Rapid Characterization and Modeling of Natural and Undefined Charge-Regulated Surfaces in Aqueous Systems

Area of Science:

• Surface Chemistry
• Colloid Science
• Environmental Engineering

Background:

• Surface charge in aqueous systems arises from functional group ionization, influencing interactions.
• Charge regulation, the variation of surface properties with separation distance, is crucial for colloid and microbial transport.
• Current methods for characterizing charge-regulated surfaces have limitations with complex or natural materials.

Purpose of the Study:

• To develop a robust and rapid method for characterizing charge-regulated surfaces.
• To determine surface equilibrium constants (K) and site densities (N) without prior material composition knowledge.
• To enable accurate modeling of electrostatic interactions in colloid and microbial transport.

Main Methods:

• Utilized zeta potential data combined with a charge-regulation and Gouy-Chapman model.
• Obtained equilibrium constants (K) and site densities (N) for various materials.
• Demonstrated the method on activated carbon, aluminum oxide, iron (hydr)oxide, feldspar, and silica sand.

Main Results:

• Successfully characterized charge-regulated surfaces using a novel method.
• Derived accurate K and N values representing the electrostatic response.
• Illustrated variations in surface charge, potential, and pH during surface interactions.

Conclusions:

• The presented method provides a readily applicable approach for characterizing charge-regulated surfaces.
• This facilitates the inclusion of charge-regulation effects in adhesion and transport studies.
• Enhances understanding of interactions involving natural and undefined materials.