CO2 Gas Research Articles

CO2 Hydrogenation on Ru Single-Atom Catalyst Encapsulated in Silicalite: a DFT and Microkinetic Modeling Study.

The critical levels of CO2 emissions reached in the past decade have encouraged researchers into finding techniques to reduce the amount of anthropogenic CO2 expelled to the atmosphere. One possibility is to capture the produced CO2 from the source of emission or even from air (i.e., direct air capture) by porous materials (e.g., zeolites and MOFs). Among the different usages of captured CO2, its conversion into light fuels such as methane, methanol, and formic acid is essential for ensuring the long-awaited circular economy. In the last years, single-atom catalysts encapsulated in zeolites have been considered to this purpose since they exhibit a high selectivity and activity with the minimum expression of catalytic species. In this study, a detailed mechanism composed by 47 elementary reactions, 42 of them in both forward and reverse directions and 5 of them that correspond to the desorption of gas products just forwardly studied), has been proposed for catalytic CO2 hydrogenation over Ru SAC encapsulated in silicate (Ru1@S-1). Periodic density functional theory (DFT) calculations along with microkinetic modeling simulations at different temperatures and pressures were performed to evaluate the evolution of species over time. The analysis of the results shows that carbon monoxide is the main gas produced, followed by formic acid and formaldehyde. The rate analysis shows that CO(g) is formed mainly through direct dissociation of CO2 (i.e., redox mechanism), whereas COOH formation is assisted by OH. Moreover, the Campbell's degree of rate control analysis suggests that the determining steps for the formation of CO(g) and CH2O(g) gas species are their own desorption processes. The results obtained are in line with recent experimental and theoretical results showing that Ru1 SACs are highly selective to CO(g), whereas few atom clusters as Ru4 increase selectivity toward methane formation.

Enhancement of CO gas sensing with ZnO nanostructures on MWCNTs films

CO gas sensing properties of 1-D ZnO nanostructures deposited on films of Multi-Wall carbon nanotubes were investigated using a vapor transport approach. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray, Raman spectroscopy, diffused reflectance spectroscopy, and photoluminescence, techniques were used to carry out the structural, morphological, and optical characterizations. The development of carbon-doped hybrid MWCNTs/ZnO nanostructures was demonstrated by the current results. The synthesized nanostructures were dense tapering belts and pedal-like crystalline structures as evidenced by their structural and morphological characteristics. Multiple networks of pure ZnO and hybrid MWCNTs-ZnO nanostructures were used to synthesize the gas sensors. Doped ZnO nanostructures sensing technique for CO gas detection was investigated in the present study. The combined impact of ZnO and MWCNTs was shown to be beneficial in boosting the response towards CO gas, as the response to CO gas at a concentration of 20 parts per million (ppm) was found to be five-times greater than that of ZnO sensors with good stability.

Assessing the sensing performance of Janus transition metal dichalcogenides (ScSSe, TiSSe and ZrSSe) for oxygen-containing toxic gas molecules such as CO, NO, NO2 and SO2

In this study, the adsorption behavior and sensing capabilities of oxygen-containing gas molecules (CO, NO, NO2, SO2) on Janus ScSSe, TiSSe, and ZrSSe nanosheets have been investigated by using Density Functional Theory (DFT). In order to find the most stable site, two sites (S site and Se site) of the nanosheets have been chosen for gas adsorption. The adsorption energy, charge transfer, work function, and electronic properties have been examined to understand the adsorption behavior. The results show chemisorption for CO, NO, and NO2 gas molecules on ScSSe, at the Sc site with energy −1.52, −1.61 and −1.41 eV respectively. Unlike ScSSe, both TiSSe and ZrSSe show weak physisorption with energy ranges from −0.09 to −0.29 eV, and −0.07 to −0.22 eV respectively. Band structures and Density of States (DOS) indicate the metallic behavior of the nanosheets. Furthermore, the recovery times for CO, NO, and NO2 gas molecules on ScSSe have also been calculated and found that in second range. In the work function calculation, the reduction of work function has been observed after adsorption of CO, NO and NO2 on the ScSSe. Therefore, Janus ScSSe stands out as a promising candidate for detecting CO, NO, and NO2 gas molecules.

