Novel PTMSP-based membranes containing elastomeric fillers: Enhanced 1-butanol/water pervaporation selectivity and permeability

Effect of Side Substituent on Comb-like Polysiloxane Membrane Pervaporation Properties During Recovery of Alcohols C2-C4 from Water

The pervaporation properties of membranes based on comb-like polysiloxanes when C2-C4 alcohols are removed from water were studied for the first time. It was established that membranes based on comb-like polysiloxanes with linear aliphatic and organosilicon substituents have increased permeability selectivity for C3+ alcohols. The obtained results were interpreted from the point of view of the solubility of the components of the separated mixture in polysiloxanes. It was shown that membranes based on polysiloxanes with linear substituents have increased butanol/water permeability selectivity (2.5-3.7). The achieved selectivity values correspond to the level of highly selective zeolite membranes, which allows for a reduction in energy consumption for the pervaporation removal of butanol by more than two times.

Incorporating Mixed-Ligand Zeolitic Imidazolate Framework into Polydimethyldiethoxysilane (PDMDES) Membrane for Enhancing Alcohol Pervaporation Recovery

In the present study, a zeolitic imidazolate framework with mixed ligands, ZIF-8-90, was synthesized and embedded into an ultrathin polydimethyldiethoxysilane (PDMDES) matrix to prepare a ZIF-8-90/PDMDES mixed matrix membrane (MMM) for the enhanced recovery of alcohols from dilute aqueous solutions via pervaporation, using a facile solution coating method. The synthesized ZIF-8-90 particles demonstrated superior hydrophobicity and thermal stability compared to those of both ZIF-8 and ZIF-90 particles. Furthermore, the hydrophobicity, thermal stability, and sorption ability for alcohols of the ZIF-8-90/PDMDES MMM were significantly improved, attributed to the incorporation of mixed-ligand ZIF-8-90. Notably, the MMMs displayed two distinct cross-sectional morphologies: (1) ZIF-8-90 particles enveloped by PDMDES polymer forming filler bulges and (2) an accumulation of ZIF-8-90 particles resembling a brick-wall-like structure. The MMM incorporating 2.5 wt % ZIF-8-90 exhibited the optimal performance among the fabricated MMMs with various ZIF-8-90 loadings, spanning from 0 to 3.2 wt %. The effects of feed concentrations and operation temperatures were systematically investigated. The best pervaporation performance was achieved using the 2.5 wt % ZIF-8-90-filled MMM, effectively separating a 5.0 wt % ethanol/water mixture at 60 °C, yielding a distinguished total flux of 7.70 kg·m-2·h-1, an improved separation factor of 9.96, and an extraordinarily high PSI of 68.99 kg·m-2·h-1. Comparative analyses highlighted the superior pervaporation performance of the ZIF-8-90/PDMDES MMM over ZIF-8/PDMDES MMM, ZIF-90/PDMDES MMM, and other MMMs, underscoring its potential for practical applications in alcohol recovery.

Membranes for bioethanol production by pervaporation

BACKGROUND

Bioethanol as a renewable energy resource plays an important role in alleviating energy crisis and environmental protection. Pervaporation has achieved increasing attention because of its potential to be a useful way to separate ethanol from the biomass fermentation process.

RESULTS

This overview of ethanol separation via pervaporation primarily concentrates on transport mechanisms, fabrication methods, and membrane materials. The research and development of polymeric, inorganic, and mixed matrix membranes are reviewed from the perspective of membrane materials as well as modification methods. The recovery performance of the existing pervaporation membranes for ethanol solutions is compared, and the approaches to further improve the pervaporation performance are also discussed.

CONCLUSIONS

Overall, exploring the possibility and limitation of the separation performance of PV membranes for ethanol extraction is a long-standing topic. Collectively, the quest is to break the trade-off between membrane permeability and selectivity. Based on the facilitated transport mechanism, further exploration of ethanol-selective membranes may focus on constructing a well-designed microstructure, providing active sites for facilitating the fast transport of ethanol molecules, hence achieving both high selectivity and permeability simultaneously. Finally, it is expected that more and more successful research could be realized into commercial products and this separation process will be deployed in industrial practices in the near future.

High Selective Composite Polyalkylmethylsiloxane Membranes for Pervaporative Removal of MTBE from Water: Effect of Polymer Side-chain

For the first time, the effect of the side-chain in polyalkylmethylsiloxane towards pervaporative removal of methyl tert-butyl ether (MTBE) from water was studied. The noticeable enhancement of separation factor during the pervaporation of 1 wt.% MTBE solution in water through the dense film (40–50 µm) can be achieved by substitution of a methyl group (separation factor 111) for heptyl (161), octyl (169) or decyl (180) one in polyalkylmethylsiloxane. Composite membrane with the selective layer (~8 µm) made of polydecylmethylsiloxane (M10) on top of microfiltration support (MFFK membrane) demonstrated MTBE/water separation factor of 310, which was 72% greater than for the dense film (180). A high separation factor together with an overall flux of 0.82 kg·m⁻²·h⁻¹ allowed this M10/MFFK composite membrane to outperform the commercial composite membranes. The analysis of the concentration polarization modulus and the boundary layer thickness revealed that the feed flow velocity should be gradually increased from 5 cm·s⁻¹ for an initial solution (1 wt.% of MTBE in water) to 13 cm·s⁻¹ for a depleted solution (0.2 wt.% of MTBE in water) to overcome the concentration polarization phenomena in case of composite membrane M10/MFFK (T_exp = 50 °C).

