Accordingly, Fig. 2(b) presents the pH effect on metal ion concentrations
and their removal efficiencies after one-hour of EC
treatment with DC = 4 mA/cm2. It is clear in the figure that the
maximum removal efficiencies for all heavy metal ions occur at
pH = 7.89 and 9.56. Lower removal efficiencies were obtained at
pH = 6.56 and 10.68. This indicates that the heavy metal ions
removal decreases in lower acidic and higher basic mediums. In
alkaline medium, the oxidation of hydroxyl ions at the anode and
the formation of Fe(OH)4 and Fe(OH)63 anions lowered the
removing capacity [5]. In strongly acidic medium, the protons in
the solution were reduced to hydrogen gas at the cathode and
the same proportion of hydroxyl ions could not be produced [5].
In addition, the pH affects the EC performance through varying
the solution physiochemical properties, such as the solubility of
metal hydroxides and the electrical conductivity, and the size of
colloidal particles of iron (III) complexes that are strongly reactive
agents with the heavy metal ions [