Ultra-stable CO₂-in-water foam by generating switchable Janus nanoparticles in-situ

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Chemical Engineering

Background:

• Silica nanoparticles (NP) can be modified with amino ligands to create Janus particles, balancing colloidal stability and interfacial activity.
• Combining modified NP with like-charged diamine surfactants can yield highly stable carbon dioxide (CO2) foam.

Purpose of the Study:

• To investigate the formation of ultra-stable CO2 foam using Janus silica nanoparticles and a diamine surfactant.
• To evaluate the impact of NP concentration on foam stability and properties.

Main Methods:

• Characterization of NP surface properties (zeta potential, TEM, TGA, titrations, NMR).
• Measurement of NP colloidal stability in brine at elevated temperatures using dynamic light scattering.
• Generation and in-situ stability measurement of CO2/brine foam at high temperature and pressure.
• Apparent viscosity measurements of foam as a function of foam quality.

Main Results:

• Ultra-stable CO2 foam was achieved with only 0.1 wt% NP at 60°C, exhibiting a bubble coarsening rate three orders of magnitude lower than surfactant alone.
• Foam bubbles remained spherical with NP present, contrasting with the polyhedral shape in less stable surfactant-only foams.
• The NP-surfactant system demonstrated maintained NP colloidal stability in high salinity and surfactant concentrations.

Conclusions:

• A novel, like-charged surfactant-NP system enables the creation of ultra-stable CO2 foam.
• Limited surfactant adsorption on NP is key to NP-stabilized foam while preserving NP colloidal stability.
• This research offers a new perspective for designing nanoparticle-surfactant systems for enhanced foam applications.