Understanding the role of atomic hydrogen on chloroethene reactions at iron surfaces

There has been increasing interest in using metallic iron fillings for remediating groundwater contaminated by chlorinated solvents. The role of atomic hydrogen in reductive dechlorination of trichloroethylene (TCE) and tetrachloroethylene (PCE) was studied. At pH = 7, TCE reaction rates were 2 ± 0.26 times faster than those for PCE when each was present at 6 μM concentration, and were 1.5 ± 0.15 times faster at 30 μM concentration. The reaction mechanism involving atomic hydrogen could be saturated at low TCE concentrations. Thus, at neutral pH values reduction by atomic hydrogen could be the dominant TCE reduction pathway only at very low TCE concentrations.