3.1.5. Effect of different cathodes
So far, the experiments have been performed with a Zn anode/
SS. cathode pair. Now, the Zn anode/Zn cathode set will be used in
order to analyse its influence on TPh (Fig. 6a) and COD (Fig. 6b).
Fig. 6a evidences that the trend of the phenolic content removal
for the two pairs of electrodes is similar. There is a rapid TPh depletion
in the first 30 min of reaction (TPh removal = 84.0%), remaining
practically constant thereafter. Nevertheless, in Fig. 6b there is
a significant difference in COD abatement for the two pairs of electrodes.
Although, in the first 15 min, they follow the same tendency,
achieving a removal of 15.0%, afterwards, the set Zn
anode/Zn cathode had a slower evolution attaining its major effi-
ciency after 45 min with 39.4%, whereas the Zn anode/SS cathode
pair had its highest removal after 30 min with 51.1%. These results
may be explained by the pH medium evolution over time (Fig. 6c).
As can be observed, the experiment with Zn anode/Zn cathode had
a slow transition from an acidic pH to neutral, taking longer time
than the other set of electrodes to dissolve metal ions to the aquatic
medium and subsequent formation of metal hydroxides necessary
to remove pollutants.
Our results point out that the operating conditions that have led
to the greatest removal efficiency of phenolic content and organic
matter of the simulated effluent by ECG were: raw pH (3.2), a
current density of 250 A/m2
, a distance between electrodes of
1.0 cm, 1.5 g/L of NaCl and the set Zn anode/SS cathode.