Carbon dioxide is a major greenhouse gas that is responsible for global warming and renders harmful effects on the atmosphere. The unconstrained release of CO2 into the atmosphere should be prevented and various techniques have been developed in this regard to capture CO2 using different solvents and other compounds. Ionic liquids are a suitable candidate to capture CO2 due to their better solubility behaviour. In this work, two ionic liquids namely tetramethylammonium bromide (TMAB) and tetraethylammonium bromide (TEAB) are employed experimentally to capture CO2 and investigate their solubility behaviour. The study is performed at the temperature values of 303 K, 313 K, and 323 K and the pressure values of 5, 10, 15, and 20 bar equivalent to 0.5, 1.0, 1.5, and 2.0 MPa respectively. The concentrations of both ionic liquid solutions are 2.5 wt%, 5.0 wt%, and 10.0 wt%. The solubility results are considered in terms of mol fraction which is the ratio of moles of CO2 captured per moles of ionic liquid. The density and viscosity values are also determined for both compounds at respective conditions. COSMO-RS is used to generate the sigma profile, sigma surface, and Henry's constant of the ions involved in the study. CO2 is found to be soluble in both ionic liquids, but TEAB showed better solubility behaviour as compared to TMAB. The solubility of CO2 is found to be increasing with the increase in pressure while it decreases with the increase in temperature.
Activity coefficient values offer insight into the intermolecular interactions between the solute and the solvent and the deviation from the ideal behavior. CO2 capture from different industrial processes is a globally pertinent issue and the search for suitable chemicals is required. To address the issue, knowledge of activity coefficient values is crucial for CO2 separation-based process. In this regard, a correlation is developed that predicts the coefficient of CO2 activity in ionic liquids by multi-nonlinear regression analysis. The correlation is developed between the pressure range of 1-50 bar and the temperature range of 298.15-33.15 K for mole fractions of 0.3, 0.5, and 0.7. Outliers' analysis is performed using the boxplot method to determine the suitability of ranges of the selected input parameters. The preceding literature does not predict the activity coefficient in relatively lower to higher temperature and pressure ranges for CO2 solubility in ionic liquids. Initially, the activity coefficient values from COSMO-RS were obtained and compared with the correlation results. The COSMO-RS and the correlation predicted results were subsequently validated with the experimental data. The average absolute error (AAE%) of the predicted correlation values is 19.53% while the root mean square error (RMSE) value is 0.465. The correlation can be used in the future to predict the CO2 activity coefficient values in ionic liquids to facilitate qualitative analyses of their CO2 capture efficiency.
The polymer-surfactant mixture has usages in numerous industries mainly in the production of daily used materials. Herein, the micellization and phase separation nature of the sodium dodecyl sulfate (SDS) and TX-100 along with a synthetic water-soluble polymer-polyvinyl alcohol (PVA) have been conducted using conductivity and cloud point (CP) measurement tools. In the case of micellization study of SDS + PVA mixture by conductivity method, the CMC values were obtained to be dependent on the categories and extent of additives as well as temperature variation. Both categories of studies were performed in aq. solutions of sodium chloride (NaCl), sodium acetate (NaOAc), and sodium benzoate (NaBenz) media. The CP values of TX 100 + PVA were decreased and enhanced in simple electrolytes and sodium benzoate media respectively. In all cases, the free energy changes of micellization (∆Gm0) and clouding (∆Gc0) were obtained as negative and positive respectively. The enthalpy (∆Hm0) and entropy (∆Sm0) changes for SDS + PVA system micellization was negative and positive respectively in aq. NaCl and NaBenz media, and in aq. NaOAc medium the ∆Hm0 values were found negative while ∆Sm0 were found negative except at the highest studied temperature (323.15 K). The enthalpy-entropy compensation of both processes was also assessed and described clearly.