Carbon Dioxide In Solutions Research Articles

Enthalpy of Solution and Solubility of Carbon Dioxide in Acetone: Experimental Measurements and Modeling

Enthalpy of Solution and Solubility of Carbon Dioxide in Acetone: Experimental Measurements and Modeling

Effect of Graphene Quantum Dots (GQDs) on the mechanical, dynamic, and durability properties of concrete

Addressing ecological concerns stemming from concrete usage is paramount, prompting exploration into additives for mitigation. Graphene quantum dots (GQDs) have been recognized for their potential to improve the mechanical attributes of cement composites. Additionally, the electrochemical reduction of a saturated solution of carbon dioxide (CO2) and monoethanolamine (CO2-MEA) effectively removes CO2 from the atmosphere. This study delves into the influence of GQDs on the mechanical and durability aspects of concrete. It is noted that the control mix of concrete without GQDs was specifically designed for concrete railway sleepers. Varied proportions of GQDs, ranging from 0.3 % to 1.2 % at 0.3 % increments, were incorporated to assess their impact on fresh and hardened concrete properties. Mechanical properties such as compressive strength, splitting tensile strength, flexural strength, and dynamic properties were evaluated. Durability assessments encompassing water absorption and chloride ion penetration were conducted. Microstructural analysis via Field Emission Scanning Electron Microscopy (FESEM) imaging and Energy-dispersive X-ray spectroscopy (EDS) elucidated the concrete's internal composition. Notably, an optimal GQDs percentage of 0.3 % was observed, signifying its efficacy in enhancing the performance of concrete. When 0.3 % of GQDs was added to concrete, compressive strength, split tensile strength, and flexural strength were enhanced by 10.8 %, 23 %, and 11 % respectively. The incorporation of GQDs resulted in a notable improvement in the fundamental frequencies and dynamic modulus of elasticity. Concurrently, a decrease in the damping ratio was observed for specimens containing GQDs. Additionally, the porosity and chloride penetration depth were lower by 6 % and 30 % for specimens with 0.3 % GQDs. The improvement in workability, mechanical, and dynamic properties of concrete, along with reducing CO2 from the atmosphere, makes GQDs an ideal eco-friendly material. This study is the first to open new pathways for the development of construction materials that are not only structurally superior but also environmentally responsible, marking a significant step forward in the field of civil engineering materials, especially in railway applications.

Time evolution of radius of bubble comprising carbon dioxide and air

The dynamics of a single bubble in an aqueous solution of carbon dioxide (CO2) and air were theoretically investigated. The time evolution of the bubble radius and that of the partial pressures of CO2 gas and air in the bubble were studied by solving the simultaneous time evolution equations for these variables analytically and numerically. It was shown that bubbles comprising CO2 gas and air, the solubilities of which in water were significantly different, exhibited peculiar behaviors that could not be expected from classical nucleation theory. The bubble radii, expressed as a function of time, exhibited peaks, kinks, and plateaus. Bubbles smaller or larger than the critical bubble radius could grow and diverge or shrink and vanish, respectively.

A new strategy to fabricate polyvinyl alcohol (PVA) foam with low thermal conductivity using PVA-citric acid solution in supercritical carbon dioxide

Polymer foams with low density have a great potential in the field of heat preservation due to good thermal insulation properties. In this work, a new method for the preparation of polyvinyl alcohol (PVA) foam with low density using PVA-citric acid (CA) solution based on supercritical carbon dioxide (scCO2) foaming technology was proposed. This approach introduced abundant water as co-blowing agent and utilized the crosslinking between CA and PVA to regulate the viscosity of solution, thereby the low density PVA foam with stable morphology was prepared. The effects of saturation time, PVA content, CA content, temperature and pressure on PVA foaming behavior were investigated. Meanwhile, the use of water as assistant solvent was explored to increase the co-blowing content and weaken the diffusion of water molecules to CO2 in the PVA-CA solution, which resulted in the successful fabrication of PVA foams with lower density and low thermal conductivity. The results showed that the minimum densities of PVA before and after addition of assistant solvent were 0.070 g/cm3 and 0.047 g/cm3, respectively. Moreover, PVA foam fabricated by the addition of assistant solvent showed the thermal conductivity of 29.68 mW/mK and the compression modulus of 2.21 MPa.

