Title: Carbon tetrachloride transformation on the surface of nanoscale biogenic magnetite particles.

Authors: McCormick, Michael L; Adriaens, Peter

Published In Environ Sci Technol, (2004 Feb 15)

Abstract: Iron-reducing conditions in subsurface environments promote dechlorination reactions via both biotic and abiotic pathways, the latter often mediated via biologically activated minerals formed by dissimilatory iron-reducing bacteria (DIRB). Here we report the major products and pathways associated with the abiotic transformation of carbon tetrachloride (CT) by nanoscale biogenic magnetite/maghemite particles produced by the DIRB Geobacter metallireducens. Product formation and free radical/carbene trapping studies indicate that CT transformation occurs via three parallel pathways. The first pathway (hydrogenolysis) results in the formation of chloroform (45-50%) via a trichloromethyl free radical (*CCl3) and possibly a trichloromethyl carbanion (**CCl3-). The second and third pathways involve a dichlorocarbene intermediate (**CCl2), which either hydrolyzes to form CO (approximately 38%) (carbene hydrolysis), or undergoes further reduction to yield methane (8-10%) (carbene reduction). The mechanism of methane formation from **CCl2 is not known, but is speculated to involve a sequence of surface coordinated carbenoid and free radical complexes. The large fraction of relatively benign products formed by the carbene-mediated pathways suggests that magnetite/maghemite particles may have a beneficial application in the remediation of CT contaminated environments.

PubMed ID: 14998017

MeSH Terms: Carbon Tetrachloride/chemistry*; Ferrosoferric Oxide; Free Radicals/chemistry; Iron/chemistry*; Methane/analysis; Oxides/chemistry*; Particle Size; Soil Pollutants/analysis*; Solvents/chemistry*; Water Pollutants/analysis*