Unveiling the potential of membrane in climate change mitigation and environmental resilience in ecosystem

Carbon capture technologies are becoming increasingly crucial in addressing global climate change issues by lowering CO2 emissions from industrial and power generation activities. Post-combustion carbon capture, which uses membranes instead of adsorbents, has emerged as one of promising and environmentally friendly approaches among these technologies. The operation of membrane technology is based on the premise of selectively separating CO2 from flue gas emissions. This provides a number of different benefits, including improved energy efficiency and decreased costs of operation. Because of its adaptability to changing conditions and its low impact on the surrounding ecosystem, it is an appealing choice for a diverse array of uses. However, there are still issues to be resolved, such as those pertaining to establishing a high selectivity, membrane degradation, and the costs of the necessary materials. In this article, we evaluate and explore the prospective applications and roles of membrane technologies to control climate change by post-combustion carbon capturing. The primary proposition suggests that the utilization of membrane-based carbon capture has the potential to make a substantial impact in mitigating CO2 emissions originating from industrial and power production activities. This is due to its heightened ability to selectively absorb carbon, better efficiency in energy consumption, and its flexibility to various applications. The forthcoming challenges and potential associated with the application of membranes in post-carbon capture are also discussed.

Carbon dioxide solubility in choline chloride-based deep eutectic solvents under diverse conditions

CONTEXT

Global warming is a severe problem experiencing the climate crisis due to rising CO₂ emissions. Deep eutectic solvents (DESs) have recently attracted a lot of attention as potential absorbents to mitigate carbon dioxide CO₂ emissions because of their large CO₂ capacities and stability under diverse conditions. Designing a potent DES requires knowledge of molecular-level understanding including structure, dynamics, and interfacial properties in DESs. In this study, we investigate the CO₂ sorption and diffusion in different DESs at different temperatures and pressure using molecular dynamics (MD) simulations. Our results demonstrate that CO₂ molecules preferentially concentrate at the CO₂-DES interface, and the diffusion of CO₂ in bulk DESs increases with increasing pressure and temperature. The solubility of CO₂ in the three DESs increases as ChCL-ethylene glycol < ChCL-urea < ChCL-glycerol at high pressure (58.6 bar).

METHODS

The initial configuration for MD simulations included DES and CO₂ and produced the solvation box using PACKMOL software. The geometries are optimized in the Gaussian 09 software at the theoretical level of B3LYP/6-311 + G*. The partial atomic charges were fitted to an electrostatic surface potential using the CHELPG method. MD simulations were carried out by using the NAMD version 2.13 software. VMD software was used to take the snapshots. TRAVIS software is used to determine spatial distribution functions.

Membrane Separation Processes and Post-Combustion Carbon Capture: State of the Art and Prospects

Membrane processes have been investigated for carbon capture for more than four decades. Important efforts have been more recently achieved for the development of advanced materials and, to a lesser extent, on process engineering studies. A state-of-the-art analysis is proposed with a critical comparison to gas absorption technology, which is still considered as the best available technology for this application. The possibilities offered by high-performance membrane materials (zeolites, Carbon Molecular Sieves, Metal Oxide Frameworks, graphenes, facilitated transport membranes, etc.) are discussed in combination to process strategies (multistage design, hybrid processes, energy integration). The future challenges and open questions of membranes for carbon capture are finally proposed.

Transient Effects Caused by Gas Depletion during Carbon Dioxide Electroreduction

The novel use of carbon dioxide (CO₂) electroreduction to generate carbon-based products which do not contribute to the greenhouse effect has promoted the vision of carbon dioxide as a renewable feedstock for future clean fuel production. Depending on the material choice for the electrocatalysis, a certain variety of products is expected from the carbon dioxide reduction reaction (CO2RR). However, as the CO₂ concentration in areas close to the working electrode (relative to the diffusive boundary layer) decreases as it is being consumed and transformed into other products, the generation of H₂ is favored to the detriment of CO₂ electroreduction. Therefore, the extent to which H₂ is produced can be used as a metric to evaluate the efficiency of CO2RR. This article proposes a model that accounts for the modes in which aqueous gas depletion evolves over time and affects the long-term CO₂ electroreduction and the corresponding pH evolution near the electrode's surface. For the latter, two main contributions are distinguished: gas depletion due to CO₂ consumption and ion generation in areas close to the electrocatalyst surface. pH is then suggested as an accurate and indirect means to measure CO₂ concentration in a liquid electrolyte. We conclude that CO₂ depletion causes a strong decay in the electrochemical reaction efficiency. In the end, we discuss several methods which may delay the onset of the adverse effects caused by gas depletion, such as the utilization of pulsed electroreduction, cycling the applied current to electrodes on and off periodically.

