Diffusion and sorption for carbon dioxide in Kapton at extremely low pressure

Pressure-dependent solubility and diffusion coefficients for carbon dioxide in glassy polymers have been well described using the “dual sorption and transport model.” However, the plastisization effect by high-pressure carbon dioxide seems to promote the pressure dependence of the sorption and transport coefficients. To avoid the relaxation process by the plastization which is superimposed on the diffusion process, the diffusion and sorption of carbon dioxide were measured at extremely low pressure (below 1 cmHg). Linear isotherms observed for CO₂ sorption into Kapton were interpreted in terms of the dual model equation at extremely low pressure. From the permeation curve of the Kapton/CO₂ system, the diffusion and permeation coefficients were obtained according to the usual manner, and both coefficients were independent of pressure. Sorption and transport parameters were obtained from sorption isotherms and average values of the permeation coefficients. The parameters thus obtained were substituted in an approximated dual sorption and transport equations at extremely low pressure and the pressure independence of the diffusion and permeation coefficients were sufficiently reproduced. It is a good technique to experiment at such extremely low pressure when the validity of the dual model is evaluated. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1013–1017, 1998     

A fundamental study on the removal of air pollutants (sulfur dioxide,nitrogen dioxide and carbon dioxide) by adsorption on activated carbon

Gravimetrically measured adsorption and desorption dynamics of sulfur dioxide, nitrogen dioxide and carbon dioxide on a commercial activated carbon are interpreted by a single-particle model based on three transport processes: macropore, micropore and sorbed-phase diffusion. Additional phenomena, concentration-dependent sorbed-phase diffusivity and sorbent non-isothermality, are incorporated to expand the applicability of the model. The dynamic sorption behaviour of all three gases is adequately described, without resorting to a different particle tortuosity factor for each sorbate. The value of the tortuosity factor (8) and the extracted diffusion coefficients are consistent with literature values. The affinity of the activated carbon for the adsorbates is, in increasing order, CO₂ < SO₂ < NO₂, while the extracted diffusion coefficients show the reverse trend, NO₂ < SO₂ < CO₂.     

Influence of casting and curing conditions on gas sorption and transport in polyimide films

Carbon dioxide and methane gas permeabilities, solubilities and diffusivities for poly [N, N′-(phenoxyphenyl)-pyromellitimide] films synthesized in our laboratory are contrasted with values measured for a chemically identical commercial polyimide film, Kapton H. The synthesized samples exhibited greater permeabilities, solubilities, and diffusivitles than those of the commercial sample. At the same time, the higher carbon dioxide permeability is associated with only a moderate reduction in permselectivity for the CO₂/CH₄ system. The increased sorption and transport coefficients for the synthesized sample are attributed to a lower degree of aggregation and orientation of this film as compared to the Kapton H sample.     

THE TRANSPORT OF CARBON DIOXIDE IN HIGH MOLECULAR WEIGHT BUFFER SOLUTIONS

The diffusion of carbon dioxide in biological media such as tissues and blood is an important physiological phenomenum. Transport of carbon dioxide in aqueous biological media causes, through chemical reactions, the simultaneous flux of several ionic species. The reversible reactions of CO₂ are coupled to amino acid dissociations of the protein species which have a large buffer capability. Due to the great difference in mobility of bicarbonate and protein, a diffusion potential evolves, which has a considerable influence upon the total CO₂ transport in the medium. The electrical potentials impede the carrier-facilitated CO₂transfer associated with the bicarbonate flux. New data on carbon dioxide transport in hemoglobin solutions are presented which clearly show the large reduction of CO₂ transport due to the electrical potentials. The experimental results correlate with diffusion potential data obtained previously. A theoretical model correctly predicts both the CO₂ transport and diffusion potential data as a function of The ionic composition of the solution. It is concluded that applied or electrical fields can have a significant effect on CO₂ transport in reactive biological media.     

