Sequestration of PCBs Congeners Present in Askarel Formulation by Adsorption on the Prepared Activated Carbons

摘要

The difficulties of managing polychlorinated biphenyls (PCBs), a persistent organic pollutant inherited from the last century, constitute a major environmental problem, due to the lack of efficient, low-cost and accessible techniques of its destruction. The options of adsorption on activated carbon, prepared from available local agroforestry by-product appear to be an effective method that reduces the bio-accumulation character of PCBs. The adsorption of PCBs molecules in aqueous solution (ethanol-water, 1:10) on chemically activated carbons with H3PO4 at different concentrations (5%, 10%, 20%, 30%) was investigated. An UV spectrophotometer is used to assess the adsorption. The adsorption rate (> 90%) and the adsorption capacity (170.24 mg/g) of the activated carbon showed the performance of the prepared activated carbon. All experiments were carried out at room temperature. The effects of contact time, absorbent masse, initial concentration, pH solution, were evaluated. The resulted adsorption data applied to four isotherm models (Freundlich (R2 =0.90), Langmuir (R2 =0.95), Tenkim (R2 =0.96), and Dubinin-Radushkevich (R2 =0.94)), lead to the interpretation of the observed adsorption phenomena. The calculated free energy E (5.06 Kj) indicated that the physio-sorption played a significant role in this adsorption mechanism. The adsorption process was entirely controlled by intra particle diffusion, and followed the pseudo-second order mechanism. These adsorption performances combined with a photo-radiation of contaminated PCBs solution could be an easier way to destroy PCBS, that is an ecologically rational elimination of POPs.