Static and dynamic adsorption studies of PolyChloroBiphenyls (PCBs) over activated carbons

Since PolyChloroBiphenyls (PCBs) have been extensively used in the past century, they are frequently detected in surface water and ground water. Due to their poor solubility, extremely low concentrations are observed in water. However, PCBs were demonstrated more recently to be highly toxic and need to be eliminated. The adsorption rapidly appeared as a key technology for their efficient and economical removal from water. In this study, activated carbons were shown to be highly efficient in the adsorption of 2-PCB under static conditions, i.e. at long contact time (several hours) when the adsorption-desorption equilibrium was reached. Under such conditions, the main key parameter was shown to be the activated carbon texture (specific surface area, porosity). Moreover, the main driving force was identified to be the combination between the very limited solubility of 2-PCB in pure water and the hydrophobic nature of the activated carbon. In turn, under dynamic conditions, i.e. at short contact time (less than 5 s), the overall adsorption process was shown to be quite inefficient and unambiguously controlled by internal surface diffusion limitations. In this later case, the operating parameters, especially the activated carbon bed morphology, played a major role.