Charged Surface-Active Impurities at Nanomolar Concentration Induce Jones-Ray Effect.

Area of Science:

• Physical Chemistry
• Surface Science
• Electrochemistry

Background:

• The Jones-Ray effect describes a minimum in electrolyte surface tension at low salt concentrations (around 1 mM).
• This phenomenon has been observed across various ion types but lacks a universally accepted explanation.
• Existing models often fail to consistently explain experimental surface tension data for salts, bases, and acids.

Purpose of the Study:

• To provide a unified mechanistic explanation for the Jones-Ray effect.
• To investigate the role of charged impurities in water on electrolyte surface tension.
• To correlate impurity concentration and adsorption with observed surface tension minima.

Main Methods:

• Development of a theoretical model incorporating charged impurities with surfactant-like surface affinity.
• Modeling the influence of salt concentration on impurity adsorption via electrostatic screening.
• Comparison of model predictions with experimental surface tension data for various electrolytes.

Main Results:

• A consistent model explaining experimental surface tension data for salts, bases, and acids was developed.
• The model attributes the Jones-Ray effect to the adsorption of charged impurities present in the nanomolar range.
• Salt-screening of electrostatic repulsion between impurities enhances their adsorption at the surface, reducing surface tension.

Conclusions:

• Charged impurities, even at trace concentrations, significantly influence electrolyte surface tension.
• The Jones-Ray effect is mechanistically explained by salt-screening enhanced impurity adsorption.
• This finding offers a new perspective on understanding surface phenomena in aqueous electrolyte solutions.