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This study investigated the enhancement in bioethanol recovery from mixed matrix membranes (MMMs) by functionalizing zeolite framework-8 (ZIF-8) with imidazolate. This study focused on the separation of ethanol from low-concentration ethanol/water mixtures (typical post-fermentation concentrations of 5–10 wt%). Specifically, ZIF-8 was modified by the shell–ligand exchange reaction (SLER) with 5,6-dimethylbenzimidazole (DMBIM), resulting in ZIF-8-DMBIM particles with improved hydrophobicity, organophilicity, larger size, and adjustable pore size. These particles were incorporated into a PEBAX 2533 matrix to produce ZIF-8-DMBIM/PEBAX MMMs using a dilution blending method. The resulting membranes showed significant performance enhancement: 8 wt% ZIF-8-DMBIM loading achieved a total flux of 308 g/m2·h and a separation factor of 16.03, which was a 36.8% increase in flux and 176.4% increase in separation factor compared with the original PEBAX membrane. In addition, performance remained stable during a 130 h cycling test. These improvements are attributed to the enhanced compatibility and dispersion of ZIF-8-DMBIM in the PEBAX matrix. In conclusion, the evaluation of nanofiller content, feed concentration, operating temperature, and membrane stability confirmed that ZIF-8-DMBIM/PEBAX MMM is ideal for ethanol recovery in primary bioethanol concentration processes. [ABSTRACT FROM AUTHOR]

In this study, Principal Component Analysis (PCA) was applied to discern the underlying trends for 31 distinct MFI (Mobil No. 5)-zeolite membranes of 11 textural, chemical, and operational factors related to manufacturing processes. Initially, a comprehensive PCA approach was employed for the entire dataset, revealing a moderate influence of the first two principal components (PCs), which collectively accounted for around 38% of the variance. Membrane samples exhibited close proximity, which prevented the formation of any clusters. To address this limitation, a subset acquisition strategy was followed, based on the findings of the PCA for the entire dataset. This resulted in an enhanced overall contribution and the revelation of diverse patterns among the membranes and the considered manufacturing factors (total variance between 55% and 77%). The segmentation of the data unveiled a robust correlation between silica (SiO2) concentration and pervaporation conditions. Additionally, a notable clustering of the chemical compositions of the preparation solutions underscored their significant influence on the operational efficacy of MFI zeolite membranes. On the other hand, an exclusive chemical composition of the preparation solution was noticed. This highlighted the high influence of the chemical composition on the operational efficiency of MFI zeolite membranes. The coupling of PCA with experimental results can provide a data-driven enhancement strategy for the manufacturing of MFI-type zeolite membranes used for ethanol/water separation. [ABSTRACT FROM AUTHOR]

High‐purity ethanol is a promising renewable energy resource, however separating ethanol from trace amount of water is extremely challenging. Herein, two ultramicroporous MOFs (UTSA‐280 and Co‐squarate) were used as adsorbents. A prominent water adsorption and a negligible ethanol adsorption identify perfect sieving effect on both MOFs. Co‐squarate exhibits a surprising water adsorption capacity at low pressure that surpassing the reported MOFs. Single crystal X‐ray diffraction and theoretical calculations reveal that such prominent performance of Co‐squarate derives from the optimized sieving effect through pore structure adjustment. Co‐squarate with larger rhombohedral channel is suitable for zigzag water location, resulting in reinforced guest‐guest and guest‐framework interactions. Ultrapure ethanol (99.9 %) can be obtained directly by ethanol/water mixed vapor breaking through the columns packed with Co‐squarate, contributing to a potential for fuel‐grade ethanol purification. [ABSTRACT FROM AUTHOR]

