Polyvinylamine/amorphous metakaolin mixed-matrix composite membranes with facilitated transport carriers for highly efficient CO2/N2 separation

Carbonic Anhydrase-Mimicking Supramolecular Nanoassemblies for Developing Carbon Capture Membranes

As a ubiquitous family of enzymes with high performance in converting carbon dioxide (CO₂) into bicarbonate, carbonic anhydrases (CAs) sparked enormous attention for carbon capture. Nevertheless, the high cost and operational instability of CAs hamper their practical relevance, and the utility of CAs is mainly limited to aqueous applications where CO₂-to-bicarbonate conversion is possible. Taking advantage of the chemical motif that endows CA-like active sites (metal-coordinated histidine), here we introduce a new line of high-performance gas separation membranes with CO₂-philic behavior. We first self-assembled a histidine-based bolaamphiphile (His-Bola) molecule in the aqueous phase and coordinated the resulting entities with divalent zinc. Optimizing the supramolecular synthesis conditions ensured that the resultant nanoparticles (His-NPs) exhibit high CO₂ affinity and catalytic activity. We then exploited the His-NPs as nanofillers to enhance the separation performance of Pebax MH 1657. The hydrogen-bonding interactions allowed the dispersion of His-NPs within the polymer matrix uniformly, as confirmed by microscopic, spectroscopic, and thermal analyses. The imidazole and amine functionalities of His-NPs enhanced the solubility of CO₂ molecules in the polymer matrix. The CA-mimic active sites of His-NPs nanozymes, on the other hand, catalyzed the reversible hydration of CO₂ molecules in humid conditions, facilitating their transport across the membranes. The resulting nanocomposite membranes displayed excellent CO₂ separation performance, with a high level of stability. At a filling ratio as low as 3 wt %, we achieved a CO₂ permeability of >145 Barrer and a CO₂/N₂ selectivity of >95 with retained performance under humid continuous gas feeds. The bio-inspired approach presented in this work offers a promising platform for designing durable and highly selective CO₂ capture membranes.

Polymeric composite membranes in carbon dioxide capture process: a review

Carbon dioxide (CO₂) emission to the atmosphere is the prime cause of certain environmental issues like global warming and climate change, in the present day scenario. Capturing CO₂ from various stationary industrial emission sources is one of the initial steps to control the aforementioned problems. For this concern, a variety of resources, such as liquid absorbents, solid adsorbents, and membranes, have been utilized for CO₂ capturing from various emission sources. Focused on membrane-based CO₂ capture, polymeric membranes with composite structure (polymeric composite membrane) offer a better performance in CO₂ capturing process than other membranes, due to the composite structure it offers higher gas flux and less material usage, thus facile to use high performed expensive material for membrane fabrication and achieved good efficacy in CO₂ capture. This compressive review delivers the utilization of different polymeric composite membranes in CO₂ capturing applications. Further, the types of polymeric materials used and the different physicochemical modifications of those membrane materials and their CO₂ capturing ability are briefly discussed in the text. In conclusion, the current status and possible perspective ways to improve the CO₂ capture process in industrial CO₂ gas separation applications are described in this review.

Preparation of Organic Crystal Seed and Its Application in Improving the Functional Period of Biodegradable Agricultural Film

White pollution caused by agricultural films has recently attracted great attention. In some areas, the content of micro plastic in the soil has reached 30 kg/ha. The most effective way to solve this problem is to replace traditional polyethylene agricultural films with degradable agricultural films. The consistency between the degradation rate and the crop growth period has become the biggest obstacle for the wide application of such novel agricultural films. In this paper, crystallinity regulation is used to adjust the functional period of degradable agricultural films. In addition, an organic nucleating agent of polyethylenimine (PEI) is selected by doping it to poly(butylene adipate-co-terephthalate) (PBAT) polymers using a double-screw extruder. The PBAT doped with 1 wt% PEI films revealed a significant increase in mechanical properties, water holding capacity, and crystallinity compared with the pure PBAT film. There was a 31.9% increase in tensile strength, a 30.5% increase in elongation at break, a 29.6% increase in tear resistance, a 30.9% decrease in water vapor permeability, and a 3.1% increase in crystallinity. Furthermore, the induction period of PBAT doped with 1 wt% PEI under photoaging (without soil) was about 160 h longer than PBAT film, and the experienced biodegradation in soil (without light) was 1 week longer than PBAT film. Experimental results exhibited that the change of degradation degree was linearly proportional to the degree of crystallinity. This study proposes a convenient, low-cost, and effective method to adjust the crystallinity and change the degradation rate.

