Abstract
In recent years, ionic liquids have received increasing interests as an effective demulsifier due to their characteristics of non-flammability, thermal stability, recyclability, and low vapor pressure. In this study, emulsion formation and types, chemical demulsification system, the application of ionic liquids as a chemical demulsifier, and key factors affecting their performance were comprehensively reviewed. Future challenges and opportunities of ionic liquids application for chemical demulsification were also discussed. The review indicted that the demulsification performance was affected by the type, molecular weight, and concentration of ionic liquids. Moreover, other factors, including the salinity of aqueous phase, temperature, and oil types, could affect the demulsification process. It can be concluded that ionic liquids can be used as a suitable substitute for commercial demulsifiers, but future efforts should be required to develop non-toxic and less expensive ionic liquids with low viscosity, and the demulsification efficiency could be improved through the application of ionic liquids with other methods such as organic solvents.
Highlights
The presence of emulsion in oil or in water has undesired consequences for industries and the environment [1]
Bin-Dahbag et al [106] investigated the effect of tetraalkylammonium sulfate and its concentration (100–1000 ppm) on the efficiency of interfacial tension (IFT) reduction in saline water in oil (W/O) emulsions (10% and 20% w/w salinity), and they observed that by increasing ionic liquid concentration to critical micelle concentration (CMC) (250 ppm), the IFT reduced from 18 to 3.36 mN/m and from 14.5 to 1.65 mN/m for 10% and 20% salinity of solutions, respectively, while increasing ionic liquids concentration above
Hezave et al [98,99] used pyridinium and imidazolium based ionic liquids to investigate their efficiency on IFT reduction of W/O emulsions with and without salt ions in the water, and they found that the IFT and CMC of ionic liquids for emulsions containing salt ions
Summary
The presence of emulsion in oil or in water has undesired consequences for industries and the environment [1] It may result in the corrosion of pumps, pipes, and related facilities. Molecules 2020, 25, 4915 produced by a combination of different organic cations and organic or inorganic anions [20] They are associated with unique characteristics such as thermal stability, non-flammability, recyclability, and low vapor pressure [21,22,23]. This review is organized into a few sections, including emulsion formation mechanisms and types, chemical demulsification system and ionic liquids application, the effects of influential parameters (concentration, cation type, and the structure of ionic liquids, anion types, molecular weight, salinity, temperature, and oil types), as well as challenges and opportunities for future applications
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