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To solve the problem of treating isobutanol-containing wastewater in industrial production, four relatively green solvents (hexamethyldisiloxane, isopentyl acetate, ethyl acetate, and propylene carbonate) were selected as the extractants for the separation of water and isobutanol. Liquid–liquid equilibrium (LLE) data for water + isobutanol + hexamethyldisiloxane/isopentyl acetate/ethyl acetate/propylene carbonate were measured at 298.2 K and 101.3 kPa. The extraction performance of the four extractants was evaluated by the distribution coefficient (D) and separation factor (S). Meanwhile, the experimental LLE data were fitted using NRTL and UNIQUAC models to obtain the regression parameters. Mixed-surface analysis based on Gibbs energy topology verified the reliability of the binary interaction parameters. The root-mean-square deviation (RMSD) of the NRTL and UNIQUAC models was less than 0.0045 and 0.0059, respectively, which indicated that the NRTL and UNIQUAC models were suitable for the study of this system.

In this study, we measured the liquid–liquid equilibrium (LLE) data of the ternary system {water + 2,2-difluoroethanol + solvent (1-hexanol, 1-heptanol, 1-octanol, and 1-nonanol)} at 303.2 K and 101.3 kPa. The distribution coefficient (D) and separation factor (S) of the solvent were calculated from the experimental data to examine the extraction performance of the solvent, and the results showed that the solvent extraction capacity increased with the increase in the number of carbon atoms. The NRTL and UNIQUAC activity coefficient models were applied to correlate the experimental values and optimize the binary interaction parameters. The reliability of the binary interaction parameters was verified by a hybrid surface analysis on the basis of the Gibbs energy topology. The root-mean-square error (RMSD) values of both models were below 0.01%, which implies that both models are suitable for correlating the LLE experimental data of this study. In addition, the interaction forces between the solvent and {water + 2,2-difluoroethanol} were also analyzed by σ-profile.

To explore the performance of n-alkanes with different alkyl chain lengths to extract ethyl acrylate from aqueous solutions, LLE data for the ternary system [water + ethyl acrylate + n-alkanes (C5, C6, C7, and C12)] were measured at 303.2 K, 101.25 kPa. Partition coefficients and separation factors were calculated as parameters for the evaluation of extractant extraction performance, where n-dodecane had the highest Sand Dvalues, indicating that it is a suitable extractant. The NRTL and UNIQUAC models were used to correlate the systems involved in this work, and the optimal binary interaction parameters were obtained. The smaller rmsd values indicate the good applicability of these two models for this ternary system, with values less than 0.88 and 0.78%, respectively. The mixed surface analysis of the Gibbs energy topology was used to test the obtained parameters, and the results showed that the parameters were reliable. In addition, the molecular force between the extractant and ethyl acrylate was determined to be van der Waals force by σ-Profile analysis and increased with the number of carbon atoms of n-alkanes.

Industrial wastewater usually contains large amounts of butanols which form azeotropic mixtures with water. Efficiently and cleanly separating these azeotropes while saving energy is an urgent problem to solve. This study used two types of solvents to measure the ternary liquid-liquid equilibrium (LLE) data for extracting n-butanol, sec-butanol, and tert-butanol from water at 298.2 K and 101.3 kPa. The obtained data was correlated with NRTL and UNIQUAC models to obtain relevant binary interaction parameters. The reliability of the binary interaction parameters was verified using a Gibbs energy topology-based mixture surface analysis method. The root mean square deviations of the two models were less than 0.0061 and 0.0072, respectively, indicating that both the NRTL and UNIQUAC models could correlate the experimental data well. The extraction performance was evaluated using the distribution coefficient (D) and the separation factor (S). Isopentyl acetate showed better extraction performance, and the differences in the molecular structures of butanols also showed regularity during the extraction process. Combined with quantum chemistry calculations, the hydrogen bond donors and acceptors between six ternary systems were analyzed using the COSMO-SAC method. The intermolecular interaction energies were calculated using the Dmol3module. Finally, through IGMH and AIM analysis, it was proved that the difference in hydrogen bond strength between isopentyl acetate/ethyl acetate and butanols with different molecular structures is the reason for this difference. This study provides basic data and parameters for the design of butanols extraction processes through a combination of experiments and quantum chemistry calculations.

Wastewater from coking and pharmaceutical processes often contain a significant amount of 2-methylpyridine, which forms an azeotropic mixture with water. Effectively and cleanly separating 2-methylpyridine from wastewater while conserving energy and obtaining high purity products is an urgent challenge. In this study, ternary liquid-liquid equilibrium (LLE) data for the extraction of 2-methylpyridine from wastewater were measured using three distinct solvents at temperatures of 303.2 K, 313.2 K, and 323.2 K. The obtained ternary data were subsequently correlated with thermodynamic models (NRTL and UNIQUAC) to get relevant binary interaction parameters, bridging a gap in Aspen Plus simulations of 2-methylpyridine separation by octanol solvents. Furthermore, the GUI tool was used to validate these parameters and the results confirmed the reliability of the obtained parameters. It was observed that as the temperature increased, the extraction performance of all systems decreased, indicating that elevated temperature are not conducive to the extraction process. Among the various components, iso-octanol showed the highest separation factor indicating better extraction efficiency of 2-methylpyridine. Additionally, this study integrated quantum chemical calculations to reveal the interaction mechanisms between different solvents, 2-methylpyridine, and water at the microscopic level. The computational results indicated that iso-octanol exhibited the most robust binding affinity with 2-methylpyridine, suggesting that iso-octanol has more excellent extraction properties.

The development and research of biomass fuels have been paid more and more attention. The production of methacrylic acid is accompanied by a large amount of water and environmental pollution. Therefore, the separation of methacrylic acid from aqueous solution is of great significance for industrial production and environmental protection. The liquid–liquid equilibrium (LLE) for ternary systems of water + methacrylic acid + alcohol solvents at 303.2 K and 101.3 kPa was investigated. Thermodynamic models (NRTL and UNIQUAC) were used to correlate and regress the experimental data. The root-mean-square deviation (RMSD %) was used to evaluate the deviation between the experimental value and the calculated value, which were 1 and 1, respectively, indicating that the extractants selected in the experiment could well separate methacrylic acid from the aqueous solution, and 1-octanol exhibits better extraction performance. The correlation of LLE data is proven by MATLAB. In addition, the binary interactive parameters of the model regression are verified by MATLAB.

In order to recover 3-methoxybutyl acetate from an aqueous solution containing 3-methoxybutyl acetate, four n-alkanols (C5–C8) with different carbon chain lengths were selected as solvents for the liquid–liquid equilibrium (LLE) experiment of water + 3-methoxybutyl acetate + n-alkanols and the LLE data were measured at 303.2 K, 101.3 kPa. And by calculating the distribution coefficient (D) and separation factor (S), the separation effect of different extractants was compared and discussed. The obtained LLE data were correlated by NRTL and UNIQUAC models, and the binary interaction parameters of each system were determined. The model data for each system passed the hybrid surface analysis test of the Gibbs energy topology, indicating that the obtained model data are reliable. The root-mean-square deviation (RMSD) of the two models was less than 0.72 and 0.58%, respectively. The σ-profiles and interaction energy analysis were used to investigate the effect of alkyl chain length on separation efficiency. The analysis showed that the longer the alkyl chain length of n-alkanols, the higher the extraction efficiency of n-alkanols.