A colourimetric method for the measuring of the mass transfer kinetics of carbon dioxide in aqueous media

• Published in: Algal research (Amsterdam) 2020-01, Vol.45, p.101717, Article 101717
• Main Authors: Ibañez, Manuel Vicente, Leonardi, Rodrigo Jorge, Morelli, Matías Nicolás, Irazoqui, Horacio Antonio, Heinrich, Josué Miguel
• Format: Article
• Language: English
• Subjects: Acid-base indicator; Carbon dioxide; Mass transfer; Microalgae; Photobioreactors; Reaction kinetics
• ISSN: 2211-9264; 2211-9264
• DOI: 10.1016/j.algal.2019.101717

•The mass transfer process of carbon dioxide is relevant for microalgae cultures.•Acid-base indicators can act as tracers for the dissolution process of carbon dioxide.•It is possible to measure nearly equal kinetic constants for different initial compositions.•This methodology could be adapted to several different types of photobioreactors.•Probably the rate controlling step it is not the transfer reaction of CO2 by itself, as the process of hydration of CO2 is. The measurement of the gas-liquid mass transfer coefficient of carbon dioxide in aqueous media is relevant in the field of phototrophic microorganism culture. Here, we present an approach that allowed the handling of a system composed of seven chemical reactions, in which the transfer process of CO2 was one of them, pursuing the objective of quantifying the rate of dissolution of carbon dioxide in a designed liquid medium. A simple methodology, involving the use of an acid-base indicator, acting as a tracer, was successfully employed. It was established, that starting from a condition distant from its unique equilibrium, through the alteration of the initial pH value of a designed arbitrary state by adding onto it exact amounts of a strong base, the incorporation of CO2, from an air current in contact with the perturbed liquid, occurred in order to restore a new balance. For each experience, achieved under the same operational conditions, it was possible to calculate nearly equal values of kinetic constants which holds information about the behaviour of the system. Collectively the results presented here suggest that this methodology could be adapted to several different systems, enlightening easier ways of incorporating the transfer kinetics of this major carbon source on the existing growth kinetic models of phototrophic microorganisms. At the same time, it highlights the fact that probably the rate-controlling step it is not the transfer reaction of CO2 by itself, as the process of hydration of CO2 is.