Minimal Kinetic Model of Direct Air Capture of CO₂ by Supported Amine Sorbents in Dry and Humid Conditions

Dilute concentration (∼400 ppm) and humidity are two important factors in the direct air capture (DAC) of CO₂ by supported sorbents. In this work, a minimal DAC CO₂ adsorption-kinetics model was formulated for supported amine sorbents under dry and humid conditions. Our model fits well with a recent DAC experiment with supported amine sorbent in both dry and humid conditions. Temperature and flow rate effects on breakthrough curves were quantitatively captured, and increasing temperature led to faster CO₂ adsorption kinetics. Moisture was shown to broaden the breakthrough curve with slower CO₂ adsorption kinetics but significantly improve the uptake capacity. The present minimal model provides a versatile platform for kinetic modeling of the DAC of CO₂ on supported amine and other chemisorption systems.