Abstract: The 1-octyl-3-methylimidazolium chloride,[C₈mim][Cl] ionic liquid (IL) was used as a novel surfactant in n-heptane/water system. The interfacial tensions (IFT) were measured and corresponding variations were investigated. An IFT reduction of 80.8% was appropriate under the IL CMC of about 0.1 mol·L^-1 and stronger effects were achieved when magnetite nanoparticles and salts were present profoundly under alkaline pHs. The equilibrium IFT data were accurately simulated with the Frumkin adsorption model. Hereafter, the saturated surface concentration, equilibrium constant and interaction parameter were obtained and their variations were demonstrated. Further, emulsion stability and contact angle of oil/water interface over quartz surface were studied. The oil/water emulsion stability was hardly changed with nanoparticles; however, the stability of oil/water+IL emulsions was significantly improved. It was also revealed that the presence of sodium and calcium chloride electrolytes fortifies the IL impact, whereas sodium sulfate weakens. From dynamic IFT data and fitting with kinetic models, it was found that the IL migration toward interface follows the mixed diffusion-kinetic control model. Consequently, the IL diffusion coefficient and the appropriate activation energy were determined.

Key words: Imidazolium ionic liquids, Interfacial tension, Magnetite nanoparticle, Emulsion stability, Frumkin adsorption model, Adsorption kinetic model

摘要： The 1-octyl-3-methylimidazolium chloride,[C₈mim][Cl] ionic liquid (IL) was used as a novel surfactant in n-heptane/water system. The interfacial tensions (IFT) were measured and corresponding variations were investigated. An IFT reduction of 80.8% was appropriate under the IL CMC of about 0.1 mol·L^-1 and stronger effects were achieved when magnetite nanoparticles and salts were present profoundly under alkaline pHs. The equilibrium IFT data were accurately simulated with the Frumkin adsorption model. Hereafter, the saturated surface concentration, equilibrium constant and interaction parameter were obtained and their variations were demonstrated. Further, emulsion stability and contact angle of oil/water interface over quartz surface were studied. The oil/water emulsion stability was hardly changed with nanoparticles; however, the stability of oil/water+IL emulsions was significantly improved. It was also revealed that the presence of sodium and calcium chloride electrolytes fortifies the IL impact, whereas sodium sulfate weakens. From dynamic IFT data and fitting with kinetic models, it was found that the IL migration toward interface follows the mixed diffusion-kinetic control model. Consequently, the IL diffusion coefficient and the appropriate activation energy were determined.

关键词: Imidazolium ionic liquids, Interfacial tension, Magnetite nanoparticle, Emulsion stability, Frumkin adsorption model, Adsorption kinetic model