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In this work, three novel imidazolium-based ionic liquids containing aromatic group in the cation combined with bis(trifluoromethylsulfonyl)imide anion were synthesized and characterized. Their thermophysical properties namely, density, viscosity, thermal decomposition, glass transition, and heat capacity were measured at various temperatures and atmospheric pressure. In addition, physicochemical properties such as molar volume (Vm) and crystal energy (UPOT) were also determined from the obtained density data. Novel group contribution parameters were obtained using Gardas and Coutinho model aiming at providing simple method to predict density and viscosity of ionic liquids.

The frequent usage of cationic dyes is in the textile and leather industries. However, they are not only utilized during the dying process, but also they are recovered at the end of the process. Hence, the removal of dye from huge quantity of wastewater is necessary. In this paper methylene blue as a cationic dye have been extracted successfully into an ionic liquid namely 1-hexyl-3-methyl-imidazolium bis (trifluoromethylsulfonyl) imide, abbreviated as [HMIM][TF2N]. To investigate the feasibility of using (IL) to dye removal from aqueous solutions batch experiments were performed under different process conditions like initial dye concentration, pH and temperature. Also adsorption data were analyzed using isotherms models and was found to conform to the principle of Lagmuir model with good correlation coefficients (R2 = 0.9896).

Due to their harmful effects on human's life and aquatic environments, designing easy and swift yet efficient methodologies to remove pollutants from water stream is one of the important tasks of the scientific community. Among the pollutants, dyes have a significant role on water pollution, because their presence, even in low concentration, impacts the aquatic life by preventing the photosynthesis process and it can be considered as toxic chemicals endangering the human's health. In this study three newly synthesized Task Specific Ionic Liquids (TSILs) incorporating different types of aromatic group on imidazolium ring namely, 1-Butyl-3-Benzoimidazolium bis(trifluoromethylsulfonyl)imide [BzBIm][NTf 2 ]; 1-Butyl-2-Phenyl-imidazolium bis(trifluoromethylsulfonyl)imide [BPhIm][NTf 2 ]; and 1-Benzyl-3-butyl-imidazolum bis(trifluoromethylsulfonyl)imide [BnBIm][NTf 2 ] have been employed to remove swiftly heavy loads (up to 1,500 ppm) of cationic Methylene Blue dye (MB) from aqueous solution without pH adjustment. The results showed that the presence of additional aromatic groups has a significant effect on the extraction efficiency of MB removal through enhancement of the π–π interactions between ILs and the aromatic structure of MB. Conductor-like Screening Model for Real Solvent (COSMO-RS) was used to analyse the IL-MB interaction in the studied systems. Finally, an original microbiological method has been designed not only to assess the toxicity of aqueous solution before and after the extraction process to reveal the industrial potential of this methodology but also to highlight the high hydrophobicity of these new TSILs.

The liquid-liquid extraction of Methylene Blue (MB) from aqueous solution was undertaken with 5 hydrophobic ionic liquids (ILs) based on bis(trifluoromethylsulfonyl)imide anion [NTf2] for comparison purpose where three of them were of commercial origin, 1-butyl-3-methyl imidazolium [BMIm], 1-hexyl-3-methylimidazolium [HMIm] and 1-octyl-3-methylimidazolium [OMIm] cations and the two other were purposely designed for this work, 1-hexyl-2-phenylimidazolium [HPhIm], and 1-benzyl-3-methyl-imidazolium [BnMIm]. Several parameters such as the place and nature of the aromatic ring, the length of the side alkyl chain and the ability to form hydrogen bonding were investigated to evaluate their impact on extraction performances. Results show that the incorporation of the functional group (aromatic group) not only led to excellent results of dye removal compared to commercially available ones but allowed easier recovery and subsequent reuse of the functionalized ILs. Conductor like Screening Model for Real Solvents (COSMO-RS) calculations were also performed to see the structural variations of the ILs their extraction capabilities of MB from water. The finding of this study may assist in reducing the pollution of wastewater from dye industries.

Ionic liquids are no longer a curiosity since they have shown tremendous potential in several key sectors of chemical sciences proven by the exponential number of publications in recent years. However, due to its toxicity and time-consuming synthesis route, these have become a technical hurdle of their use in pilot or industrial scales. Notably their syntheses not only time and energy consuming but also rather of dirty nature with the use of molecular solvents for synthesis and purification steps, leading to high production cost and impeding the possible further industrial outcome. In this preliminary work, we have developed a neat and quick synthesis pathway of di-cationic ionic liquids, reducing not only the necessary time from days to minutes but also the overall energy consumption resulted in high purity, increasing their potential as green alternative to common molecular organic solvents.