Effects of sodium chloride on adsorption at different interfaces and aggregation behaviors of disulfonate gemini surfactants

Abstract

Schematic illustration of NaCl effects on the adsorption of Cn-DADS molecules at different interfaces (Cl− is not shown).

Surface and Interfacial Tension Behavior of Salt Water Containing Dissolved Amphiphilic Compounds of Crude Oil: The Role of Single-Salt Ionic Composition

“…At the same concentration of ionic/non-ionic surfactants in the water, below or above the critical micelle concentration (cmc), the surface/interface affinity of surfactants increases with an increasing ionic strength of water. − This is owing to the salt-out effect on the hydrophobic tail of surfactants. In fact, although it is possible that minor parts of surfactants become transferred to the oil phase, their major parts become adsorbed at the interface. − Besides, in the case of ionic surfactants, hydrophilic heads can pack more closely at the interface as a result of the counterion effect, in which the salt ions decrease the repulsion force between the charged heads of surfactants. , Owing to the salt-out and counterion effects, as the ionic strength increases, the ST/IFT of water decreases. With further increases in the ionic strength, above the optimal, the salt-out effect leads to the transfer of a larger part of surfactants to the bulk of the oil phase (or out of the interface) and, thus, increases the ST/IFT. − Besides, in the case of ionic surfactants, the effective size of charged hydrophilic heads is reduced as a result of high concentrations of salt ions of high ionic strengths …”

“…59−61 Besides, in the case of ionic surfactants, hydrophilic heads can pack more closely at the interface as a result of the counterion effect, in which the salt ions decrease the repulsion force between the charged heads of surfactants. 63,64 Owing to the salt-out and counterion effects, as the ionic strength increases, the ST/IFT of water decreases. With further increases in the ionic strength, above the optimal, the salt-out effect leads to the transfer of a larger part of surfactants to the bulk of the oil phase (or out of the interface) and, thus, increases the ST/IFT.…”

Assessing salt-surfactant synergistic effects on interfacial tension from molecular dynamics simulations

“…Both compounds can act cooperatively to reduce the IFT to ultralow values and can improve the stability of oil/water microemulsions [9]. Also, similar synergistic interactions were observed experimentally when using salts as additives [10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

“…However, in the present work, equilibrium MD simulations of the liquid/liquid interface were conducted, where neither the dynamic effects or the interactions with the rock are taken into consideration. Regarding static IFT reductions, some experimental works seemed to show stronger effects at higher salinity concentrations up to 2.0 M [16,[20][21][22]. For this reason, three preliminary calculations were carried out to find the salinity concentration that maximized the static IFT reduction effect in the considered oil/water/surfactant systems: (i) no significant change on the equilibrium IFT was observed at 0.5 molal of NaCl, (ii) a statistically meaningful reduction effect was detected at 2.0 molal of NaCl and (iii) the IFT was increased when calculated at 6.0 molal of NaCl.…”

Properties of Mixed System of N‐Coco Propylene Bis‐guanidine Acetate (CPGA) and Nonionic Surfactants

“…The equilibrium contact angle of the mixed system CPGA/AEO 9 is larger than that of the either single surfactant, while for the mixed system CPGA/APG1214, the equilibrium contact angle of the mixture is lower than that of single CPGA and when α CPGA is 0.5, the equilibrium contact angle is obviously smaller than that of single APG1214, too. Apparently, the CPGA/APG1214 mixture exhibits the synergistic effect in cutting down the equilibrium contact angle, but the CPGA/AEO 9 mixture does not, which may be related to its capabilities to reduce the surface tension of solutions, [38] or may be the result of interacting with parafilm to change its surface properties.…”