Membrane Processes for Direct Carbon Dioxide Capture From Air: Possibilities and Limitations

The direct capture of CO2 from air (DAC) has been shown a growing interest for the mitigation of greenhouse gases but remains controversial among the engineering community. The high dilution level of CO2 in air (0.04%) indeed increases the energy requirement and cost of the process compared to carbon capture from flue gases (with CO2 concentrations around 15% for coal power plants). Until now, solid sorbents (functionalized silica, ion exchange resins, metal–organic frameworks, etc.) have been proposed to achieve DAC, with a few large-scale demonstration units. Gas-liquid absorption in alkaline solutions is also explored. Besides adsorption and absorption, membrane processes are another key gas separation technology but have not been investigated for DAC yet. The objective of this study is to explore the separation performances of a membrane unit for CO2 capture from air through a generic engineering approach. The role of membrane material performances and the impact of the operating conditions of the process on energy requirement and module production capacity are investigated. Membranes are shown to require a high selectivity in order to achieve purity in no more than two stages. The specific energy requirement is globally higher than that of the adsorption and absorption processes, together with higher productivity levels. Guidelines on the possibilities and limitations of membranes for DAC are finally proposed.

High-temperature CO2 perm-selectivity of yttrium-doped SDC ceramic–carbonate dual-phase membranes

New Y-doped SDC ceramic–carbonate dual-phase membranes were prepared, characterized and evaluated, presenting high CO₂ perm-selective properties.

Powering the next industrial revolution: transitioning from nonrenewable energy to solar fuels via CO2 reduction

Solar energy has been used for decades for the direct production of electricity in various industries and devices; however, harnessing and storing this energy in the form of chemical bonds has emerged as a promising alternative to fossil fuel combustion. The common feedstocks for producing such solar fuels are carbon dioxide and water, yet only the photoconversion of carbon dioxide presents the opportunity to generate liquid fuels capable of integrating into our existing infrastructure, while simultaneously removing atmospheric greenhouse gas pollution. This review presents recent advances in photochemical solar fuel production technology. Although efforts in this field have created an incredible number of methods to convert carbon dioxide into gaseous and liquid fuels, these can generally be classified under one of four categories based on how incident sunlight is utilised: solar concentration for thermoconversion (Category 1), transformation toward electroconversion (Category 2), natural photosynthesis for bioconversion (Category 3), and artificial photosynthesis for direct photoconversion (Category 4). Select examples of developments within each of these categories is presented, showing the state-of-the-art in the use of carbon dioxide as a suitable feedstock for solar fuel production.

Solar energy has been used for decades for the direct production of electricity in various industries and devices. However, harnessing and storing this energy in the form of chemical bonds has emerged as a promising alternative to fossil fuels.

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.

Parametric Process Design and Economic Analysis of Post-Combustion CO2 Capture and Compression for Coal- and Natural Gas-Fired Power Plants

For the envisaged large number of commercial-scale carbon capture and storage (CCS) projects that are to be implemented in the near future, a number of issues still need to be resolved, the most prominent being the large capital and operational costs incurred for the CO2 capture and compression process. An economic assessment of the capture and compression system based on optimal design data is important for CCS deployment. In this paper, the parametric process design approach is used to optimally design coal and natural gas monoethanolamine (MEA)-based post-combustion CO2 absorption–desorption capture (PCC) and compression plants that can be integrated into large-scale 550 MW coal-fired and 555 MW natural gas combined cycle (NGCC) power plants, respectively, for capturing CO2 from their flue gases. The study then comparatively assesses the energy performance and economic viabilities of both plants to ascertain their operational feasibilities and relative costs. The parametric processes are presented and discussed. The results indicate that, at 90% CO2 capture efficiency, for the coal PCC plant, with 13.5 mol.% CO2 in the inlet flue gas, at an optimum liquid/gas ratio of 2.87 kg/kg and CO2 lean loading of 0.2082 mol CO2/mol MEA, the CO2 avoidance cost is about $72/tCO2, and, for the NGCC PCC plant, with 4.04 mol.% CO2 in the inlet flue gas, at an optimum liquid/gas ratio of 0.98 kg/kg and CO2 lean loading of 0.2307 mol CO2/mol MEA, the CO2 avoidance cost is about $94/tCO2.

