Nitrogen and argon adsorption on non-graphitized carbon black. Application of DFT

Analysis of adsorption equilibria of nitrogen at 77 K and argon at 77 and 87.3 K on non-graphitized carbon black (NGCB) is considered with a Non- Local Density Functional Theory (NLDFT). It was shown that nitrogen and argon adsorption isotherms could be quantitatively correlated with a version of NLDFT accounting for the amorphous nature of NGCB and its surface roughness. Instead of being calculated from some standard equations, such as the 10-4-3 Steele equation, the solid-fluid potential is obtained experimentally from adsorption isotherms and it was found to be a fast decaying function that becomes negligibly small at a distance of about two collision diameters from the surface. The model presented in this paper implicitly accounts for the energetic heterogeneity of the disordered graphite surface and yet it retains the simplicity of the conventional NLDFT as applied to graphitized thermal carbon black. The approach may be further extended to slit pores whose walls are non-graphitized surface, and such an approach will raise questions on the conventional approach where pore walls are assumed to behave like a graphite surface