Transport and Permeation Properties of a Ternary Gas Mixture in a Medium-Size Polysulfone Hollow Fiber Permeator

Abstract

Permeation properties were analyzed for a mixture of CO₂, O₂, and N₂ in a medium-size polysulfone hollow fiber permeator with a net permeation area of 4.22 m². Measurements were conducted as a function of feed composition, reject flow rate, and feed pressure. Results included variations in species permeability, separation factor, permeate enrichment, reject depletion, and stage cut as a function of system parameters. Variations in permeation properties show strong dependence on feed composition, reject flow rate, and feed pressure. Permeability of carbon dioxide was higher at larger feed pressures and higher carbon dioxide content in the feed stream. Effect of increasing the reject flow rates on the permeability of carbon dioxide was affected by the system pressure and the carbon dioxide content in the feed stream. At low pressures, increase of the reject flow rate resulted in a decrease of carbon dioxide permeability. The opposite behavior was obtained at higher feed pressures. Increase of the reject flow rate reduced the gas residence time within the permeator. Increase of reject flow rate reduced species residence within the permeator and in turn increased resistance to species transport within the permeator. However, higher system pressures and carbon dioxide content in the feed stream resulted in larger levels of membrane plasticization, which increased the permeation rates of all species. The combined efféct of reducing the species residence time within the permeator and the level of membrane plasticization favored the permeation of carbon dioxide versus the other two species. Variations in other permeation properties, which include oxygen and nitrogen permeabilities, stage cut, permeate enrichment in carbon dioxide, and reject depletion in carbon dioxide, were also explained in terms of resistances encountered within the permeator and the membrane.     

Temperature effects on permeation of modified atmosphere gas mixtures through a low density polyethylene package film

Permeation of CO₂ and O₂ through a low density polyethylene film was studied with CO₂-N₂ mixtures in the temperature range 263-283 K, and with CO₂-O₂-N₂ mixtures in the range 257-313 K. The temperature dependence of the permeabilities of these gases agreed with the Arrhenius expression. The activation energy for carbon dioxide diffusion was between 3.53 × 10⁴ and 3.74 × 10⁴J/mol; the activation energy for oxygen diffusion was 3.13 × 10⁴J/mol. The pre-exponential constant for oxygen was higher than that of carbon dioxide in various mixtures. It was also found that the pre-exponential constant of carbon dioxide decreased with increasing CO₂ concentration in the mixtures.     

Microstructure relaxation process of polyhexafluoropropylene after swelling in supercritical carbon dioxide

This paper studies the process of relaxation of a polymer after swelling in supercritical carbon dioxide. Polyhexafluoropropylene (PHFP) was chosen as the object for investigation. The relaxation process was monitored by a change of the permeability coefficients for a number of gases. Thin polymeric films of PHFP were modified by different treatments: drying to a constant weight, annealing at a temperature slightly higher than the glass‐transition temperature, and swelling in supercritical carbon dioxide. The permeability coefficients of six gases, He, H₂, O₂ N_2, CO₂, and CH₄, were measured after each stage of the treatment. It was shown that the permeability coefficients in the films were increased by 2.4 times for He, 3.6 for H₂, 5.9 for O₂, 8.1 for N₂, 6.7 for CO₂, and 10.9 for methane. The permeability coefficients of the same gases were measured 50 days later after swelling in supercritical carbon dioxide. A decrease in the permeability coefficient demonstrated that the relaxation process had taken place. Nevertheless, the values exceeded the initial ones for annealed samples by 2.0 times for He, 2.4 for H₂, 1.8 for O₂, 1.7 for N₂, 1.7 for CO₂, and 1.3 for methane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43105.     

Modification of ABS Membrane by PEG for Capturing Carbon Dioxide from CO2/N2 Streams

Carbon dioxide capture and storage (CCS) has been propounded as an important issue in greenhouse gas emissions control. In this connection, in the present article, the advantages of using polymeric membrane for separation of carbon dioxide from CO₂/N₂ streams have been discussed. A novel composition for fabrication of a blend membrane prepared from acrylonitrile-butadiene-styrene (ABS) terpolymer and polyethylene glycol (PEG) has been suggested. The influence of PEG molecular weight (in the range of 400 to 20000) on membrane characteristics and gas separation performance, the effect of PEG content (0–30 wt%) on gas transport properties, and the effect of feed side pressure (ranging from 1 to 8 bar) on CO₂ permeability have been studied. The results show that CO₂ permeability increases from 5.22 Barrer for neat ABS to 9.76 Barrer for ABS/PEG20000 (10 wt%) while the corresponding CO₂/N₂ selectivity increases from 25.97 to 44.36. Furthermore, it is concluded that this novel membrane composition has the potential to be considered as a commercial membrane.     

