Hydrate equilibrium of carbon dioxide in aqueous solutions of 1,4-cyclohexanedione as a thermodynamic inhibitor

Solubility modeling of vapor-liquid equilibrium of water, carbon dioxide, and methane in protic ionic liquids with carboxylate anions

Abstract The mathematical complexity of climate modeling presents significant challenges to teaching climate change at the undergraduate level. Here, we address this challenge with the CAMBIO climate model, a set of ordinary time-dependent differential equations that simulate carbon exchanges between Earth’s atmosphere, ocean, and land reservoirs. Students obtain solutions to versions of these equations that embed a series of feedbacks, progressively adding (i) temperature-dependent Henry’s law equilibration of carbon dioxide (CO 2 ) between oceans and atmosphere, (ii) reductions in global albedo as parameterized by anticipated reductions in Earth’s cryosphere, and (iii) reductions in the efficiency of terrestrial CO 2 fertilization parameterized by observed changes in net atmosphere–land CO 2 fluxes. As validation, we find that the range of anthropogenic warming produced by this progression plausibly replicates the range of published warming values, even for a fixed Charney equilibrium climate sensitivity. We have found that students taking an undergraduate general education course on modeling Earth’s climate with minimal prerequisites and no programming experience can learn the necessary programming skills to write the code to create CAMBIO from the ground up. Creating and implementing CAMBIO themselves helps students develop skills needed to understand the nonlinear processes inherent in climate dynamics, including feedbacks, time delays, reservoir stocks, and flows between reservoirs. We also describe an analytical solution to the CAMBIO equations that reproduces observed log-linear increases in atmospheric and oceanic carbon reservoirs. We conclude with pedagogical insights regarding the use of scaffolded Python/Jupyter Notebooks, as a way to reach a wide range of students. Significance Statement The computational model presented here, CAMBIO, provides a pedagogical resource that bridges the gap between qualitative instruments (e.g., feedback diagrams) and quantitative tools such as global climate models (GCMs). By filling this gap, CAMBIO provides students (and instructors) a means of efficiently obtaining quantitative answers to “what-if” questions, such as questions exploring the consequences of an earlier or later timeline for reductions in global anthropogenic carbon emissions, variations in temperature thresholds for the onset of ice/albedo feedback, and the vulnerability of key natural ecosystem services (such as the planetary “CO 2 fertilization effect”) to higher global temperatures. Insights derived from such investigations, in turn, can provide a starting point for generating hypotheses to explain the variability of projections of more complex climate models, even when subject to identical carbon emission scenarios.

BackgroundThe carbonic anhydrase (CA) enzyme plays an important role in the equilibration of carbon dioxide and bicarbonate (HCO3) under the production of H+ ions. Emerging evidence suggest that CA activity may play a fundamental regulatory role on respiratory control mechanisms in obstructive sleep apnea (OSA). Clinical trials suggest that CA inhibitors significantly reduce OSA.MethodsData from three separate cohorts of healthy volunteers and patients with OSA were used to quantify CA activity in whole blood and cerebrospinal fluid (CSF). The influence of the CA inhibitory drugs acetazolamide and sulthiame, on CA activity in-vitro/in-vivo, was assessed. The association between CA-inhibitor plasma concentration and HCO3, as well as the influence of HCO3 on the apnea-hypopnea severity was determined.ResultsStability of CA activity in stored blood was high. CA activity in whole blood contained five times higher activity compared with CSF. The CA-inhibitory drugs dose-dependently reduced CA activity in-vitro/in-vivo. The CA inhibitor sulthiame reduced venous HCO3 concentration (P = 0.022). The reduction of HCO3 was linked to improvement of OSA (P = 0.040).ConclusionsCA-inhibitory drugs reduced CA activity in whole blood suggesting a therapeutic role of CA inhibition in OSA. The findings also suggest that an activated CA system may constitute a pathophysiological mechanism in some forms of OSA.Clinical trial registrationN/A.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11325-025-03430-z.