Mixed matrix membranes incorporated with small pore zeolite UZM-5 for enhanced CO2/CH4 separation

Mixed matrix membranes (MMMs), which is polymeric matrix incorporated with inorganic filler materials, appear to be potential candidate for CO2 separation. Current work focuses on fabrication of MMMs incorporated with varying loading of small pore zeolite UZM-5 and modified UZM-5 for CO2/CH4 separation. Zeolite UZM-5 was firstly synthesized and then modified by using 3-aminopropyltriethoxysilane (APTES). MMMs was fabricated by incorporating zeolite UZM-5 and modified UZM-5 (NH2-UZM-5) into polysulfone (PSF) matrix. Both modified and unmodified zeolite UZM-5 were characterized via Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscope (FESEM) and Brunauer-Emmett-Teller (BET) analysis. The fabricated membranes were characterized using FTIR, XRD, TGA and FESEM analysis. The successful synthesis of zeolite UZM-5 was proven by XRD analysis. FESEM analysis of the membranes revealed that the successful the MMMs were successfully fabricated with even distribution of zeolites in the polymer matrix. In CO2 and CH4 gas permeation and separation study for the membranes, the highest CO2/CH4 ideal selectivity of 33.1 was obtained by the MMMs with 1 % NH2-UZM-5, which was a significant enhancement of 212 % in CO2/CH4 ideal selectivity as compared to the pristine PSF membrane.

Energy mechanism of gas channeling channels in complex fracture networks for CO2 injection in ultra-low permeability reservoirs

The injection of CO2 into ultra-low permeability can enhance production as well as accomplish storage of carbon. However, the gas channeling phenomenon is serious and there is a lack of explanation of the energy mechanism. Based on the current state of CO2 gas channeling in the Y29-105 well group located in the Huang 3 block of Jiyuan Oilfield, this study utilises the ABAQUS finite element cohesion model to explore the mechanical evolution of the CO2 channel expansion process. And according to the size of the cross-flow channel, intra-fracture pressure, damage displacement and expansion pressure, it is divided into the unconnected stage, the inter-well connected stage and the well group connected stage. Furthermore, we also established energy judgment criteria for the expansion behaviour of gas channeling channels, including stopping at natural fractures, extending along natural fractures, and directly crossing natural fractures. Upon comparison with theoretical and experimental results, it was determined that the energy discrimination criterion is appropriate for expansion along natural fractures and cross natural fractures. It can be seen that our research results can offer energy mechanism support for preventing, controlling, and predicting large-scale CO2 injection in ultra-low permeability reservoirs.

Preventive effects of transcutaneous CO2 application on disuse osteoporosis and muscle atrophy in a rat hindlimb suspension model

We previously demonstrated that transcutaneous CO2 application promotes muscle fiber-type switching, fracture healing, and osteogenesis by increasing blood flow and angiogenesis. Here, we aimed to investigate the preventive effects of transcutaneous CO2 application on disuse osteoporosis and muscle atrophy in a rat hindlimb suspension model. Eleven-week-old male Sprague-Dawley rats were divided into hindlimb suspension (HS), HS with transcutaneous CO2 application (HSCO2), and control groups. HSCO2 rats were administered transcutaneous 100 % CO2 gas in their bilateral hindlimbs, five times a week for 20 min. After 3 weeks, we harvested the gastrocnemius, femur, and tibia for assessment. Histological analysis revealed a significant decrease in the gastrocnemius myofiber cross-sectional area in HS rats compared to the control rats, whereas HSCO2 rats exhibited a significant increase compared to HS rats. Micro-computed tomography showed significant bone atrophy in the trabecular and cortical bones of the femur in HS rats compared to those of the control rats, whereas significant improvement was noted in HSCO2 rats. Histological analysis of the proximal tibia revealed more marrow adipose tissue in the HS rats than in the control rats. However, in the HSCO2 rats, fewer marrow adipose tissue and osteoclasts were observed. Moreover, HSCO2 rats had more osteoblasts and higher expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and vascular endothelial growth factor (VEGF) than the HS rats. The gastrocnemius and distal femur of HSCO2 rats also exhibited elevated PGC-1α and VEGF expression and upregulation of the myogenesis markers and osteogenesis markers compared to those of HS rats. This treatment effectively prevented disuse osteoporosis and muscle atrophy by promoting local angiogenesis and blood flow. PGC-1α is crucial for promoting this angiogenic pathway. Transcutaneous CO2 application may be a novel preventive procedure for disuse osteoporosis and muscle atrophy, complementing medication and rehabilitation.

