Mixed matrix membranes for CO2 separations by incorporating microporous polymer framework fillers with amine-rich nanochannels

A Review on the Application of Deep Eutectic Solvents in Polymer-Based Membrane Preparation for Environmental Separation Technologies

The use of deep eutectic solvents (DESs) for the preparation of polymer membranes for environmental separation technologies is comprehensively reviewed. DESs have been divided into five categories based on the hydrogen bond donor (HBD) and acceptor (HBA) that are involved in the production of the DESs, and a wide range of DESs' physicochemical characteristics, such as density, surface tension, viscosity, and melting temperature, are initially gathered. Furthermore, the most popular techniques for creating membranes have been demonstrated and discussed, with a focus on the non-solvent induced phase separation (NIPS) method. Additionally, a number of studies have been reported in which DESs were employed as pore formers, solvents, additives, or co-solvents, among other applications. The addition of DESs to the manufacturing process increased the presence of finger-like structures and macrovoids in the cross-section and, on numerous occasions, had a substantial impact on the overall porosity and pore size. Performance data were also gathered for membranes made for various separation technologies, such as ultrafiltration (UF) and nanofiltration (NF). Lastly, DESs provide various options for the functionalization of membranes, such as the creation of various liquid membrane types, with special focus on supported liquid membranes (SLMs) for decarbonization technologies, discussed in terms of permeability and selectivity of several gases, including CO2, N2, and CH4.

Carbon Dioxide Capture by Emerging Innovative Polymers: Status and Perspectives

A significant amount of research has been conducted in carbon dioxide (CO2) capture, particularly over the past decade, and continues to evolve. This review presents the most recent advancements in synthetic methodologies and CO2 capture capabilities of diverse polymer-based substances, which includes the amine-based polymers, porous organic polymers, and polymeric membranes, covering publications in the last 5 years (2019-2024). It aims to assist researchers with new insights and approaches to develop innovative polymer-based materials with improved capturing CO2 capacity, efficiency, sustainability, and cost-effective, thereby addressing the current obstacles in carbon capture and storage to sooner meeting the net-zero CO2 emission target.

Membrane Separation Technology in Direct Air Capture

Direct air capture (DAC) is an emerging negative CO2 emission technology that aims to introduce a feasible method for CO2 capture from the atmosphere. Unlike carbon capture from point sources, which deals with flue gas at high CO2 concentrations, carbon capture directly from the atmosphere has proved difficult due to the low CO2 concentration in ambient air. Current DAC technologies mainly consider sorbent-based systems; however, membrane technology can be considered a promising DAC approach since it provides several advantages, e.g., lower energy and operational costs, less environmental footprint, and more potential for small-scale ubiquitous installations. Several recent advancements in validating the feasibility of highly permeable gas separation membrane fabrication and system design show that membrane-based direct air capture (m-DAC) could be a complementary approach to sorbent-based DAC, e.g., as part of a hybrid system design that incorporates other DAC technologies (e.g., solvent or sorbent-based DAC). In this article, the ongoing research and DAC application attempts via membrane separation have been reviewed. The reported membrane materials that could potentially be used for m-DAC are summarized. In addition, the future direction of m-DAC development is discussed, which could provide perspective and encourage new researchers' further work in the field of m-DAC.

Theoretical models for gas separation prediction of mixed matrix membranes: effects of the shape factor of nanofillers and interface voids

In this work, a new model is developed by modifying the existing Maxwell–Wagner–Sillars (MWS) model to predict the gas separation properties of mixed matrix membranes (MMMs). The new modified MWS model, for the first time, provides the simultaneous exploration of the role of nanofillers/matrix interface voids and the exact geometrical shape of nanofillers in predicting the gas separation properties of MMMs. To unveil the crucial role of nanofillers/matrix interface voids, a mixed matrix membrane is considered a three-component system composed of the polymer matrix as the continuous component, nanofillers as the dispersed component and the interface voids between the two components. Moreover, the new model elucidates the role of the exact ellipsoidal shape of nanofillers within the membrane on the gas separation of MMMs by considering the shape factor of nanofillers. The newly developed modified MWS model is accurately able to predict the gas permeation of MMMs with a lower average absolute relative error (%AARE) of around 8% compared with the around 30% for conventional models such as the Maxwell model, Bruggeman model, Lewis–Nielsen model and Pal model and even compared with the modified Maxwell model (∼24%).

