To investigate long-term CO2 behavior in geological formations and quantification of possible CO2 leaks, it is crucial to investigate the potential mobility of CO2 dissolved in brines over a wide range of spatial and temporal scales and density distributions in geological media. In this work, the mass transfer of aqueous CO2 in brines has been investigated by means of a chemical potential gradient model based on non-equilibrium thermodynamics in which the statistical associating fluid theory equation of state was used to calculate the fugacity coefficient of CO2 in brine. The investigation shows that the interfacial concentration of aqueous CO2 and the corresponding density both increase with increasing pressure and decreasing temperature; the effective diffusion coefficients decrease initially and then increase with increasing pressure; and the density of the CO2-disolved brines increases with decreasing CO2 pressure in the CO2 dissolution process. The aqueous CO2 concentration profiles obtained by the chemical potential gradient model are considerably different from those obtained by the concentration gradient model, which shows the importance of considering non-ideality, especially when the pressure is high.

In this paper, the methodology of non-equilibrium thermodynamics is introduced for kinetics research of CO 2 capture by ionic liquids, and the following three key scientific problems are proposed to apply the methodology in kinetics research of CO 2 capture by ionic liquids: reliable thermodynamic models, interfacial transport rate description and accurate experimental flux. The obtaining of accurate experimental flux requires reliable experimental kinetics data and the effective transport area in the CO 2 capture process by ionic liquids. Research advances in the three key scientific problems are reviewed systematically and further work is analyzed. Finally, perspectives of non-equilibrium thermodynamic research of the kinetics of CO 2 capture by ionic liquids are proposed.

The coupling behaviors of mass transfer of aqueous CO2 with mineral reactions of aqueous CO2 with rock anorthite are investigated by chemical potential gradient and concentration gradient models, respectively. SAFT1-RPM is used to calculate the fugacity of CO2 in brine. The effective diffusion coefficients of CO2 are obtained based on the experimental kinetic data reported in literature. The calculation results by the two models and for two cases (mass transfer only and coupling mass transfer with mineral reaction) are compared. The results show that there are considerable discrepancies for the concentration distribution with distance by the concentration gradient and chemical potential gradient models, which implies the importance of consideration of the non-ideality. And the concentrations of aqueous CO2 at different distances by the concentration gradient model are higher and further than that by the chemical potential gradient model. The mineral reaction plays a considerable role for the CO2 geological sequestration when the time scale reaches 10 years for the anorthite case.

Thermodynamic and dynamic investigations are needed to study the sequestration capacity, CO2 leakage, and environmental impacts. The results of the phase equilibrium and densities for CO2-sequestration related subsystems obtained from the proposed thermodynamic model on the basis of statistical associating fluid theory equation of state were summarized. Based on the equilibrium thermodynamics, preliminary kinetics results were also illustrated with chemical potential gradient as the driving force. The proposed thermodynamic model is promising to represent phase equilibrium and thermodynamic properties for CO2-sequestration related systems, i.e. CO2-(H2S)-H2O-ions (such as Na+, K+, Ca2+, Mg2+, Cl-, CO32-), and the implementation of thermodynamic model into kinetics model to adjust the non-ideality of species is vital because of the high pressure for the investigation of the sequestration process.

In this paper, the research framework for specific structure crystallization modeling has been proposed in which four steps are required in order to investigate the rigorous crystallization modeling by thermodynamics. The first is the activity coefficient model of the solution, the second is Solid-Liquid equilibrium, the third and fourth are the dissolution and crystallization kinetics modeling, respectively. Our investigations show that the mechanisms of complex structure formation and microphase transition can be analyzed by combining the dissolution and crystallization kinetics modeling. Moreover, the formation mechanism of the porous KCl has been analyzed, which may provide a reference for the porous structure formation in the advanced material synthesis

The concentration of CO2 in atmosphere has been increasing greatly because of the fossil fuel combustion, which leads to a significant climate changes. CO2 is one of the most important greenhouse gases being responsible for about 64% of the enhanced "greenhouse effect" [1], and the disposal of anthropogenic CO2 has become an important issue of worldwide concern. Geological sequestration, generally refers to the injection of CO2 into deep geological formations such as deep saline aquifers, depleted hydrocarbon reservoirs or deep coalbeds, is attracting great attention [2] because of the large capacity and long residence time [3]. To predict the sequestration potential, to study the long-term behavior of CO2, and to estimate the potential for CO2 leakage in the geologic reservoirs, it is necessary to study the transport rate of CO2 in porous media with aqueous solutions. In the present work, the transport rate of CO2 in porous media with aqueous solutions is described and predicted by the Gibbs free energy gradient modeling based on linear nonequilibrium thermodynamics, and the Statistical Associating Fluid Theory equation of state is used to calculate the Gibbs free energy of the components in the investigated systems. The effects of temperature and pressure are analyzed.

Microstructure technologies have attracted interests in chemistry, chemical engineering, and biotechnology. To investigate the mass transfer of ions and crystallization of crystals in microscale and then to explain the formation mechanism of the porous structure materials, a microscale mathematical model for mass transfer processes coupling with local reactions is proposed in which the chemical potential gradient Δμ is used as the driving force to avoid the discontinuity of the kinetics equations in the micro-channels. Meanwhile, the dissolution kinetics of KCl at 298.15 K is measured to determine the dissolution rate constant kd and the average area of crystals Ac. The investigation for the fractional crystallization process of carnallite shows that the calculated mixing time versus channel width agree with the Einstein diffusion equation, which validates that the model can be used to describe the ion diffusion very well. Meanwhile, to have an accurate Δμ of KCl, in the channel width of or narrower than 2.0×10-6 m, it is enough to consider the diffusion only, while in the channel width of or wider than 2.0×10-5 m, diffusion should be coupled with reaction. The investigation also shows the vital of the consideration of the ionic activity coefficient for the investigated systems in micron scales. Moreover, the new formation mechanism of the porous structures in the inorganic material fabrication will be proposed from the process simulation for the synthesis of porous KCl, which will provide a reference for the porous structure formation in the advanced inorganic material synthesis.

This paper quantifies the theoretical limit of energy consumption for the removal of 20 representative organic contaminants (9 chlorinated alkyl hydrocarbons, 3 chlorinated alkenes, 3 brominated methanes, 5 aromatic hydrocarbons and their derivatives) in the United States Environmental Protection Agency (U.S. EPA) Priority Pollutant List by physical procedures. The general rules of the theoretical limit of energy consumption with different initial concentrations at 298.15 K and 1.01325 × 105 Pa by NRTL, UNIQUAC and Wilson models are obtained from the thermodynamic analysis with our previously established method based on the thermodynamic first and second law. The results show that the waste treatment process needs a high energy consumption and the theoretical limit of energy consumption for organic contaminant removal increases with decreasing initial concentrations in aqueous solutions. The theoretical limit of energy consumption decreases with the more C-H bonds being replaced by C-Cl or C-Br bonds in chlorinated methanes, ethanes, ethenes or brominated methanes except for 1,1,2,2-tetrachloroethane, and the energy consumption for the removal of chlorinated methanes is higher than that of chlorinated ethanes with the same C-H bonds being replaced by C-Cl bonds. For the removal of chlorinated ethenes, brominated methanes and benzene and its derivatives studied, the energy consumption has corresponding relationship with solubility and the energy consumption is higher for the removal of organics with higher solubility.