Investigation of ionic liquid adsorption and interfacial tension reduction using different crude oils; effects of salts, ionic liquid, and pH.

The results revealed the significant effect of NaCl, KCl, CaCl, MgCl, CaSO, MgSO, and NaSO and pH values of 3.5-11 on the interfacial tension (IFT) reduction using three types of neutral, acidic, and basic crude oils, especially for acidic crude oil (crude oil II) as the pH was changed from 3.5 to 11 (due to saponification process). The findings showed the highest impact of pH on the IFT of crude oil II with a reducing trend, especially for the pH 11 when no salts exist. The results revealed that the salts except MgCl and CaCl led to a similar IFT variation trend for the case of distilled water/crude oil II. For the MgCl and CaCl solutions, a shifting point for IFT values was inevitable. Besides, the dissolution of 1-dodecyl-3-methyl imidazolium chloride ([Cmim][Cl]) with a concentration of 100-1000 ppm eliminates the effect of pH on IFT which leads to a reducing trend for all the examined crude oils with minimum IFT of 0.08 mN/m. Finally, the [Cmim][Cl] adsorption (under pH values) for crude oils using only NaSO was measured and the minimum adsorption of 0.41 mg surfactant/g Rock under the light of saponification process was obtained.