Regeneration of Five Activated Carbons with Methanol

The regeneration characteristics of five commercially available granular activated carbons with methanol were evaluated. Three of the adsorbents were bituminous base carbons, while the remaining two were manufactured from lignite coal and wood. The adsorbates were p-chlorophenol, and two-ring, four-ring and eight-ring azo dyes. The rate of regeneration of the five adsorbents appeared to be sensitive to the molecular weight of the adsorbate; decreasing with increasing molecular weight. During the methanol regeneration of the p-chlorophenol and two-ring dye, an upper limit for capacity recovery was observed for all adsorbents, suggesting that a maximum recoverable capacity has been obtained. This phenomenon was not observed for the remaining two adsorbates due to exceedingly slow extraction rates. The extraction efficiences obtained for p-chlorophenol and the two-ring dye were found to correlate with the adsorption energies of these adsorbates on activated carbon. The extraction efficiency was observed to decreased with increasing adsorption energy.