Journal of Applied Electrochemistry

, Volume 21, Issue 6, pp 537–542 | Cite as

Mass transfer at the gas evolving inner electrode of a concentric cylindrical reactor

  • M. F. El-Sherbiny
  • A. A. Zatout
  • M. Hussien
  • G. H. Sedahmed
Papers

Abstract

Mass transfer coefficients for an oxygen evolving vertical PbO2 coated cylinder electrode were measured for the anodic oxidation of acidified ferrous sulphate above the limiting current. Variables studied included the ferrous sulphate concentration, the anode height, the oxygen discharge rate and the anode surface roughness. The mass transfer coefficient was found to increase with increasing O2 discharge rate,V, and electrode height,h, according to the proportionality expressionKV0.34h0.2. Surface roughness with a peak to valley height up to 2.6 mm was found to increase the rate of mass transfer by a modest amount which ranged from 33.3 to 50.8% depending on the degree of roughness and oxygen discharge rate. The present data, as well as previous data at vertical oxygen evolving electrodes where bubble coalescence is negligible, were correlated by the equationJ=7.63 (Re. Fr)−0.12, whereJ is the mass transferJ factor (St. Sc0.66).

Keywords

Oxygen Mass Transfer Surface Roughness Discharge Rate Sulphate Concentration 

Notation

a1,a2

constants

A

electrode area (cm2)

C

concentration of Fe2+ (M)

d

bubble diameter (cm)

D

diffusivity (cm2 s−1)

e

electrochemical equivalent (g C−1)

F

Faraday's constant

g

acceleration due to gravity (cm s−2)

h

electrode height (cm)

IFe2+

current consumed in Fe2+ oxidation A

Io2

current consumed in O2 evolution, A

K

mass transfer coefficient (cm s−1)

m

amount of Fe2+ oxidized (g)

P

gas pressure (atm)

p

pitch of the threaded surface (cm)

Q

volume of oxygen gas passing any point at the electrode surface (cm3 s−1)

R

gas constant (atm cm3 mol−1 K−1)

r

peak-to-valley height of the threaded surface (cm)

t

time of electrolysis (s)

T

temperature (K)

μ

solution viscosity (g cm−1 s−1)

V

oxygen discharge velocity as defined by Equation 3 (cm s−1)

Z

number of electrons involved in the reaction

Sh

Sherwood number (Kd/D)

Re

Reynolds number (ρVd/μ)

Sc

Schmidt number (v/D)

J

mass transferJ factor (St. Sc0.66)

St

Stanton number (K/V)

Fr

Froude number (V2/dg)

ρ

Solution density, g cm−3

v

Kinematic viscosity (cm2 s−1)

ϕ

bubble geometrical parameter defined in [31]

ϑ

fractional surface coverage

δ

diffusion layer thickness (cm)

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Copyright information

© Chapman and Hall Ltd 1991

Authors and Affiliations

  • M. F. El-Sherbiny
    • 1
  • A. A. Zatout
    • 1
  • M. Hussien
    • 1
  • G. H. Sedahmed
    • 1
  1. 1.Chemical Engineering Department, Faculty of EngineeringAlexandria UniversityAlexandriaEgypt

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