Adsorption of ions at the interface oil|aqueous electrolyte and at interfaces with adsorbed alcohol

How do ions contribute to brine-hydrophobic hydrocarbon Interfaces? An in silico study

“…In many geo-and petro-chemical processes, biphasic oil-brine systems are subjected to drastic salinity alteration; for example, improving oil production by injecting sea water into the subsurface reservoirs [67]. Characteristics of the oil-saltwater interface have been traditionally investigated by focusing on the role of polar (functionalized) compounds of the crude oil [9,11,15,49], whereas the impact of aromatic and aliphatic species (major non-polar constituents of typical crude oils) has been largely neglected in former investigations.…”

“…Evidently, brine-oil interface largely impacts the performance of LSWF process. However, the interfacial contribution of ions at oil-brine interfaces is not fully understood [9], due to the difficulty of probing nanoscopic phenomena at interfaces by direct experimental observation, and because of the complex chemistry of crude oils [10][11][12]. The discrete character of ions becomes especially important in the tightly confined medium of porous minerals, where continuum theory fails to provide a detailed picture of the ions behavior [13].…”

Adsorption of Ions at Uncharged Insoluble Monolayers

“…The nature of the repulsive forces that act on Na + and Cl – seems to be well understood: these are the screened image potential at low concentration and the hydration repulsion at high . The same two forcesimage and hydrationallow for the quantitative understanding of the surface tension, the interfacial tension and the surface dipolar χ-potential of a NaCl solution. The model holds with good accuracy for many salts (any combination of Li + , Na + , K + , Rb + , Cs + , Mg 2+ , Ca 2+ , Ba 2+ , La 3+ , OH – , F – , Cl – , SO 4 2– , CO 3 2– ), provided that the bulk activity coefficients and the surface charge accumulated due to the difference in the ion hydration are accounted for. ,, …”

“…The promising results from the comparison between interfaces of varying hydrophobic phases lead us to the idea to investigate the interactions of ions and uncharged monolayers . It is well-known that many surfactants form an oil-like liquid expanded (LE) film at the W|G surface. , By changing the area of the spread monolayer, one alters the thickness and the density of this LE film (Figure ).…”

“…One proof is the finding of Ralston and Healy that the adsorption of KCl is very close to zero at the monolayer spread around octadecanol crystals, while one would expect it to be closer to the negative value of the adsorption found for KCl at the water|decanol interface, i.e., there is a significant attraction of K + and Cl – toward the condensed octadecanol monolayer that is absent at the neat W|G, W|alkane and W|decanol interfaces. The equilibrium spreading pressures of Frumkin and Pankratov suggest that even salts that desorb , strongly at W|G and W|O (K 2 SO 4 , CaCl 2 ) are actually adsorbed by the ethylpalmitate monolayer. Another indication for attraction is the effect of the electrolyte on the adsorption constant K a of oil-soluble alcohols adsorbed at the oil|brine interface; the fact that the experimental values of K a in Figure 5 in ref stand above the theoretical line (that accounts for image and hydration forces only) points at additional ion-monolayer attraction.…”