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We propose a new method, using the ambient temperature adsorption of methanol in the Henry law region as a molecular probe, to determine the concentration of surface oxygen functional groups (Ca) on carbon adsorbents. Two adsorbents: porous A5 and non-porous Carbopack F have been chosen here as experimental examples. The theoretical Henry constant (Ka) is the product of the intrinsic interaction between a methanol molecule and one functional group, a, having a concentration (Ca) and is estimated by carrying out a volume integration of the Boltzmann factor for methanol interacting with the functional group. Our results show that Ca determined with methanol for A5 compares well with that determined previously with water as the molecular probe (Nguyen, 2014 [1]); and both are in good agreement with results from Boehm titration. For Carbopack F, we find that Ca, determined by methanol adsorption, gives more realistic concentrations than those obtained by Boehm titration, which are subject to large errors because of the very low concentration of the functional groups. The method proposed here is fast and easy to implement, and serves as an alternative to the Boehm titration technique.

A new and simple method, using water as a potential molecular probe, is proposed for the determination of the concentration of surface oxygen groups on carbon adsorbents. The procedure is based on a determination of the Henry constant between a water molecule and a functional group from the volume integration of the Boltzmann factor over the accessible space around the functional group. Three porous carbons are used in this study to test the new method: A-5, RF-100 and RF-200. The results obtained are in good agreement with those measured by Boehm titration. This new method can be applied to adsorbents containing small concentrations of oxygen groups where the Boehm titration method may give unreliable results.

Adsorption of water on graphitized carbon black at various temperatures has been studied with a new molecular model of graphitized carbon black using Monte Carlo simulation. The model is a collection of graphene layers, modelled by the Steele potential, and a number of phenol groups forming clusters of various sizes which are placed randomly at the graphene edge sites to give an O/C ratio of 0.006. The results are compared with experimental data reported by Kiselev et al. [1] in 1968 for a range of temperatures, and for the first time a reconciliation between the experimental data and simulation has been successfully achieved. The simulation results show that water adsorbs preferentially around the functional groups to form clusters, which then grow and merge at the edges of the graphene layers, rather than adsorbing onto the basal planes of the graphene because the electrostatic interactions (hydrogen bonding) between water molecules are stronger than the basal plane-water dispersion interactions.

Experiments at several temperatures were carried out for adsorption of non-polar and polar fluids on a highly graphitized carbon black, Carbopack F, which is composed of a basal plane of graphene and functional groups at the edges of the graphene layers. By comparing the experimental Henry constants with the theoretical Henry constants, calculated for adsorption on an ideal basal plane of graphite, we can determine the different relations and mutual influences between the various interactions, fluid–basal plane, fluid–functional group and fluid–fluid interactions, in the initial stages of adsorption.

Accessible volume, geometrical area and accessible pore size distribution are the fundamental structural parameters in the characterization of porous solids. We provide a novel “inverse” procedure, which is based on the mass balance and an MC optimization scheme, to determine these parameters from the analysis of experimental adsorption isotherms for a number of commonly used activated carbons: BPL, AX-21 and Norit. Our results, based on a kernel of model pores generated from GCMC simulations, are compared with, and shown to be different from, the results obtained from the conventional method. We show that the discrepancies arise from an incorrect evaluation of both micropore and mesopore sizes.