Insights into Zwitterionic Surfactant Interactions at the Oil-Water Interface by Interferometry Experiments and MDS...

Area of Science:

• Colloid and Surface Science
• Physical Chemistry
• Petroleum Engineering

Background:

• Zwitterionic surfactants are crucial in various industrial applications, including enhanced oil recovery (EOR).
• Understanding surfactant-oil interactions at interfaces is key to optimizing EOR processes.
• Dodecyl dimethyl sulfopropyl betaine (DSB-12) and hexadecyl dimethyl sulfopropyl betaine (DSB-16) are zwitterionic surfactants with varying chain lengths.

Purpose of the Study:

• To investigate and compare the interaction performance of DSB-12 and DSB-16 with n-octadecane oil surfaces.
• To elucidate the underlying mechanisms governing these interactions using both experimental and simulation approaches.
• To provide a foundation for developing more effective surfactants for reservoir exploitation and EOR.

Main Methods:

• Macroscopic experiments utilizing interfacial interferometry technology for real-time monitoring of interfacial thickness and mass.
• Thermodynamic analysis based on the Langmuir model to determine aggregation spontaneity.
• Kinetic analysis of a three-step dynamic model (adsorption, arrangement, aggregation).
• Microscopic simulations using molecular dynamics (MD) to obtain interfacial configuration and energy.

Main Results:

• DSB-16 demonstrated superior interaction performance, stability, and strength compared to DSB-12.
• Thermodynamic analysis indicated higher aggregation spontaneity for DSB-16 (ΔGagg = -5.94 kJ/mol) versus DSB-12 (ΔGagg = 24.08 kJ/mol).
• MD simulations revealed significant differences in final interaction energy (ΔEfin = 48–88 kcal/mol) between DSB-16 and DSB-12.
• Distinct interaction mechanisms were proposed: 'response enhancement' and 'deposition activity' for DSB-16, and 'response decrease' and 'elution activity' for DSB-12.

Conclusions:

• The differing interaction performances of DSB-12 and DSB-16 are attributed to variations in their interaction forms and forces at the oil-water interface.
• DSB-16 exhibits favorable characteristics for enhanced oil recovery due to its stronger interfacial interactions.
• This research establishes a valuable platform for investigating surfactant-oil interactions, crucial for advancing EOR technologies.