A new triaxial apparatus to study the mechanical and fluid flow aspects of carbon dioxide sequestration in geological formations

Climate scientists are practically unanimous in the belief that anthropogenic greenhouse gas contributions have added to the thickness and thus the effectiveness of the greenhouse gas layer, leading to a warming of the planet (IPCC, 2005 [1]). Engineers and scientists around the globe are researching and developing measures to reduce greenhouse gas emissions. These measures have included proposals to sequester carbon dioxide (CO₂) in deep geological formations (Perera et al., in press [18]). For CO₂ sequestration in deep geological reservoirs to become a feasible strategy to reduce greenhouse gas emissions, a sound understanding of the manner by which mechanical properties and permeability changes with the introduction of CO₂ to the geological reservoir will influence the stability of that reservoir is required. Thus there is a need to develop laboratory equipment capable of simulating the CO₂ injection and storage process for deep geological CO₂ sequestration under the expected in situ pressure (confinement and fluid) and temperature conditions. Triaxial experiment has been identified as the best method for this purpose (Perera et al., 2011b [19]). Therefore, we present a new high-pressure triaxial apparatus which can provide the high confining and fluid injection pressures and elevated temperatures expected for deep geological CO₂ sequestration. The new setup can be used to conduct mechanical and permeability testing on intact or fractured natural rock samples or synthetic rock samples subjected to high-pressure injection of up to three fluid phases (gas and/or liquid) at high pressures and temperatures corresponding to field conditions. The equipment is capable of delivering fluids to the sample at injection pressures of up to 50 MPa, confining pressures of up to 70 MPa and temperature up to 50 °C and will continuously record fluid injection and confining pressures, axial load and displacement, radial displacement and independent outflow rates for liquid and gas fluid phases (under drained conditions).Leakage tests have confirmed the effectiveness of the device at pressures up to its maximum capacities. Additionally the temperature-pressure relationship for the hydraulic oil used to apply confining pressure to the sample has been calibrated to account for the influence of changes in temperature on confining pressure. Several permeability tests (using N₂ and CO₂ as the injection fluid and 10 MPa confining pressure) and one strength test are reported for black coal samples from the Sydney Basin, New South Wales. According to the results of the permeability tests, coal mass permeability decreases with increasing effective stress for both gases. However, the permeability for N₂ gas is much higher than CO₂. Moreover, test results are consistent with matrix swelling due to the adsorption of CO₂ in coal. The strength testing results are in agreement with the results of testing carried on similar black coal samples from literature, certifying the ability for the new device to accurately measure strength and deformation properties of rock under deep ground conditions.     

Modelling permeation of modified atmosphere gas mixtures through a low density polyethylene package film

Permeation of individual gases through a low density polyethylene package film with CO₂-N₂ and CO₂-O₂-N₂ mixtures was simulated with a simple mathematical model. Permeabilities of carbon dioxide were of the order of 10 ^?12 m³/s m²atm/m with CO₂-N₂ systems. Including oxygen in the system did not change carbon dioxide permeabilities. Permeabilities of oxygen were of the order of magnitude of 10^?9m³/sm²atm/m with this system. When a CO₂-O₂-N₂ mixture was humidified no substantial change was observed in CO₂ permeability, but the O₂ permeability decreased almost 10 times. These results and the mathematical model presented may help in the modified atmosphere package design to increase the shelf life of produce.     

Mechanism of gas transport of NH3‐plasma‐treated poly(phenylene oxide) membrane

The effect of NH₃‐plasma treatment on glassy poly(phenylene oxide) (PPO) membranes on the diffusion process for carbon dioxide (CO₂), oxygen (O₂), and nitrogen (N₂) was investigated from the permeability measurements. The sorption equilibria and permeation behavior for O₂ and CO₂ in untreated PPO membranes were simulated well in terms of the dual‐mode sorption and mobility model. For O₂ transport, NH₃‐plasma treatment on PPO membrane had an influence on the diffusion process of Henry's law species, whereas for CO₂ transport, it promoted the transport of Langmuir mode, presumably through an increased Langmuir capacity constant for CO₂. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1845–1852, 2000     

The Filtration Properties of Atropa belladonna Plant Cell Suspensions; Effects of Hydrodynamic Shear and Elevated Carbon Dioxide Levels on Culture and Filtration Parameters