ВЛИЯНИЕ ПРИМЕНЕНИЯ ДИОКСИДА УГЛЕРОДА НА КАЧЕСТВО ИКРЫ ЛОСОСЕВОЙ ЗЕРНИСТОЙ

In this paper, we present the results on the effect of carbon dioxide application in the technology of salmon caviar on the quality of finished product. The dependence of the mechanical strength of eggs on the aggre- gate state of carbon dioxide during caviar processing with gaseous CO2 and its solutions at different stages of the technological process is shown. The negative effect of carbon dioxide solutions on the condition of salmon egg’s membrane was concluded, since the membrane strength reduced, which was accompanied by an increase in the manifestation of defects in the burst eggs and, as a result, liquid sediment in the product. The rational duration of carbon dioxide treatment of salmon eggs was determined and it made 25–30 minutes. The directions of further research on caviar CO2 technologies were determined.

Addressing the Effectiveness and Molecular Mechanism of the Catalytic CO2 Hydration in Aqueous Solutions by Nickel Nanoparticles.

Hydration of carbon dioxide in water solution is the rate limiting step for the CO2 mineralization process, a process which is at the base of many carbon capture and utilization (CCU) technologies aiming to convert carbon dioxide to added-value products and mitigate climate change. Here, we present a combined experimental and computational study to clarify the effectiveness and molecular mechanism by which nickel nanoparticles, NiNPs, may enhance CO2 hydration in aqueous solutions. Contrary to previous literature, our kinetic experiments recording changes of pHs, conductivity, and dissolved carbon dioxide in solution reveal a minimal effect of the NiNPs in catalyzing CO2 hydration. Our atomistic simulations indicate that the Ni metal surface can coordinate only a limited number of water molecules, leaving uncoordinated metal sites for the binding of carbon dioxide or other cations in solution. This deactivates the catalyst and limits the continuous re-formation of a hydroxyl-decorated surface, which was a key chemical step in the previously suggested Ni-catalyzed hydration mechanism of carbon dioxide in aqueous solutions. At our experimental conditions, which expand the investigation of NiNP applicability toward a wider range of scenarios for CCU, NiNPs show a limited catalytic effect on the rate of CO2 hydration. Our study also highlights the importance of the solvation regime: while Ni surfaces may accelerate carbon dioxide hydration in water restricted environments, it may not be the case in fully hydrated conditions.

In-situ formation of CO2-incorportaed solid sorbent for dispersive solid phase extraction of phenolic compounds from water and wastewater samples prior to gas chromatography-flame ionization detector

BackgroundHerein, a new extraction procedure based on in-situ formation of carbon dioxide-incorporated solid sorbent was introduced for dispersive solid phase extraction of phenolic compounds from aqueous samples. In this study, incorporation of carbon dioxide into the structure of a diamine led to the formation of a solid compound in the sample solution that adsorbed the analytes. ResultsThe sample solution was mixed with isophorone diamine and placed under carbon dioxide stream. By doing so, isophorone diamine reacted with carbon dioxide and produced a carbamic acid analogue. It was dispersed into the sample solution as tiny particles that adsorbed the analytes. The adsorbed analytes were eluted by a volatile organic solvent and concentrated more by the vaporization of the eluate. The extraction procedure was done at low temperature to limit the releasing carbon dioxide from the produced compound. To obtain the reliable results, the method was validated and the obtained limits of detection and quantification were in the ranges of 0.29–41 and 0.96–1.3 ng/mL, respectively. Acceptable relative standard deviation (≤7.3%) and coefficient of determination (≥0.994) values confirmed the method repeatability and linearity. High enrichment factors (410–435) and extraction recoveries (82–87%) were attained with the introduced method. Significance and noveltyIn this work, a chemical reaction was done between isophorone diamine and carbon dioxide in solution. The produced product (sorbent) was insoluble in solution and dispersed in whole parts of the solution as tiny particles. A high contact area between the sorbent and analytes provided high extraction efficiency for the analytes. The method was successful utilized in determining target analytes in real samples and the matrix effect of the samples had no important effect on the obtained results.

Theoretical Study of Formation of Hydrates from High-Concentration Metastable Solution of Carbon Dioxide in Water at Various Gas Concentrations

Theoretical Study of Formation of Hydrates from High-Concentration Metastable Solution of Carbon Dioxide in Water at Various Gas Concentrations

Modeling and simulation of an enzymatic reactive absorption process in the internal zone of a rotating packed bed apparatus

A kinetic model of carbon dioxide absorption within an internal of a rotating packed bed (RPB) apparatus was developed using experimental data. Kinetics of the chemical reaction between carbon dioxide and aqueous solution of N-methyldiethanolamine with and without carbonic anhydrase additive were determined in a flat phase contact surface batch stirred reactor and implemented into the model. Overall pressure drop and absorption efficiency within a metal foam internal were modeled and compared with experimental measurements. The model's predictions of CO2 absorption and pressure drop fit mostly within 20% error range. Validated model served as a tool for further absorption process simulations and sensitivity analysis.

