The Effect of Ionic Strength on Protonation Constant of Monoethanolamine in Water at 303K

Amine-based absorption is a reactive system in which mass transfer and chemical reaction take place simultaneously. Protonation constant (pK_a) is an important equilibrium reaction parameter that can be determined experimentally. The objective of this study is to evaluate the pK_a of monoethanolamine (MEA) at different ionic strengths ranging from 0.01 to 6 moles of NaCl/kg of water at 303K by a potentiometric titration method. The results show that the pK_a values, in general, increase as the ionic strengths increase. Moreover, the activity coefficients of species were also determined by the extended Debye-Hückel model. The pK_a data and the activity coefficients obtained from this work could then be used for the kinetic and thermodynamic modeling in the absorber and desorber design. (paper)