The filtration properties of Atropa belladonna plant cell suspensions cultured at different bioreactor stirrer speeds and gas-phase carbon dioxide levels were measured. Cell cake compressibility did not vary significantly with culture time, shear intensity or carbon dioxide concentration. Average cell cake permeability decreased by c. 70% with increasing stirrer speeds between 400 and 1000 rpm, and could be correlated with concomitant reductions in cell aggregate size. Permeability was more responsible than other culture parameters, such as growth, cell membrane integrity and protein release, to levels of hydrodynamic energy dissipation in the range 10⁶–10⁹ J m⁻³. Cell cake permeability was significantly affected by carbon dioxide levels of 10 and 15%, but not 2%. Average permeability at 15% CO₂ was reduced by c. 50% compared with the air-sparged control culture, even though aggregate size, morphological characteristics and filtered cake compressibility were unaltered. A distinctive pattern of permeability change over the course of the cultures was observed when the reactor conditions were not inhibitory to growth; however, this pattern was destroyed at medium-to-high shear levels and high carbon dioxide concentrations. © 1997 SCI.     

Permeability and separability of methane and carbon dioxide across meso-porous Mg-Al hydrotalcite and activated carbon media

Hydrotalcite and activated carbon (AC) are known to exhibit certain level of affinity for CO₂. If the materials are constructed for use as an adsorptive film or adsorbent in gas separation application, more of CO₂ can be permeated and separated from the other component gas mixture. In this study, permeability of carbon dioxide across the materials was found to increase almost linearly with increase in the respective gas flow rate but the permeability was nearly independent of pressure, attesting to their meso-porosity. The permeability remained constant at ≈6×10⁻³ mol m/m² s Pa, apparently due to the dominance of Knudsen diffusion mechanism. The separability of gas increased with increase in the inlet flow rate and pressure. Hydrotalcite film deposited on porous alumina substrate demonstrated the highest separability factor of 91, followed by bast AC (separability factor=13) and core AC (separability factor=11). Methane was found to permeate preferentially through the three porous media due to hindered diffusion of CO₂ as a result of the affinitive force attributed to high charged density in the interlayer spacing of Mg-Al hydrotalcite structures that sequestered CO₂.     

Analysis on the dyeing of polypropylene fibers in supercritical carbon dioxide

Polypropylene fibers were dyed in supercritical carbon dioxide system and the results were compared with those of fiber dyed in water system. Dye uptake value calculated by a UV spectrum indicated that polypropylene fiber dyeing was much better in carbon dioxide than in water. Optical microscopical analysis showed that dye molecules had diffused thoroughly into fiber in CO₂ because of the excellent compatibility between the dye and the CO₂. X-ray and birefrigence analysis demonstrated that plastification caused by the implementation of CO₂ made molecular chain more mobile and led to an increase in the dyeing of polypropylene fibers. Moreover a mechanical test and DSC analysis indicated that the fiber structure was not damaged when the fabric was dyed at 100 °C. Hence dyeing polypropylene using CO₂ as a transport medium was very feasible and worthy of further development.     

Effect of nanodiamond additives on the structure and gas‐transport properties of a poly(phenylene–isophtalamide) matrix

Nanodiamonds (NDs) are specific carbon nanoparticles approximately 5 nm in diameter with a large and accessible surface containing functional groups. Poly(phenylene–isophtalamide) (PA)–ND composites were prepared by solid‐phase dispersal and used for dense film formation. The PA–ND composites were analyzed by Fourier transform infrared spectroscopy. The membrane structure was determined on the basis of density measurement and morphological study by atomic force microscopy. The gas‐transport properties were measured over a wide range of temperatures from 30 to 100 °C for the following series of penetrants: H₂, N₂, O₂, and CO₂. The experimental data of gas permeability were compared with the permeability values calculated from Maxwell's model. Data on the permeability and diffusion coefficients were used to calculate the activation energies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46320.     

