1 research outputs found
Adsorption of Zwitterionic Surfactant on Limestone Measured with High-Performance Liquid Chromatography: Micelle–Vesicle Influence
Herein
is presented a new methodology to determine the static adsorption
of a zwitterionic surfactant on limestone in three different aqueous
media [high-performance liquid chromatography (HPLC) water, seawater,
and connate water] with the use of HPLC at room temperature and 70
°C. The results showed that, in both HPLC water and seawater,
the surfactant adsorption followed a monolayer Langmuir tendency.
In contrast, for connate water, the surfactant presented a new adsorption
profile, characterized by two regions: (i) At surfactant concentrations
below 1500 mg L<sup>–1</sup>, an increase of adsorption is
observed as the amount of divalent cations increases in the aqueous
media. (ii) At surfactant concentrations above 1500 mg L<sup>–1</sup>, the adsorption decreases because the equilibrium, monomer ⇆
micelle ⇆ vesicle, is shifted to the formation of vesicles,
giving as a result a decrease in the concentration of monomers, thus
reducing the interaction between the surfactant and the rock, and
therefore, lower adsorption values were obtained. The behavior of
the surfactant adsorption under different concentrations of divalent
cations was well-described by the use of a new modified Langmuir model:
(dΓ/d<i>t</i>)<sub>ads</sub> = <i>k</i><sub>ads</sub><i>c</i>(Γ<sub>∞</sub> – Γ)
– <i>k</i><sub>cmc</sub>(<i>c</i> – <i>c</i><sub>cmc</sub>)<sup><i>n</i></sup>Γ<i>H</i>(<i>c</i> – <i>c</i><sub>cmc</sub>). It was also observed that, as the temperature increases, the adsorption
is reduced because of the exothermic nature of the adsorption processes