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The Fenton reagent, a mixture of H2O2 and Fe2+, is a powerful oxidant that could be
used to reduce the COD values of industrial wastewater. It has been suggested that acetic acid
could significantly reduce the efficiency of the decomposition of organic compounds. This
study mainly focused on studying the decomposition behavior of acetic acid, isopropyl alcohol
and ethanol by the Fenton reaction. All the experiments were done using aqueous solutions of
ethanol (0.05 M), isopropyl alcohol (0.04 M) and acetic acid (0.04 M). The Fenton reagent
was composed of 0.04 M H2O2 and 0.0027 M Fe2+. The Fenton reaction was initiated by
introducing 1.0 mL of the reagent to 100.0 mL of the organic solution. The residual amounts
of the Fe2+, FI2O2 and COD values were determined on hourly basis for 5 to 6 hours using
standard methods. According to the experimental data, the reduction o f COD was about 60 %
for ethanol and isopropyl alcohol solutions and about 30 % for acetic acid. The consumption
of H2O2 during the reaction was about 55% for both ethanol and isopropyl alcohol and about
35% for acetic acid. In addition, the Fe2+ to Fe3+ ratio was similar for ethanol and isopropyl
alcohol and it was significantly different for acetic acid. These experimental data suggest that
under similar experimental conditions, the decomposition of ethanol and isopropyl alcohol is
different from acetic acid by the Fenton reagent. It has been suggested that acetic acid forms
stable complexes with Fe3+ that is produced by the oxidation o f Fe2+ during the Fenton
reaction. As a result, the catalytic cycle of Fe2+ and Fe3+ might have been interrupted by acetic
acid. In order to prevent the formation of Fe3+- acetic acid complexes, citric acid was added as
a competitive ligand. The addition of small amounts of citric acid along with the Fenton
reagent significantly improved the decomposition of acetic acid and a 55 % reduction was
observed after 5 hours. On the other hand, decomposition of ethanol was not significantly
influenced by the addition of citric acid under similar experimental conditions to acetic acid.