The paper studies the operation of a highly mineralized water purification system with a reverse osmosis unit for the needs of a metalworking enterprise. It identifies the reasons for the unsatisfactory operation of the water purification system and develops recommendations for its improvement based on the assessment of water quality in samples at water treatment stages and the assessment of the tendency of the feed water to form silt on reverse osmosis membranes. The work aims to develop an effective technology for purifying highly mineralized water, which contains both ammonium and iron ions, based on the study of the existing water purification system at the enterprise. Groundwater is chloride-sulphate calcium-magnesium and does not meet the requirements for drinking water in terms of turbidity, total mineralization, total hardness, ammonium, total iron, silicates, magnesium, manganese, sodium, strontium, and chlorides. Standard methods were used to determine water quality indicators at various water treatment stages. Highresolution scanning electron microscopy was used to analyze the surface of the filter material grain. The elemental composition of the filter material grain and its surface sediment were analyzed locally using energy dispersive spectrometry. The hypothetical composition of groundwater and the quality of water at various water treatment stages were investigated; the silt density index, the Langelier index, and the Gibbs energy of carbon dioxide equilibrium in the aerator were calculated; the aeration system performance was assessed. The reasons for the performance slowdown of the reverse osmosis unit and the frequent replacement of the pressure filter media were identified. The tested water supplied to the reverse osmosis unit does not meet the requirements for total hardness and total iron. The insufficiency of the specific air flow rate in the aerator was proven. Mudding of granular filter material with calcium carbonate and amorphous silicon was observed. Technical solutions are proposed to increase the efficiency of aeration-degassing and iron removal at the preliminary water purification stage before reverse osmosis. The proposed solutions will be relevant for the design and operation of process flows for complex groundwater purification.

Using the Experimental Cross-Association Energy and Artificial Neural Network for Modeling the Phase Equilibrium of Carbon Dioxide–Water System: What Advances Can Be Achieved?

Abstract A few key methodological uncertainties remain for the carbonate clumped isotope community. One is how to compare data among published data sets that are not anchored to the InterCarb Carbon Dioxide Equilibrium Scale (I‐CDES). A second is how temperature calibrations of calcite compare to those of other carbonate minerals in the I‐CDES—particularly dolomite and apatite—which can elucidate several Earth system dynamics. Previous calibrations of the clumped isotope thermometer for dolomite are discrepant from one another and variably (dis)agree with calibrations developed for calcite; apatite calibrations have not yet been compared between laboratories using carbonate‐based standardization. Here we report I‐CDES standardized values for a suite of 11 carbonates that are commonly measured by the clumped isotope community to aid future comparisons of non‐I‐CDES data sets. In addition, 17 dolomite samples (25–1,200°C) and five apatite samples (1–38°C) of known precipitation temperature were measured using carbonate‐based standardization. Excellent agreement between calcites and dolomites heated to similar temperatures (1,100–1,200°C) suggests no mineral‐specific differences in absolute acid fractionation factor. We show that calcite and dolomite regressions largely agree but are sensitive to sample characteristics, regression method, and how equations are statistically compared. We suggest that there is no need for a dolomite‐specific clumped isotope calibration, although our results suggest that further work is necessary to determine the influence of sample characteristics on this relationship. The apatite calibration equation defined in this study is statistically indistinguishable from calcite‐based calibrations; we corroborate previous findings that an apatite‐specific calibration is unnecessary.

A generic machine learning model for CO2 equilibrium solubility into blended amine solutions

To limit global warming below 2°C by 2100, we must drastically reduce greenhouse gas emissions and additionally remove ~100-900 Gt CO2 from the atmosphere (carbon dioxide removal, CDR) to compensate for unavoidable emissions. Seaweeds (marine macroalgae) naturally grow in coastal regions worldwide where they are crucial for primary production and carbon cycling. They are being considered as a biological method for CDR and for use in carbon trading schemes as offsets. To use seaweeds in carbon trading schemes requires verification that seaweed photosynthesis that fixes CO2 into organic carbon results in CDR, along with the safe and secure storage of the carbon removed from the atmosphere for more than 100 years (sequestration). There is much ongoing research into the magnitude of seaweed carbon storage pools (e.g., as living biomass and as particulate and dissolved organic carbon in sediments and the deep ocean), but these pools do not equate to CDR unless the amount of CO2 removed from the atmosphere as a result of seaweed primary production can be quantified and verified. The draw-down of atmospheric CO2 into seawater is via air-sea CO2 equilibrium, which operates on time scales of weeks to years depending upon the ecosystem considered. Here, we explain why quantifying air-sea CO2 equilibrium and linking this process to seaweed carbon storage pools is the critical step needed to verify CDR by discrete seaweed beds and nearshore and open ocean aquaculture systems prior to their use in carbon trading.

