Adsorption behavior of anionic surfactants to silica surfaces in the presence of calcium ion and polystyrene sulfonate

Zilong Liu,Pegah Hedayati,Ernst J.R Sudhölter,Robert Haaring,Abdur Rahman Shaik,Naveen Kumar

doi:10.1016/j.colsurfa.2020.125074

Abstract

Adsorption behavior of surfactants to rock surfaces is an important issue in oil recovery, especially in the process of surfactant flooding. The surfactant loss through adsorption to rock surfaces makes such process economically less feasible. Here, we investigated the adsorption behavior of anionic surfactants (alcohol alkoxy sulfate, AAS) onto silica with quartz crystal microbalance with dissipation monitoring. The results demonstrated that the surfactant adsorption followed the Langmuir adsorption isotherm. Up to solution pH 10, surfactant adsorption slightly increased with increasing pH. The higher pH leads to more anionic surface sites for binding with an anionic surfactant with the help of a calcium cation bridging. The amount of anionic surfactant binding also increases with increasing calcium ion concentration up to 50 mM. It was found that sodium ions were able to exchange calcium ions near the silica surface, which would reduce the affinity for surfactant adsorption. The effect of the polyanion polystyrene sulfonate (PSS) on the anionic AAS adsorption was investigated to learn the possible competitive adsorptions. Indeed, this was found. Upon addition of 50 ppm PSS to a 0.05 wt% AAS containing solution, the adsorption of AAS was reduced by about 85 %. The obtained results show the interplay of different interacting species affecting the overall degree of anionic surfactant adsorption to silica surfaces. Optimal tuning of the process conditions according to these results will contribute to a more efficient use of anionic surfactants in enhanced oil recovery.

Highlights

With the increase of oil production demand, surfactant flooding as part of enhanced oil recovery (EOR) is receiving substantial attention [1,2,3], and has been used to trigger residual oil release and to acquire higher recoveries from reservoir rocks
It is of importance to determine the amount of alcohol alkoxy sulfate (AAS) surfactant adsorption to silica surfaces to understand this route of surfactant loss
That the AAS adsorption to the silica surface under these conditions does not stop at arriving the critical micelle concentration (CMC) suggests that the affinity of AAS monomers to adsorb to the surface is similar to the affinity towards the micelles

Summary

Introduction

With the increase of oil production demand, surfactant flooding as part of enhanced oil recovery (EOR) is receiving substantial attention [1,2,3], and has been used to trigger residual oil release and to acquire higher recoveries from reservoir rocks. In surfactant-water-rock systems, the adsorption process of surfactants mainly contains four steps [11,12,13]. The first step is surfactant adsorption through electrostatic interactions between hydrophilic head groups of surfactants and the charged sites of rock surfaces. The second step involves the interaction of hydrophobic parts of ongoing surfactants in solution with previously adsorbed surfactants, leading to surface aggregates such as hemi-micelles. The amount of surfactant adsorption relies on the chemistry of the rock (i.e., its chemical compositions and surface charges), the kinds of surfactants, and water chemistry (i.e., salinity, present ions, solution pH) [6,7,13,14,15,16]. No systematic study has appeared to explore the effect of various cations and polyelectrolytes on the surfactant adsorption

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