• A new strategy to prepare ultrathin silicone composite membrane was proposed. • A PDMDES active layer was fabricated with its low-surface-energy monomer DMDES. • The PDMDES active layer possessed sub-micrometer sized thickness. • A high flux of 7565.6 g·m−2·h−1 was achieved for 9 wt% ethanol/water separation. • Stable intrinsic separation ability was achieved under different conditions. Silicone-based polymers are the most popular materials to prepare pervaporation (PV) membranes for bioethanol recovery from fermentation process. However, the existing silicone composite membranes mostly exhibited limited permeance for ethanol/water separation, which can be attributed to the thick active silicone layers resulting from insufficient spreading of the polymer casting solution on the porous substrate. In the present study, we propose the use of low-surface-energy monomer into casting solution to enhance its spreading ability for ultrathin silicone membrane fabrication. In specific, a poly(dimethyldiethoxylsilane) (PDMDES) casting solution was prepared by limited polymerization of its low-surface-energy monomer dimethyldiethoxylsilane (DMDES), and was then casted on a porous substrate. We show that the surface energy of the partially polymerized casting solution maintained low, and an ultrathin PDMDES active layer with thickness of sub-micrometer size was obtained. The physicochemical properties of the PDMDES membrane were further characterized by ATR-FTIR, XRD and TGA, respectively. Upon optimized preparation and operation conditions, the PDMDES composite membrane exhibited a superior flux of 7565.6 g·m−2·h−1, while maintained a comparable separation factor when compared to traditional PDMS membranes. Our strategy provides new insights into the development of ultrathin silicone membranes for enhanced bioethanol recovery. [ABSTRACT FROM AUTHOR]

Silicalite-1 zeolite membranes were prepared on porous tubular α-Al 2 O 3 supports by a secondary growth method. The influences of the Si/Al ratio and the amount of deposited MFI (silicalite-1 and ZSM-5) seed crystals on membrane pervaporation (PV) performance for the separation of ethanol/water (binary) and ethanol/water/succinic acid (ternary) mixtures were investigated. The prepared membranes were characterized by X-ray diffraction and scanning electron microscopy, and the Si and Al distributions in the membrane layers were determined by energy-dispersive X-ray line scanning. Each silicalite-1 membrane was composed of two layers: an MFI-seed-crystal layer that grew on the support surface, and another gel-derived silicalite-1 top layer that formed on the seed crystal layer. The texture of the MFI seed layer (i.e., the deposited amount and the Si/Al ratio) was found to play an important role in the separation process. When silicalite-1 seed crystals were used, the ethanol separation factor was high in the binary ethanol/water system, but lower in the presence of succinic acid. However, when ZSM-5 seeds were used, the ethanol separation factor in the ternary system improved. These results suggest that silicalite-1 membranes prepared using ZSM-5 seed crystals are effective for the recovery of ethanol in the presence of organic acids. [ABSTRACT FROM AUTHOR]

• LDDLT plasma was used to etch the surface of MMMs for PV separation. • The thickness of separation layer reduced and more ZIF-L nanosheets were exposed. • The PV performance for ethanol separation was greatly improved by plasma etching. • Plasma etched-ZIF-L/PDMS MMMs had long-term stability for ethanol recovery. Mixed matrix membranes (MMMs) have been shown great performance and remarkable stability for diverse molecular separations. Considering that the density of MOFs is usually higher than that of polymer doping solution, the upper separation layer surface of MMMs is enriched by the polymer matrix, compromising the membrane performance. In this study, the asymmetric separation layer of MOF-filled MMMs was etched by the long-distance and dynamic low-temperature (LDDLT) plasma for enhanced ethanol permselective pervaporation. The thickness of separation layer decreased and the MOF amount on surface increased after the LDDLT plasma etching, which dramatically reduced the molecular permeation resistance and improved the membrane performance. Under optimal plasma conditions, the etched MMMs exhibited the superior permeation flux of 1120 g·m−2·h−1 (60% more than that of unetched membrane) and the separation factor of 12.3 (1.16 times as much as that of unetched membrane) in separation of 5 wt% ethanol aqueous solution at 40 °C. [ABSTRACT FROM AUTHOR]

The separation of low molecular weight organic compounds such as the ethanol from aqueous solutions represents an important area to be investigated and increment the range of applications of forward osmosis. This investigation assesses the effects of using different draw solutes for ethanol separation from dilute aqueous solutions. The influence of glucose, sucrose, sodium chloride, and magnesium chloride was evaluated in terms of total permeate, reverse solute and ethanol fluxes. Inorganic solutes promoted higher total permeate and ethanol fluxes than the organic solutes (2.5 and 1.5 times higher in average, respectively) for the same molar concentration, while presenting only 1.1 times higher reverse solute fluxes. Despite the lower ethanol flux promoted by the organic draw solutes, these osmotic agents promoted higher concentration of ethanol in the total permeate flux, suggesting that they can also be alternatives for specific processes. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4499-4507, 2017 [ABSTRACT FROM AUTHOR]

