Abstract
Mass transfer at carbon fibre electrodes has been studied using the mass transfer controlled reduction of potassium hexacyanoferrate(III) to potassium hexacyanoferrate(II). Different geometrical configurations have been assessed in a flow-by mode, namely bundles of loose fibres with liquid flow parallel to the fibres, carbon cloth with flow parallel to the cloth and carbon felt with liquid flow through the felt. For comparison, mass transfer rates at a single fibre have been measured; the experimental data fit the correlationSh=7Re 0.4. The same correlation can be used as a first approximation for felts. Mass transfer for fibre bundles and cloth under comparable conditions is much lower owing to channelling.
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Abbreviations
- c :
-
reactant concentration (mol m−3)
- c 0 :
-
reactant concentration atx=0 (mol m−3)
- c L :
-
reactant concentration atx=L (mol m−3)
- d :
-
fibre diameter (m)
- D :
-
diffusion coefficient (m2 s−1)
- F :
-
Faraday number (96 487 C)
- h :
-
depth of the electrode (m)
- i :
-
current density (A m−2)
- I :
-
current (A)
- k :
-
mass transfer coefficient (m s−1)
- L :
-
length of the electrode (m)
- n :
-
number of electrons
- S :
-
specific surface area (m2 m−3)
- u :
-
(superficial) velocity (m s−1)
- V R :
-
reactor volume (m3)
- w :
-
width of electrode (m)
- x :
-
distance in flow direction (m)
- β:
-
current efficiency
- η:
-
electrode efficiency
- λ:
-
characteristic length (m)
- v :
-
kinematic viscosity (m2 s−1)
- ϱ ns :
-
normalized space velocity (m3 m−3s−1)
- Re :
-
Reynolds number (ud/v)
- Sh :
-
Sherwood number (kd/D)
- Sc :
-
Schmidt number (v/D)
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Schmal, D., Van Erkel, J. & Van Duin, P.J. Mass transfer at carbon fibre electrodes. J Appl Electrochem 16, 422–430 (1986). https://doi.org/10.1007/BF01008853
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DOI: https://doi.org/10.1007/BF01008853