The degradation of organic dyes by corona discharge Page: 3 of 16

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materials. Two articles have reported the oxidation of
biomolecules in the laboratory using corona discharge. One
of these reported the oxidation of NADH and NADPH [3]; the
other reported the rapid destruction of hemoglobin [4].
Corona discharge has also been shown to oxidize a
polyethylene surface and induce the graft polymerization of
acrylamide [5], and to oxidize inorganic molecules. One
report claimed that mixtures of SFg and water subjected to
point-to-plane 50 Hz ac corona discharges produced only
stable gaseous by-products of SOF2 and SO2F2 as detected by
GC or GC-MS [6]. Another study reported the oxidation of
copper, silver, and gold foils [7].
Oxygen free radicals and related species have been shown
to effectively destroy several organic hazardous species. A
reaction process that breaks down industrial solvents,
pesticides, dioxins, PCB's, and munitions chemicals into
smaller, safer products has been demonstrated using titanium
dioxide as a catalyst and the sun's ultraviolet light. In
this process, hydroxyl radicals and peroxide ions are
believed to break down the hazardous organics into water,
carbon dioxide, and some very dilute acids [8]. Others have
shown that a reaction involving the superoxide ion (02) will
convert PCB's into bicarbonate of soda and halide ions. This
is accomplished via the in situ electrolytic reduction of
dissolved oxygen [1]. The same authors suggested that 02
generated in solution can react with PCB's to form HC1 and
carbonic acid.
Reaction rates, kinetics, and mechanisms of the effects
from corona discharge have also been studied. SOx and NOx
have been successfully removed from iron-ore sintering
machine flue gas using high energy electrons in the presence
of NH3. Oxidation by corona discharge creates ammonium
sulfate and ammonium nitrate precipitates [9,10]. Similar
tests have been run on synthetic coal-fired boiler flue gases
[10],
Sulfur dioxide has been converted to sulfuric acid mist by
corona discharge. The rate-determining step was the
formation of atomic oxygen by electrical discharge. The
concentration of SO2 was 500-3000 ppm in a flowing humid air
mixture. Optimum reaction rates occurred at 70% relative
humidity and above a 15% oxygen concentration [11]. S02
removal was enhanced when the liquid surface was subjected to
corona discharge, with the bulk of the acid deposition within
the chamber. Gas-phase oxidation of S02 in the absence of
water was minimal [12],
A negatively charged electrode placed in the gas phase
above grounded water will generate superoxide (02) [13] and
ozone (03) [8]. In the presence of iron salts, superoxide can
also be converted to hydrogen peroxide and the highly
reactive hydroxyl radical [14] . Reports indicate that ion
species created by corona discharge in air at atmospheric
pressure also include CO3, CC>3(H20)X, (x=l,2), 0 , N02, 0 ,
O3, NO+, N02 + , N2 and H+(H20)n (n^9) [15-17]. These ions ahd
radicals are highly unstable and may react with a broad
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Goheen, S.C.; McCulloch, M.; Durham, D.E. & Heath, W.O. The degradation of organic dyes by corona discharge, article, February 1, 1992; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc1092124/m1/3/ocr/: accessed December 10, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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