Adsorptive properties of microporous carbons: primary and secondary micropore filling

A study has been made of the mechanisms of micropore filling with particular reference to the adsorptive properties of two samples of activated charcoal cloth, having predominantly narrow slit-shaped pores, and a coke-based carbon, having a wider distribution of micropores. Nitrogen adsorption data at 77 K have been analysed by use of the αs-method and the Dubinin-Radushkevich equation. Integral heats of adsorption for a range of organic adsorptives have been derived from heat of immersion data in conjunction with physisorption data. The findings support the view that there are two distinctive mechanisms of micropore filling: (a) a primary process, which takes place at very low p/p° and involves enhanced adsorbent-adsorbate interactions and (b) a secondary process, which leads to a more gradual approach to the plateau of a Type I isotherm and is the result of co-operative effects associated with the filling of wider micropores (the supermicropores of Dubinin).