Manipulation of Fibril Surfaces in Nanocellulose-Based Facilitated Transport Membranes for Enhanced CO2 Capture

Recent progress on CO2 separation membranes

Presently, excessive carbon dioxide emissions represent a critical environmental challenge. Thus, urgent efforts are required to develop environmentally friendly and low-energy technologies for carbon dioxide treatment. In this case, membrane separation technology stands out as a promising avenue for CO2 separation, with selective membrane materials of high permeability playing a pivotal role in this process. Herein, we categorize CO2 separation membranes into three groups: inorganic membranes, organic membranes, and emerging membranes. Moreover, representative high-performance membranes are introduced and their synthesis methods, gas separation performances, and applications are examined. Furthermore, a brief analysis of the challenges encountered by carbon dioxide separation membrane materials is provided together with a discussion on the future research direction. It is expected that this review will provide some potential insights and guidance for the future development of CO2 separation membranes, which can promote their development.

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.

Biopolymeric Nanocomposites for CO2 Capture

Carbon dioxide (CO2) impacts the greenhouse effect significantly and results in global warming, prompting urgent attention to climate change concerns. In response, CO2 capture has emerged as a crucial process to capture carbon produced in industrial and power processes before its release into the atmosphere. The main aim of CO2 capture is to mitigate the emissions of greenhouse gas and reduce the anthropogenic impact on climate change. Biopolymer nanocomposites offer a promising avenue for CO2 capture due to their renewable nature. These composites consist of biopolymers derived from biological sources and nanofillers like nanoparticles and nanotubes, enhancing the properties of the composite. Various biopolymers like chitosan, cellulose, carrageenan, and others, possessing unique functional groups, can interact with CO2 molecules. Nanofillers are incorporated to improve mechanical, thermal, and sorption properties, with materials such as graphene, carbon nanotubes, and metallic nanoparticles enhancing surface area and porosity. The CO2 capture mechanism within biopolymer nanocomposites involves physical absorption, chemisorption, and physisorption, driven by functional groups like amino and hydroxyl groups in the biopolymer matrix. The integration of nanofillers further boosts CO2 adsorption capacity by increasing surface area and porosity. Numerous advanced materials, including biopolymeric derivatives like cellulose, alginate, and chitosan, are developed for CO2 capture technology, offering accessibility and cost-effectiveness. This semi-systematic literature review focuses on recent studies involving biopolymer-based materials for CO2 capture, providing an overview of composite materials enriched with nanomaterials, specifically based on cellulose, alginate, chitosan, and carrageenan; the choice of these biopolymers is dictated by the lack of a literature perspective focused on a currently relevant topic such as these biorenewable resources in the framework of carbon capture. The production and efficacy of biopolymer-based adsorbents and membranes are examined, shedding light on potential trends in global CO2 capture technology enhancement.

Membrane-Based Technologies for Post-Combustion CO2 Capture from Flue Gases: Recent Progress in Commonly Employed Membrane Materials

Carbon dioxide (CO2), which results from fossil fuel combustion and industrial processes, accounts for a substantial part of the total anthropogenic greenhouse gases (GHGs). As a result, several carbon capture, utilization and storage (CCUS) technologies have been developed during the last decade. Chemical absorption, adsorption, cryogenic separation and membrane separation are the most widely used post-combustion CO2 capture technologies. This study reviews post-combustion CO2 capture technologies and the latest progress in membrane processes for CO2 separation. More specifically, the objective of the present work is to present the state of the art of membrane-based technologies for CO2 capture from flue gases and focuses mainly on recent advancements in commonly employed membrane materials. These materials are utilized for the fabrication and application of novel composite membranes or mixed-matrix membranes (MMMs), which present improved intrinsic and surface characteristics and, thus, can achieve high selectivity and permeability. Recent progress is described regarding the utilization of metal-organic frameworks (MOFs), carbon molecular sieves (CMSs), nanocomposite membranes, ionic liquid (IL)-based membranes and facilitated transport membranes (FTMs), which comprise MMMs. The most significant challenges and future prospects of implementing membrane technologies for CO2 capture are also presented.

