3.1. Preliminary experiments
3.1.1. Initial pH
Previous studies established that initial pH was an essential factor
for the EC process and played an important role in the removal of the
contaminants from oily wastewater [1]. A pH series from 3 to 11 was
studied to determine the effects of initial pH on the removal efficiencies
of COD, turbidity and hardness. The reactions for these three conditions
were as follows [23]: