The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray effect refers to the observation that at extremely low salt concentration the surface tension decreases in apparent contradiction with thermodynamics. Determining the mechanism that is responsible for this Jones-Ray effect is important for theoretically predicting the distribution of ions near surfaces. Here we show that this surface tension decrease can be explained by surfactant impurities in water that create a substantial negative electrostatic potential at the air-water interface. This potential strongly attracts positive cations in water to the interface lowering the surface tension and thus explaining the signature of the Jones-Ray effect. At higher salt concentrations, this electrostatic potential is screened by the added salt reducing the magnitude of this effect. The effect of surface curvature on this behavior is also examined and the implications for unexplained bubble phenomena is discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces.

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10 results in Timothy Duignan in Authors: Timothy Duignan

Prediction of the Osmotic/activity Coefficients of Alkali Hydroxide Electrolytes

Liquid water simulation using hydrogen bond corrected SCAN and neural network potentials.

Towards predictive design of electrolyte solutions by accelerating ab initio simulation with neural networks.

Quantifying the hydration structure of sodium and potassium ions: taking additional steps on Jacob’s Ladder

A Method for Accurately Predicting Solvation Structure

Surfactant Impurities Can Explain the Jones-Ray Effect

Elucidating the effects of solvent-ionomer interactions on copper catalyst layers for CO2 electrolysis to multicarbon products

Predicting the properties of salt water using neural network potentials and continuum solvent theory

The Born Model Can Accurately Describe Electrostatic Ion Solvation.

Impurities Limit the Capacitance of Carbon Based Supercapacitors

10 results in Authors: Timothy Duignan