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A novel method for the preparation of cellulose–polydimethylsiloxane (PDMS) blend membranes for organic solvent nanofiltration (OSN) and ethanol pervaporation is presented. The elegance of this approach lies in the use of trimethylsilyl cellulose (TMSC), a hydrophobic cellulose derivative, for blend membrane fabrication followed by simple hydrolysis to convert TMSC back to cellulose. The use of TMSC not only allows cellulose processing in common organic solvents, but also enables the creation of highly compatible cellulose–PDMS blend membranes. The appropriate composition of the blend membrane gave the best OSN performance with more than 10 L m−2 h−1 bar−1 acetone permeance and around 750 Da molecular weight cut-off. This blend membrane can be used for OSN with any other solvents regardless of their polarity. The same membrane also showed an excellent pervaporation performance with a separation factor of 14 and a flux of 1.6 kg m−2 h−1 using a 5 wt% ethanol water mixture at room temperature. The blending of PDMS with cellulose resulted in a 100% increase of the separation factor when compared with pure PDMS. This surprising performance is a consequence of the good miscibility of the blending polymers, which can be obtained through this unique pathway. Overall, this study demonstrates a simple, efficient, and scalable method that is the only possible way reported to date to combine the superiority of cellulose and PDMS as a low-cost and stable membrane for solvent separation. [ABSTRACT FROM AUTHOR]

Cellulose is widely regarded as an environmentally friendly, natural and low cost material which can significantly contribute to the sustainable economic growth. In this study, cellulose composite membranes were prepared via regeneration of trimethylsilyl cellulose (TMSC), an easily synthesized cellulose derivative. The amorphous hydrophilic feature of the regenerated cellulose enabled fast permeation of water vapour. The pore-free cellulose layer thickness was adjustable by the initial TMSC concentration and acted as an efficient gas barrier. As a result, a 5000 GPU water vapour transmission rate (WVTR) at the highest ideal selectivity of 1.1 × 106 was achieved by the membranes spin coated from a 7% (w/w) TMSC solution. The membranes maintained a 4000 GPU WVTR with a selectivity of 1.1 × 104 in mixed-gas experiments, surpassing the performances of previously reported composite membranes. This study provides a simple way to not only produce high performance membranes but also advance cellulose as a low-cost and sustainable membrane material for dehumidification applications. [ABSTRACT FROM AUTHOR]

To date, it is still a challenge to prepare high-flux and highselectivity microporous membranes thinner than 20 nm without introducing defects. In this work, we report for the first time the application of cellulose membranes for selective separation of small molecules. A freestanding cellulose membrane as thin as 10 nm has been prepared through regeneration of trimethylsilyl cellulose (TMSC). The freestanding membrane can be transferred to any desired substrate and shows a normalized flux as high as 700 Lm-2h-1 bar-1 when supported by a porous alumina disc. According to filtration experiments, the membrane exhibits precise size-sieving performances with an estimated pore size between 1.5-3.5 nm depending on the regeneration period and initial TMSC concentration. A perfect discrimination of anionic molecules over neutral species is demonstrated. Moreover, the membrane demonstrates high reproducibility, high scale-up potential, and excellent stability over two months. [ABSTRACT FROM AUTHOR]

Challenging molecular separation tasks continue to drive the need for advanced membranes, which could combine high productivity and selectivity with outstanding chemical resistance and mechanical robustness. Here, ultra-thin, sub-100 nm carbon molecular sieve (CMS) membranes based on a polymer of intrinsic microporosity precursor were fabricated and characterized with respect to their separation performance for six gases, He, H 2 , N 2 , O 2 , CO 2 and CH 4. The rarely reported in thin CMS membranes physical aging was tracked until near-equilibrium was reached. The use of commercially available, small pore size (2–5 nm) γ-alumina-coated α-alumina ceramic supports allowed for an easy membrane precursor fabrication by a simple solution coating process. The subsequent application of a protective polydimethylsiloxane layer, as often done in research and membrane production, assured excellent defect control and produced CMS composite membranes with very high membrane permselectivities (e.g. CO 2 /CH 4 = 84.5, H 2 /CH 4 = 360). No significant deviations from bulk properties in terms of the chemical decomposition were discovered in the film thickness range of 60–300 nm. However, a surprisingly massive acceleration of the physical aging in comparison to the bulk was detected in all sub-100 nm membranes including the precursor polymer. All CMS membranes reached near-equilibrium gas transport properties within 1–1.5 months providing a rare opportunity to study aging-stabilized performance. For the aging-stabilized sub-100 nm membranes a decrease in gas permeabilities of up to 3 orders of magnitude was detected. Remarkably, sub-100 nm CMS membranes showed significantly increased selectivities typical to thick isotropic CMS membranes pyrolyzed at 100–200 °C higher temperatures. A clear aging-related shift to more significant size sieving behavior occurred for the majority of the studied CMS membranes throughout the aging period. Overall, our study provides an important observation that excessive reduction of the selective layer thickness, especially in initially highly microporous materials (PIMs, CMS etc.), may not present the best strategy for the optimization of the long-term membrane performance. Image 1 • Sub-100 nm carbon molecular sieves made from a PIM precursor were characterized. • Near-equilibrium gas transport properties reached within ~1.5 months. • Massive losses of permeance and substantial increases in selectivity upon aging. • Ultrathin CMS thickness not preferred for optimum membrane performance. [ABSTRACT FROM AUTHOR]