Pervaporation is a membrane separation technology applied especially for the dehydration of organic solvents. Since its excellent permselectivity toward water, sodium alginate has been identified as the promising membrane material for the pervaporative dehydration of ethanol. Hybrid alginate membranes filled with various amount of magnetite (Fe 3 O 4 ) and crosslinked using four different agents, i.e. calcium chloride (AlgCa), phosphoric acid (AlgP), glutaraldehyde (AlgGA) and citric acid (AlgC) were prepared and applied in pervaporative dehydration of ethanol. In this paper, the correlation between chemical composition, structure and morphology, and separation properties of membranes is discussed. [ABSTRACT FROM AUTHOR]

BACKGROUND Polybenzoxazine ( PBZ) membranes have received increasing attention for serving as a high performance membrane for pervaporation processes owing to their good mechanical properties, high chemical resistance, high thermal stability, and low synthesis cost. This study aims to develop PBZ membrane and NaA-PBZ mixed matrix membrane ( MMM) for purification of ethanol/water mixtures using a pervaporation process and to investigate the effects of preparation parameters on the membrane performance, including precursor concentrations, number of dippings, amount of NaA zeolite loading, temperature, and ethanol concentration. RESULTS It was found that PBZ membrane and NaA-PBZ MMM exhibited excellent stability in all feed ethanol concentrations tested, with a low degree of swelling. The highest separation factor of the pure PBZ membrane was more than 10 000 while the NaA-PBZ MMM was even higher, up to and, in some cases, higher than 100 000 with the highest permeation flux of 1071 g m−2 h−1 when using 25 wt% PBZ precursor with 15 wt% NaA zeolite loading. The permeation flux of MMM increased with increase in temperature or a decrease in the feed ethanol concentration. Swelling increased when the ethanol concentration was increased, revealing the hydrophobic behavior of NaA-PBZ MMM. CONCLUSION The membranes are capable of purifying ethanol over a wide feed ethanol concentration range with excellent performance and properties that promise great potential for use in bioethanol purifying applications. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

[Display omitted] • A new cadmium-based coordination network is synthesized. • sql-Cd exhibits the second-highest ethanol uptake (62.5 wt%) at ambient conditions. • Ethanol with 99% purity can be directly obtained. • sql-Cd can be combined with chitosan to form a filter film. Bioethanol is an essential energy source and is produced from agricultural feedstocks. However, raw bioethanol contains much water and methanol, and the traditional distillation approach has hardly removed it. Adsorptive separation of ethanol from water and methanol by adsorbents is an energy-efficient and promising method to produce fuel-grade ethanol. In this work, by regulating the pore surface in a new coordination network, [Cd(4-pmntd)(tpa)] (4-pmntd = N,N'-Bis(4-pyridymethy) naphthalene diimide; tpa = terephthalic acid), we target ultrahigh ethanol uptake and efficient ethanol/water separation, surpassing most benchmark materials. Explicitly, the ethanol uptake of Cd(4-pmntd)(tpa) (62.5 wt% at 100 kPa and 298 K) has the second-highest adsorption capacity among all the metal–organic frameworks (MOFs). In addition, Cd(4-pmntd)(tpa) gives ethanol/water selectivity of 32 toward a mixture of ethanol and water. Dynamic breakthrough measurements confirmed the excellent separation of ethanol and water. Under different ethanol/water ratios, Cd(4-pmntd)(tpa) extracts a low ethanol concentration from an ethanol/water mixture and produces ethanol in 99.1% purity in one step. Spectroscopic measurement and grand canonical Monte Carlo (GCMC) simulations provide critical insight into the adsorption/separation mechanism. The framework can form rich intermolecular C-H guest ...π host , C-H guest ...O host and C-H host ...O guest interactions with ethanol molecules because of the suitable pore size and pore surface set in Cd(4-pmntd)(tpa). Thus, the adsorption enthalpies for ethanol in Cd(4-pmntd)(tpa) reached 66.16 kJ/mol, but only 29.44 kJ/mol and 49.21 kJ/mol for water and methanol, respectively. Moreover, the porous material exhibits good stability and can be easily combined with chitosan to form filter film, which is vital for potential industrial applications. [ABSTRACT FROM AUTHOR]

