Decolorization of C.I. Reactive Red 2 in O3, Fenton-like and O3/Fenton-like hybrid systems

The decolorization of C.I. Reactive Red 2 using ozone-related, Fenton-like-related and ozone/Fenton-like hybrid systems was studied. The UV, H2O2, UV/Fe3+ and H2O2/Fe3+ systems did not achieve significant decolorization at pH 7; decolorization rates followed the order: pH 10 > pH 7 > pH 4 in the O3 and UV/O3 systems and followed the opposite order in the case of the UV/H2O2 system. Decolorization rate constants were consistent with pseudo-first-order kinetics. In the O3 system, decolorization rate declined as dye concentration increased. The decolorization rate constants at pH 7·followed the order UV/O3/H2O2/Fe3+ (5.78 h−1) > UV/O3/H2O2 (5.33 h−1) > UV/H2O2/Fe3+ (4.59 h−1) > UV/H2O2 (4.08 h−1) > UV/O3 (2.91 h−1) = O3 (2.91 h−1) ≥ UV/O3/Fe3+ (2.90 h−1) > O3/Fe3+ (2.42 h−1) > O3/H2O2/Fe3+ (2.03 h−1) > O3/H2O2 (1.42 h−1).