Mechanism responsible altering in interfacial tension and emulsification of the crude oil-water system with nano Gemini surface active ionic liquids, salts and pH

Gemini surface active ionic liquids (GSAILs) exhibit desired activities for enhanced oil recovery (EOR). This study explores the simultaneous effects of homologous series of imidazolium nano GSAILs, [C n im-C 4 -imC n ][Br 2 ], n = 4, 8, and 12 with individual and mixture of NaCl, MgCl 2 salts and also with aqueous phase pH on the crude oil–water system. In the presence of the medium and long alkyl chain GSAILs, electrolytes can establish extra 93.1 and 52.6% reductions in interfacial tension (IFT) and the critical micelle concentration (CMC), compared to the salt-free system, respectively. These were while, the IFT and the CMC were initially decreased with the concentration of electrolytes and then a slight increase was corresponding with the short alkyl chain GSAIL. Results also revealed 79.2% more IFT reductions under pH 9.5 compared to the natural pH as well as high stability of GSAILs within the wide pH range of (2.5–9.5). Meanwhile, crude oil and electrolyte aqueous solutions showed one day emulsification indices within (40–85)% with little decrease after one week. Remarkably, an emulsification index of more than 90% could be achieved at pH 9.5. • The GSAILs can reduce the crude oil-water IFT to ultra-low values. • Excellent stability of the Gemini SAILs was revealed under salinity and a wide pH range. • Salts continuously reduce the IFT and CMC of long alkyl chain GSAILs while a minimum was appropriate for the short alkyl chain. • A remarkable emulsification capability was corresponding in the presence of salts. • Increasing pH gives high IFT reductions and emulsion indices.