Minimization of the deactivation of palladium catalysts in the hydrodechlorination of trichloroethylene in wastewaters

Abstract

The deactivation of carbon- and alumina-supported palladium catalysts used for trichloroethylene (TCE) hydrodechlorination in wastewaters at mild conditions is studied in this work. TCE concentrations are in the interval of industrial wastewaters (200–900ppm, corresponding to 1.54–6.92mmol/L). Reaction studies have been performed in both batch slurry reactor and continuous fixed bed reactor. In both cases, a deactivation model (considering first-order kinetics for the main reaction, first-order deactivation kinetics, and the residual activity of the deactivated catalyst) has been proposed and experimentally validated. In general terms, carbon-supported catalysts are the most stable. Deactivation behavior can be explained in terms of the aqueous-phase redox and complexation equilibria of the active phase. The effect of different operation approaches, such the modification of the pH or the addition of alkalinity sources has been tested, being observed that the addition of sodium carbonate largely increases the catalyst stability.