Decolorization of C.I. Reactive Red 2 by catalytic ozonation processes

• Published in: Journal of hazardous materials Vol. 153; no. 3; pp. 1052 - 1058
• Main Authors: Wu, Chung-Hsin, Kuo, Chao-Yin, Chang, Chung-Liang
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30.05.2008; Elsevier
• Subjects: Applied sciences; C.I. Reactive Red 2; Catalysis; Catalytic ozonation; Catalytic reactions; Chemical engineering; Chemistry; Color; Coloring Agents - chemistry; Coloring Agents - radiation effects; Exact sciences and technology; General and physical chemistry; Manganese - chemistry; Manganese Compounds - chemistry; Mn(II); MnO 2; Naphthalenesulfonates - chemistry; Naphthalenesulfonates - radiation effects; O 3; Oxidants - chemistry; Oxides - chemistry; Ozone - chemistry; Pollution; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Titanium - chemistry; Triazines - chemistry; Triazines - radiation effects; Ultraviolet Rays; UV/TiO 2; Waste Disposal, Fluid - methods; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - radiation effects; Water Purification - methods; MnO 2; C.I. Reactive Red 2; O 3; Mn(II); Catalytic ozonation; UV/TiO 2; MnO2; Discoloration; Catalytic reaction; O3; Ozone; Ozonization; Ultraviolet radiation; UV/TiO2; Reactive dye; pH; Physicochemical purification; Kinetics; Rate constant; Titanium oxide; Catalyst
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2007.09.058

This study adopted O 3, UV/TiO 2/O 3, O 3/Mn(II) and O 3/MnO 2 systems to assess the decolorization efficiency of C.I. Reactive Red 2 (RR2). The decolorization rate increased with concentrations of Mn(II) and MnO 2 in the ranges 0.05–0.1 and 0.05–0.8 g/l, respectively. However, when 0.5–3 g/l TiO 2 was added, the effect of TiO 2 dosage for RR2 decolorization was insignificant in the UV/TiO 2/O 3 system. At pH 2, the decolorization rate constants of O 3, O 3/Mn(II) (0.05 g/l), O 3/Mn(II) (0.1 g/l), O 3/Mn(II) (0.15 g/l), O 3/MnO 2 (0.05 g/l) and O 3/MnO 2 (0.8 g/l) were 0.816, 2.001, 3.173, 3.087, 1.040 and 1.648 min −1, respectively. After 5 min of reaction, the decolorization rates followed the order O 3/Mn(II) > O 3/MnO 2 > O 3 > UV/TiO 2/O 3; however, the TOC removal did not vary among these systems. Adding ethanol reduced the decolorization rate of the UV/TiO 2/O 3 and O 3/MnO 2 systems and did not affect the decolorization rate of O 3/Mn(II). Decolorization in UV/TiO 2/O 3, O 3/Mn(II) and O 3/MnO 2 systems is suggested to proceed by mainly radical-, surface- and radical-type mechanisms, respectively. Additionally, direct ozonation cannot be ignored in O 3/Mn(II) and O 3/MnO 2 systems.