Equilibrium Concentrations Of CO2 Research Articles

Experimental and Theoretical Investigation of Supercritical Processes: Kinetics of Phase Transitions in Binary “2-Propanol—CO2” System

Studies of phase transition kinetics are important for such supercritical processes as supercritical drying, adsorption, micronization, etc. In supercritical technologies, “organic solvent—CO2” systems are often formed, the properties of which strongly depend on the system parameters. In this article, the kinetic curves of phase transitions in the “2-propanol—CO2” system were investigated experimentally and theoretically. Experimental studies were carried out in a 250 mL high-pressure apparatus at temperatures of 313 and 333 K and pressures of 6.3 and 7.8 MPa with and without the addition of alginate porous gel. Theoretical studies were carried out using the mass transfer equation, the Peng-Robinson equation of state, and the Van der Waals mixing rules, with Python being used for the calculations. The mass transfer coefficients and equilibrium concentrations of CO2 in the liquid phase were determined using the BFGS optimization method.

Emissions and CO2 Concentration—An Evidence Based Approach

The relation between CO2 emissions and atmospheric CO2 concentration has traditionally been treated with more or less complex models with several boxes. Our approach is motivated by the question of how much CO2 must necessarily be absorbed by sinks. This is determined by accepted measurements and the global carbon budget. Observations lead to the model assumption that carbon sinks, similar to oceans or the biosphere, are linearly dependent on CO2 concentration on a decadal scale. In particular, this implies the falsifiable hypothesis that oceanic and biological CO2 buffers have not significantly changed in the past 70 years and are not saturated in the foreseeable future. A statistical model with two parameters is built from the global carbon budget and two testable assumptions. This model explains the relation between CO2 emission and historical CO2 concentration data very well. The model gives estimates of the natural emissions, the pre-industrial CO2 equilibrium concentration levels, the half-life time of an emission pulse, and the future CO2 concentration level from a given emission scenario. It is validated by an ex-post forecast of the last 20 years. The important result is that, with the stated polices emission scenario of the International Energy Agency (IEA), the future CO2 concentrations will not rise above 475 ppm. The model is compared with the carbon module of the Bern model, mapping their complex impulse response functions (IRFs) to a single time variant absorption parameter.

Correction to “Measurement and Prediction of the Heat of Adsorption and Equilibrium Concentration of CO2 on Zeolite 13X”

RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Measurement and Prediction of the Heat of Adsorption and Equilibrium Concentration of CO2 on Zeolite 13X”Karen N. SonKaren N. SonMore by Karen N. Sonhttp://orcid.org/0000-0003-0910-356X, Gregory E. CmarikGregory E. CmarikMore by Gregory E. Cmarik, James C. KnoxJames C. KnoxMore by James C. Knox, Justin A. WeibelJustin A. WeibelMore by Justin A. Weibel, and Suresh V. Garimella*Suresh V. GarimellaMore by Suresh V. Garimellahttp://orcid.org/0000-0003-1421-2912Cite this: J. Chem. Eng. Data 2020, 65, 8, 4172Publication Date (Web):July 7, 2020Publication History Published online7 July 2020Published inissue 13 August 2020https://doi.org/10.1021/acs.jced.0c00546Copyright © 2020 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views465Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (512 KB) Get e-Alerts Get e-Alerts

Inorganic carbon acquisition in the acid-tolerant alga Chlorella kessleri.

