Understanding the Adsorption of Polycyclic Aromatic Hydrocarbons from Aqueous Phase onto Activated Carbon

Non-competitive adsorption of polycyclic aromatic hydrocarbons (PAHs) from water onto activated carbon was studied alongside the performance of CO2-activated petroleum coke as a low-cost adsorbent. PAH adsorption was a two-stage process: a short, fast initial period followed by a long, slow period corresponding to the intra-particle diffusion of PAH molecules in macropores and micropores. The adsorption capacity was determined by total surface area accessible to PAH and the availability of active surface chemical groups. The positive dependence of adsorption capacity on surface oxygen groups and temperature was observed, suggesting a chemical nature of PAH adsorption. The interaction between PAH-activated carbon was however, weak and energetically similar to that of hydrogen bonds. Overall, PAH adsorption was an exothermic process that combined physisorption and chemisorption. CO2-activated petroleum coke had a greater SSA-normalized capacity than coal-derived commercial activated carbon (0.26 vs. 0.19 mg/m2). The capacity was significantly increased by post-oxidation to 0.62 mg/m2.MAS