Aqueous solutions of amines can be selective absorbents for the separation of carbon dioxide (CO2) from industrial effluents. Because of different chemical reactions, the mechanisms of CO2 absorption in 2-amino-2-methyl-1-propanol (hindered primary amine) or 2-aminoethanol (primary amine) will differ. These mechanisms are analyzed via the extents of reactions and enthalpies of solution, derived from a thermodynamic model representative of {CO2/amine/water} systems. The model was optimized to fit literature solubility data and tested by comparison of calculated and experimental enthalpy values. New experimental enthalpies of solution were collected for aqueous solutions of 2-amino-2-methyl-1-propanol (w(amine) = 0.1500, and w(amine) = 0.3000) at 372.9 K and pressures from 0.5 to 3.2 MPa.