Applicability of adsorption equations to argon, nitrogen and volatile organic compound adsorption onto activated carbon

This research evaluates adsorption equations for argon, nitrogen, and volatile organic compound adsorption onto several commercially available activated carbons that represented a broad range of pore volume character, from predominantly microporous to predominantly mesoporous. For all these carbons, both the recently introduced (Paulson PD, Cannon FS, submitted to Carbon) Modified Freundlich equation and the Dubinin-Astakhov equation accurately characterized adsorption behavior in the relative pressure range of 1.0 × 10^-5 to 0.1 for argon adsorption onto six different activated carbons and for nitrogen adsorption onto two different activated carbons. In particular, the Modified Freundlich equation offered a slightly better fit to the experimental data for mesoporous carbons in the full relative pressure range, and to all activated carbons in the relative pressure range of 10^-2.5 to 0.1. Micromerities' density functional analysis software further used this argon and nitrogen adsorption data to characterize these activated carbons by their pore volume distribution. The Modified Freundlich's v_OMF term correlated best to the cumulative pore volume up to 60 angstrom and the Dubinin-Astakhov's v_ODA term correlated best to the cumulative pore volume up to 30 angstrom as determined via density functional theory. In addition, the research herein identified a consistency in the adsorption behavior of methylisobutylketone, m-xylene, and argon at their respective boiling points.