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MASS TRANSPORT EFFECTS ON THE KINETICS OF NITROBENZENE REDUCTION BY IRON METAL. (R827117)
Citation:
Scherer, M. M., K. Johnson, J. C. Westall, AND P. G. Tratnyek. MASS TRANSPORT EFFECTS ON THE KINETICS OF NITROBENZENE REDUCTION BY IRON METAL. (R827117). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 35:2804-2811, (2001).
Description:
To evaluate the importance of external mass transport on the overall rates of
contaminant reduction by iron metal (Fe0), we have compared measured
rates of surface reaction for nitrobenzene (ArNO2) to estimated rates
of external mass transport in a permeable reactive barrier (PRB). The rate of
surface reaction was measured at a polished Fe0 rotating disk
electrode (RDE) in an electrochemical cell, and the rate of mass transport was
estimated from a correlation for mass transport in packed-bed reactors. The
kinetics of ArNO2 reduction were studied in pH 8.4 borate buffer at a
potential below which an oxide film would form. The cathodic current measured in
this system was dependent on the electrode rotation rate, and the measured
first-order heterogeneous rate coefficient for surface reaction
[krxn = (1.7 ? 0.2) ? 10-3 cm
s-1] was about 10 times faster than the first-order mass
transport rate coefficient (kmt src="/ncer/pubs/images/ap.gif"> 2 ? 10-4 cm
s-1) estimated for PRBs. The similarity between rates of
surface reaction and mass transport suggest that it may be important to consider
mass transport processes in the design of PRBs for contaminants such as
nitroaromatics that are highly reactive with Fe0.