The adsorption equilibrium of methane (CH4) and carbon dioxide (CO2) on the metal–organic framework (MOF) UiO-66 is studied via molecular simulation. UiO-66 is a versatile MOF with vast potential for various adsorption processes, such as biogas upgrading, CO2 capture, and natural gas storage. The molecular simulations employ the grand canonical Monte Carlo (GCMC) method, covering a temperature range of 298–343 K and pressures up to 70 bar for CH4 and 30 bar for CO2. The accuracy of different forcefields in describing the adsorption equilibria is evaluated. Two modelling approaches are explored: (i) lumping each hydrogen atom in the MOF framework to the heavy atom it is bonded to (united atom approximation) and (ii) considering explicit hydrogen atoms. Additionally, the influence of electrical charges on CO2 adsorption is also evaluated. The findings indicate that the most effective forcefield to describe the adsorption equilibrium is a united atom forcefield based on the TraPPE parametrization. This approach also yields an accurate calculation of the isosteric heat of adsorption. In the case of CO2, it is observed that the use of electrical charges enhances the prediction of the heat of adsorption, especially in the low-coverage region.

Abstract Recent interlaboratory efforts have enabled methodological refinements in carbonate clumped isotope geochemistry, including the adoption of a carbonate‐based reference frame, the InterCarb Carbon Dioxide Equilibration Scale (I‐CDES). This calcite‐based standardization scheme aims at simplifying sample preparatory routines and ensuring identical treatment for all standards and unknowns. While the I‐CDES is a major step forward for the production of coherent results by laboratories for calcite, two aspects of this reference frame may only approximate but not ensure the principle of identical treatment of standards and unknowns because (a) the 90°C‐acid digestion temperature favored by I‐CDES is not achievable by all analytical setups and (b) the clumped isotope systematics of other carbonate minerals, if reported within a calcite reference frame only, may introduce uncertainties. We present an upgraded Kiel IV carbonate device—the “Franken‐Kiel”—performing acid digestions up to a theoretical 135°C, an enhancement over the factory‐default temperature of 70°C. The optimized setup considerably reduces the reaction time needed for digesting samples and yields good precision on Δ47 (i.e., long‐term standard deviations of 0.027 and 0.005‰ for calcite and dolomite standards, respectively). We further re‐evaluated the Δ47‐T relationship for calcite and dolomite directly in the I‐CDES and showed consistency between the produced temperature calibration and previous calibrations for calcite. We propose a mineralogy correction for dolomite in the I‐CDES that allows to partially reconcile theory with experimentation. Overall, the Franken‐Kiel showed excellent performance and warrants further tests on more recalcitrant carbonates, such as siderite and magnesite at higher acidification temperatures.

Equilibrium absorption of CO2 in aqueous solution of N-dimethylamino ethanol and 2-(ethylamino)ethanol, measuring and thermodynamic modeling

Early detection of quality alterations in corn grains stored in vertical prototype silos using real-time monitoring of carbon dioxide and equilibrium moisture content

CCS is expected to become an important contribution to the mitigation of carbon dioxide emissions. Transportation of CO2 from the capture site to the permanent storage reservoir plays a key role, and transportation by ship is now viewed as a relevant alternative for certain combinations of captured CO2 volume and distance.This paper presents experimental equipment, methods and new results for the water content of carbon dioxide and impure carbon dioxide in equilibrium with hydrates at temperatures between (-55 and -10)°C and pressures between (3 and 120) bar, hence in both vapour and liquid phases. The experimental data are compared with predictions from two thermodynamic models: the Cubic-Plus-Association equation of state and an approach using Multi-Fluid Helmholtz Energy Approximation (MFHEA) equations of state (EoS). In all cases, the hydrate-forming conditions are modelled by the solid solution theory of van der Waals and Platteeuw.

Thermodynamic modeling of gas hydrate phase equilibrium of carbon dioxide and its mixture using different equations of states

A volumetric system was used to assess carbon-based adsorbents for evaluation of the gas separation, equilibrium, and kinetics of oxygen (O2), nitrogen (N2), and carbon dioxide (CO2) adsorption on granular activated carbon (GAC) and functionalized GAC at 298, 308, and 318 K under pressures up to 10 bar. The effects of ZnCl2, pH, arrangement of the pores, and heat-treatment temperature on the adsorptive capabilities of O2, N2, and CO2 were evaluated. High-performance O2 adsorption resulted with a fine sample (GAC-10-500) generated with a 0.1 wt % loading of ZnCl2. The optimal sample structure and morphology were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, and powder X-ray diffraction. On the basis of the adsorption–desorption results, the fine GAC provides a surface area of 719 m2/g. Moreover, it possessed an average pore diameter of 1.69 nm and a micropore volume of 0.27 m3/g. At 298 K, the adsorption capacity of the GAC-10-500 adsorbent improved by 19.75% for O2 but was not significantly increased for N2 and CO2. Isotherm and kinetic adsorption models were applied to select the model best matching the studied O2, N2, and CO2 gas uptake on GAC-10-500 adsorbent. At 298 K and 10 bar, the sip isotherm model with the highest potential adsorption difference sequence and gas adsorption difference compared with pure GAC adsorbent as O2 > N2 > CO2 follows well for GAC-10-500. Eventually, the optimal sample is more effective for O2 adsorption than other gases.