Insights into the catalytic mechanism of calcium species during char-H2O/CO2 gasification based on molecular reaction dynamics

Calcium has a definite catalytic effect in char gasification and affects the distribution and composition of gasification products. Therefore, a deep understanding of the reaction properties and mechanism of calcium in gasification is of great significance for the gasification process. Reactive Force Field Molecular Dynamics (ReaxFF MD), an approach for exploring complex chemical reactions, has provided an indispensable aid to the insightful study of the reaction properties of calcium in coal gasification processes. In this work, ReaxFF MD was adopted to construct gasification reactions with different conditions, and the effect of calcium on the products during the gasification was investigated by counting the distribution of the gasification products as well as the changes of calcium species in different conditions. At the same time, the catalytic mechanism of calcium in char during gasification was further investigated by calculating the charge and electrostatic potential of the gasification agent and the gasification agent after calcium binding, as well as the radial distribution function between different atoms. Research has shown that during gasification, the release of calcium from char combined with oxygen atoms in the gasifying agent leads to a decrease in the O–H or C=O bond energy, which promotes the cracking of the gasifying agent. It is worth noting that in comparison to CO2, Ca can easily form ionic bonds with O in the H2O molecule during the gasification process, which leads to easier breaking of the O–H bonds.

Assessing sediment CO2 effluxes in the coastal ecosystem of North Sumatra, Indonesia

Coastal wetlands including mangrove play a vital role in regulating the local and global carbon cycle. Coastal areas contribute greatly to the carbon exchange process due to the complex interactions that occur between the atmosphere, land, and oceans. One of the important components in coastal carbon dynamics is CO2 gas exchange between soil, water and the atmosphere. This study aims to assess CO2 efflux across various land covers (namely natural mangrove, restored mangrove, and converted mangroves to oil palm and aquaculture pond) in the coastal areas of North Sumatra Province, and analyze the effect of sea tides and ebbs on the rate of CO2 efflux and their connection with the number and area of macrozoobenthos burrows. We applied direct sampling by using the static closed chamber method attached to portable CO2 analyzer. The mean of CO2 efflux in natural mangrove forest land covers was 866±585 mgCO2/m2/h during low tide conditions and 1137±792 mgCO2/m2/h during high tide conditions, followed by oil palm plantations at 760.71±341 mgCO2/m2/h, restored mangroves during low tide of 575.24±326 mgCO2/m2/h and 597.11±180 mg CO2/m2/h during high tide conditions, and the lowest was recorded in ponds at 588.55±358 mgCO2/m2/h. Further, we observed that tidal conditions affect the magnitudes of CO2 efflux in natural and restored mangrove forests, and we did not observe similar pattern in oil palms and ponds since these land covers were not influenced by regular tidal input. We also observed that no significant relationship between the number and area of macrozoobenthos burrows and CO2 efflux. Our findings suggest that CO2 effluxes in coastal wetlands are highly dynamic and presumably driven by complex factors and therefore, understanding their magnitudes and drivers requires extensive measurement covering large spatial and temporal scales.

14C AMS measurement of CO2 samples with the high throughput HVE gas interface system

Abstract The newly designed HVE gas interface enables the AMS measurement of carbon samples in CO2 form. The CO2, e.g. resulting from the sample combustion in an elemental analyzer, is adsorbed in a zeolite trap and subsequently transferred to a motor-driven syringe. Once diluted with He, the gas mixture is transferred into the ion source of the AMS system. A carbon ion beam is formed in the ion source and mass-analyzed by the AMS system, resulting in 13C/12C and 14C/12C isotopic ratios. The HVE gas interface features two traps and two syringes to maximize the sample throughput, which results in more than 10 samples per hour. The first performance results of CO2 gas sample AMS measurements that were performed with the HVE gas interface in combination with the HVE 210 kV AMS system are presented in this paper. The measurements show that the gas interface contribution to the 14C/12C background is in the 10–15 level and to the precision is at or below 1%.