Calculation of Cathodic Limiting Current Density in Weak Acids: Part I. Aqueous CO2 Solutions

The limiting current density for the hydrogen evolution reaction in aqueous saturated carbon dioxide solutions needed revisiting, as the basic understanding of the underlying reaction mechanism in weak acids has changed over the past few years. We now know that the direct reduction of undissociated carbonic acid on a metal surface in aqueous carbon dioxide solutions is not significant, as was thought before, and that there is only a single dominant pathway for hydrogen evolution: reduction of free hydrogen ions. The main role of weak carbonic acid is to provide additional hydrogen ions via buffering. Therefore, a new mathematical model was needed for calculation of the limiting current density for hydrogen ion reduction, that accounts for both hydrogen ion diffusion in the boundary layer and simultaneous buffering provided by dissociation of weak carbonic acid. The new model relies on analytically solving the co-diffusion of hydrogen ions and carbonic acid in the mass transfer boundary layer, with simultaneous homogenous chemical reactions. The new expression for the limiting current density takes the form: The performance of the new model was successfully validated by comparing it with experimental data over a broad range of conditions.

Wear-Resistant Hydrophobic Coatings from Low Molecular Weight Polytetrafluoroethylene Formed on a Polyester Fabric

The paper presents a comparative analysis of the surface structure and morphology of hydrophobic coatings formed on a polyester fabric from various types of low molecular weight tetrafluoroethylenes by a new method. The low molecular weight compounds used include: ultrafine polytetrafluoroethylene of the FORUM® trademark prepared through thermo-gas-dynamic decomposition of industrial polytetrafluoroethylene waste, and tetrafluoroethylene telomers, synthesized by radiation-chemical initiation from fluoromonomers in acetone, butyl chloride and trimethylchlorosilane solutions. The formation of coatings consists in deposition of low molecular weight tetrafluoroethylenes from solutions in supercritical carbon dioxide and organic solvents. The contact angle and water absorption of the polyester fabric with coatings containing the specified water-repellents are determined. The resistance of the achieved effect to various types of wear—washing, dry cleaning and abrasionis evaluated. The hydrophobic properties of the fabric are found to be affected by the coating plasticity characterized by the stiffness coefficient. The importance of this indicator to targeted changes in fabric properties is proved. All the considered types of low molecular weight polytetrafluoroethylene (PTFE) are shown to be effective water-repellents for the polyester fabric.

A Wide Bandgap Semiconducting Magnesium Hydrogel: Moisture Harvest, Iodine Sequestration, and Resistive Switching.

Water harvesting from the ubiquitous moisture is pivotal for delivering fresh water to earth's arid/semiarid regions, and sequestration of iodine from the solution is crucial for environmental safety due to its severe effect on human metabolic processes. In this context, herein, a multifunctional supramolecular metallohydrogel (Mg@TAEA) is synthesized through direct mixing of magnesium nitrate hexahydrate and the low molecular weight gelator tris(2-aminoethyl)amine. Electron microscopy reveals that Mg@TAEA is sculptured in vertically grown well-oriented micrometer-sized flakes. The porous crystalline material (52 m2/g) was found to be an efficacious host matrix for water harvesting from moisture (847 mg/g). Mg@TAEA shows effective (513 mg/g) iodine sequestration from solution and adsorption of carbon dioxide (15 mg/g). The wide bandgap semiconducting Mg@TAEA (3.6 eV) material is a potential candidate for building memory devices, and the Ion/Ioff ratio of the device based on the indium tin oxide (ITO)/Mg@TAEA/Ag heterostructure was found to be ∼62. We further extended our work by analyzing the charge transport properties of the system and found space charge limited conduction (SCLC) and trap-filled SCLC to be responsible for the nonlinear transport behavior observed in the device.

Adjustable Underwater Gas Transportation Using Bioinspired Superhydrophobic Elastic String

Dynamic and precise manipulation of the gas flow in a liquid environment through a facile and reliable approach is of great importance for directional gas transportation and multiphase chemical reactions. In this research, elastic superhydrophobic strings were prepared by a one-step, non-fluorinated dip-coating strategy. The surface-treatment string demonstrated a good superaerophilicity underwater. By simply elongating or shortening superaerophilic strings, the gas flux underwater was precisely manipulated in a gas-siphon underwater experiment. The result reveals that a large strain of the treated string induces a low gas flow, and a rope woven with more strings results in a larger range of gas flow regulation. The elastic superhydrophobic/superaerophilic string was utilized to adjust the reaction time of carbon dioxide and sodium hydroxide aqueous solution successfully. Furthermore, in a wet oxidation experiment for treating simulated flue gas composed of nitric oxide (NO), nitrogen and oxygen, superhydrophobic and stretched strings with a strain of 200% demonstrated a 7.9% higher NO removal efficiency than that of untreated strings. Interestingly, NO removal efficiency can be regulated by mechanical stretching of gas-conducting strings. We believe that this facile and low-cost approach provides a valid method of on-demand manipulation of the gas flow for underwater gas transportation.