Simulating CO2 leakage from sub-seabed storage to determine metal toxicity on marine bacteria

CO₂ storage in sub-seabed marine geological formations has been proposed as an adequate strategy to mitigate high CO₂ concentration from the atmosphere. The lack of knowledge about the potential risks of this technology on marine bacteria population in presence of metals has lead us to perform laboratory-scale experiments in order to evaluate its consequences. Thus, the effects of Zn and Cd were studied under acid conditions on Roseobacter sp. and Pseudomonas litoralis. Bacterial abundance (cellsmL^-1), growth rates (μ, h^-1), relative inhibitory effects of CO₂ (RI_CO2), and production of Extracellular Polysaccharides Substances (EPS) (μgGlucosecells^-1) were evaluated. A decreasing exopolysaccharides (EPS) production was found under low pH. Bacterial abundance as well as growth rates showed negative effects. Data obtained in this work are useful to determine the potential effects associated with enrichment of CO₂ and metals on the marine ecosystem.

Structure–activity relationships of Cu–ZrO2 catalysts for CO2 hydrogenation to methanol: interaction effects and reaction mechanism

A systematic study on the Cu–ZrO₂ catalysts with different oxygen vacancy concentrations and interaction gives a new approach for understanding the reaction mechanism of CO₂ hydrogenation to methanol.

Impact of high pCO2 on shell structure of the bivalve Cerastoderma edule

Raised atmospheric emissions of carbon dioxide (CO2) result in an increased ocean pCO2 level and decreased carbonate saturation state. Ocean acidification potentially represents a major threat to calcifying organisms, specifically mollusks. The present study focuses on the impact of elevated pCO2 on shell microstructural and mechanical properties of the bivalve Cerastoderma edule. The mollusks were collected from the Baltic Sea and kept in flow-through systems at six different pCO2 levels from 900 μatm (control) to 24,400 μatm. Extreme pCO2 levels were used to determine the effects of potential leaks from the carbon capture and sequestration sites where CO2 is stored in sub-seabed geological formations. Two approaches were combined to determine the effects of the acidified conditions: (1) Shell microstructures and dissolution damage were analyzed using scanning electron microscopy (SEM) and (2) shell hardness was tested using nanoindentation. Microstructures of specimens reared at different pCO2 levels do not show significant changes in their size and shape. Likewise, the increase of pCO2 does not affect shell hardness. However, dissolution of ontogenetically younger portions of the shell becomes more severe with the increase of pCO2. Irrespective of pCO2, strong negative correlations exist between microstructure size and shell mechanics. An additional sample from the North Sea revealed the same microstructural-mechanical interdependency as the shells from the Baltic Sea. Our findings suggest that the skeletal structure of C. edule is not intensely influenced by pCO2 variations. Furthermore, our study indicates that naturally occurring shell mechanical property depends on the shell architecture at μm-scale.

High-throughput screening of metal-porphyrin-like graphenes for selective capture of carbon dioxide

Nanostructured materials, such as zeolites and metal-organic frameworks, have been considered to capture CO2. However, their application has been limited largely because they exhibit poor selectivity for flue gases and low capture capacity under low pressures. We perform a high-throughput screening for selective CO2 capture from flue gases by using first principles thermodynamics. We find that elements with empty d orbitals selectively attract CO2 from gaseous mixtures under low CO2 pressures (~10(-3) bar) at 300 K and release it at ~450 K. CO2 binding to elements involves hybridization of the metal d orbitals with the CO2 π orbitals and CO2-transition metal complexes were observed in experiments. This result allows us to perform high-throughput screening to discover novel promising CO2 capture materials with empty d orbitals (e.g., Sc- or V-porphyrin-like graphene) and predict their capture performance under various conditions. Moreover, these findings provide physical insights into selective CO2 capture and open a new path to explore CO2 capture materials.

