Most of the crude oils in the world are produced as water-crude oil emulsions. Removal of water from the emulsions is one of the major issues in the industry and the process is completed before transportation and refining. One of the methods to remove water is through demulsification. In the present study, ionic liquids, non-volatile and non-toxic solvents, are used as demulsifiers. Three ionic liquids (ILs), namely 1-ethyl-3-methylimidazolium acetate (EMIM-AC), 1-butyl-3-methylimidazolium chloride (BMIM-Cl) and 1-butyl-3-methylimidazolium hydrogen sulfate (BMIM-HSO4), were evaluated to treat a heterogeneous mixture of crude oil and water. The bottle tests were conducted at 60 °C and salinity of 50,000 ppm. Response surface methodology (RSM) was used to study the effect of IL type, its concentration, and residence time towards demulsification efficiency. The developed correlation gave a high correlation coefficient, R2 of 0.924. Analysis shows that the IL concentration gives the highest influence on the demulsification efficiency, followed by the residence time and the type of ionic liquid. Among the three ILs investigated, 1000 ppm BMIM-HSO4 achieved the highest demulsification efficiency, where complete separation (100 demulsification efficiency) was attained within 30 min. BMIM-Cl achieved 72 efficiency after an hour while the EMIM-AC reached maximum separation after 52 min with 45 efficiency. © 2022