Application of the method of discrete-pulse energy input for water degassing in municipal and industrial boilers

The main advantages and disadvantages of chemical and physical degassing of liquids are considered. It was found that hydrodynamic cavitation should be considered as an important alternative to acoustic cavitation, both in terms of performance and, above all, in terms of energy saving. The processing of two liquids - acidic condensate and model solution (solution of carbon dioxide in distilled water) was performed. The dynamics of changes in the content of dissolved carbonic acid depending on the duration of hydrodynamic treatment in order to determine the optimal processing duration to achieve the required degree of degassing are studied. Liquids were treated on a l laboratory-scale plant developed as part of the implementation of the method of discrete-pulse energy input into heterogeneous media, which creates conditions for intensive growth of vapor bubbles and their removal. The pH values were obtained and the concentrations of carbonic acid in the acidic condensate and the model solution were calculated from the duration of their processing. It was found that the main change in the pH of the model solution and acidic condensate occurs approximately during the first two minutes of processing. The increase in pH and, consequently, the decrease in the dissolved carbonic acid content of both liquids for several days are explained by the relaxation process during which carbon dioxide microbubbles emerge from the liquid, which did not have time to leave the liquid. Data from experimental studies of the dynamics of dissolved carbonic acid content, together with theoretical studies of the growth of gaseous bubbles in liquid and the evolution of a set of vapor bubbles to a critical value of gas content can be used to optimize cavitation degassing processes and justify optimal parameters of these processes. The proposed method of degassing can be used for reagent-free neutralization of acid condensate, which will improve the environment by reducing wastewater (chemically contaminated neutralized condensate and waste water softeners) and rational use of water resources by reducing the need for natural water. Also, the proposed method of liquid degassing can be used in the food industry, in particular, in the production of juices, beverages, vegetable oils, etc.

The Effect of Water and Sodium Hydrogen Bicarbonate Content on Flexible Polyurethane's Microstructure, Water and Mechanical Properties

The Effect of Water and Sodium Hydrogen Bicarbonate Content on Flexible Polyurethane's Microstructure, Water and Mechanical Properties

Chloride Induced Corrosion and Carbonation in 3D Printed Concrete

The durability of reinforced concrete structures is dependent on the ability of the concrete cover to combat the ingress of chlorides and carbon dioxide in marine and urban environments. In recent years, interest in additive manufacturing, specifically referring to extrusion based three-dimensional concrete printing (3DCP), has been growing in the construction industry. Despite this being a promising technology that can save construction time, costs and resources, certain issues regarding the lack of fusion between subsequent printed layers have been brought to light. Research has shown that the lack of fusion at the interlayer regions can act as ingress pathways for corrosion contaminants, such as carbon dioxide and chloride aqueous solution, that can cause deterioration. This study investigates the interlayer bond strength (flexural strength) and durability performance of 3D printed concrete subjected to pass times between 0 and 30 min and compares the results to reference cast concrete of the same concrete mixture. The durability study includes Durability Index testing (oxygen permeability, water sorptivity and chloride conductivity index), accelerated concrete carbonation and chloride-induced corrosion. The results show that the cast samples outperform printed samples, yielding greater flexural strength and durability properties, and emphasize the importance of improving the 3DCP interfacial bond. Cast samples are shown to have randomly distributed, compact voids compared to the interconnected and elongated pores located at the interlayer regions of printed samples. In addition, printed samples yield lower interlayer bond strength and durability properties with an increase in pass time, which is attributed to surface moisture evaporation as well as the thixotropic behaviour of the concrete mixture. Good relationships between the mechanical strength and durability performance are also presented.