The ability of the freshwater alga, Chlorella kessleri, to maintain a carbon concentrating mechanism when grown at acid pH was investigated. The alga grows over the pH range 4.0-9.0 and was found to take up bicarbonate and CO2 actively when grown at pH 6.0. However, when grown at acid pH (below 5.5), it does not have active CO2 uptake. The acidotolerant species maintained an internal pH of 6.1-7.5 over the external pH range 4.5-7.5, thus the pH difference between the cell interior and the external medium was large enough to allow for the diffusive uptake of CO2 at acid external pH. Mass spectrometric monitoring of O2 and CO2 fluxes by suspensions of C. kessleri, grown at acid pH, and maintained at pH 7.5 showed that the rates of O2 evolution did not exceed those of CO2 uptake. The final CO2 compensation concentrations of 14.0-17.7 µM reached by photosynthetic cells were above the CO2 equilibrium concentration in the external medium, indicating a lack of active CO2 uptake at acid pH. Chlorella kessleri accumulated CO2 with internal concentrations that were 9.9, 18.7 and 22.7-fold that of the external medium for cells grown, respectively, at pH 4.5, 5.0 and 5.5. The ability of C. kessleri cells to accumulate high intracellular concentrations of inorganic carbon at acid pH would provide a sufficiently high concentration of CO2 at the active site of Rubisco thus allowing the alga to maintain growth rates similar to those at alkaline pH.

Measurement and modeling of CO2 diffusion coefficient in Saline Aquifer at reservoir conditions

AbstractStorage of CO2 in deep saline aquifers is a promising techniques to mitigate global warming and reduce greenhouse gases (GHG). Correct measurement of diffusivity is essential for predicting rate of transfer and cumulative amount of trapped gas. Little information is available on diffusion of GHG in saline aquifers. In this study, diffusivity of CO2 into a saline aquifer taken from oil field was measured and modeled. Equilibrium concentration of CO2 at gas-liquid interface was determined using Henry’s law. Experimental measurements were reported at temperature and pressure ranges of 32–50°C and 5900–6900 kPa, respectively. Results show that diffusivity of CO2 varies between 3.52–5.98×10−9 m2/s for 5900 kPa and 5.33–6.16×10−9 m2/s for 6900 kPa initial pressure. Also, it was found that both pressure and temperature have a positive impact on the measures of diffusion coefficient. Liquid swelling due to gas dissolution and variations in gas compressibility factor as a result of pressure decay was found negligible. Measured diffusivities were used model the physical model and develop concentration profile of dissolved gas in the liquid phase. Results of this study provide unique measures of CO2 diffusion coefficient in saline aquifer at high pressure and temperature conditions, which can be applied in full-field studies of carbon capture and sequestration projects.

Carbon-concentrating mechanisms in acidophilic algae

M.M. Diaz and S.C. Maberly. 2009. Carbon-concentrating mechanisms in acidophilic algae. Phycologia 48: 77–85. DOI: 10.2216/08-08.1Seven phylogenetically diverse strains of microalgae were isolated from a naturally acidic lake and river system in Patagonia. Half-saturation constants for CO2 at atmospheric levels of oxygen varied between 2 and 12.7 µmol L−1. CO2 uptake was oxygen sensitive in the spheroidal form of Watanabea sp. (Trebouxiophyceae), Palmellopsis sp. (Chlorophyceae) and an unidentified Prymnesiophyte but insensitive in the ellipsoidal form of Watanabea sp. and in Euglena mutabilis (Euglenophyta). The kinetic evidence suggests that a carbon-concentrating mechanism (CCM) is absent in Palmellopsis sp. and Gloeochrysis sp. (Chrysophyta) and the spheroidal form of Watanabea sp. but present in the ellipsoidal form of Watanabea sp. The low K½, 2 µmol L−1 in the unidentified Prymnesiophyte suggests that a CCM may be present, but the kinetic responses were oxygen sensitive; although, K½ was not affected by oxygen. Carbon uptake in E. mutabilis was not oxygen sensitive, but the K½ was 6.4 µmol L−1, which makes the diagnosis of the presence of a CCM equivocal. The results for Watanabea sp. appear to be the first where different forms of the same species possess or lack a CCM when grown under identical conditions. Rates of growth of Watanabea sp., largely comprising the spheroidal form, were between 86 and 95% of maximal rates at air equilibrium concentrations of CO2, depending on the oxygen concentration. The high affinity of these species for CO2, even in the apparent absence of a CCM, suggests that when an acid lake is close to atmospheric equilibrium, rates of photosynthesis and growth are unlikely to be limited by CO2.

