(351o) Regenerability of Activated Carbon Used for Adsorption of Polycyclic Aromatic Hydrocarbons

The polycyclic aromatic hydrocarbons (PAHs) are priority pollutants due to their toxic, carcinogenic, and mutagenic effects. The PAHs presence in several hydrocarbon streams is directly dependent on the origin and characteristics of the petroleum and on the processes to which the raw material was submitted. Activated carbons may deal with PAHs compounds present in the heavy mineral oil. Some advantages such as low-energy demand, possibility of adsorbent regeneration, broad availability of adsorbents and possibility of adsorption from the liquid phase on activated carbons make this an interesting field of research. In this study, successive column experiments were carried out using a granular activated carbon (Norit 830W) to evaluate the reduction in capacity along continuous cycles and optimal operational conditions. A column simulation model, using the particle parameters obtained from batch studies, was applied to predict breakthrough curves for adsorption and desorption runs. After several cycles, using solvent or inert gas, a decrease in PAH adsorption capacity was observed. The adsorption capacity of 185 mg/g, assessed in terms of PAHs, was obtained for the fresh activated carbon sample. A slight decrease (ca. 6%) in adsorbent capacity was observed after three adsorption/desorption cycles using n-hexane as solvent in the desorption step. For desorption with inert gas at 150°C, the capacity was kept essentially constant after the 5^th cycle, an interesting characteristic for a continuous operation process. A conceptual continuous process was simulated using the proposed model and evaluated based on productivity in terms of volume of treated oil per mass of adsorbent per time, showing a maximum value of 0.53 m³/(kg ads.).h at space velocity of ca. 4 h^-1.