Novel Composite Membranes Based on Chitosan Copolymers with Polyacrylonitrile and Polystyrene: Physicochemical Properties and Application for Pervaporation Dehydration of Tetrahydrofuran

Pervaporation has been applied for tetrahydrofuran (THF) dehydration with novel composite membranes advanced by a thin selective layer composed of chitosan (CS) modified by copolymerization with vinyl monomers, acrylonitrile (AN) and styrene, in order to improve the chemical and mechanical stability of CS-based membranes. Composite membranes were developed by depositing a thin selective layer composed of CS copolymers onto a commercially-available porous support based on aromatic polysulfonamide (UPM-20^®). The topography and morphology of the obtained materials were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Thermal properties and stability were determined by coupled evolved gas analysis (EGA-MS). Transport properties were estimated in pervaporation dehydration of THF. The effect of operating parameters for the pervaporation dehydration of THF such as feed compositions and temperatures (295, 308 and 323 K) was evaluated. It was shown that CS modification with different vinyl monomers led to a difference in physical and transport properties. The composite membrane with the thin selective layer based on CS-PAN copolymer demonstrated optimal transport properties and exhibited the highest water content in the permeate with a reasonably high permeation flux.

Separation of Organic Compounds from ABE Model Solutions via Pervaporation Using Activated Carbon/PDMS Mixed Matrix Membranes

The pervaporation separation of organic compounds from acetone-butanol-ethanol (ABE) fermentation model solutions was studied using activated carbon (AC) nanoparticle-poly (dimethylsiloxane) (PDMS) mixed matrix membranes (MMM). The effects of the operating conditions and nanoparticle loading content on the membrane performance have been investigated. While the separation factor increased continuously, with an increase in the concentration of nanoparticles, the total flux reached a maximum in the MMM with 8 wt % nanoparticle loading in PDMS. Both the separation factor for ABE and the total permeation flux more than doubled for the MMM in comparison to those of neat PDMS membranes prepared in this study.

One-Step Assembly of Molecular Separation Membranes by Direct Atomizing Oligomers

Polymeric membranes are important materials for efficient sieving of targeted components at the molecular level and have made significant advancement in many industrial applications such as biofuel production, water purification, fuel combustion, and carbon dioxide capture. Although their separation efficiencies have been widely investigated, lack of more efficient, greener, and lower-cost membrane fabrication mechanisms is still a major hurdle for mass production, because the conventional membrane-making process is always time-consuming, highly inefficient, and consumes a large amount of organic solvents. Herein we report a one-step assembly concept capable of directly processing low-viscosity oligomers into polymer-based molecular separation membranes in an ultrafast and green manner. This process was implemented by alternate atomizing-depositing of low-viscosity oligomers and reaction auxiliary agents onto a rotating support and followed by an ultrafast interfacial reaction under solvent-free conditions. Without the need for dissolution processing of polymer, solvent evaporation, and any post-treatments, the whole technological process could be accomplished within a few seconds/minutes, which is 2-3 orders of magnitude faster than conventional solution-coating technologies. The universality of this facile approach has also been demonstrated by successfully producing various defect-free polymeric membranes and homodispersed nanohybrid membranes with excellent and stable performance for bioalcohol production and recovery of different trace organics from dilute solutions.

Multiblock Copolymer Grafting for Butanol Biofuel Recovery by a Sustainable Membrane Process

Biobutanol is an attractive renewable biofuel mainly obtained by the acetone-butanol-ethanol (ABE) fermentation process. Nevertheless, the alcohol concentration has to be limited to a maximum of 2 wt % in ABE fermentation broths to avoid butanol toxicity to the microorganisms. The pervaporation (PV) membrane process is a key sustainable technology for butanol recovery in these challenging conditions. In this work, the grafting of azido-polydimethylsiloxane (PDMS-N3) onto a PDMS-based multiblock copolymer containing alkyne side groups led to a series of original membrane materials with increasing PDMS contents from 50 to 71 wt %. Their membrane properties were assessed for butanol recovery by pervaporation from a model aqueous solution containing 2 wt % of n-butanol at 50 °C. The membrane flux J50μm for a reference thickness of 50 μm strongly increased from 84 to 192 g/h m(2) with increasing PDMS content for free-standing dense membranes with thicknesses in the range of 38-95 μm. At the same time, the intrinsic butanol permeability increased from 1.47 to 4.68 kg μm/h m(2) kPa and the permeate butanol content was also strongly improved from 38 to 53 wt %, corresponding to high and very high membrane separation factors of 30 and 55, respectively. Therefore, the new grafted copolymer materials strongly overcame the common permeability/selectivity trade-off for butanol recovery by a sustainable membrane process.

Preparation and pervaporation characteristics of novel ethanol permselective polyelectrolyte–surfactant complex membranes

Recovery of ethanol from a low concentration aqueous solution is a critical step for biofuel production.