Diffusion coefficients at infinite dilution of carbon dioxide and methane in water, ethanol, cyclohexane, toluene, methanol, and acetone: A PFG-NMR and MD simulation study

Diffusion coefficients at infinite dilution are important basic data for all processes involving mass transfer. They can be obtained from studying samples in equilibrium using nuclear magnetic resonance spectroscopy with pulsed field gradients (PFG-NMR), a technique which is widely used in chemistry but is only rarely applied in engineering studies. This advantageous technique was employed here to measure the self-diffusion coefficients of diluted solutions of carbon dioxide and methane in the pure solvents water, ethanol, cyclohexane, toluene, methanol, and acetone at 298.15 K. For the systems (carbon dioxide + water) and (carbon dioxide + ethanol), measurements were also carried out at 308.15 K, 318.15 K and 333.15 K. Except for (methane + water) and (methane + toluene), no literature data for the methane-containing systems were previously available. At the studied solute concentrations, there is practically no difference between the self-diffusion coefficient and the mutual diffusion coefficient. The experimental results are compared to experimental literature data as well as to results from semi-empirical methods for the prediction of diffusion coefficients at infinite dilution. Furthermore, molecular dynamics simulations were carried out for all systems to determine the diffusion coefficient at infinite dilution based on force fields that were taken from the literature, and the results are compared to the experimental data and those from the classical prediction methods.

AI-PCSAFT approach: New high predictive method for estimating PC-SAFT pure component properties and phase equilibria parameters

In this work, a new approach based on the association of Artificial intelligence method (AI) and PC-SAFT equation of state is applied to conceive a model for estimating the solubility of solid drugs in supercritical carbon dioxide. Neuro-equation of state approach (NES) is the new technique that takes benefit from the advantages of both ANN and PC-SAFT equation of state. The new method decomposes into three main stages, first the optimization of direct ANN for predicting solids-scCO2 phase equilibria (where 15 binary systems are used), then the ANN inverse is performed to be an alternative to group contribution methods (GCMs) for estimating the pure components and physical properties (reduce the uncertainty committed in estimating these properties) and enhance the PCSAFT equation of state to estimate phase equilibria parameters and finally, ANN-PCSAFT approach is used to estimate the solubility of 213 solid solutes in supercritical carbon dioxide. The performance strategy has been carried out using a linear regression analysis of the predicted versus experimental outputs, as an indication of the predictive ability of the developed method.The new approach is successfully applied to the phase equilibria modeling for 213 binary systems with high accuracy (the comparison in terms of average absolute relative deviation (AARD %) showed a variation from 2 to 6%) and allowed to enhance the phase equilibria modeling by reducing the number of optimized parameters and surpass the main drawbacks faced in this area mainly the non-availability of physical properties and EOS pure component properties and the limitation of the equation of state.

Ab-Initio Molecular Dynamics Simulation of Condensed-Phase Reactivity: The Electrolysis of Ammonia and Ethanimine in Aquatic Carbon Dioxide Solutions

The re-use of wastewater is an increasingly important subject. Most recently, several attempts were reported to convert wastewater in harmless or even valuable substances by the use of electrical current. Electrochemistry is an old approach. The renewed interest stems from the fact that electrical current is often available in abundance, for example from solar energy in arid regions, while clean water is not. Experimentally, one has to deal with very many products which are the result of many reaction steps. Here, theory can help. Using Car–Parrinello molecular dynamics, we simulate the first few reaction steps of the electrolysis of wastewater. On the basis of previous studies, we investigate the reaction of carbon dioxide and nitrogen compounds. The results show a great variety of reaction steps and resulting products. Some of them are technologically interesting, such as hydrogen and formic acid.

Development of novel wet sublimation cascade refrigeration system with binary mixtures of R744/R32 and R744/R290

The use of carbon dioxide (R744) in refrigeration systems is usually limited by its triple point temperature of −56.5 °C; an objective of this study was to extend the range of this natural refrigerant to include low-temperature applications. A novel wet sublimation cascade refrigeration system was developed using low-GWP mixtures of R744 with hydrocarbons (HCs) and hydrofluorocarbons (HFCs) as low-temperature refrigerants. With propane (HC-290) and difluoromethane (HFC-32) serving as solvents for solid carbon dioxide, temperatures as low as −72 °C were obtained in a closed cycle system with mixtures containing 67% CO2 by mass. Visualisation experiments were performed to illustrate the crystallisation of a supersaturated carbon dioxide solution. The excess solute was visible as clouding or crystals, depending on the saturation level of the solution. High heat transfer rates, up to 3465 W m–2K−1, were obtained in the sublimator/evaporator section, resulting in low wall superheat values, indicating potential industrial applicability of the carbon dioxide-based slurry-like fluid. The pressure–mole fraction and temperature–mole fraction diagrams were constructed to study the system parameters working with binary mixtures. Moreover, vapour pressures of the binary mixtures of R744/R290 and R744/R32 at the temperature of –72.5 °C were experimentally obtained.