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

Abstract

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, [Cnim-C4-imCn][Br2], n = 4, 8, and 12 with individual and mixture of NaCl, MgCl2 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.