Study of different effects on foaming process of biodegradable PLA/starch composites in supercritical/compressed carbon dioxide

AbstractMicrocellular foaming of biodegradable and biocompatible PLA/starch composites in supercritical/compressed CO2 has been studied. The purpose of this study is to explore the potential application of this kind of materials in medical materials or drug containers. The rate of CO2 uptake and CO2 equilibrium concentration in PLA/starch composites were studied by performing sorption and desorption experiments. The effects of a series of variable factors, such as saturation time and saturation temperature on the foaming morphology were studied through SEM observation and density measurement. The experimental results show that, while keeping other variables unchanged, longer saturation time leads to reduced bulk foam densities and different saturation pressures result in different bulk foam densities. The crystallinity of PLA–starch sample was characterized by differential scanning calorimetry. It indicates that the foaming treatment with supercritical CO2 increased the crystallinity of PLA/starch composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Accelerated Mass Transfer of CO2 in Reservoir Brine Due to Density-Driven Natural Convection at High Pressures and Elevated Temperatures

In this paper, the mass transfer of CO2 into a reservoir brine sample is studied experimentally at high pressures and elevated temperatures. The equilibrium concentration of CO2 in the reservoir brine and the density of CO2-saturated brine are measured by saturating the brine with CO2. The mass-transfer rate of CO2 into the brine is determined by monitoring the pressure decay inside a closed, visual, high-pressure PVT cell. It is found that the density of the brine with dissolved CO2 increases linearly with CO2 concentration. As CO2 gradually dissolves into the brine by molecular diffusion, a concentration-induced density gradient is generated near the CO2−brine interface. Under the influence of gravity, this concentration-induced density gradient causes natural convection, which accelerates the mass-transfer rate of CO2 into the brine. The modified diffusion equation with an effective diffusivity is applied to model the mass-transfer process. It is found that the determined effective diffusivities of CO2...

SOURCE OF INORGANIC CARBON FOR PHOTOSYNTHESIS IN TWO MARINE DINOFLAGELLATES1

Inorganic carbon uptake was investigated in two marine dinoflagellates, Amphidinium carterae Hulburt and Heterocapsa oceanica Stein. Mass spectrometric and potentiometric assays indicated that both species lacked external carbonic anhydrase (CA). The presence of internal CA was demonstrated by potentiometric assay and by the inhibition of photosynthesis upon the addition of 500 μM ethoxyzolamide a membrane‐permeable inhibitor of CA. The capacity for bicarbonate transport was investigated by comparing the calculated rate of spontaneous CO2 formation at pH 8.2 and 25°C with the rate of photosynthesis after the addition of 100 μM NaHCO3. Both species appeared to have a very limited capacity for direct bicarbonate uptake. Monitoring of CO2 and O2 fluxes in both species by mass spectrometry demonstrated a rapid uptake of CO2 on illumination, to concentrations below the CO2 equilibrium concentration, indicating an effective selective uptake of CO2. This dependence of photosynthesis on free CO2 alone suggests that these species are CO2 limited in their natural environment because the CO2 concentration of seawater is very low.

Activation of 1-Aminocyclopropane-1-carboxylate Oxidase by Carbon Dioxide

1-Aminocyclopropane-1-carboxylate (ACC) oxidase requires CO2/HCO3− as an essential activator for its activity. Taking advantage that the equilibrium concentrations of CO2 and HCO3− vary with pH and that the interconversions of CO2 and HCO3− arc slower at low temperature, we identified CO2 rather than HCO3− as the active species involved in the activation process. Preincubation of the enzyme with a saturating concentration of CO2 resulted in increased activation of the enzyme when preincuhation pH was raised, indicating that CO2 reacted with an enzyme group having an alkaline pKa. It is suggested that the CO2 activation of ACC oxidase involves the formation of a carhamate. CO2 increases the Vmax of the reaction but decreases the affinity of the enzyme toward its substrate ACC. A plausible reaction scheme accounting br the CO2 activation process is presented.

