Three-Step Catalytic Detoxification Process of Wastewater Containing Chlorinated Aromatic Compounds:  Experimental Results and Modeling Issues

Detoxification of water containing chlorinated aromatic compounds is performed in a single fixed bed using a periodic sequence of three steps: transient adsorption, catalytic hydrogenation, and thermal regeneration. The solid is both the adsorbent (activated carbon) and the catalyst (2.6% ruthenium loading). For chlorophenols, the end products are cyclohexanol and sodium chloride diluted in less than 2% of the amount of processed water. Adsorption is the critical step. The whole breakthrough curve is easily modeled. Conversely, the model fails to describe the early beginning which governs the purity of the effluent. The reaction step is performed under mild conditions (T < 353 K, P < 0.4 MPa) and is governed by the transient desorption of the pollutant, the catalytic reaction, and the mass-transfer processes. Thermal regeneration under hydrogen flow restores the adsorbent capacity and catalytic activity.