A Sensor Probe with Active and Passive Humidity Management for In Situ Soil CO2 Monitoring.

Soil CO2 concentration and flux measurements are important in diverse fields, including geoscience, climate science, soil ecology, and agriculture. However, practitioners in these fields face difficulties with existing soil CO2 gas probes, which have had problems with high costs and frequent failures when deployed. Confronted with a recent research project's need for long-term in-soil CO2 monitoring at a large number of sites in harsh environmental conditions, we developed our own CO2 logging system to reduce expense and avoid the expected failures of commercial instruments. Our newly developed soil probes overcome the central challenge of soil gas probes-surviving continuous exposure to soil moisture while remaining open to soil gases-via three approaches: a 3D printed housing (economical for small-scale production) following design principles that correct the usual water permeability flaw of 3D printed materials; passive moisture protection via a hydrophobic, CO2-permeable PTFE membrane; and active moisture protection via a low-power micro-dehumidifier. Our CO2 instrumentation performed well and yielded a high-quality dataset that includes signals related to a prescribed fire as well as seasonal and diel cycles. We expect our technology to support underground CO2 monitoring in fields where it is already practiced and stimulate its expansion into diverse new fields.

Exploring MOF-Derived CuO/rGO Heterostructures for Highly Efficient Room Temperature CO2 Sensors.

In response to the urgent need for advanced climate change mitigation tools, this study introduces an innovative CO2 gas sensor based on p-p-type heterostructures designed for effective operation at room temperature. This sensor represents a significant step forward, utilizing the synergistic effects of p-p heterojunctions to enhance the effective interfacial area, thereby improving sensitivity. The incorporation of CuO nanoparticles and rGO sheets also optimizes gas transport channels, enhancing the sensor's performance. Our CuO/rGO heterostructures, with 5 wt % rGO, have shown a notable maximum response of 39.6-500 ppm of CO2 at 25 °C, and a low detection limit of 2 ppm, indicating their potential as high-performance, room-temperature CO2 sensors. The prepared sensor demonstrates long-term stability, maintaining 98% of its initial performance over a 30-day period when tested at 1-day intervals. Additionally, the sensor remains stable under conditions of over 40% relative humidity. Furthermore, a first-principles study provides insights into the interaction mechanisms with CO2 molecules, enhancing our understanding of the sensor's operation. This research contributes to the development of CO2 monitoring solutions, offering a practical and cost-effective approach to environmental monitoring in the context of global climate change efforts.

Study of soil heterotrophic respiration as a function of soil moisture under different land covers

The relationship between soil heterotrophic respiration (Rh) and soil moisture has been often studied using disturbed soil samples and simple gravimetric and volumetric soil moisture indicators. The objective of this study was to investigate the relationship between Rh and soil moisture in terms of water-filled porosity (WFP), matric potential (Ψm), and relative soil gas diffusivity (Dp/Do) using undisturbed soil cores obtained under different land covers. Soil CO2 efflux, WFP, and Ψm were measured in undisturbed soil samples (250 cm3) collected in the 0–5 cm soil layer (without any vegetation or living roots) under laboratory conditions by combining a CO2 gas analyzer, a scale, and precision mini-tensiometers. For each site and land cover, we also measured soil chemical properties, soil physical properties, and soil microbial composition using phospholipid fatty acid analysis. Grassland soils had the largest total microbial biomass (6275 ng g−1), followed by soils from riparian (5327 ng g−1), and cropland (2745 ng g−1) sites. Bacteria were the dominant group representing 46% (SD = 5%) of the total microbial biomass across all sites and land covers. Maximum Rh was 1.88 (SD = 0.40) μmol CO2 m−2 s−1 in grassland, 1.64 (SD = 0.82) μmol CO2 m−2 s−1 in riparian, and 0.94 (SD = 0.56) μmol CO2 m−2 s−1 in cropland soils. Considering all land cover and soil types, our observations revealed that peak Rh occurred at mean WFP = 0.81 ,Ψm = −6 kPa, and Dp/Do = 0.003. Thus, we recommend avoiding the traditional field capacity definition of −33 kPa for representing peak microbial activity. Water-filled porosity was a more consistent predictor of Rh than Ψm or Dp/Do across soils with contrasting organic matter content, total microbial biomass, soil texture, and soil structure.