In this study, green bio-membranes were investigated. Alginate membranes were prepared by crosslinking of sodium alginate in calcium chloride aqueous solution. By fabricating membranes simply using three abundant cheap materials i.e. sodium alginate, salt and water, we have demonstrated membranes with acceptable performance for OSN with excellent chemical stability. Membranes prepared on three different polymeric supports (PAN, crosslinked PAN and Cellulose) showed similar performance. The alginate membranes were also spun coated on glass plate and laminated on alumina support. Great chemical stability was observed towards various solvents including dimethylformamide and dimethylsulfoxide. Characterization tests with FTIR, SEM, AFM and contact angle were carried out. Using same support, many parameters were explored such as the alginate concentration and the post treatment such as drying, crosslinking or precipitating in non-solvent. The range of the membranes permeance was 0.08–1.8 L/m2 h bar depending on conditions used. The nanofiltration experiments revealed a molecular weight cut off of about 1200 g/mol when tested with dyes such as Methyl Orange, Brilliant Blue and vitamin B12 in methanol. We initiated the preparation of fully green organic solvent nanofiltration membranes using green routes by preparing alginate selective layer on top of cellulose support. This study demonstrates that alginate membranes can be a promising candidate for green organic solvent nanofiltration. Image 1 • Nanofiltration membranes with selective crosslinked alginate biofilm were prepared on PAN or cellulose supports and tested for OSN. • DMF stable composite membranes were prepared of such crosslinked biofilms on crosslinked PAN supports. • Freestanding biofilms of alginates were prepared and mounted on porous alumina and non-woven polyester and tested for DMSO and DMF. • The membranes were resistant to harsh organic solvents and had a molecular weight cut-off of 1200 g/mol. • The entire fabrication is green, from a biopolymer dissolved at room temperature in water to crosslinking in salt/water solution. • The prepared membranes are marked as a promising beginning of green OSN. [ABSTRACT FROM AUTHOR]

Synthetic membranes with a high selectivity for demanding molecular separations and high permeance have a large potential for the reduction of energy consumption in separation processes. Herein, for the first time, the fabrication of an ultrathin layered macrocycle membrane for molecular separation in organic solvent nanofiltration using per‐6‐amino‐β‐cyclodextrin as a monomer for membrane manufacturing by interfacial polymerization is reported. Compared to a regular nonfunctionalized cyclodextrin, a higher reactivity is observed, enabling a very fast membrane formation under mild conditions. The formed membrane is composed of a layered structure of polymerized cyclodextrin, which shows high stability in different organic solvents. The membrane exhibits excellent separation performance for organic solvent nanofiltration, both with nonpolar and polar solvents. Most importantly, this new membrane type can discriminate between molecules with nearly identical molecular weights but different shapes. The unmatched high permeance and shape selectivity of the membranes can be attributed to the ultralow thickness, controlled microporosity, as well as the layered macrocycle structure, which makes the membranes promising for high‐performance molecular separation in the chemical and biochemistry industry. [ABSTRACT FROM AUTHOR]

We developed composite membranes by stacking functionalized nanospheres (20 nm size) with a high density of H-bonds. The functionalized nanospheres were formed by a click-reaction in toluene between the polybutadiene segment of poly(styrene- b -butadiene- b -styrene) (PS- b -PB- b -PS) triblock copolymer and an azodicarbonyl (PTAD) compound. The strong hydrogen-bond interaction promoted by the pendant urazole groups of the PTAD-modified copolymer is an important parameter for obtaining stable and defect-free membranes, acting in analogy to self-healing systems. The hydrodynamic transport is facilitated by the high porosity of the membranes and the unique hourglass-shaped pores. The composite membrane has water permeation as high as 60 L m−2 h−1 bar−1 and can exclude more than 95% of proteins with a molecular weight as small as 12 kg mol−1. This novel class of nanoparticle-stacked membranes has therefore excellent separation properties for biomolecular separation. Image 1 • Membrane with self-healing properties. • Coatings based on particles modified by click chemistry. • Pores with hourglass shape with high water permeation and selectivity. [ABSTRACT FROM AUTHOR]