CO 2 separation of polymer membranes containing silica nanoparticles with gas permeable nano-space

Innovative eco-friendly hydroxyethylcellulose matrix-based composite for enhanced gas separation: Insights from performance and structural characterization

With increasing concern for the environment, the demand for carbon dioxide separation, a key contributor to global warming, has escalated. Therefore, this paper focuses on carbon dioxide separation by creating an hydroxyethyl cellulose (HEC)(C2H6O2)x*(C6H7O2(OH)3)n/silver tetra fluoroborate (AgBF4)/aluminum nitrate (Al(NO3)3) composite film, demonstrating excellent separation performance with a permeance of 1.0 GPU and a selectivity of 100. Silver ions enhance the solubility of carbon dioxide, aiding in its separation, and we determined the optimal aluminum composition to stabilize the silver ions. To analyze this, we examined the cross-sections using SEM, confirming a selective layer of 1.7 μm for carbon dioxide separation. Furthermore, TGA, FT-IR, and NMR analyses were conducted to investigate the interaction between the polymer and additives. This revealed that the increased polymer chain due to the interaction between Ag and HEC, along with stabilized Ag facilitated by the addition of Al, maximized the interaction with carbon dioxide via the empty s-orbital. Additionally, SEM-EDX, UV-vis, XRD, XPS analyses were employed to elucidate the movement of ions within the membrane. These results provide insights into the performance of membranes based on cellulose polymer and offer valuable insights for future applications in gas separation technologies.

Advancements in Gas Separation for Energy Applications: Exploring the Potential of Polymer Membranes with Intrinsic Microporosity (PIM)

Membrane-based Polymers of Intrinsic Microporosity (PIMs) are promising candidates for energy-efficient industrial gas separations, especially for the separation of carbon dioxide over methane (CO2/CH4) and carbon dioxide over nitrogen (CO2/N2) for natural gas/biogas upgrading and carbon capture from flue gases, respectively. Compared to other separation techniques, membrane separations offer potential energy and cost savings. Ultra-permeable PIM-based polymers are currently leading the trade-off between permeability and selectivity for gas separations, particularly in CO2/CH4 and CO2/N2. These membranes show a significant improvement in performance and fall within a linear correlation on benchmark Robeson plots, which are parallel to, but significantly above, the CO2/CH4 and CO2/N2 Robeson upper bounds. This improvement is expected to enhance the credibility of polymer membranes for CO2 separations and stimulate further research in polymer science and applied engineering to develop membrane systems for these CO2 separations, which are critical to energy and environmental sustainability. This review aims to highlight the state-of-the-art strategies employed to enhance gas separation performances in PIM-based membranes while also mitigating aging effects. These strategies include chemical post-modification, crosslinking, UV and thermal treatment of PIM, as well as the incorporation of nanofillers in the polymeric matrix.

Alshgari R, Jamal M, Uz Zaman S, Umar M, Rafiq S, Muhammad N, Fawad JB, Shafiee SA. Deep Eutectic Solvent Coated Cerium Oxide Nanoparticles Based Polysulfone Membrane to Mitigate Environmental Toxicology

In this study, ceria nanoparticles (NPs) and deep eutectic solvent (DES) were synthesized, and the ceria-NP's surfaces were modified by DES to form DES-ceria NP filler to develop mixed matrix membranes (MMMs). For the sake of interface engineering, MMMs of 2%, 4%, 6% and 8% filler loadings were fabricated using solution casting technique. The characterizations of SEM, FTIR and TGA of synthesized membranes were performed. SEM represented the surface and cross-sectional morphology of membranes, which indicated that the filler is uniformly dispersed in the polysulfone. FTIR was used to analyze the interaction between the filler and support, which showed there was no reaction between the polymer and DES-ceria NPs as all the peaks were consistent, and TGA provided the variation in the membrane materials with respect to temperature, which categorized all of the membranes as very stable and showed that the trend of stability increases with respect to DES-ceria NPs filler loading. For the evaluation of efficiency of the MMMs, the gas permeation was tested. The permeability of CO2 was improved in comparison with the pristine Polysulfone (PSF) membrane and enhanced selectivities of 35.43 (αCO2/CH4) and 39.3 (αCO2/N2) were found. Hence, the DES-ceria NP-based MMMs proved useful in mitigating CO2 from a gaseous mixture.

