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Advisor(s)
Abstract(s)
Zero valent iron (ZVI) has been extensively used as a reactive medium for the reduction of Cr(VI) to Cr(III)
in reactive permeable barriers. The kinetic rate depends strongly on the superficial oxidation of the iron
particles used and the preliminary washing of ZVI increases the rate. The reaction has been primarily
modelled using a pseudo-first-order kinetics which is inappropriate for a heterogeneous reaction. We
assumed a shrinking particle type model where the kinetic rate is proportional to the available iron surface
area, to the initial volume of solution and to the chromium concentration raised to a power ˛ which
is the order of the chemical reaction occurring at surface. We assumed α= 2/3 based on the likeness
to the shrinking particle models with spherical symmetry. Kinetics studies were performed in order to
evaluate the suitability of this approach. The influence of the following parameters was experimentally
studied: initial available surface area, chromium concentration, temperature and pH. The assumed order
for the reaction was confirmed. In addition, the rate constant was calculated from data obtained in different
operating conditions. Digital pictures of iron balls were periodically taken and the image treatment
allowed for establishing the time evolution of their size distribution.
Description
Keywords
Chromium reduction Reactive permeable barriers Heterogeneous kinetics
Citation
Publisher
Elsevier