This project determined the thermodynamic potentials for various reactions
between reduced manganese (Mn+2), manganese oxide (MnO2(s)),
chlorine dioxide (C102), and potassium permanganate (KMnO4). Based on
these findings, laboratory analyses were performed to determine if these
reactions would occur under simulated water treatment plant conditions.
In addition, a speciation procedure was developed to quantify the various
species of manganese and chlorine dioxide present in a single
sample. The reactions and the speciation procedure were evaluated at
TOC concentrations ranging from < 1.0 mg/L to 5.0 mg/L and at pH 6.0 and
8.0. The speciation procedure yielded a reliable measure of Mn+2,
insoluble manganese, and Mn+7; however, the Mn+7 evaluation could be
disrupted by the presence of free chlorine. The determination of C102
and C102- concentrations was also possible; however, the C102-
concentration was subject to error.
The laboratory analyses revealed that C102 was unable to oxidize
either Mn+2 or MnO2(s) to Mn+7 under any of the thermodynamically
favored conditions. Both KMn04 and C102 selectively oxidized reduced
organic material before reducing the concentration of Mn+2. When C102
and KMnO4 were added simultaneously, the ClO2 reacted preferentially
with the reduced materials. Only after the C102 concentration was
exhausted did the MnO- begin to oxidize the reduced species.
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