Fabrication, Facilitating Gas Permeability, and Molecular Simulations of Porous Hypercrosslinked Polymers Embedding 6FDA-Based Polyimide Mixed-Matrix Membranes

Novel polymers applied in economic membrane technologies are a perennial hot topic in the fields of natural gas purification and O₂ enrichment. Herein, novel hypercrosslinked polymers (HCPs) incorporating 6FDA-based polyimide (PI) MMMs were prepared via a casting method for enhancing transport of different gases (CO₂, CH₄, O₂, and N₂). Intact HCPs/PI MMMs could be obtained due to good compatibility between the HCPs and PI. Pure gas permeation experiments showed that compared with pure PI film, the addition of HCPs effectively promotes gas transport, increases gas permeability, and maintains ideal selectivity. The permeabilities of HCPs/PI MMMs toward CO₂ and O₂ were as high as 105.85 Barrer and 24.03 Barrer, respectively, and the ideal selectivities of CO₂/CH₄ and O₂/N₂ were 15.67 and 3.00, respectively. Molecular simulations further verified that adding HCPs was beneficial to gas transport. Thus, HCPs have potential utility in fabrication of MMMs for facilitating gas transport in the fields of natural gas purification and O₂ enrichment.

CuO Modified by 7,7,8,8-Tetracyanoquinodimethane and Its Application to CO2 Separation

7,7,8,8-Tetracyanoquinomethane (TCNQ) was added to polyvinylpyrrolidone (PVP)/CuO composites to modify and prevent agglomeration of the particles, and thus the CuO particles were well dispersed to a small size, thereby increasing CO₂ solubility and separation performance. When the separation performance of the PVP/CuO/TCNQ composite membrane was measured for CO₂/N₂ gases, a CO₂ separation of about 174 was measured. This improvement in performance was attributed to the fact that TCNQ was applied to PVP and CuO to prevent agglomeration between particles with surface modification. Due to TCNQ, CuO could be dispersed to a small size in PVP; the bonds between chains in PVP weakened; the interaction between molecules weakened; and the free volume increased, as confirmed by FT-IR, TGA, and UV-Vis spectroscopy.

Gas Adsorption and Diffusion Behaviors in Interfacial Systems Composed of a Polymer of Intrinsic Microporosity and Amorphous Silica: A Molecular Simulation Study

We investigate the adsorption and diffusion behaviors of CO₂, CH₄, and N₂ in interfacial systems composed of a polymer of intrinsic microporosity (PIM-1) and amorphous silica using grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. We build model systems of mixed matrix membranes (MMMs) with PIM-1 chains sandwiched between silica surfaces. Gas adsorption analysis using GCMC simulations shows that gas molecules are preferentially adsorbed in microcavities distributed near silica surfaces, resulting in an increase in the solubility coefficients of CO₂, CH₄, and N₂ compared to bulk PIM-1. In contrast, diffusion coefficients obtained from MD simulations and then calibrated using the dual-mode sorption model show different tendencies depending on gas species: CO₂ diffusivity decreases in MMMs compared to PIM-1, whereas CH₄ and N₂ diffusivities increase. These differences are attributed to competing effects of silica surfaces: the emergence of larger pores as a result of chain packing disruption, which enhances gas diffusion, and a quadrupole-dipole interaction between gas molecules and silica surface hydroxyl groups, which retards gas diffusion. The former has a greater impact on CH₄ and N₂ diffusivities, whereas the latter has a greater impact on CO₂ diffusivity due to the strong quadrupole-dipole interaction between CO₂ and surface hydroxyls. These findings add to our understanding of gas adsorption and diffusion behaviors in the vicinity of PIM-1/silica interfaces, which are unobtainable in experimental studies.

