Decolorization efficiency and kinetics of typical reactive azo dye RR2 in the homogeneous Fe(II) catalyzed ozonation process

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2013-11, Vol.233, p.14-23
• Main Authors: Zhang, Xian-bing, Dong, Wen-yi, Yang, Wei
• Format: Article
• Language: English
• Subjects: activation energy; Azo dye; azo dyes; chemical engineering; Decolorization; equations; Ferrous catalyzed ozonation; Kinetic model; mass transfer; ozonation; ozone; reaction kinetics; Reactive Red 2; temperature
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2013.07.098

Effect of Fe(II) dosage on the decolorization rate constant k2. (CB0=0.45mM, Qg=12Lh−1, Cg=10mg/L, Fe(II) dosage was 0, 0.2, 0.4, 0.9, 1.8, and 3.6mM, initial pH=7; T=298K.) [Display omitted] •Fe(II) can significantly improve the efficiency of RR2 dye ozonation.•Kinetics was studied based on Danckwerts surface renewal theory.•Effect of operating parameters were studied and optimized.•A possible degradation mechanism was proposed.•Temperature effect on rate constant was proposed by a modified Arrhenius Equation. The decolorization efficiency and gas–liquid reaction kinetics of Reactive Red 2 (RR2, C.I. 18200) dye by ferrous catalyzed ozonation process (O3/Fe(II)) in a semi-batch reactor were evaluated. The results indicate that RR2 dye ozonation is an irreversible second order reaction. Danckwerts surface renewal theory was used to specify the gas–liquid mass transfer progress and to determine the second order reaction rate constant k2. It is also found that Fe(II) can enhance the degradation efficiency of RR2 dye, and the k2 values were 1056M−1s and 2248M−1s when Fe(II) dosage were 0 and 0.9mM, respectively. The optimum O3/Fe(II) combination was 2mgL−1min−1 ozone dosage rate with initial Fe(II) dosage of 0.9mM when RR2 dye initial concentration was 0.45mM at pH 7. Increasing of the ozone inlet gas concentration and gas flow rate will increase the mass transfer coefficients and therefore increase k2. Furthermore, k2 is observed associate with temperature and can be expressed by a modified Arrhenius Equation with activation energy Ea of 26.3kJmol−1. A possible degradation mechanism between ozone and RR2 dye in O3/Fe(II) process was discussed.