Depuración de efluentes contaminados por hidrocarburos aromáticos policíclicos mediante carbones activadosevaluación del proceso de adsorción

Résumé

[EN] Polycyclic aromatic hydrocarbons (PAH) constitute an important class of highly toxic environmental pollutants. As a consequence of their low biodegradability, adsorption on activated carbon is nowadays one of the most attractive techniques for the removal of PAH from wastewater. Despite having been the subject of plentiful studies in the literature, investigation of the rate and mechanisms of the adsorption process itself and the role of the characteristics of the adsorbent are still ambiguous and remain unclear. In this work, the performance of carbon adsorbents as a media for polycyclic aromatic hydrocarbons removal has been studied. To attain this goal, an exhaustive analysis of the chemical and textural characteristics of the selected activated carbon was carried out, in order to throw some light on the forces involved in the adsorption process. Moreover, the role of the functionalities of activated carbons on the adsorption was explored by evaluating adsorbents with similar porosity and different surface chemistry. The results confirmed that adsorption depended strongly on the pore-size distribution of the adsorbent, with micropores being the active sites for adsorption. However, the adsorption behaviour should not be exclusively linked to the porosity of the carbons, functionalization of the carbon surface strongly influenced the overall adsorption capacity of carbons. Adsorbents with a higher non-polar character have to be more efficient for PAH adsorption. This behaviour has been linked to the presence of dispersive interactions between the basal planes and the polyaromatic structure of the hydrocarbon. The interaction of the organic compound with the carbon sites is highly dependent on the solvent affinity for these active sites, as the competitive adsorption of the solvent becomes important. However, one must also take into account the dimensions of the molecules, and therefore the accessibility to the porosity of the adsorbents.