Amine-based Carbon Dioxide Absorption: The Ionic Strength Effect on the Monoethanolamine Protonation Constant at Temperatures from 313 to 333K

Amine-based absorption has been extensively used for carbon dioxide (CO 2 ) removal processes, such as CO 2 absorption from flue gas as well as from natural gas. As a reactive system in which the chemical reaction, as well as mass transfer, occur simultaneously, an experimental determination of equilibrium reaction constants, e.g. acid dissociation/protonation constant (K a ), is, therefore, necessary to be conducted. This study aims to evaluate the ionic strength effect from 0.06 to 6.0 m (mol/kg water) on the K a value of monoethanolamine (MEA) at temperatures between 313 and 333K. The experimental results indicate that the pK a values tend to be increasing as the ionic strength increases. This is contradicting to the temperature effect where the pK a values tend to be decreasing as the temperature increases. Furthermore, the extended Debye-Huckel formulation was implemented to predict the species activity coefficients.