Transition to Henry's law in ultra-low concentration adsorption equilibrium for n-pentane on BPL activated carbon

Experimental data for n-pentane adsorbed on BPL activated carbon in a nitrogen environment are reported at ultra-low concentrations into the Henry's law region. We introduce two methods to prepare pre-equilibrated samples at known loadings. The samples were analyzed by a purge and trap method. Adsorption data were measured at loadings from 1.0 to 0.0001 mol kg(-1) and pressures of 6 to 5 x 10(-10) kPa. The transition into the Henry's law region occurs over a range of loadings near 0.01 mol kg(-1) for all temperatures. The data are compared with the DR, Langmuir, and Toth equations. We discuss how the three equations transition into the Henry's law region, and how well they describe the data. Since the DR equation does not have a proper Henry's law region, we show where this equation no longer applies. The Toth equation describes the data better than the Langmuir equation. (C) 2008 Elsevier Ltd. All rights reserved.