Ceramic-Polymer Composite Membranes for Water and Wastewater Treatment: Bridging the Big Gap between Ceramics and Polymers

Clean water supply is an essential element for the entire sustainable human society, and the economic and technology development. Membrane filtration for water and wastewater treatments is the premier choice due to its high energy efficiency and effectiveness, where the separation is performed by passing water molecules through purposely tuned pores of membranes selectively without phase change and additional chemicals. Ceramics and polymers are two main candidate materials for membranes, where the majority has been made of polymeric materials, due to the low cost, easy processing, and tunability in pore configurations. In contrast, ceramic membranes have much better performance, extra-long service life, mechanical robustness, and high thermal and chemical stabilities, and they have also been applied in gas, petrochemical, food-beverage, and pharmaceutical industries, where most of polymeric membranes cannot perform properly. However, one of the main drawbacks of ceramic membranes is the high manufacturing cost, which is about three to five times higher than that of common polymeric types. To fill the large gap between the competing ceramic and polymeric membranes, one apparent solution is to develop a ceramic-polymer composite type. Indeed, the properly engineered ceramic-polymer composite membranes are able to integrate the advantages of both ceramic and polymeric materials together, providing improvement in membrane performance for efficient separation, raised life span and additional functionalities. In this overview, we first thoroughly examine three types of ceramic-polymer composite membranes, (i) ceramics in polymer membranes (nanocomposite membranes), (ii) thin film nanocomposite (TFN) membranes, and (iii) ceramic-supported polymer membranes. In the past decade, great progress has been made in improving the compatibility between ceramics and polymers, while the synergy between them has been among the main pursuits, especially in the development of the high performing nanocomposite membranes for water and wastewater treatment at lowered manufacturing cost. By looking into strategies to improve the compatibility among ceramic and polymeric components, we will conclude with briefing on the perspectives and challenges for the future development of the composite membranes.

"All Polyimide" Mixed Matrix Membranes for High Performance Gas Separation

To improve the interfacial compatibility of mixed matrix membranes (MMMs) for gas separation, microporous polyimide particle (AP) was designed, synthesized, and introduced into intrinsic microporous polyimide matrix (6FDA-Durene) to form "all polyimide" MMMs. The AP fillers showed the feature of thermal stability, similar density with polyimide matrix, high porosity, high fractional free volume, large microporous dimension, and interpenetrating network architecture. As expected, the excellent interfacial compatibility between 6FDA-Durene and AP without obvious agglomeration even at a high AP loading of 10 wt.% was observed. As a result, the CO2 permeability coefficient of MMM with AP loading as low as 5 wt.% reaches up to 1291.13 Barrer, which is 2.58 times that of the pristine 6FDA-Durene membrane without the significant sacrificing of ideal selectivity of CO2/CH4. The improvement of permeability properties is much better than that of the previously reported MMMs, where high filler content is required to achieve a high permeability increase but usually leads to significant agglomeration or phase separation of fillers. It is believed that the excellent interfacial compatibility between the PI fillers and the PI matrix induce the effective utilization of porosity and free volume of AP fillers during gas transport. Thus, a higher diffusion coefficient of MMMs has been observed than that of the pristine PI membrane. Furthermore, the rigid polyimide fillers also result in the excellent anti-plasticization ability for CO2. The MMMs with a 10 wt.% AP loading shows a CO2 plasticization pressure of 300 psi.

The Effects of PEI Hollow Fiber Substrate Characteristics on PDMS/PEI Hollow Fiber Membranes for CO2/N2 Separation

The CO2 separation from flue gas based on membrane technology has drawn great attention in the last few decades. In this work, polyetherimide (PEI) hollow fibers were fabricated by using a dry-jet-wet spinning technique. Subsequently, the composite hollow fiber membranes were prepared by dip coating of polydimethylsiloxane (PDMS) selective layer on the outer surface of PEI hollow fibers. The hollow fibers spun from various spinning conditions were fully characterized. The influence of hollow fiber substrates on the CO2/N2 separation performance of PDMS/PEI composite membranes was estimated by gas permeance and ideal selectivity. The prepared composite membrane where the hollow fiber substrate was spun from 20 wt% of dope solution, 12 mL/min of bore fluid (water) flow rate exhibited the highest ideal selectivity equal to 21.3 with CO2 permeance of 59 GPU. It was found that the dope concentration, bore fluid flow rate and bore fluid composition affect the porous structure, surface morphology and dimension of hollow fibers. The bore fluid composition significantly influenced the gas permeance and ideal selectivity of the PDMS/PEI composite membrane. The prepared PDMS/PEI composite membranes possess comparable CO2/N2 separation performance to literature ones.