Adsorption of sodium dodecyl sulfate, Triton X100 and their mixtures to shale and sandstone: A comparative study

In this paper, batch experiments of sediment/aqueous systems were conducted to evaluate the adsorption of SDS, TX100 and their mixtures (1:2; 1:1 and 2:1 SDS:TX100 mass ratio) onto local shale and sandstone. Adsorption of surfactants was assessed using a surface tension technique for surfactant concentrations less than surfactant monomer saturation (CMC). It is shown that the amount of TX100 adsorbed to shale (7.5 g/kg) are greater than those adsorbed to sandstone (1.5 g/kg). SDS showed negligible affinity for adsorption on both adsorbents. The amounts of both TX100 adsorbed to shale or sandstone can be decreased and minimized when they are mixed with SDS. While adsorption of TX100–SDS mixtures on shale reduced to 4.5 g/kg (40% reduction in comparison to adsorption of TX100), adsorption to sandstone decreased tremendously to 0.3 g/kg (80% reduction in comparison to adsorption of TX100). Furthermore, micellization behavior was assisted through mixing. CMCs of mixtures reduced to 0.1 wt.% in presence of shale compared to 0.15 wt.% for TX100 and 0.1 wt.% for SDS. Similarly, CMC of mixtures reduced to 0.03 wt.% in presence of sandstone in comparison to 0.05 for pure TX100 and 0.1 wt.% for SDS. Because of their ability to minimize amounts adsorbed in different adsorbents, mixed anionic–nonionic surfactant particularly TX100–SDS may show potential advantages in SEAR and EOR applications.