• Robust hybrid PVA membranes filled with particles of chitosan derivatives. • Impact of enhanced hydrophilicity on the ethanol/water separation. • Membrane with 3 wt% of phosphorylated or sulphated CS showing the highest PSI. • Comparison of PVA_CS membranes with congruent Alg_CS and other hybrid PVA membranes. The series of novel hybrid poly(vinyl alcohol) (PVA) membranes filled with chitosan particles (CS) and its four derivatives: phosphorylated (CS-P), crosslinked with glutaraldehyde (CS-GA), glycidol-modified (CS-G) and sulphated (CS-SO 3) chitosan were prepared and tested in the pervaporative separation process of a water/ethanol mixture. The influence of various types of chitosan particles, as well as their loadings, on transport properties of the membranes was discussed. Consequently, the addition of chitosan particles into the PVA matrix was found to significantly change its hydrophilicity and have a positive impact on the efficiency of ethanol dehydration. The best performance in terms of the highest separation factor (263.3) and PSI (380.3 kg·m−2·h−1) was shown for a PVA membrane filled with the phosphorylated chitosan particles (3 wt% CS-P), which significantly outperformed not only other materials considered in this study, but also other hybrid PVA-based membranes described in the literature. [ABSTRACT FROM AUTHOR]

A seeding-free synthesis strategy was developed for the preparation of dense and phase-pure MFI zeolite membranes based on "like grows like" principle. Through covalent modification of the porous ceramic supports by using 1H,1H,2H,2H-perfluoroalkyltriethoxysilanes (POTS), the support surface was changed from hydrophilic to hydrophobic, which promotes the nucleation and growth of hydrophobic MFI zeolite membranes. Thin, well-intergrown and phase-pure MFI zeolite membranes, with a thickness of about 2.0–3.0 μm, can be facilely prepared on POTS-modified supports like Al 2 O 3 and TiO 2 at 175 °C for 24 h. No cracks, pinholes or other visible macroscopic defects are observed in the membrane layer. The MFI zeolite membranes were evaluated in the hydrophobic separation of 5.0 wt% ethanol/water mixture at 75 °C by pervaporation. The MFI zeolite membrane prepared on the POTS-modified TiO 2 disk shows high pervaporation separation for ethanol recovery. At 75 °C, a separation factor of 103 and total flux of 2.56 kg/m2h can be obtained, which is promising to extract bio-alcohols from the fermentation broth. Image 1 • A novel strategy is developed for seeding-free synthesis of MFI zeolite membranes based on "like grows like" principle. • Hydrophobic MFI membranes tend to grow well on the hydrophobic support surface. • Thin and well-intergrown MFI membranes can be easily prepared on POTS-modified supports. • The MFI membranes prepared on POTS-modified TiO 2 supports show high pervaporation performance. [ABSTRACT FROM AUTHOR]

Silicalite-1 membranes with high pervaporation performance were prepared successfully on a silica-particle-coated tubular silica support using a gel-free steam-assisted conversion (SAC) method. The effects of the silica-particle layer formed on the top surface of the silica support and the physical properties of the silica particles themselves on the membrane-formation process were investigated. The silica particles coated served as the additional silica source for growing the silicalite-1 seed crystal layer into the silicalite-1 membrane. As a result, it was possible to form a dense and continuous membrane even under gel-free conditions. Furthermore, it was found that the properties of the silica particles, such as their primary particle diameter, had a determining effect on their solubility during the steam treatment, that is, on the supply rate of the silica source. The silicalite-1 membrane obtained using the spherical-silica-particle-coated support had an approximately 9-μm-thick separation layer and showed very high pervaporation performance, exhibiting a separation factor of 105 and a flux of 3.72 kg m−2 h−1 for a 10 wt % ethanol/water mixture at 323 K. Thus, the gel-free SAC method can be used with a silica support coated with silica particles to readily prepare high-performance membranes without producing any chemical waste. [ABSTRACT FROM AUTHOR]