Since the denitri®cation of nitrate by Fe0 involves
reaction at the metal surface, it was anticipated that the
quantity of metal surface area should strongly in¯uence
the kinetics of nitrate reduction. The quantity of available
surface area is among the most signi®cant experimental
variables aecting contaminant reduction rates.
Increasing the concentration of iron particles in the solution,
although making little dierence in the ®nal removal
eciency in excess of iron dosage, will speed up
the initial reaction, providing more active sites of iron
particles for collision of nitrate ions to reduction. The
nitrate reduction rate pro®les with dierent iron content
in terms of kobs, the observed ®rst-order reaction rate
constant, are shown in Fig. 2.