Theoretically, to achieve EC, coagulating ions are
generated from the sacrificial electrode by electro oxidation
to form coagulants which are able to destabilize the
suspended particles present in the water. The destabilized
particles then aggregate to form flocs. Additionally,
electroflotation (EF) also occurs in EC cell. The O2 and H2
bubbles produced from the electrodes are entrapped into the
flocs and are finally float up to the surface of water [16].
The main reactions occurring at the electrodes are as
follows:
When aluminum and graphite are used as anode and
cathode, respectively.
At aluminum anode,
Al → Al3+ + 3e-
(1)
2H2O → O2 + 4H+
+ 4e-
(2)
At graphite cathode,
3H2O + 3e- → 3/2H2 + 3OH-
(3)
In solution,
Al3+ + 3H2O ↔ Al(OH)3 + 3H+
(4)
When copper and graphite are used as anode and cathode,
respectively.
At copper anode,
Cu → Cu2+ + 2e-
(5)
At graphite cathode,
2H2O + 2e- → 2H2 + 2OH-
(6)
In solution,
Cu2+ + 2OH- ↔ Cu(OH)2 (7)
EC not only provides a fast rate of pollutant removal and
simplicity of operation, but also requires no chemical
additive. Therefore, it would produce less sludge [17-19].
These beneficial properties render EC more suitable than
conventional physico-chemical treatment processes.
In this study, the electrocoagulation-electroflotation
process was used to determine the influence of the key
parameters on the algae removal efficiency including
electrode material, agitation, current density and initial pH.
The removal mechanism was also investigated.