Long service life IrO2/Ta2O5 electrodes for electroflotation |
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Authors: | R Mráz J Krýsa |
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Affiliation: | (1) Department of Inorganic Technology, University of Chemical Technology, Technicka 5, 166 28 Prague 6, Czech Republic |
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Abstract: | Ti/IrO2-Ta2O5 electrodes prepared by thermal decomposition of the respective chlorides were successfully employed as oxygen evolving electrodes for electroflotation of waste water contaminated with dispersed peptides and oils. Service lives and rates of dissolution of the Ti/IrO2-Ta2O5 electrodes were measured by means of accelerated life tests, e.g. electrolysis in 0.5M H2SO4 at 25°C and j = 2 A cm–2. The steady-state rate of dissolution of the IrO2 active layer was reached after 600–700 h (0.095 g Ir h–1 cm–2) which is 200–300 times lower than the initial dissolution rate. The steady-state rate of dissolution of iridium was found to be proportional to the applied current density (in the range 0.5–3 A cm–2 ). The oxygen overpotential increased slightly during electrolysis (59–82 mV for j = 0.1 A cm–2 ) and the increase was higher for the lower content of iridium in an active surface layer. The service life of Ti/IrO2 (65 mol%)-Ta2O5 (35 mol%) in industrial conditions of electrochemical devices was estimated to be greater than five years.List of symbols
a
constant in Tafel equation (mV)
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b
slope in Tafel equation (mV dec–1)
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E
potential (V)
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f
mole fraction of iridium in the active layer
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j
current density (A cm–2)
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l
number of layers
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m
Ir
content of iridium in the active layer (mg cm–2)
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r
dissolution rate of the IrO2 active layer ( g Ir h–1 cm–2)
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T
c
calcination temperature (°C)
- O
2
oxygen overpotential (mV)
- ![Delta](/content/k7015p3373771817/xxlarge916.gif)
O
2
difference in oxygen overpotential (mV)
- A
service life in accelerated service life tests (h)
- S
service life in accelerated service life tests related to 0.1 mg Ir cm–2 (h)
- p
polarization time in accelerated service life tests (h) |
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Keywords: | |
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