1-butanol adsorption on activated carbon in supercritical CO2: Experimental measurements and thermodynamic modeling

This study presents the first investigation of the equilibrium adsorption of 1-butanol on activated carbon in a supercritical CO₂ environment, covering a temperature range of 313 K to 353 K and pressures from 10.0 MPa to 20.0 MPa. A fixed-bed column setup, combined with flame ionization detection, enabled the accurate quantification of equilibrium adsorption in supercritical CO₂. The Dubinin–Astakhov (DA) equation was used to model the equilibrium data and derive physically meaningful parameters: E_VOC (interaction energy between VOC and adsorbent) and W_0,VOC (saturated adsorption volume). Among the alcohol-based VOCs tested, 1-butanol consistently showed the strongest affinity for the activated carbon surface, due to its molecular structure and lower volatility. In addition to confirming common trends such as the effect of CO₂ density on adsorption capacity, this study uniquely shows that adsorption energy increases systematically with VOC molecular size, and that saturated adsorption volume is inversely related to saturated fugacity of VOCs. These findings offer a new thermodynamic perspective that links microscopic molecular properties to macroscopic adsorption behavior, thereby enhancing our understanding of VOC adsorption under supercritical CO₂ conditions.