Efforts to improve the interfacial activity of surfactants and the demand for low interfacial tensions (IFT)/critical micelle concentrations (CMCs) for operations under harsh conditions, have persuaded scientists to search for effective and resistive materials. For this aim, surface-active ionic liquids (SAILs) with amphiphilic nature and unique properties have received much interest in recent decades, due to their high interfacial activity, recyclability, environmental friendliness, and stability under high salinity and temperature conditions. Although the information on properties and use of SAILs is limited, a comprehensive compilation is required to understand state-of-the-art technological advances in SAILs area. Accordingly, this chapter first describes some of the basic concepts and characteristics of SAILs and then explains how the IFT and CMC change in the presence of SAILs. Then, a comprehensive overview on the effects of alkyl chain length, head group, and anion present in the chemical structure of SAILs is presented. A comparison of the performance of different structural SAILs is also provided. The following section is devoted to the review of influence of operating conditions such as temperature, presence of electrolytes, pH, and nature of phases, on SAILs performance. Thereafter, a brief discussion on relevant aspects of green chemistry is provided. Developments in the use of SAILs in different processes such as emulsion stabilization, suspension of inherent insoluble materials, as well as solid-phase extraction are also included. The current chapter attempts to provide an outlook of SAILs applications and will serve as an inspiration for further extensive research on SAILs
