Carbon dioxide physical dissolution

Notice that four of these steps (s2 through s5) are chemical or electrochemical steps, while step Si denotes the physical dissolution of carbon dioxide as it moves from the gas phase into the electrolyte phase. 

Experimental investigations of carbon dioxide mineral trapping have been started, but there is little understanding of the processes involved on the molecular level, due to the complex nature of the brine and the physical conditions present in the brine aquifers. One such complexity issue is the dissolution of CO2 from the gaseous phase into aqueous solution. This process is thermodynamically unfavorable with a ArG° value of 2.00 kcal/mol, in pure water at STP [3]. This becomes even more thermodynamically unfavorable as salts are introduced into the solution. Figure 17.1 shows how the solubility of CO2 in aqueous solution is also dependent upon the salt concentration and salt composition, even from simple salt solutions. According to Fig. 17.1, there is no correlation with size and the ability for the solution to uptake the C02. 

Bowers, P. G. Rubin, M. B. Noyes, R. M. An-dueza, D. Carbon Dioxide Dissolution as a Relaxation Process A Kinetics Experiment for Physical Chemistry, J. Chem. Educ. 1997, 74, 1455-1458. 

In this chapter, we present results of the testing of a broad spectrum of polymers in carbon dioxide over a range of temperatures and pressures and evaluation of the effect of the high pressure carbon dioxide on the chemical/physical properties of materials tested. The testing was performed in a static manner with four controlled variables, namely temperature, pressure, treatment time and decompression time. The evaluation of the interaction of high pressure carbon dioxide with polymers included sorption and swelling behavior, solubility issue, plasticization and crystallization, and mechanical properties. The results of these evaluations are discussed in three sections Sorption, Swelling and Dissolution of Carbon Dioxide in Polymers at Elevated Pressure, Thermal Properties, and Mechanical Properties. ... 

Biological activities, such as photosynthesis and respiration, physical phenomena, such as natural or induced turbulence with concomitant aeration, and above all processes such as the precipitation and dissolution of CaC03 and of other minerals influence pH regulation through their respective abilities to decrease and increase the concentration of dissolved carbon dioxide. Besides photosynthesis and respiration, other biologically mediated reactions affect the H" ion concentrations of natural waters. Oxygenation reactions often lead to a decrease in pH, whereas processes such as denitrification and sulfate reduction tend to increase pH. 

On the contrary, the gas dissolution foaming process, and in particular the high-pressure or supercritical CO2 gas dissolution foaming, allows obtaining micro-and nanoporous polymers. In this technique CO2 is used as a physical blowing agent [39,57-59] this gas is one of the best options for this kind of process because of its excellent characteristics of diffusion in the supercritical state and the mild conditions to reach this state (31°C and 7.3 MPa). Last but not the least, carbon dioxide is a green solvent that can be removed without residue or production of any pollutant compound [60,61]. 

Practice Problem A Which of the following processes is a physical change (a) evaporation of water (b) combination of hydrogen and oxygen gas to produce water (c) dissolution of sugar in water (d) separation of sodium chloride (table salt) into its constituent elements, sodium and chlorine (e) combustion of sugar to produce carbon dioxide and water. 

Capture processes were developed in the past to remove acid gases such as carbon dioxide and hydrogen sulfide (H2S) from natural gas. They are mainly based on chemical and physical dissolution of the acid gas in aqueous solutions of amines. The technique is considered as mature enough to be adapted in next future to the treatment of post combustion effluents. The new processes should take into account difference from natural gas treatment such as temperature, pressure or composition of the effluent. However one major barrier for the integration into industrial sites in the few coming years is the economical cost of the so called ton of CO2 avoided. Specific researches are then carried out on both the technology and the choice of the absorbent solutions. 

Absorption in alkaline solution is a common principle used in acid gases capture processes operating for decades in natural gas treatment. The reference absorbent is aqueous solution of monoethanolamine (MEA). The mechanism of capture is a combination of chemical and physical dissolution. The chemical dissolution is based on an acido-basic reaction. The reaction must be reversible in order to regenerate the absorbent solution and recover carbon dioxide for storage. The physical dissolution, usually observed fot high partial pressure of CO2, can be improved by addition of specific physical solvent. 

The increase of partial pressure of carbon dioxide forces the physical dissolution. This mechanism is purely mechanical and results in the apparition of molecular CO2 in the solution. This physical dissolution is particularly considerate in the treatment of natural gas in which partial pressure of carbon dioxide can reach hundreds of bars. In the case of CO2 capture in industrial effluent, partial pressure of CO2 remains below atmospheric pressure and carbon dioxide is mainly chemically absorbed with formation of carbamate and hydrogen carbonate. 

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