Recent developments in nanocellulose-based aerogels as air filters: A review

Today, one of the world's critical environmental issues is air pollution, which is the most important parameter threatening human health and the environment. Synthetic polymers are widely used in industrial air filter production; however, they are incompatible with the environment due to their secondary pollution. Using renewable materials to manufacture air filters is not only environmentally friendly but also essential. Recently, a new generation of biopolymers called cellulose nanofiber (CNF)-based hydrogels have been proposed, with three dimensional (3D) nanofiber networks and unique physical and mechanical properties. CNFs have become a hot research topic for application as air filter materials because they can compete with synthetic nanofibers due to their advantages, such as abundant, renewable, nontoxic, high specific surface area, high reactivity, flexibility, low cost, low density, and network structure formation. The main focus of the current review is the recent progress in the preparation and employment of nanocellulose materials, especially CNF-based hydrogels, to absorb PM and CO2. This study summarizes the preparation methods, modification strategies, fabrications, and further applications of CNF-based aerogels as air filters. Lastly, challenges in the fabrication of CNFs, and trends for future developments are presented.

Current and Potential Applications of Green Membranes with Nanocellulose

Large-scale applications of nanotechnology have been extensively studied within the last decade. By exploiting certain advantageous properties of nanomaterials, multifunctional products can be manufactured that can contribute to the improvement of everyday life. In recent years, one such material has been nanocellulose. Nanocellulose (NC) is a naturally occurring nanomaterial and a high-performance additive extracted from plant fibers. This sustainable material is characterized by a unique combination of exceptional properties, including high tensile strength, biocompatibility, and electrical conductivity. In recent studies, these unique properties of nanocellulose have been analyzed and applied to processes related to membrane technology. This article provides a review of recent synthesis methods and characterization of nanocellulose-based membranes, followed by a study of their applications on a larger scale. The article reviews successful case studies of the incorporation of nanocellulose in different types of membrane materials, as well as their utilization in water purification, desalination, gas separations/gas barriers, and antimicrobial applications, in an effort to provide an enhanced comprehension of their capabilities in commercial products.

Comparative investigation on removal characteristics of tetracycline from water by modified wood membranes with different channel walls

The alkali-innocuous citric acid (CA) modified wood membranes (WMs) have been developed as facile, economical, and effective adsorption membranes to remove tetracycline (TC) from water. However, TC removal by modified WMs with different types of wood channel walls have rarely been compared. Therefore, in this study, modified WMs were prepared with pinewood (PW) and basswood (BW). The PW and BW WMs before and after modification were characterized by SEM, EDX, XRD, ATR-FTIR, TGA, contact angle and zeta potential. After modification, cellulose I in cellulose crystal structures of raw WM transformed to cellulose II and the contents of carboxylic groups for PW and BW were enhanced to make the hydrophilicity of WM surface increased. Compared with modified PW WMs, particles formed on the channel walls of modified BW WMs containing vessel pits to make more carboxylic groups introduced. The TC adsorption breakthrough curves showed that the 6 wt% alkali- CA modified BW had an effective filtration volume of 1968 bed volume (BV) compared with the 4 wt% alkali-CA modified PW of 1205 BV as the influent TC and breakthrough point were chosen at 2 and 0.5 mg/L, respectively. At low pH, TC complex with WM surfaces through Lewis acid-base interaction. Zwitterionic TC was shown to favor adsorption onto WM via hydrogen bonding at pH of around 5. With further increasing pH, TC adsorption efficiency decreased due to the electrostatic repulsion. The costs of modified BW and PW are about 0.0054-0.0126 US$/m³ and 0.01-0.024 US$/m³ for a low TC concentration effluent (0-0.5 mg/L), respectively. This work shed a new sight on how to develop economical and effective adsorption WMs for contaminants removal from water.

Effect of Mobile Carrier on the Performance of PVAm-Nanocellulose Facilitated Transport Membranes for CO2 Capture

Facilitated transport membranes obtained by coupling polyvinylamine with highly charged carboxymethylated nanocellulose fibers were studied considering both water sorption and gas permeation experiments. In particular, the effect of the L-arginine as a mobile carrier was investigated to understand possible improvements in CO₂ transport across the membranes. The results show that L-arginine addition decreases the water uptake of the membrane, due to the lower polyvinylamine content, but was able to improve the CO₂ transport. Tests carried on at 35 °C and high relative humidity indeed showed an increase of both CO₂ permeability and selectivity with respect to nitrogen and methane. In particular, the CO₂ permeability increased from 160 to about 340 Barrer when arginine loading was increased from 0 to 45 wt%. In the same conditions, selectivity with respect to nitrogen was more than doubled, increasing from 20 to 45. Minor improvements were instead obtained with respect to methane; CO₂/CH₄ selectivity, indeed, even in presence of the mobile carrier, was limited to about 20.