Characteristics of Inorganic–Organic Hybrid Membranes Containing Carbon Nanotubes with Increased Iron-Encapsulated Content for CO2 Separation

Novel inorganic–organic hybrid membranes Fe@MWCNT/PPO or Fe@MWCNT-OH/SPPO (with a new type of CNTs characterized by increased iron content 5.80 wt%) were synthesized for CO2 separation. The introduction of nanofillers into the polymer matrix has significantly improved the hybrid membrane’s gas transport (D, P, S, and αCO2/N2), magnetic, thermal, and mechanical parameters. It was found that magnetic casting has improved the alignment and dispersion of Fe@MWCNTs. At the same time, CNTs and polymer chemical modification enhanced interphase compatibility and the membrane’s CO2 separation efficiency. The thermo-oxidative stability and mechanical and magnetic parameters of composites were improved by increasing new CNTs loading. Cherazi’s model turned out to be suitable for describing the CO2 transport through analyzed hybrid membranes.

Reversible assembly of silica nanoparticles at water-hydrocarbon interfaces controlled by SDS surfactant

Achieving reversible and tunable assembly of silica nanoparticles at liquid-liquid interfaces is vital for a wide range of scientific and technological applications including sustainable subsurface energy applications, catalysis, drug delivery and material synthesis. In this study, we report the mechanisms controlling the assembly of silica nanoparticles (dia. 50 nm and 100 nm) at water-heptane and water-toluene interfaces using sodium dodecyl sulfate (SDS) surfactant with concentrations ranging from 0.001-0.1 wt% using operando ultrasmall/small-angle X-ray scattering, cryogenic scanning electron microscopy imaging and classical molecular dynamics simulations. The results show that the assembly of silica nanoparticles at water-hydrocarbon interfaces can be tuned by controlling the concentrations of SDS. Silica nanoparticles are found to: (a) dominate the interfaces in the absence of interfacial SDS molecules, (b) coexist with SDS at the interfaces at low surfactant concentration of 0.001 wt% and (c) migrate toward the aqueous phase at a high SDS concentration of 0.1 wt%. Energetic analyses suggest that the van der Waals and electrostatic interactions between silica nanoparticles and SDS surfactants increase with SDS concentration. However, the favorable van der Waals and electrostatic interactions between the silica nanoparticles and toluene or heptane decrease with increasing SDS concentration. As a result, the silica nanoparticles migrate away from the water-hydrocarbon interface and towards bulk water at higher SDS concentrations. These calibrated investigations reveal the mechanistic basis for tuning silica nanoparticle assembly at complex interfaces.

Analysis of the EU-27 Countries Energy Markets Integration in Terms of the Sustainable Development SDG7 Implementation

The article presents the results of research related to the SDG7 sustainable development implementation analysis. The goal is to provide affordable and clean energy. Its implementation will allow for development that will simultaneously provide the possibility of economic growth and the achievement of an optimal level of citizens’ health and life. The research was conducted for the countries of the European Union EU-27. During the analysis, the indicators proposed by Eurostat were used. The research aimed to examine the progress in EU member states’ energy markets integration. In order to carry out the indispensable research, it was necessary to use a spatial information system. Cluster analysis, as well as TSA analysis, were applied. The conducted research made it possible to verify the posed hypotheses and showed that the energy transformation process of the EU-27 countries is so complicated and heterogeneous that it has given rise to new independent and unique clusters. The authors also verified the adopted set of SDG7 achievement indicators using multiple regression. Additional indicators were also proposed that could complement the set and clarify its analyses.

