Surface chemistry of activated carbons and its relevance for effects of relative humidity on adsorption of chlorinated organic vapors

The effects of relative humidity (RH) on the adsorption of methylene chloride (METH) and 1,1,1-trichloroethane (TCEA) on two commercial activated carbons, made from bituminous coal (carbon BPL) and coconut shell (carbon PCB), were studied. Three levels of RH were tested by tracking the breakthrough curves of each adsorbate eluted from a fixed-bed adsorption column. Adsorption capacities for these adsorbates were decreased with increase of RH. The magnitude of the effect of water vapor on adsorption is greater for carbon BPL and METH than for carbon PCB and TCEA. The results of the effect of water vapor on the adsorption capacity observed in this study were further examined based on the chemical characterization of activated carbons and the fundamental physical differences between the adsorbates.