Effects of Divalent Salts on the Interfacial Activity of the Mixed Surfactants at the Water/Model Oil Interface

Abstract

In our previous report, the mixed cationic/anionic surfactant system consisting of N‐dodecyl‐N‐methylpyrrolidinium bromide (L12) and sodium dodecyl sulfate (SDS) showed good interfacial tension (IFT) reduction of water/model oil (Vtoluene:V n‐decane = 1:1). In the present study, the effects of divalent salts (MgCl2 or CaCl2) on the interfacial activity were systematically evaluated. The additional Mg2+ ions greatly reduced the IFT to an ultralow value, whereas Ca2+ ions caused the generation of the precipitates and resulted in increased IFT values. The precipitates disappeared in binary divalent salt solutions, and the IFT values remained at a low level. Based on the valence, polarizability, and hydrated radius of the ions, we proposed a model to explain the abnormal changes. The effects of NaCl and temperature were investigated to further verify our proposed mechanism. Moreover, the additional divalent salts obviously enhanced the stability of L12/SDS stabilized emulsions.

Synergistic Effect of Low Salinity Surfactant Nanofluid on the Interfacial Tension of Oil–Water Systems, Wettability Alteration, and Surfactant Adsorption on the Quartz Surface

“…The first model oil (model oil A) was prepared by adding 10,000 ppm of stearic acid into the base oil. The second model oil (model oil B) was prepared by adding 10,000 ppm of n -decylamine in the base oil. − Moreover, during contact angle measurement, a small amount of oil-soluble dye (Sudan Black) was mixed with model oils to add color to the transparent model oil phase for better visibility during contact angle studies.…”

Effects of inorganic metal ions on the mixture of single polyoxyethylene chain carboxylate surfactant and Gemini quaternary ammonium surfactant

“…In particular, the synergistic effect of Mg 2+ on surfactants has been reported in many studies. [38][39][40][41] Combined with the significant increase of the zeta potential of the mixed system caused by a small amount of Ca 2+ , it can be preliminarily speculated that there is another stronger interaction between Mg 2+ /Ca 2+ and AE 7 C-Na/ ADQ-12 except the electrostatic interaction which forces metal ions and mixed surfactants to form new complexes.…”

Effect of Fe(III) Species on the Stability of a Water-Model Oil Emulsion with an Anionic Sulfonate Surfactant as an Emulsifier

“…Davis et al found that the addition of Na + reduced the electrostatic repulsion force of the anionic surfactant and allowed the surfactant to accumulate more closely on the oil–water interface, enhancing the stability of O/W emulsions stabilized by sodium lauryl ether sulfate. Compared with monovalent ions, divalent ions, such as calcium ions (Ca 2+ ) and magnesium ions (Mg 2+ ), have more significant effects on the emulsion stability, which may be attributed to the difference in the chemical structure and valence state. − Kazemzadeh et al pointed out that the interaction of asphaltene with Ca 2+ and Mg 2+ in the water phase caused a more stable water-in-crude oil emulsion, which resulted in droplets with a smaller average area and a lower value of interfacial tension . Previous studies have mainly been focused on the effects of monovalent and divalent cations on the stability of emulsions stabilized by different emulsifiers.…”