Impact of Saltwater Environments on the Coalescence of Oil-in-Water Emulsions Stabilized by an Anionic Surfactant

Abstract

The impact of salts on the stability of oil-in-water emulsions to coalescence was studied to aid in minimizing the impact of emulsified oils on natural water systems. Oil-in-water emulsions were fabricated from mineral oil, deionized water, and sodium lauryl ether sulfate. As salt (NaCl) concentrations increased from 0 to 1.25 M, an increase in emulsion stability to coalescence was observed over an aging period of 56 days. ζ potential and interfacial tension measurements showed that salt decreased the electrostatic repulsion of the anionic surfactant and allowed the surfactant to pack more densely at the oil−water interface. Dynamic interfacial tension measurements showed that surfactant adsorption rates increased with salt. As a result of faster adsorption kinetics, oscillating droplet tensiometry showed a decrease in the dilatational modulus when salt was present. An extended DLVO theory was used to calculate the interaction energy between droplets. These calculations agreed well with our experimental results indicating the importance of hydration forces at high salt concentrations and small droplet separation distances. The presence of salt allowed for close surfactant packing and faster surfactant adsorption kinetics, which prevented coalescence and created conditions favorable for the formation of a stable Newton black film.

Effect of Dynamic Ageing on the Stability of Oil-in-Water Emulsions with Anionic and Nonionic Surfactants in High-Salinity Water

“…According to Table , the CMC was 33 ppm for SLES and agreed with other published experiments. , Previously established by Kedar and Bhagwat, the addition of 0.17 M NaCl reduced the CMC of SLES and crude oil from approximately 320 ppm (salt-free) to approximately 140 ppm, and the surface excess concentration calculated was approximately 2 × 10 –6 mol/m 2 for the saline emulsion . Thus, we can expect an increase in the surface excess concentration for SLES with increasing salt concentration to some extent, as more anionic surfactant molecules can pack at the oil/water interface due to charge screening . This assumption is verified by the data in Table , which shows that the surface excess concentration for SLES is 6.38 × 10 –6 mol/m 2 with the addition of 0.42 M NaCl.…”

“…It has been shown that without the addition of surfactants and salt, the charge at the oil-water interface is negative (−120 32 to −100 mV 18 ) due to the adsorption of hydroxide ions from water. 18,33 The results in Figure 1 show that for the nonionic surfactant, 100 ppm of Triton X-100 reduced the ζ potential toward zero. This is due to the limited adsorption of hydroxide ions onto the O/W interface caused by the energetically favorable adsorption of the electrostatically neutral surfactant onto the oil drops surface.…”

Impacts of Frazil Ice on the Effectiveness of Oil Dispersion and Migration of Dispersed Oil

“…Oil coalescence may affect the fate of dispersed oil in frazil ice. Coalescence is the main reason for the destabilization of an oil-in-water emulsion. , Dispersed oil encapsulated in frazil ice is thus predictably destabilized because of the increasing droplet sizes. Meanwhile, dispersed oil would probably be destabilized by the freeze–thaw process when oil is released along with the melting ice .…”

A review on the applications of nuclear magnetic resonance (NMR) in the oil and gas industry: laboratory and field-scale measurements

“…In addition, the authors argued that these developments could move benchtop NMR closer to direct industrial applications. Various water-in-oil emulsions were tested regards their stability following addition of either sodium chloride (NaCl) or calcium chloride (CaCl 2 ) (Davis et al 2021;Doğan et al 2020;Ling et al 2018). Different types of oil were used in their study such as paraffin oil, xylene, and modified crude oil in which asphaltene or acidic component was removed, respectively.…”