Zero-valent aluminum based trimetallic particles comprising a combination of catalytically effective amounts (1 wt%) of palladium and zero-valent iron on the aluminum surface were synthesized and tested for the dechlorination of chlorinated methanes in batch reactors. XRD analysis indicated the trimetallic particles present in zero-valent form of all three components. Trimetallic Pd/Fe/Al particles showed a very rapid degradation of carbon tetrachloride leading to a surface normalized rate constant (kSA) of approximately 0.03 L/h/m2, two orders of magnitude higher than that of reported data on zero-valent iron particles under near neutral pH conditions. Hydrocarbons including methane and ethane were the major products that accounted for about 38% and 27% of the carbon tetrachloride lost, respectively. Repetitive addition of carbon tetrachloride showed no loss of activity of Pd/Fe/Al particles for more than 20 cycles. In the absence of palladium, the degradation rate decreased by a factor of 10 suggesting palladium serves as a catalyst. Analysis of anions in the solution revealed that the chloride accounted for 75% of the carbon tetrachloride lost. Metallic ions for aluminum and iron were determined to be about 0.02 and 20 mg/L, respectively at the end of the experiment. No palladium ion was measured.
Keywords: aluminum, dechlorination, groundwater remediation, iron, palladium, zero-valent metal