A review on the emerging applications of cellulose, cellulose derivatives and nanocellulose in carbon capture

Carbon capture can be implemented at a large scale only if the CO₂ selective materials are abundantly available at low cost. Since the sustainable requirement also elevated, the low-cost and biodegradable cellulosic materials are developed into CO₂ selective adsorbent and membranes recently. The applications of cellulose, cellulosic derivatives and nanocellulose as CO₂ selective adsorbents and membranes are reviewed here. The fabrication and modification strategies are discussed besides comparing their CO₂ separation performance. Cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) isolated from cellulose possess a big surface area for mechanical enhancement and a great number of hydroxyl groups for modification. Nanocellulose aerogels with the large surface area were chemically modified to improve their selectivity towards CO₂. Even with the reduction of surface area, amino-functionalized nanocellulose aerogels exhibited the satisfactory chemisorption of CO₂ with a capacity of more than 2 mmol/g was recorded. Inorganic fillers such as silica, zeolite and MOFs were further incorporated into nanocellulose aerogels to enhance the physisorption of CO₂ by increasing the surface area. Although CO₂ adsorbents developed from cellulose and cellulose derivatives were less reported, their applications as the building blocks of CO₂ separation membranes had been long studied. Cellulose acetate membranes were commercialized for CO₂ separation, but their separation performance could be further improved with silane or inorganic filler. CNCs and CNFs enhanced the CO₂ selectivity and permeance through polyvinyl alcohol coating on membranes, but only CNF membranes incorporated with MOFs were explored so far. Although some of these membranes surpassed the upper-bound of Robeson plot, their stability should be further investigated.

Analysis of CO2 Facilitation Transport Effect through a Hybrid Poly(Allyl Amine) Membrane: Pathways for Further Improvement

Numerous studies have been reported on CO₂ facilitated transport membrane synthesis, but few works have dealt with the interaction between material synthesis and transport modelling aspects for optimization purposes. In this work, a hybrid fixed-site carrier membrane was prepared using polyallylamine with 10 wt% polyvinyl alcohol and 0.2 wt% graphene oxide. The membrane was tested using the feed gases with different relative humidity and at different CO₂ partial pressures. Selected facilitated transport models reported in the literature were used to fit the experimental data with good agreement. The key dimensionless facilitated transport parameters were obtained from the modelling and data fitting. Based on the values of these parameters, it was shown that the diffusion of the amine-CO₂ reaction product was the rate-controlling step of the overall CO₂ transport through the membrane. It was shown theoretically that by decreasing the membrane selective layer thickness below the actual value of 1 µm to a value of 0.1 µm, a CO₂ permeance as high as 2500 GPU can be attained while maintaining the selectivity at a value of about 19. Furthermore, improving the carrier concentration by a factor of two might shift the performances above the Robeson upper bound. These potential paths for membrane performance improvement have to be confirmed by targeted experimental work.

Recent developments on polymeric membranes for CO2 capture from flue gas

Polymeric membranes have been widely considered as one of the next-generation technologies for CO2 capture from fossil fuel-derived flue gases. This separation modality requires novel polymeric materials that possess efficient CO2/N2 separation properties, as well as chemical and mechanical stability for a multiyear membrane lifetime. In this paper, recent developments in polymeric membranes tailored for post-combustion carbon capture are reviewed. The selected polymeric materials encompass ether oxygen-rich polymers, polynorbornenes, ionic liquid membranes, and facilitated transport membranes. In each of the selected materials, noteworthy research efforts for material design and membrane formation are highlighted. The performances of the selected materials are compared in the CO2/N2 selectivity-CO2 permeance plot. As the only class of materials reviewed herein that have demonstrated the fabrication of thin-film composite membranes in scale, facilitated transport membranes have shown both high selectivity and permeance at relevant conditions for post-combustion carbon capture. However, comprehensive field tests are needed to resolve the technical gap between the material development and the commercial application.