Bicarbonate assimilation by fresh-water charophytes and higher plants: I. Membrane transport of bicarbonate ions is not proven

Although it is generally believed thatChara and some fresh-water angiosperms transport bicarbonate ions inwards across their plasma membranes, there has been no direct demonstration of such transport in these plants. The (indirect) arguments for their transporting HCO 3 − are arguments against the inward diffusion of CO2 at the observed rates. They rest on calculations of the equilibrium concentration of CO2 or of the maximum rate at which CO2 might be produced from HCO 3 − at the pH of the medium outside the cells. SinceChara acidifies the medium over about half the cell surface during C assimilation, these calculations have been based on questionable premises. We propose a model forChara in which the acidification is attributed to active efflux of H+, and we calculate that both the equilibrium concentration of CO2 and its rate of production outside the cell can be high enough to support the observed rates of C assimilation, without postulating transport of the species HCO 3 − or H2CO3. Calculations are presented also for alternative models in which there is membrane transport of HCO 3 − . The first includes symport of H+ with HCO 3 − , again dependent on active H+ efflux. In the second, there is active electrogenic transport of HCO 3 − . In this case the low pH in the medium outside the cell is caused by the dissociation of H2CO3 produced by hydration of CO2 which leaks from the cell cytoplasm. All three models are consistent with the observations to date, but the first is more economical of postulates. It can also explain the apparent transport of HCO 3 − by fresh-water angiosperms such asEgeria.

Foliar Nitrogen Loss and CO2Equilibrium as Influenced by Three Soybean (Glycine max) Postemergence Herbicides

‘Forrest’ soybean [Glycine max(L.) Merr.] infested with entireleaf morningglory [Ipomoea hederacea(L.) Jacq. var.integriusula Gray] were treated in the field with three postemergence herbicides, dinoseb (2-sec-butyl-4,6-dinitrophenol), sodium salt of acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid}, and 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid]. Foliar nitrogen (N) loss, transpiration, and CO2equilibrium concentrations were measured from 4 to 148 h after treatment. In morningglory foliar N loss was increased by dinoseb, decreased by acifluorfen, and first increased and then decreased by 2,4-DB treatments. Transpiration in this weed species was decreased by all three herbicides. In soybean, N loss was increased and transpiration decreased with dinoseb; acifluorfen did not affect either activity; and 2,4-DB decreased both processes during one sampling period. In both plant species dinoseb increased the CO2equilibrium concentration within 4 h after treatment. Treatments with acifluorfen and 2,4-DB initially increased the CO2concentration in morningglory with major increases noted at the onset of chlorosis 52 h after treatment. In soybean, some significant decreases in CO2equilibrium concentrations occurred with the lowest rate of all three herbicides.

