Decolorization of C.I. Reactive Red 2 in O 3, Fenton-like and O 3/Fenton-like hybrid systems

Abstract

The decolorization of C.I. Reactive Red 2 using ozone-related, Fenton-like-related and ozone/Fenton-like hybrid systems was studied. The UV, H 2O 2, UV/Fe 3+ and H 2O 2/Fe 3+ systems did not achieve significant decolorization at pH 7; decolorization rates followed the order: pH 10 > pH 7 > pH 4 in the O 3 and UV/O 3 systems and followed the opposite order in the case of the UV/H 2O 2 system. Decolorization rate constants were consistent with pseudo-first-order kinetics. In the O 3 system, decolorization rate declined as dye concentration increased. The decolorization rate constants at pH 7·followed the order UV/O 3/H 2O 2/Fe 3+ (5.78 h −1) > UV/O 3/H 2O 2 (5.33 h −1) > UV/H 2O 2/Fe 3+ (4.59 h −1) > UV/H 2O 2 (4.08 h −1) > UV/O 3 (2.91 h −1) = O 3 (2.91 h −1) ≥ UV/O 3/Fe 3+ (2.90 h −1) > O 3/Fe 3+ (2.42 h −1) > O 3/H 2O 2/Fe 3+ (2.03 h −1) > O 3/H 2O 2 (1.42 h −1).