Tailoring the local catalytic microenvironment of metal centers NH2 groups to enhance the CO2RR performance of Ni based catalysts

Efficient catalytic reduction of the main greenhouse gas CO2 into high value-added chemicals is an important measure to alleviate the greenhouse effect and energy depletion. Metal nitrogen (M-N4) macrocyclic complexes have attracted increasing attention in the field of electrocatalytic CO2 reduction (CO2RR) due to the precise adjustment of the catalytic active site according to the requirements and the flexible modification of the external ligand structure. Nevertheless, the poor activity and low selectivity of reduction products restrict their widespread application in electrocatalytic CO2RR. Herein, a combination of nanoscale and molecular level method has been developed to construct easily obtainable 4NH2-NiPc/NH2-CNT hybrid material, in which amino groups are connected to provide electrons toward the central Ni-N4 site to promote the electrocatalytic CO2RR catalytic activity. As a result, the catalyst 4NH2-NiPc/NH2-CNT mainly produces CO in the electrocatalytic CO2RR, which exhibits a Faradaic efficiency of CO (FECO) higher than 92 % within a wide overpotential range of −0.70 to −0.95 V vs. RHE, and provides excellent stability with a current density of 12 mA cm−2 at −0.80 V vs. RHE. In addition, 4NH2-NiPc/NH2-CNT reaches its maximum FECO value of 96 % at −0.8 V vs. RHE, which is approximately 3.1 times that of the original unmodified NiPc/CNT, demonstrating excellent promotion of electrochemical performance. Similarly, compared to NiPc/CNT without amino modification, the current density of 4NH2-NiPc/NH2-CNT exceeds it by more than twice. The research results indicate that promoting role of electron substituted amino groups in catalysis dispersion and electronic environment coordination. This study proposes a promising strategy of introducing amino groups into molecular catalysts and hybridizing with carbon nanotube to enhance the electrocatalytic conversion of CO2 to deep reduction products.

Investigating the Relationship between Urbanization and Air Pollution Using Google Earth Engine Platform: A Case Study of Istanbul

Rapid population growth in megacities such as Istanbul has led to various effects, such as industrialization, urbanization, loss of green areas, increasing vehicle traffic, and higher consumption of fossil fuels. These reasons, along with many other environmental factors, contribute to the rise of air pollution in urban life. This study aimed to examine the relationship between urbanization and air pollution in Istanbul. For this purpose, land cover maps covering Istanbul province were produced using Landsat-5 (TM), Landsat-8 (OLI), and Sentinel-2 (MSI) images for the years 1996 to 2021 at three-year intervals on the Google Earth Engine platform. Land cover for classification purposes was divided into five different classes: forest, water surface, urban area, and bare land, and classified using a random forest machine learning algorithm. To examine the impact of this urban area growth on air pollution, in the second step of the study, the column number density values of Sentinel 5P (TROPOMI) data for SO2, NO2, CO, and O3 gases for 2019, 2020, and 2021 were analyzed. The averages of the data from 39 air pollution monitoring stations across Istanbul were also examined. According to this classification, the urban area expanded from 491 km2 in 1996 to 1222 km2 by 2021. Considering the total surface area of Istanbul province, the urban area, which was 9% in 1996, reached 23% by 2021. The TROPOMI values were calculated as follows: the average column number density values for SO2, NO2, CO, and O3 were 0.0003538 mol/m², 0.0339514 mol/m², 0.0000984 mol/m², and 0.1453515 mol/m², respectively. Similarly, the gas concentrations of SO2, NO2, CO, and O3 measured from the ground stations were calculated as 6.603 µ/m3, 786,815 µ/m3, 43.763 µ/m3 and 45.773 µ/m3, respectively. Correlations between urbanization and TROPOMI values revealed a positive correlation of 0.39, 0.02, and 0.80 for SO2, NO2, and CO gases, while a negative correlation of 0.25 was found for O3 gas. The study also examined correlations between TROPOMI and ground station measurements, resulting in positive correlations of 0.55, 0.66, and 0.16 for SO2, NO2, and CO gases, respectively, while a negative correlation of 0.05 was found for O3 gas. Based on these findings, among the air pollutants studied both through TROPOMI and ground station data, the highest correlation was observed for CO gas.

