A study of groundwater matrix effects for the destruction of trichloroethylene using fe/Pd nanoaggregates

Iron nanoaggregates have been prepared using the sodium borohydride reduction method and post-coated with Pd using aqueous phase electro-deposition. The Fe/Pd nanoaggregates were used to examine dechlorination of trichloroethylene (TCE) with regard to matrix effects using materials representative of a potential zero-valent metal remediation site surrounding the Paducah gaseous diffusion plant in Paducah, KY. A surface-area-normalized first-order rate constant of 1.4 X 10^-1 Lm^-2 h ^-1 was obtained for the case of ideal dechlorination of 19.6 mg L^-1 TCE at room temperature and pH 6.2 using 0.5 g L^-1 Fe/Pd (0.42 wt % Pd) loading. This value decreases by an order of magnitude to 1.9 X 10^-2 l^-2 b^-1 when the reaction is carried out in a realistic background matrix when the pH is high (8.8). For all variables tested, Pd content has the most impact on reaction rates. Circulating batch-column experiments are used to study dechlorination under flow conditions and demonstrate the ability of nonstabilized Fe/Pd nanoaggregates to remove significant amounts of TCE (80-90%) over a broad range of groundwater velocities (12.9-83 ft per day) using moderate metal loadings (0.23-0.5 g L^-1).