Methods of Ensuring Energy Security with the Use of Hard Coal—The Case of Poland

In this article, the authors present methods based on hard coal that may ensure energy security for European Union countries. The research was carried out based on the example of Poland. The main reason for which coal is being gradually withdrawn from the energy mixes in EU countries is its negative impact on the natural environment and the health of citizens and economic factors related to domestic fuel production. The authors propose the creation of energy–chemical clusters as a solution to these problems. It is assumed that the clusters would operate following the principles of the circular economy. We also propose methods for the optimization of the production and transport costs within the cluster. Then, we conduct profitability analysis of the proposed waste management methods. At the level of the designated cluster, using network algorithms enabled us to reduce the transport costs by at least 50%. It is possible to obtain rare earth elements (REEs) worth USD 22,970 from 1 Mg of ash. At the level of the analyzed cluster, this leads to an annual profit of USD 3.5 billion. The profit related to algae production at the cluster level is approximately USD 2.5 bn.

Recent Advances in Polymer-Inorganic Mixed Matrix Membranes for CO2 Separation

Since the second industrial revolution, the use of fossil fuels has been powering the advance of human society. However, the surge in carbon dioxide (CO2) emissions has raised unsettling concerns about global warming and its consequences. Membrane separation technologies have emerged as one of the major carbon reduction approaches because they are less energy-intensive and more environmentally friendly compared to other separation techniques. Compared to pure polymeric membranes, mixed matrix membranes (MMMs) that encompass both a polymeric matrix and molecular sieving fillers have received tremendous attention, as they have the potential to combine the advantages of both polymers and molecular sieves, while cancelling out each other's drawbacks. In this review, we will discuss recent advances in the development of MMMs for CO2 separation. We will discuss general mechanisms of CO2 separation in an MMM, and then compare the performances of MMMs that are based on zeolite, MOF, metal oxide nanoparticles and nanocarbons, with an emphasis on the materials' preparation methods and their chemistries. As the field is advancing fast, we will particularly focus on examples from the last 5 years, in order to provide the most up-to-date overview in this area.

Advances in the Use of Nanocomposite Membranes for Carbon Capture Operations

The adoption of nanodoped membranes in the areas of gas stream separation, water, and wastewater treatments due to the physical and operational advantages of such membranes has significantly increased. The literature has shown that the surface structure and physicochemical properties of nanodoped membranes contribute significantly to the interaction and rejection characteristics when compared to bare membranes. This study reviews the recent developments on nanodoped membranes, and their hybrids for carbon capture and gas separation operations. Features such as the nanoparticles/materials and hybrids used for membrane doping and the effect of physicochemical properties and water vapour in nanodoped membrane performance for carbon capture are discussed. The highlights of this review show that nanodoped membrane is a facile modification technique which improves the membrane performance in most cases and holds a great potential for carbon capture. Membrane module design and material, thickness, structure, and configuration were identified as key factors that contribute directly, to nanodoped membrane performance. This study also affirms that the three core parameters satisfied before turning a microporous material into a membrane are as follows: high permeability and selectivity, ease of fabrication, and robust structure. From the findings, it is also observed that the application of smart models and knowledge-based systems have not been extensively studied in nanoparticle-/material-doped membranes. More studies are encouraged because technical improvements are needed in order to achieve high performance of carbon capture using nanodoped membranes, as well as improving their durability, permeability, and selectivity of the membrane.

"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.

Preparation of Ni nanoparticles by liquid-phase reduction to fabricate metal nanoparticle-polyimide composite films

Nickel-nanoparticle-containing polyimide composite films were prepared by liquid-phase reduction of Ni²⁺ ions with potassium borohydride (KBH₄). The nanoparticles were amorphous with diameters of approximately 10-20 nm, depending on the KBH₄ concentration and reduction temperature. At high KBH₄ concentrations, the nanoparticles appeared to contain various nickel boride species. The number of nanoparticles and Ni content both increased upon repeated adsorption/reduction of Ni²⁺ ions, where the particle growth was inhibited by the rigid polymer chain and the formation of smaller particles was favored.

