Novel interfacially-polymerized polyamide thin-film composite membranes: Studies on characterization, pervaporation, and positron annihilation spectroscopy

Preparation and Characterization of Polyphenylsulfone (PPSU) Membranes for Biogas Upgrading

Asymmetric polyphenylsulfone (PPSU) membranes were fabricated by a non-solvent induced phase inversion method. Glycerin and silica nanoparticles were added into the polymer solution to investigate their effects on the material properties and gas separation performance of prepared membranes. The morphology and structure of PPSU membranes were analyzed by scanning electron microscopy (SEM), the surface roughness of the selective layer was analyzed by atomic force microscopy (AFM), and the surface free energy was calculated based on the contact angle measurements by using various solvents. The gas separation performance of PPSU membranes was estimated by measuring the permeability of CO₂ and CH₄. The addition of glycerin as a nonsolvent into the polymer solution changed the cross-section structure from finger-like structure into sponge-like structure due to the delayed liquid-liquid demixing process, which was confirmed by SEM analysis. The incorporation of silica nanoparticles into PPSU membranes slightly increased the hydrophilicity, which was confirmed by water contact angle results. PPSU membrane fabricated from the polymer solution containing 10 wt.% glycerin showed the best CO₂/CH₄ selectivity of 3.86 and the CO₂ permeability of 1044.01 Barrer. Mixed matrix PPSU membrane containing 0.1 wt.% silica nanoparticles showed the CO₂/CH₄ selectivity of 3.16 and the CO₂ permeability of 1202.77 Barrer.

Bioadhesion-inspired fabrication of robust thin-film composite membranes with tunable solvent permeation properties

Dopamine chemistry arising from marine mussel bioadhesion principles has attracted growing interest in designing and fabricating robust thin films/membranes for various chemical separation processes.

The development of novel Nexar block copolymer/Ultem composite membranes for C2-C4 alcohols dehydration via pervaporation

Novel composite membranes comprising sulfonated styrenic Nexar pentablock copolymers were developed by dip-coating on poly(ether imide) hollow fibers for pervaporation dehydration of C2-C4 alcohols. The advantages of using block copolymers as the selective layer are (1) their effectiveness to synergize the physicochemical properties of different chemical and structural moieties and (2) tunable nanoscale morphology and nanostructure via molecular engineering. To achieve high-performance composite membranes, the effects of coating time, ion exchange capacity (IEC) of the copolymer, and solvent systems for coating were investigated. It is revealed that a minimum coating time of 30 s is needed for the formation of a continuous and less-defective top layer. A higher IEC value results in a membrane with a higher flux and lower separation factor because of enhanced hydrophilicity and stretched chain conformation. Moreover, the composite membranes prepared from hexane/ethanol mixtures show higher separation factors and lower fluxes than those from the hexane solvent owing to microdomain segregation induced by ethanol and a smooth and dense top selective layer. These hypotheses were verified by atomic force microscopy and positron annihilation spectroscopy. The newly developed composite membranes demonstrate impressive separation performance with fluxes exceeding 2 kg/m(2) h and separation factors more than 200 for isopropyl alcohol and n-butanol dehydration from 85/15 wt % alcohol/water feed mixtures at 50 °C.

Polysulfonamide Thin-Film Composite Membranes Applied to Dehydrate Isopropanol by Pervaporation

To dehydrate the isopropanol (IPA) by the pervaporation separation process at 25°C, the polysulfonamide thin-film composite (TFC) membranes were prepared via the interfacial polymerization of diamines including 1,3-diaminopropane (DAPE), 1,3-cyclohexanediamine (CHDA) and m-phenylenediamine (MPDA) with 1,3-benzenedisulfonyl dichloride (BDSC) on the surface of modified asymmetric polyacrylonitrile (mPAN) membrane. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) Spectrometry, atomic force microscope (AFM) and water contact angle (WCA) measurements were applied to analyze chemical structure, surface roughness and hydrophilicity of the polymerized layer of composite membrane. In the dehydration of aqueous isopropanol solutions, the DAPE-BDSC/mPAN membrane had the higher permeation flux and the similar water concentration in permeate compared with the CHDA-BDSC/mPAN and MPDA-BDSC/mPAN membranes. The pervaporation performance of the composite membrane was affected by the chemical structure of the polysulfonamide polymer.