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Surface tensions at elevated pressure depend strongly on bulk phase saturation
Journal article   Peer reviewed

Surface tensions at elevated pressure depend strongly on bulk phase saturation

Zachary R. Hinton and Nicolas J. Alvarez
Journal of colloid and interface science, v 594, pp 681-689
15 Jul 2021
DOI: https://doi.org/10.1016/j.jcis.2021.02.114
PMID: 33780771
Featured in Collection :   UN Sustainable Development Goals @ Drexel

Abstract

Chemistry Chemistry, Physical Physical Sciences Science & Technology
Hypothesis: Understanding interfacial phenomena at elevated pressure is crucial to the design of a variety of processes, modeling important systems, and interpreting interfacial thermodynamics. While many previous studies have offered insight into these areas, current techniques have inherent drawbacks that limit equilibrium measurements. Experiments: In this work, we adapt the ambient microtensiometer of Alvarez and co-workers into a high pressure microtensiometer (HPMT) capable of experimentally quantifying a wide range of interfacial phenomena at elevated pressures. Particularly, the HPMT uses a microscale spherical interface pinned to the tip of a capillary to directly measure surface tension via the Laplace equation. The stream of microscale bubbles used to pressurize the system ensures quick saturation of the bulk phases prior to conducting measurements. The HPMT is validated by measuring the surface tension of air-water as a function of pressure. We then measure the surface tension of CO2 vapor and water as a function of pressure, finding lower equilibrium surface tension values than originally reported in the literature. Findings: This work both introduces further development of a useful experimental technique for probing interfacial phenomena at elevated pressures and demonstrates the importance of establishing bulk equilibrium to measure surface tension. The true equilibrium state of the CO2-water surface has a lower tension than previously reported. We hypothesize that this discrepancy is likely due to the long diffusion timescales required to ensure saturation of the bulk fluids using traditional tensiometry. Thus we argue that previously reported elevated pressure measurements were performed at non-equilibrium conditions, putting to rest a long standing discrepancy in the literature. Our measurements establish an equilibrium pressure isotherm for the pure CO2-water surface that will be essential in analyzing surfactant transport at elevated pressures. (C) 2021 Published by Elsevier Inc.

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12 citations in Web of Science
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Web of Science research areas
Chemistry, Physical
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