite membranes. The synthesized copolymers show high molecular weights in the range of 44–56 kDa. We were able to fabricate thin film composite (TFC) membranes by dip coating procedure using PAN-r-PEGMA copolymers and the porous PAN support membrane. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied to analyze the surface morphology of the composite membranes. The microscopy analysis reveals the formation of the defect free skin selective layer of PAN-r-PEGMA copolymer over the porous PAN support membrane. Selective layer thickness of the composite membranes was in the range of 1.32–1.42 μm. The resulting composite membrane has CO2 a permeance of 1.37 × 10−1 m3/m2·h·bar and an ideal CO2/N2, selectivity of 65. The TFC membranes showed increasing ideal gas pair selectivities in the order CO2/N2 > CO2/CH4 > CO2/H2. In addition, the fabricated composite membranes were tested for long-term single gas permeation measurement and these membranes have remarkable stability, proving that they are good candidates for CO2 separation.