3-Aminopropyltriethoxysilane-aided cross-linked chitosan membranes for gas separation: grand canonical Monte Carlo and molecular dynamics simulations

Molecular simulations were performed to consider the structural and transport properties of chitosan/3-aminopropyltriethoxysilane (APTEOS) mixed matrix membranes (MMMs). In order to consider the presence of APTEOS content on the performances of membrane, various amounts of APTEOS were added to the polymeric matrix as a cross-linker. Structural characterizations such as radial distribution function (RDF), fractional free volume (FFV) and X-ray diffraction (XRD) were carried out on the simulated cells. Self-diffusivity and solubility of membranes were calculated using mean square displacement (MSD) and adsorption isotherms, respectively. Additionally, permeability and permselectivity of CO₂ and N₂ gases were calculated by grand canonical Monte Carlo and molecular dynamics methods. The system temperature was set to 298 K using a Nose-Hoover thermostat. According to the results, upon increasing APTEOS loading, CO₂ permeability increases until 10 wt.% loading. Then, by adding 20 wt.% of APTEOS, CO₂ permeability decreases, which could be related to higher crystallinity. XRD graphs indicated that the crystallinity decreased when adding 10 wt.% APTEOS, while higher APTEOS content (up to 20 wt.%) led to higher crystallinity percentage, consistent with permeability results. Compared to literature reports, the present simulation indicated higher accuracy for defining the structural and transport properties of APTEOS cross-linked chitosan MMMs. Graphical abstract 3-Aminopropyltriethoxysilane-aided cross-linked chitosan membranes for gasseparation.

Modeling of Gas Permeation through Mixed-Matrix Membranes Using Novel Computer Application MOT

The following article proposes a modern computer application MOT (Membrane Optimization Tool) for modeling of gas transport processes through mixed-matrix membranes (MMMs). The current version of the application is based on the Maxwell model, which can be successfully used to model gas transport through the simplest types of hybrid membranes without any defects. The application has been verified on the example of four types of hybrid membranes, consisting of various types of polymer matrix, such as: poly (vinyl acetate), 2, 2′-BAPB + BPADA, Ultem, hyperbranched polyimide (ODPA-MTA) and zeolite 4A. The average absolute relative error (AARE) and root-mean-square error (RMSE) were calculated in order to compare the theoretical MOT-predicted results with the experimental results. It was found that the AARE ranges from 29% to 36%, while the RMSE is in the range of 10% to 29%. The article presents also the comparison of MOT-predicted data obtained with Maxwell and Bruggeman models. To obtain more accurate reproduction of experimental results, further versions of the proposed application will be extended with next-generation permeation models (Lewis–Nielsen, Pal, modified Maxwell or Felske models), allowing for the description of transport in more complex systems with the possibility of taking into account possible defects.

Modeling the Effects of Interfacial Characteristics on Gas Permeation Behavior of Nanotube-Mixed Matrix Membranes

Theoretical approaches that accurately predict the gas permeation behavior of nanotube-containing mixed matrix membranes (nanotube-MMMs) are scarce. This is mainly due to ignoring the effects of nanotube/matrix interfacial characteristics in the existing theories. In this paper, based on the analogy of thermal conduction in polymer composites containing nanotubes, we develop a model to describe gas permeation through nanotube-MMMs. Two new parameters, "interfacial thickness" (a_int) and "interfacial permeation resistance" (R_int), are introduced to account for the role of nanotube/matrix interfacial interactions in the proposed model. The obtained values of a_int, independent of the nature of the permeate gas, increased by increasing both the nanotubes aspect ratio and polymer-nanotube interfacial strength. An excellent correlation between the values of a_int and polymer-nanotube interaction parameters, χ, helped to accurately reproduce the existing experimental data from the literature without the need to resort to any adjustable parameter. The data includes 10 sets of CO₂/CH₄ permeation, 12 sets of CO₂/N₂ permeation, 3 sets of CO₂/O₂ permeation, and 2 sets of CO₂/H₂ permeation through different nanotube-MMMs. Moreover, the average absolute relative errors between the experimental data and the predicted values of the proposed model are very small (less than 5%) in comparison with those of the existing models in the literature. To the best of our knowledge, this is the first study where such a systematic comparison between model predictions and such extensive experimental data is presented. Finally, the new way of assessing gas permeation data presented in the current work would be a simple alternative to complex approaches that are usually utilized to estimate interfacial thickness in polymer composites.