The Effect of CO on the Exothermic Characteristics of Low-Temperature Oxidation in Coal

ABSTRACT In recent years, abnormally high concentrations of CO gas have often been detected in goaf areas of coal mines in China, which have posed a serious threat to safe production in coal mines and the life and safety of underground personnel. The effect of CO on the exothermic characteristics of low-temperature oxidation in coal was studied by analyzing the exothermic characteristics, heat release, oxidation stages, and activation energy of coal at different CO concentrations using a C600 microcalorimeter. The experimental results indicated that CO promoted the coal oxidation at low temperature, but inhibited it after reaching 144°C. When the CO concentration is 30%, the exothermic characteristics of coal in low-temperature oxidation adsorption stage were significantly affected, with the heat flow value decreased by 27.0% and the initial exothermic temperature point moved forward by 3.9 K. In the later stage of the oxidation reaction, the heat release of coal was linearly negatively correlated with CO concentration. The higher the concentration, the lower the heat release. These findings contribute to understanding the combustion mechanism of coal in high-concentration CO atmosphere and provide valuable insights for designing and optimizing coal utilization technologies.

Exploitation of Pore Structure for Increased CO2 Selectivity in Type 3 Porous Liquids.

CO2 capture requires materials with high adsorption selectivity and an industrial ease of implementation. To address these needs, a new class of porous materials was recently developed that combines the fluidity of solvents with the porosity of solids. Type 3 porous liquids (PLs) composed of solvents and metal-organic frameworks (MOFs) offer a promising alternative to current liquid carbon capture methods due to the inherent tunability of the nanoporous MOFs. However, the effects of MOF structural features and solvent properties on CO2-MOF interactions within PLs are not well understood. Herein experimental and computational data of CO2 gas adsorption isotherms were used to elucidate both solvent and pore structure influences on ZIF-based PLs. The roles of the pore structure including solvent size exclusion, structural environment, and MOF porosity on PL CO2 uptake were examined. A comparison of the pore structure and pore aperture was performed using ZIF-8, ZIF-L, and amorphous-ZIF-8. Adsorption experiments here have verified our previously proposed solvent size design principle for ZIF-based PLs (1.8× ZIF pore aperture). Furthermore, the CO2 adsorption isotherms of the ZIF-based PLs indicated that judicious selection of the pore environment allows for an increase in CO2 selectivity greater than expected from the individual PL components or their combination. This nonlinear increase in the CO2 selectivity is an emergent behavior resulting from the complex mixture of components specific to the ZIF-L + 2'-hydroxyacetophenone-based PL.

A comprehensive mathematical model considering multiple mechanisms for CO2 displacement of methane in shale nanopores

With the rise in energy demand, shale gas exploitation has gained prominence, particularly through the use of carbon dioxide (CO2) injection for enhanced gas recovery. However, the intricate gas flow mechanisms within this process in shale nano-pores remain poorly understood, which greatly limited the accurate numerical simulation of shale gas production by CO2 injection. This study investigates the flow mechanisms of CH4 and CO2 gases in shale nano-pores, developing an improved apparent relative permeability model for the two-component CH4–CO2 gas, incorporating multiple transport mechanisms. Sensitivity analysis includes factors such as pressure, pore radius, viscosity correction effects, flow mechanisms, and composition fractions. Key findings from this study are as follows: (1) Increasing pore radius or decreasing pressure enhances the apparent permeability of CH4–CO2 gas, with pressure effects becoming negligible above 20 MPa. (2) The impact of viscosity correction on gas permeability diminishes with higher pressure or larger pore radius, becoming negligible for pore radii over 10 nm. (3) Larger pore radii increase slip flow and Knudsen diffusion, while molecular and surface diffusion proportions decrease; surface diffusion and slip flow dominate at high pressures. (4) A higher CH4–CO2 component ratio increases CH4 permeability and decreases CO2 permeability, with minimal influence from pressure and pore radius. These results can improve numerical simulations for shale gas production by using CO2 injection.

