Salting-in/Salting-out Mechanism of Carbon Dioxide in Aqueous Electrolyte Solutions

Abstract

The solvation of carbon dioxide in sea water plays an important role in the carbon circle and the world climate. The salting-out/salting-in mechanism of CO 2 in electrolyte solutions still remains elusive at molecule level. The ability of ion salting-out/salting-in CO 2 in electrolyte solution follows Hofmeister Series and the change of water mobility induced by salts can be predicted by the viscosity B-coefficients. In this work, the chemical potential of carbon dioxide and the dynamic properties of water in aqueous NaCl, KF and NaClO 4 solutions are calculated and analyzed. According to the viscosity B-coefficients, NaClO 4 (0.012) should salt out the carbon dioxide relative to in pure water, but the opposite effect is observed for it. Our simulation results suggest that the salting-in effect of NaClO 4 is due to the strongly direct anion-CO 2 interaction. The inconsistency between Hofmeister Series and the viscosity B-coefficient suggests that it is not always right to indicate whether a salt belongs to salting-in or salting-out just from these properties of the salt solution in the absence of solute.

Salt-Enhanced CO2-Responsiveness of Microgels

“…The solubility of CO 2 in NaCl solution without the microgels is even lower than that in water. 48 These results well connect NaCl-enhanced CO 2 -responsiveness to NaCl-enhanced CO 2 capture ability of the microgels. In addition, the experiments were done by bubbling with 10 vol % CO 2 gas, leading to a CO 2 capture ability of the microgels of about 101.1 mL/g (i.e., ca.…”

“…While the exact mechanism is not understood, the oceanic storage of CO 2 has studied for years. 48,49 It is reported that the association between CO 2 and cation or anion is not preferred compared to water−CO 2 pair, 48 and salting-out effect makes a few of the dissolved CO 2 exist as CO 2 (aq), if NaCl is added. 49 According to Hard−Soft Acid−Base theory, CO 2 is a hard acid and ether oxygen and sulfonates are hard bases, allowing them to complex to form cross-links physically with CO 2 as an intermediate (Scheme 1).…”

“…We ascribe tentatively this observation at low temperatures to the forming of new cross-links with CO 2 as an intermediate (Figures S14 and S15), and its surpassing over breakage of direct intra/interchain interactions, − resulting in an increase in apparent cross-link degree. While the exact mechanism is not understood, the oceanic storage of CO 2 has studied for years. , It is reported that the association between CO 2 and cation or anion is not preferred compared to water–CO 2 pair, and salting-out effect makes a few of the dissolved CO 2 exist as CO 2 (aq), if NaCl is added . According to Hard–Soft Acid–Base theory, CO 2 is a hard acid and ether oxygen and sulfonates are hard bases, allowing them to complex to form cross-links physically with CO 2 as an intermediate (Scheme ).…”

On the Effect of Pre-formed Scales in Mitigating Corrosion of Steels in CO2 Environments

“…This effect has also been observed by a number of researcher who found that increasing the salt concentration of the solution can reduce the corrosion rate of the target metal either by assisting the formation of a stable protection film or by reducing the solubility of corrosion accelerants such as oxygen, H 2 S or like in this case CO 2 in the solution [7,23,24]. The salting out effect, as discussed by Zhang et al [25], results in ions indirectly 'expelling' the non-polar solute of CO 2 . The Na + ions strengthen the H 2 O-H 2 O hydrogen bond which decreases the solubility of CO 2 in the water.…”

Thermodynamic modeling of gas solubility in aqueous solutions of quaternary ammonium salts with the e-CPA equation of state

“…The definition of gas solubility is the maximum quantity of gas that can dissolve in a certain quantity of solvent or quantity of solution at a specified temperature or pressure (in the case of gaseous solutes) [80]. Salting-in and salting-out are defined as the increment and reduction of the solubility of a gas due to the presence of ionic species in a solvent [81].…”