Transformation of Chlorinated Methanes by Nanoscale Iron Particles

This paper examines the potential of using laboratory-synthesized nanoscale iron particles to transform chlorinated methanes. The iron particles have diameters on the order of 1–100 nm (0.001–0.1 μm). Palladized iron particles were prepared by depositing palladium (0.05–1% Pd by weight) on the surface of iron. Batch experiments were conducted to compare reactions of chlorinated methanes with palladized nanoscale iron, nanoscale iron, and commercial grade iron particles (～10 μm). Rapid transformations of tetrachloromethane (CT) and trichloromethane (CF) were achieved with the palladized nanoscale iron particles. Typically 0.1 mM CT or CF was reduced below detection limits within 1 h. Methane and dichloromethane (DCM) were the major end products. Yields of methane and DCM from CT were 52% and 23%, respectively. Little degradation of DCM was observed within 72 h. With the nanoscale iron and commercial-grade iron particles, much slower reactions of chlorinated methanes were observed. Kinetic analyses indicated that the surface area-normalized rate coefficients kSA of the nanoscale iron and commercial grade iron particles were one to two orders of magnitude lower than those of the palladized nanoscale iron.