Microbial and Quality Attributes of Beef Steaks under High-CO2 Packaging: Emitter Pads versus Gas Flushing.

Over 21 days of cold storage, the quality and microbial composition of beef steaks in response to different high-CO2 packaging conditions achieved by flushing gas mixtures or embedding gas emitters into the packages were studied. The results revealed that the high levels of CO2, achieved by either the gas flushing or the CO2 emitter pads, effectively controlled the number of aerobic counts. The headspace CO2 increased quickly in response to using the CO2 emitter pads, and the meat samples presented different pH levels and surface color (a* and b*) values compared to the samples packaged with the gas flushing technique. Excessive accumulation of gas in the packages that contained CO2 emitters resulted in package swelling and higher levels of drip loss. The longest overall quality and attractive red color of the meat samples were observed when the packages were initially flushed with the headspace gas mixture containing high levels of oxygen. Overall, using CO2 emitters for meat packaging can be suggested when a topfilm with proper permeability to O2 and CO2 gases is used to regulate the internal CO2/O2 and gas/product ratios.

Multicomponent adsorption mechanism of CO2, SO2, NO, and C7H8 from flue gases on nitrogen-doped biochar: Experimental and computational insights

The comprehensive control of CO2 and gaseous pollutants in coal-fired flue gas is urgent and difficult. As a green low-cost adsorbent, nitrogen-doped biochar has potential application in the control technology of flue gas pollutants. Still, its multi-component adsorption characteristics for flue gas are unclear. In this study, the multi-component adsorption characteristics of CO2, SO2, NO, and C7H8 on nitrogen-doped biochar were explored at different temperatures (25–120 °C), and the competitive mechanism of multi-component adsorption was revealed through continuous adsorption experiments and numerical calculation. The adsorption capacities of CO2, SO2, NO, and C7H8 by nitrogen-doped biochar can reach 38.1, 78.9, 3.1, and 245.2 mg/g, among which CO2, SO2, and C7H8 show strong competitive effects. Their adsorption capacities are decreased by 42 % (CO2), 28 % (SO2), and 27 % (C7H8) respectively compared with the single-component adsorption. This is because there are not only more C7H8 adsorption sites on nitrogen-doped carbon, but also C7H8 can partially occupy the adsorption sites of SO2 and CO2 during multi-component adsorption. Combined with the calculation results of density functional theory, the competitive ability of the three gases can be ranked as follows: C7H8 > SO2 > CO2.

High stability and strong hydrophobic hindrance effect of core–shell NaX/polyacrylate composite for CO2 capture

It is well known that zeolite NaX excels at capturing CO2 in dry flue gas, but maintaining its excellent CO2 adsorption capacity in the presence of water remains a huge challenge. In order to significantly reduce the water adsorption of NaX while ensuring its high CO2 adsorption performance, a millimeter-sized spherical NaX/polyacrylate composite with a core–shell structure has been successfully developed through the structural modulation strategy. Here, NaX was uniformly crystallized inside the hydrophobic polyacrylate, and the crystal structure was in situ modulated using functionalized tetraethylenepentamine, so that the unique coupling of the two structures and functions achieves strong hydrophobic hindering performance. Compared with the pristine NaX, NaX/polyacrylate shows a 64.77 % reduction in water adsorption (25 °C, 11 % RH) of 5.20 mmol·g−1. The modulated nanocrystals expose more accessible adsorption active sites, so that the CO2 working capacity of the composite increases to 1.3 times that of NaX. To the best of our knowledge, this is the best case of a material that can retain excellent adsorption performance even after hydrophobic modification. More importantly, the CO2 capacity hardly declined in 100 adsorption–desorption cycles. This work provides a generalized solution to enhance the surface hydrophobicity of zeolite-like materials while maintaining their high CO2 adsorption capacity in practical applications.