In this study, the adsorption of polyaromatic hydrocarbons (PAHs) from heavy naphthenic oils (HNOs) on commercial activated carbons was evaluated. Among the aromatics, polycyclic aromatic hydrocarbons (PAHs) are usually present in heavy oils and are contaminants that have potential carcinogenic and mutagenic characteristics. Oils with of PAH concentration less than 3 wt % are labeled as noncarcinogenic. The HNO samples used in this study had a high content of PAHs (ca. 8 wt %). Batch experiments were carried out to evaluate the adsorption capacity of activated carbons for PAHs (>160 mg/g), and to estimate the mass transfer parameters of the adsorption process. The pore diffusion model and the pore−surface diffusion model were applied to interpret and validate the kinetic experimental results. The results indicated the efficiency of activated carbons as potential adsorbent to adjust the polycyclic aromatics content of HNO.

The adsorption of naphthalene and pyrene on two different types of commercial activated carbons was studied by batch and column experiments. Adsorption equilibrium was measured at three different temperatures. Heats of adsorption were estimated from the equilibrium results and compared to other previous reports. From the column experiments, using parameters obtained from the batch experiments and literature correlations, effective surface diffusivities were estimated for naphthalene and pyrene on both adsorbents in different feed concentrations. The corrected diffusivities, using Darken equation, appear to be almost constant for naphthalene (ca. 1.3 · 10 −8 cm 2 /min), and for pyrene (ca. 2.3 · 10 −10 cm 2 /min), in both activated carbons.

Continuous adsorption and desorption of polycyclic aromatic hydrocarbons (PAHs) from heavy naphthenic oils (HNOs) were performed using commercial activated carbon on fixed bed experiments. In part 1, HNO samples with high PAH content (ca. 8 wt %) were treated in batch adsorption experiments, showing decrease in PAH concentration to ca. 3%. In this study, successive column experiments were carried out to study the reduction in capacity along continuous cycles and optimal operational conditions. A column simulation model, using the particle parameters obtained in the previous study, was applied to predict breakthrough curves for adsorption and desorption runs. After several cycles of adsorption/desorption, using solvent or inert gas, only a slight decrease in PAH adsorption capacity was observed. Selectivities for PAH adsorption in relation to aromatics adsorption were also estimated from the adsorption breakthrough curves data. 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 at space velocity of ca. 4 h–1.