Role of Granular Activated Carbon Surface Chemistry on the Adsorption of Organic Compounds. 1. Priority Pollutants

Uptake of two synthetic organic contaminants (SOCs), trichloroethylene and trichlorobenzene, by one coal-based and one wood-based granular activated carbon (GAC), modified using liquid-phase oxidation (HNO3) and heat treatment in an inert atmosphere (N2), and by several different as-received GACs was compared. Carbons were characterized by elemental analysis, surface area and pore size distribution, water vapor adsorption, acid−base adsorption characteristics measured using the Boehm technique, and a mass titration/pH equilibration method to determine the pHpzc. The results of isotherm experiments with the surface-treated coal- and wood-based carbons indicated that carbon surface acidity played an important role on the adsorption of hydrophobic SOCs. It was found that increasing surface acidity increased the polarity of the surface and reduced adsorption of hydrophobic SOCs by GAC. However, no significant trend was evident for as-received carbons; their behavior differed significantly from surface-treated carbons. The Boehm characterization technique did not appear to be a robust predictor of surface reactivity of as-received carbons toward low-molecular weight hydrophobic target compounds. However, the Boehm method was useful for correlating the reactivity of carbon surfaces precleaned by acid-washing and heat treatment, and subsequently modified with a single oxidant, as done in this study.