Due to the fast reaction of H2O2 with Fe2+ in the beginning
stage of the oxidation reaction as shown earlier in Fig. 2(a and
b), applying UV light in the early stages may not be necessary.
Therefore, Fenton and photo-Fenton processes were combined
in this part of the experiment in order to compare the efficiencies
of photo-Fenton and combined Fenton/photo-Fenton processes.
The initial concentrations of H2O2 and Fe2+ were set as follows:
[H2O2] = 0.667 M, [Fe2+] = 6.67×10−2 M. The reaction
was started with a Fenton reaction for 15 min before the UV
lamp was turned on.