Abstract. Iodine and carbonate species are important components in marine and dust aerosols, respectively. The non-ideal interactions between these species and other inorganic and organic compounds within aqueous particle phases affect hygroscopicity, acidity, and gas–particle partitioning of semivolatile components. In this work, we present an extended version of the Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model by incorporating the ions I−, IO3-, HCO3-, CO32-, OH−, and CO2(aq) as new species. First, AIOMFAC ion interaction parameters for aqueous solutions were determined based on available thermodynamic data, such as water activity, mean molal activity coefficients, solubility, and vapor–liquid equilibrium measurements. Second, the interaction parameters for the new ions and various organic functional groups were optimized based on experimental data or, where data are scarce, alternative estimation methods such as multiple linear regression or a simple substitution by analogy approach. Additional bulk water activity and electrodynamic balance measurements were carried out to augment the database for the AIOMFAC parameter fit. While not optimal, we show that the use of alternative parameter estimation methods enables physically sound predictions and offers the benefit of a more broadly applicable model. Our implementation of the aqueous carbonate–bicarbonate–CO2(aq) system accounts for the associated temperature-dependent dissociation equilibria explicitly and enables closed- or open-system computations with respect to carbon dioxide equilibration with the gas phase. We discuss different numerical approaches for solving the coupled equilibrium conditions and highlight critical considerations when extremely acidic or basic mixtures are encountered. The fitted AIOMFAC model performance for inorganic aqueous systems is considered excellent over the whole range of mixture compositions where reference data are available. Moreover, the model provides physically meaningful predictions of water activity under highly concentrated conditions. For organic–inorganic mixtures involving new species, the model–measurement agreement is found to be good in most cases, especially at equilibrium relative humidities above ∼ 70 %; reasons for deviations are discussed. Several applications of the extended model are shown and discussed, including the effects of ignoring the auto-dissociation of water in carbonate systems, the effects of mixing bisulfate and bicarbonate compounds in closed- or open-system scenarios on pH and solution speciation, and the prediction of critical cloud condensation nucleus activation of NaI or Na2CO3 particles mixed with suberic acid.

Calibration of the dual clumped isotope thermometer for carbonates

The phase stability and equilibria of carbon dioxide are investigated from 125-325K and 1-10 000 atm using extensive molecular dynamics (MD) simulations and the Two-Phase Thermodynamics (2PT) method. We devise a direct approach for calculating phase diagrams, in general, by considering the separate chemical potentials of the isolated phase at specific points on the P-T diagram. The unique ability of 2PT to accurately and efficiently approximate the entropy and Gibbs energy of liquids allows for assignment of phase boundaries from relatively short (∼100ps) MD simulations. We validate our approach by calculating the critical properties of the flexible elementary physical model 2, showing good agreement with previous results. We show, however, that the incorrect description of the short-range Pauli force and the lack of molecular charge polarization lead to deviations from experiments at high pressures. We, thus, develop a many-body, fluctuating charge model for CO2, termed CO2-Fq, from high level quantum mechanics (QM) calculations that accurately capture the condensed phase vibrational properties of the solid (including the Fermi resonance at 1378cm-1) as well as the diffusional properties of the liquid, leading to overall excellent agreement with experiments over the entire phase diagram. This work provides an efficient computational approach for determining phase diagrams of arbitrary systems and underscores the critical role of QM charge reorganization physics in molecular phase stability.

Information on the temperature of formation or alteration of carbonate minerals can be obtained by measuring the abundance of the isotopologues 47 and 48 (Δ47 and Δ48 values) of CO2 released during acid dissolution. The combination of these two proxies can potentially provide a greater insight into the temperature of formation, particularly if the carbonate minerals form by non-equilibrium processes. We have precipitated calcium carbonates at seven temperatures between 5 and 65°C and measured their δ48 values using a Thermo-253 plus isotope ratio mass spectrometer. The values were transformed to Δ48 values in the conventional manner and then converted to the carbon dioxide equilibrium scale. Using the Δ48 values, we have established an empirical calibration between temperature and Δ48 values: [Formula: see text] CONCLUSIONS: The calibration line produced allows the determination of the temperature of natural carbonates using the Δ48 values and agrees with the measurements of the Δ47 and Δ48 values of some carbonates assumed to have formed under equilibrium conditions.