Liquid-liquid equilibrium data have been determined for imidazolium ionic liquid ([C(4)mim]Cl, [C(6)mim]Cl, [C(4)mim]Br, [C(6)mim]Br, [C(8)mim]Br, [C(10)mim]Br) + salt (KOH, K2HPO4, K2CO3, K3PO4) aqueous biphasic systems at T = 298.15 K, and in part at T = (308.15 to 318.15) K. Factors affecting the binodal curves such as nature of ionic liquids and salts and temperature are also studied. The binodal curves are fitted to a three-Parameter equation, and the tie-lines were described by the Othmer-Tobias and Bancroft equations. It is found that an increase in temperature caused no significant expansion of the two-phase area. However, the binodal curves became more close to the origin with an increase in alkyl chain length of the ionic liquids (ILs), and the ionic liquids with the Br anion are easier to form two phases compared to those with the Cl- anion. These data are expected to be useful for the development and design of the extraction process using ILs based on aqueous biphasic systems.