GAC: pore structure versus dye adsorption

Field‐spent carbons that had been catalytically reactivated were analyzed for adsorption capacity in relation to pore structure. Laboratory tests compared several virgin and reactivated granular activated carbons (GACs) with regard to pore‐size distributions versus their water‐phase adsorption capacity for several adsorbates. Pore‐size characterizations employed N2 adsorption isotherms, as interpreted by the density functional theory (DFT) model. These were compared with previous results that employed the Barrett, Joyner, and Halenda model, as adapted by the authors. The newly developed DFT model offered better correlations to water‐phase adsorption behavior, although it also exhibited an apparent anomaly in the 8–12‐Å pore‐width range. For the coal‐based GACs used in this study, the pore sizes that provided the greatest adsorption capacity correlated well with the dimensions of the adsorbates; small‐compound adsorption correlated most strongly with micropore volume, and larger dye adsorption correlated most strongly with mesopore plus large micropore volume. Coefficients of determination (r2) exceeded 0.95 when the appropriate range of DFT pore‐volume distribution was compared with dye or p‐nitrophenol adsorption capacity.