FACILITATED TRANSPORT OF CARBON DIOXIDE: A REVIEW

The effect of reversible chemical reaction upon the diffusion of carbon dioxide in thin liquid film membranes is reviewed. Particular emphasis is placed upon the hydration reaction of CO₂ and catalysis thereof. Theoretical analysis is developed for equilibrium, near-equilibrium and near-diffusion regimes. The important effects of weak acid buffers, proteins and amines upon CO₂ transport are also discussed, as well as the significance of diffusion potentials, particularly in the case of protein systems. Results of experimental investigations of facilitated CO₂ transport are reviewed, as well as general aspects of CO₂ transport in biological systems and absorbers.     

Modification of polycarbonate membrane by polyethylene glycol for CO2/CH4 separation

In this study, permeation of carbon dioxide (CO₂) and methane (CH₄) through the polycarbonate/polyethylene glycol (PC/PEG) blend membrane was investigated. The effect of PEG content (0–5 wt%) on the permeability and selectivity was studied. Permeability measurements were carried out at pressures of 1–7 bar and at room temperature. The membranes were characterized by Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and density measurement. The results revealed that the PC/PEG blends are miscible/partially miscible without considerable micro-phase separation. The effect of PEG content and gas pressure on the diffusion and solubility of coefficients were also investigated and analyzed. It was concluded that the most influential parameter for the permeation is the diffusion coefficient of the gases. The permeability and selectivity decrease as the operating pressure and PEG content are increased. Furthermore, the results showed that the addition of 5 wt% of PEG into PC increases the CO₂/CH₄ selectivity from 26.6 ± 0.99 to 40.9 ± 2.14 (more than 53%) at 1 bar.     

Facilitated transport of carbon dioxide through an immobilized liquid membrane of K2CO3/KHCO3 aqueous solution

The facilitated transport of CO₂ through a hydrophilic polymeric membrane immobilized with K₂CO₃/ KHCO₃ buffer solution has been investigated. The reactions of dissolved CO₂ in electrolyzed alkaline solution must consider hydration of CO₂ with water, chemical reaction of CO₂ with OH^- and dissociation of HCO ₃ ^2- into CO ₃ ^2- . It is necessary to simplify these reactions as a simple model, which is used to analyze the transport system. From experiments in the liquid membrane with alkaline buffer solution, it is shown that the flux of CO₂ into K₂CO₃KHCO₃ aqueous solution can be enhanced by the presence of CO ₃ ^2- . A diffusion model with an overall reaction based on the film theory is proposed that predicts the experimentally observed facilitation factor with reasonable accuracy. The present model is compared with the rigorous diffusion model involving the complicated conventional chemical reactions.     

Effects of preparation conditions on the morphology and gas permeation properties of polyethylene (PE) and ethylene vinyl acetate (EVA) films

In this study, the effect of film preparation conditions on the gas permeation properties of polyethylene (PE) and ethylene vinyl acetate (EVA) films (containing 18 and 28 wt% vinyl acetate) was investigated. Film blowing and phase inversion methods were applied in the production of PE and EVA films, respectively. The permeation of pure oxygen and carbon dioxide gases was measured at room temperature. The results indicated that with the increase of PE film thickness, permeability and solubility of O₂ and CO₂ in these films decreased; but the diffusivities of gases through PE films increased. In addition, in the case of EVA copolymers, by increasing the content of vinyl acetate, the permeability of CO₂ increased. The rate of increase in CO₂ permeability was different for samples having different preparation conditions. For example, the samples prepared using chloroform as the solvent instead of THF, showed lower CO₂ permeability. Also, the morphological studying of film structure indicated that the higher CO₂ permeability for the samples made from THF solvent is due to the existing of higher porosity in the under layer polymer area. Also scanning electron microscopy (SEM) micrographs showed that with the usage of phase inversion method, there will be a thin dense layer near to the glass substrate.     

The permeability of gases through reacting solutions: the carbon dioxide—bicarbonate membrane system

The transport of a gas across a stationary liquid film containing reactive species is investigated for the purpose of determining gas permeabilities or mass transfer coefficients in reacting solutions. Under limiting conditions when the reaction time constant far exceeds the diffusional time constant, the flux of the transported gas follows Fick's law of diffusion. Analytical series solution for the contribution of the chemical reaction to the transport process is obtained using the technique of perturbation analysis; criteria for the validity of various terms in the series solution are presented. The permeability of carbon dioxide in water and in 1N NaHCO₃?Na₂CO₃ solution is estimated. It is shown that a high degree of accuracy in the data is necessary for obtaining separate estimates of diffusivity and solubility by this technique.