Measurements and Dubinin–Astakhov correlation of adsorption equilibria of toluene, acetone, n-hexane, n-decane and methanol solutes in supercritical carbon dioxide on activated carbon at temperature from 313 to 353 K and at pressure from 4.2 to 15.0 MPa

Adsorption equilibria of five volatile organic compounds (VOCs) (toluene, acetone, n-hexane, n-decane and methanol) on activated carbon in supercritical carbon dioxide were studied. Measurements were performed with a fixed bed method for activated carbon fine particles (ca. 74–147 μm diameter), a specific surface area at 1300 m2/g and a mean pore diameter, micropore volume of 0.687 nm and 0.441 cm3/g, respectively. Characteristic adsorption isotherms varied greatly for each VOC that can be attributed to differences in two interactions, VOC and activated carbon, VOC and supercritical carbon dioxide in the bulk phase, respectively. Adsorption amount of each VOC increased with increasing temperature and decreasing pressure. Adsorption isotherm equilibria could be correlated with the Dubinin–Astakhov equation using two parameters within 6.5% of average relative deviation. The parameters of the Dubinin–Astakhov equation were found to be a function of the chemical species, carbon dioxide density and VOC molar volume. These results indicate a possibility of developing a predictive model for the adsorption equilibria.

Figure optionsDownload as PowerPoint slideHighlights
► Adsorption equilibria of toluene, acetone, n-hexane, n-decane and methanol on activated carbon are reported.
► Adsorption isotherms strongly depend on solute and carbon dioxide density.
► Data can be correlated with the Dubinin–Astakhov equation.
► Correlation parameters are a function of VOC molar volume and carbon dioxide density.