Desalination 211 (2007) 72–86 Presented at the 9th Environmental Science and Technology Symposium, September 1–3, 2005, Rhodes, Greece. Organized by the Global NEST organization and prepared with the editorial help of the University of Aegean, Mytilene, Greece and the University of Salerno, Fisciano (SA), Italy. *Corresponding author. Effect of system parameters and of inorganic salts on the decolorization and degradation of Procion H-exl dyes. Comparison of H 2 O 2 /UV, Fenton, UV/Fenton, TiO 2 /UV and TiO 2 /UV/H 2 O 2 processes A. Riga a,c , K. Soutsas b , K. Ntampegliotis a , V. Karayannis a,d , G. Papapolymerou a * a Department of Mathematical and Physical Sciences, b Department of Forestry, Technological Educational Institute of Larissa, Larissa, 411 10, Greece Tel. +30 (2410) 684333; Fax +30 (2410) 610803. email: papapoly@teilar.gr c Department of Mechanical and Industrial Engineering, University of Thessaly, Volos, 383 34, Greece d Department of Pollution Control Technologies, Technological Educational Institute of West Macedonia, Kozani, Kila, 50100, Greece Received 25 December 2005; revised 6 April 2006; accepted 6 April 2006 Abstract Reactive dyes are extensively used in the last years due to their superior performance, but they are environmentally hazardous. In the present work, the decolorization and degradation of commercial reactive azo dyes (Procion Navy H-exl, Procion Crimson H-exl and Procion Yellow H-exl) were studied using five advanced oxidation processes (AOPs): H 2 O 2 /UV, Fenton, UV/Fenton, TiO 2 /UV and TiO 2 /UV/H 2 O 2 . The dependence of the decolorization on the system parameters (solution pH, dye and reactants initial concentrations, and TiO 2 loading) and on the presence of salts (NaCl, Na 2 CO 3 , NaHCO 3 , Na 2 SO 4 , NaNO 3 and Na 3 PO 4 ) was investigated. The decolorization (determined by spectrophotometric analysis) and the degradation (determined as TOC reduction) were compared for the different processes examined. The decolorization of the Procion H-exl solutions considered was found to strongly depend on the system parameters in all five AOPs. Although decolorization is very fast for the Fenton process and becomes even faster for the UV/Fenton process, degradation rates are relatively low for these two methods. Addition of H 2 O 2 increases the decolorization and especially the degradation rates for the TiO 2 /UV process. The H 2 O 2 /UV and doi:10.1016/j.desal.2006.04.082 0011-9164/07/$– See front matter © 2007 Published by Elsevier B.V.