Simulating CO₂ leakages from CCS to determine Zn toxicity using the marine microalgae Pleurochrysis roscoffensis

Due to the current climate change and ocean acidification, a new technology for CO2 mitigation has been proposed, the Carbon dioxide Capture and Storage (CCS). However, there is an ecological risk associated with potential CO2 leakages from the sub-seabed storages sites. To evaluate the effects related to CO2 leakages, laboratory-scales experiments were performed using the marine microalgae Pleurochrysis roscoffensis. Five Zn concentrations were tested at different pHs to study Zn toxicity under acidified conditions. Seawater was collected and submitted to acidification by means of CO2 injection and by HCl addition. Results showed differences between both acidification techniques: while microalgae growth was enhanced by CO2 supply, reaching the optimal growth at pH 6.5 and full inhibition at pH 5.5, HCl acidification growth was inhibited at pH 6.5. Although small concentrations of Zn were positive for P. roscoffensis growth, Zn toxicity increased at lower pHs, and more severely on samples acidified with HCl. The conclusions obtained in this work are useful to address the potential effects on the marine ecosystem related to changes in metal bioavailability during CO2 leakages scenarios.

Development Trends in Porous Adsorbents for Carbon Capture

Accumulation of greenhouse gases especially CO2 in the atmosphere leading to global warming with undesirable climate changes has been a serious global concern. Major power generation in the world is from coal based power plants. Carbon capture through pre- and post- combustion technologies with various technical options like adsorption, absorption, membrane separations, and chemical looping combustion with and without oxygen uncoupling have received considerable attention of researchers, environmentalists and the stake holders. Carbon capture from flue gases can be achieved with micro and meso porous adsorbents. This review covers carbonaceous (organic and metal organic frameworks) and noncarbonaceous (inorganic) porous adsorbents for CO2 adsorption at different process conditions and pore sizes. Focus is also given to noncarbonaceous micro and meso porous adsorbents in chemical looping combustion involving insitu CO2 capture at high temperature (>400 °C). Adsorption mechanisms, material characteristics, and synthesis methods are discussed. Attention is given to isosteric heats and characterization techniques. The options to enhance the techno-economic viability of carbon capture techniques by integrating with CO2 utilization to produce industrially important chemicals like ammonia and urea are analyzed. From the reader's perspective, for different classes of materials, each section has been summarized in the form of tables or figures to get a quick glance of the developments.

Mesoporous carbon adsorbents from melamine-formaldehyde resin using nanocasting technique for CO2 adsorption

Mesoporous carbon adsorbents, having high nitrogen content, were synthesized via nanocasting technique with melamine-formaldehyde resin as precursor and mesoporous silica as template. A series of adsorbents were prepared by varying the carbonization temperature from 400 to 700°C. Adsorbents were characterized thoroughly by nitrogen sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), elemental (CHN) analysis, Fourier transform infrared (FTIR) spectroscopy and Boehm titration. Carbonization temperature controlled the properties of the synthesized adsorbents ranging from surface area to their nitrogen content, which play major role in their application as adsorbents for CO2 capture. The nanostructure of these materials was confirmed by XRD and TEM. Their nitrogen content decreased with an increase in carbonization temperature while other properties like surface area, pore volume, thermal stability and surface basicity increased with the carbonization temperature. These materials were evaluated for CO2 adsorption by fixed-bed column adsorption experiments. Adsorbent synthesized at 700°C was found to have the highest surface area and surface basicity along with maximum CO2 adsorption capacity among the synthesized adsorbents. Breakthrough time and CO2 equilibrium adsorption capacity were investigated from the breakthrough curves and were found to decrease with increase in adsorption temperature. Adsorption process for carbon adsorbent-CO2 system was found to be reversible with stable adsorption capacity over four consecutive adsorption-desorption cycles. From three isotherm models used to analyze the equilibrium data, Temkin isotherm model presented a nearly perfect fit implying the heterogeneous adsorbent surface.