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In this study, liquid–liquid equilibrium measurements were performed for different ternary, water (or brine)/decane or dodecane/mono-propylene glycol ether (C 3 P 1 ) or di-propylene glycol ether (C 3 P 2 ) systems in order to build the so-called fish phase diagrams (temperature as a function of surfactant for a given polar-apolar solvent mixture) and to compare them to the well-known water (or brine)/decane or dodecane/ethylene glycol mono-butyl ether (C 4 E 1 ) phase diagrams. The study is motivated by the lower toxicity of the C x P y compared to the corresponding C x E y . Toxicity is of particular importance for any use of such molecules in the environment. Like in the presence of C 4 E 1 , the formation of Winsor type I → III → II phase transitions with increasing temperature was observed for the C x P y systems. The LCST (Lower Critical Solution Temperature) and UCST (Upper Critical Solution Temperature) of the newly studied systems were determined. The values of the γ 0 parameter (in mole fraction), the minimum value of surfactant needed to form Winsor III, increased in comparison to the C 4 E 1 systems. The value of γ ˜ (in mole fraction), minimum value of surfactant needed to reach Winsor IV from Winsor III, was comparable using C 4 E 1 and C 3 P 1 , and lower in the presence of C 3 P 2 . The substitution of decane by dodecane led to a stronger water affinity of C 4 E 1 and C 3 P 2 as greater values of the LCST and UCST have been observed in the presence of dodecane. By contrast, a lower hydration of C 4 E 1 and C 3 P 1 was found when increasing the NaCl content in brine. It can be concluded that less toxic C 3 P 1 and C 3 P 2 can be envisaged as a substitute of the contested C 4 E 1 to formulate microemulsions and particularly Winsor III systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Extraction of dibenzothiophene was investigated from model fuel (n-octane). • Two different Deep Eutectic Solvents were synthesized and used as extractive agents. • The structures of Deep Eutectic Solvents were confirmed by FTIR and H-NMR analyses. • Liquid-liquid equilibrium was modeled by the NRTL model. Among the most important causes of air pollution we may refer to hydrocarbon fuels with a large content of organosulfur compounds. These compounds must be removed to the level of standard concentration for which different techniques are commonly in use. Since, desulfurization of aromatic sulfur compounds, such as thiophenes, is not possible by common methods such as hydrodesulfurization, other methods should be considered. In recent years, scientists have focused on extractive desulfurization using Deep Eutectic Solvents (DES) as a new method for removing organosulfurs from hydrocarbon fuels. In this research, two new DESs are synthesized. As the model fuel, we used n-octane, and dibenzothiophene (DBT) was chosen as the organosulfur content with a 1000 ppm concentration. DESs were synthesized by mixing quaternary ammonium salts and trifluoroacetic acid in a heating method. The structures of DESs were confirmed by FTIR and H-NMR analyses. The extraction process was first carried out at temperatures ranging from 25 to 40 °C. The results showed that the best temperature was 35 °C. Then, the effect of fuel to DES mass ratio (i.e. different compositions of feed), on extraction efficiency was examined. For thermodynamic modeling of liquid–liquid equilibrium the Non Random Two Liquid (NRTL) activity coefficient model was implemented. The parameters of the NRTL model were correlated using the binary data obtained from solubility experiments. Finally, the adjusted parameters were used for predicting ternary phase equilibrium data obtained in this work. The root mean square deviation from experimental data was less than 0.11% for each solvent. [ABSTRACT FROM AUTHOR]