温州ミカン果皮中におけるCO<sub>2</sub>, O<sub>2</sub>, N<sub>2</sub>ガスの透過性について

Even though there is a relation between the physical properties of the peel of satsuma mandarin and preservability of the fruit during the distribution process, few papers have been reported on the gas permeability through the peel and other properties.In this paper, we presented the steady state and non-steady state methods to measure the permeability constants of CO2, O2 and N2 through the peel of satsuma mandarin. These methods were improved ones on the sweep gas method which was used to measure the gas permeability of packaging film. Furthermore some observations of the respiratory characteristics of the peel were performed in order to use in calculating the permeability constants.1. Permeability constant of CO2 through the peel was measured by the steady state method.(1) 92 percent of CO2 production by the peel was exhausted from the albedo side. The amounts were 1.43×10-2[cm3/cm2/hr] for the fruit collected on Nov. 14 and 2.41×10-2[cm3/cm2/hr] on Dec. 15 in 1975 respectively (Fig. 3, Fig. 4).(2) CO2 concentration in the atmosphere enclosed with the hemispherical peel and plastic plate increased gradually and then reached its equilibrium state in more than ten hours. Equilibrium concentrations of CO2 were 4.7 percent for the fruit collected on Nov. 14 and 8.0 percent on Dec. 15 respectively (Fig. 5).(3) By substituting these values into equation (1), the permeability constants of CO2 through the peel of satsuma mandarin were obtained to be 11.3×10-4[cm3/cm/hr/cmHg] for the fruit collected on Nov. 14 and 11.5×10-4[cm3/cm/hr/cmHg] on Dec. 15 respectively (Tab. 1).2. In measuring by the non-steady state method, permeability constants of CO2, O2 and N2 through the peel were 8.9×10-4, 5.2×10-4 and 4.7×10-4[cm3/cm/hr/cm Hg] in order (Tab. 1).3. The difference of the magnitude of the permeability constants among three gases was proven by measuring the gauge pressure in the atmosphere enclosed with the hemispherical peel and plastic plate when both the flavedo and albedo sides of the peel were filled with different pure gas (Fig. 8).

Storage of mushrooms in pre‐packs: The effect of changes in carbon dioxide and oxygen on quality

AbstractMushrooms (Agaricus bisporus) were picked at the “button” stage (velum differentiated but unbroken) and stored for 3 to 5 days at 2 or 18 °C in styrene punnets (pre‐packs) overwrapped with one of a range of plastic films. Concentrations of carbon dioxide and oxygen were measured inside the pre‐packs at intervals. When the packs were opened, internal and external browning, loss of weight and diameter of the mushrooms were measured and subjective assessments of quality were made. These parameters were compared with those of mushrooms stored in unwrapped punnets.As a result of the mushroom respiration, the internal atmosphere of the prepack was rapidly modified until, after about 24 h, a rough equilibrium concentration of CO2 and O2 was established in the range 4 to 10% CO2 and 11 to 17% O2 at 2 °C or 8 to 15% CO2 and 1 to 2% O2 at 18 °C; the mean concentration was dependent on the type of film. An equation, applicable to five out of six films that were tested, is proposed to describe the relationship between the equilibrium CO2 concentrations at 18 °C and the permeability data of the film.At 18 °C, the gas changes inside the pre‐packs prevented opening of the pileus and, in combination with prevention of water loss by the film, slowed down deterioration of the mushrooms. However, concentrations of CO2 much above or below 10 to 12% were associated with increased internal browning. At 2 °C overwrapping generally caused slight external browning of the pileus.The relevance of the results are discussed in relation to the commercial marketing of pre‐packed mushrooms.

Carbon Dioxide in the Surface Water of the Ice-covered Bering Sea

DETERMINATION of the equilibrium concentration of CO2 in the ocean surface with respect to air is necessary in order to understand the interaction of CO2 between the atmosphere and the ocean. The concentration of CO2 in water depends on its physical, chemical and biological properties. The oceans, therefore, act as both sources and sinks for CO2 in the air. Keeling1 reported that high concentrations of CO2 in the ocean appeared near the equator and were lower in the sub-tropics of all oceans. Areas along the west coasts of continents where upwelling occurs have high CO2 concentrations. In the polar regions, patterns are more complicated primarily because of a lack of seasonal data. Measurements of the equilibrium concentration of CO2 with respect to air in the surface waters of the Kara and Barents Seas during the late summer showed that the surface waters were supersaturated with CO2 near the mouths of the Ob and Yenisey Rivers and undersaturated in the Barents Sea2. The present study was undertaken to measure the actual distribution of CO2 between the atmosphere and the sea over open leads and polynyi in the ice-covered Bering Sea. Previous measurements of CO2 in ice-covered seas were made by Kelley3 in the water under the Arctic Ocean pack ice near Ice Island T-3.