The management of wastewater from a conventional biodiesel
production plant using waste cooking oil as feedstock was carried
out at a laboratory scale and at ambient temperature (around
30
°
C) with two steps; the recovery of biodiesel by acid protonation
followed by the electrochemical treatment of the residual (aque-
ous) waste liquid. For the first step, raw biodiesel wastewater in
Table 1
was acidified by the addition of concentrated sulphuric
acid (conc. H
2
SO
4
, Merck) as a proton donor to the indicated final
pH (range from 2.5 to 9.3), and mixed by shaking for 2 h to ensure
protonation was complete. Consequently, the properties of the ob-
tained biodiesel were then characterized by using Fourier trans-
form infrared (FTIR) spectroscopy (DF 3 C206A type) and ASTM
and EN standard methods.
The remaining discharged wastewater (aqueous phase) from the
first step after extraction of the salvaged biodiesel phase was then
treated by the second stage, namely electro-oxidation. Prior to treat
such wastewater, the feasibility of using the electro-oxidation reac-
tionon the residual aqueousphase after biodieselrecovery wasthen
investigated by using a rotating disk electrode (RDE) at a speed of
3000 rpm with a Potentiostat/Galvanostat (Auto Lab, model PG sta-
to). Two platinum rods, each with a total surface area of 0.794 cm
2
,
were used as counter and working electrodes, respectively, and the
Ag/AgCl electrode was used as the reference electrode. The scan
potential was varied between +2500 mV/Ag/AgCl and
2500 mV/
Ag/AgCl at a scan rate of 0.5 mV/s. Consequently, the treatment