(111c) Static Adsorption Modelling of a Cationic Gemini Surfactant in Different Rocks

The need to minimize surfactant adsorption on rock surfaces has been a challenge in chemical enhanced oil recovery (cEOR). This requires an accurate understanding of the adsorption mechanism on rocks. The static adsorption of an in-house cationic gemini surfactant on different rocks has been studied in this paper. Two different classes of rocks have been studied, namely sandstones and carbonates. XRD and XRF studies were conducted for rock samples. The adsorption of cationic gemini surfactant is very high in the case of sandstone due to strong electrostatic attraction. Different types of sandstones have also been analyzed. Each type showed a similar trend but a different amount of surfactant adsorption. On the other hand, the adsorption of cationic gemini surfactant on carbonates is not as significant as that of sandstone. However, there exists multilayer adsorption in the case of Indiana limestone. The quantity of surfactant adsorption noticed was around ~2 mg/g-rock. Firstly, the adsorption is due to the presence of some impurities present in the carbonate rocks. Then, the multilayer adsorption is due to the adsorption of counterions present in the cationic gemini surfactant.

Modeling of adsorption experimental data helps in estimating the extent of adsorption and, hence, optimize the process. We have applied curve-fitting on the experimental data using several adsorption isotherms, such as Langmuir, Freundlich, Redlich-Peterson, and Sips isotherms. The curve fitting was carried out using the Levenberg Marquardt algorithm to estimate the model parameters. The error metrics consist of mean squared error and coefficient of determination. Sips model was found out to be the most appropriate among all. This paper reports the adsorption mechanism of a novel cationic gemini surfactant in different types of rocks based on experimental data and isotherm modeling.