A New Experimental Method to Determine the Henry’s Law Constant of a Volatile Organic Compound Adsorbed in Soil

Abstract

This paper presents a new mechanical method to determine Henry’s law constant (HLC) of a volatile organic compound (VOC). This method is an extension of the one proposed by Ouoba et al. (2010) to determine the water activity in porous media. This work focuses on TCE and aims at characterizing its liquid-vapor equilibrium in various cases in the form of a pure liquid phase or dissolved in an aqueous solution, adsorbed or not in a natural soil. A liquid phase is disposed in a closed chamber whose volume can be incrementally increased. The recording of the total gas pressure leads to evaluating the vapor partial pressure of a volatile compound even in the case of an aqueous solution. This method has been validated using various aqueous solutions of TCE and the HLC obtained is in agreement with the literature. Then, the validity of Henry’s law has been asserted in the case of an aqueous solution of TCE adsorbed in a hygroscopic soil. Indeed, a linear relation between the vapor partial pressure of TCE and its concentration has been obtained while the HLC is about 16% lower. This result highlights the influence of adsorption phenomena on vapor/liquid equilibrium.

Gibbs Energy and Helmholtz Energy

“…[365][366][367][368][369][370][371][372][373][374][375][376][377][378][379][380] With increasing concern for the environmental dynamics of natural and anthropogenic substances, for their biological impact in general and on human health (environmental risk assessment) in particular, physicochemical/thermodynamic work on dilute aqueous solutions has increased significantly. New instruments have been developed [381][382][383][384][385][386][387] and relevant data compilations have become available. [365][366][367][368][369][370][371][372][373]380 in this introductory chapter, i have not covered any experimental details -the reader is referred to the relevant chapters of this book and to the pertinent review articles and monographs cited as references.…”

Sample handling for electronic nose technology: State of the art and future trends

“…Using Henry's law volatility constants it's possible to estimate the composition of the gaseous phase if the composition of the measurement sample is known. This opens the way for optimal planning of both sampling, handling and measurement procedures [34,35]. The SHS advantages are simplicity, low price and absence of specific additional equipment (pumps, mixers, etc.).…”