Cellulose acetate based sustainable nanostructured membranes for environmental remediation

Membrane-based gas separation has a great potential for reducing environmentally hazardous carbon dioxide (CO₂) gas. The polymeric membranes developed for CO₂ capturing have some limitations in their selectivity and permeability. There is a need to overcome these issues and developed such membranes having high-performance CO₂ capture with cost-effectiveness. The present study aimed to synthesize mixed matrix membranes (MMMs) having improved properties CO₂ adsorption performance and stability than that of pure polymer. Further, the effect on CO₂ adsorption by increasing the filler concentration in MMMs was investigated. The MMMs were synthesized by incorporating (1-5 wt%) Cu-MOF-GO composites as filler into cellulose-acetate (CA) polymer matrix by adopting the solution casting method. The performance of MMMs was studied by changing the Cu-MOF-GO composite concentration (1-5 wt%) in the polymer matrix at 45 °C up to 15 bar. Morphological analysis by using SEM confirms that by increasing the concentration of Cu-MOF-GO more than 3% will result in their agglomeration in MMM. The successful incorporation of MOF within the polymer matrix of MMMs was confirmed through the presence of functional groups using FTIR and Raman spectroscopy. XRD analysis revealed that pure CA changes its semi-crystalline behaviour into crystalline by the addition of Cu-MOF-GO. The maximum tensile stress and strain rate of MMMs was 45.1 N/mm² and 12.8%. In addition, with an increase in (4-5 wt%) Cu-MOF-GO concentration the hydrophilicity of MMMs decreases. The maximum uptake rate of CO₂ was 1.79 mmol/g and 7.98 wt% at 15 bar. The adsorption results conclude that Cu-MOF-GO composite and CA-based MMM can be effective for CO₂ capture.

Ultra-permeable intercalated metal-induced microporous polymer nano-dots rooted smart membrane for environmental remediation

Energy efficient CO₂ separation using ultrathin smart membranes must possess efficient permeation performance, higher surface area and hydrostatic stability at industrially relevant high pressures. However, ultrathin membranes are susceptible to lower surface area, plasticization and swelling which reduces the performance at higher pressure under humidified conditions. This paper evaluates the routes for the potential intercalated effect of metal-induced microporous polymers (MMPs) dots into a cellulose-based polymer matrix to enhance promising properties, including the surface area, CO₂ permeation performance, plasticization resistance and hydrostatic stability of ultrathin smart membranes at high pressure. The MMP dots-rooted smart membrane demonstrated 55 nm thickness of ultrathin selective layer with a higher surface of 220 cm². The enhancement of CO₂ permeability from 14.1 to 108.9 Barrer and CO₂/CH₄ ideal selectivity from 11.8 to 31.1 was observed due to the integration of MMP dots into the cellulose polymer. This result could be due to enhancement of nitrogen lone pair electron interactions with CO₂ followed by amines group which improved the CO₂ adsorption on the membrane surface. The MMP dots-rooted membrane demonstrated plasticization resistance up to 26 bar pressure, as compared to a pristine polymer membrane which is a percentage increase of 160% under humidified conditions. The resulting ultrathin smart membrane exhibited stable performance for a duration of 200 h under humidified conditions which confirmed the higher hydrostatic stability of the membrane. These findings confirmed the potential of MMP dots materials for the development of an industrial scale CO₂ separation process using intercalated membranes.

Efficient Facilitated Transport Polymer Membrane for CO2/CH4 Separation from Oilfield Associated Gas

CO₂ enhanced oil recovery (CO₂-EOR) technology is a competitive strategy to improve oil field economic returns and reduce greenhouse gas emissions. However, the arbitrary emissions or combustion of the associated gas, which mainly consists of CO₂ and CH₄, will cause the aggravation of the greenhouse effect and a huge waste of resources. In this paper, the high-performance facilitated transport multilayer composite membrane for CO₂/CH₄ separation was prepared by individually adjusting the membrane structure of each layer. The effect of test conditions on the CO₂/CH₄ separation performance was systematically investigated. The membrane exhibits high CO₂ permeance of 3.451 × 10^-7 mol·m^-2·s^-1·Pa^-1 and CO₂/CH₄ selectivity of 62 at 298 K and 0.15 MPa feed gas pressure. The cost analysis was investigated by simulating the two-stage system. When the recovery rate and purity of CH₄ are 98%, the minimum specific cost of separating CO₂/CH₄ (45/55 vol%) can be reduced to 0.046 $·Nm^-3 CH₄. The excellent short-to-mid-term stability indicates the great potential of large industrial application in the CH₄ recovery and CO₂ reinjection from oilfield associated gas.