Micropore Size Distribution and Surface Characteristics Co-influence on 4-Chlorophenol Adsorption Mechanism from Organic Solvents.

The effects of co-influence of pore size distribution and surface chemistry of activated carbon (AC) on the p-chlorophenol (PCP) adsorption from water, heptane, and cyclohexane have been studied. To modify the surface basicity, commercial activated carbon and ash-free commercial activated carbon were subjected to heat treatment in a hydrogen atmosphere. The ACs were also oxidized with hydrogen peroxide to increase the acidity. All applied modifications caused negligible changes in the porous texture and a significant modification on the surface characteristics. The adsorption of PCP was carried out in static conditions at an ambient temperature. The time needed to obtain the adsorption equilibrium from organic solvent was shorter than from water. The boundary layer effect was found to increase in the direction of water < cyclohexane < heptane and was heteroatom-dependent. The equilibrium adsorption isotherms showed all spectrum of isotherm types according to the Giles classification. The strong relationship between the volume of the PCP adsorbed and the volume of ACs micropore with size smaller than 1.6 nm was presented. This work shows that the surface heterogeneity influences the adsorption mechanism in the low adsorbate concentration range, more specifically, the final adsorption capacity is pore-size-dependent regardless of the kind of solvent used.