Estimation of Correlation between Electrical Conductivity and CO2 Absorption in a Monoethanolamine Solvent System

Abstract

The present paper reports the ionic conductivities of carbamic acid (C2H5ONH3+) and carbamate (C2H5ONHCOO–) by analyzing the measured electrical conductivity (EC) variation according to the amount of CO2 absorbed in an aqueous monoethanolamine (MEA) solvent system. On the basis of these conductivities, the study also investigates the correlation between EC variation and the amount of CO2 absorbed in five MEA solvents with a concentration range of 0.1 M to 0.5 M. The study is underpinned by several assumptions, and a CO2 absorption experiment is carried out with the five MEA solvents. The ionic conductivity of C2H5ONH3+ and C2H5ONHCOO– is calculated as 73.60 S·cm2·mol–1·z–1 and 16.40 S·cm2·mol–1·z–1, respectively. An average error between the estimated EC (ECc) variation calculated via the correlation equation and the measured EC (ECm) variation obtained from the experiments is 6.92 % in five MEA solvents. However, the ECc in the 0.5 M MEA system is 10.22 % lower than ECm. This difference may be ascribed to the substantial deviation from the assumptions of the 0.5 M solvent due to its relatively high concentration which decreases the ionic activity coefficient of existing ions in the solvent.