Enhanced degradation of tetrachloroethylene by green rusts with platinum.

This study presents an experiment which characterizes reductive dechlorination of tetrachloroethylene (PCE) by green rusts (GRs) in the presence of Pt using a batch reactor system. Relative to GR alone, the rate of PCE reduction in GR suspensions was greatly enhanced with the addition of Pt(IV) (95% of PCE was removed in 30 h). PCE was mostly transformed to a nonchlorinated byproduct, acetylene rather than trichloroethylene, and the carbon mass recovery was 98% at the last sampling point. The reduction of PCE was four times faster for GR-F(Pt) than for GR-CO3(Pt), mainly due to the higher Fe(ll) content of GR-F. The estimated kinetic rate constants of GR-Cl(Pt) increased significantly (i.e., 0.17, 0.21, and 1.01 h(-1), respectively) with an incremental addition of Pt from 0.5 to 2 mM. X-ray diffraction analysis showed the transformation of GR to magnetite as an oxidation product. X-ray photoelectron spectroscopy analysis revealed that the oxidation was coupled to the reduction of Pt (IV to 0) on the GR surfaces. The scanning electron microscope with energy dispersive spectrometer measurement showed the formation of Pt particles on the surfaces of GRs modified with the Pt(IV).