color and COD removal efficiency gradually decreased with an
increase in the initial concentration. This is due to non-availability
of sufficient number of hydroxyl radicals. The presumed
reason is that when the initial concentration of DB71 is increased,
the OH concentration is not increased correspondingly.
However, the higher the concentration, the more the
dye decolorized in 20 min. This happens because the increase
in concentration enhances the interaction between the dye
and OH (Wu et al., 2010