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

Abstract

Amine-based absorption is a reactive system in which mass transfer and chemical reaction take place simultaneously. Protonation constant (pKa) is an important equilibrium reaction parameter that can be determined experimentally. The objective of this study is to evaluate the pKa 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 pKa 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 pKa 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.