• Fenton process;
  • reactive black 5;
  • decolorization;
  • kinetics;
  • thermodynamics


The decolorization and degradation efficiency of the azo dye Reactive Black 5 (RB5) by Fenton system were investigated in this study. The operation parameters such as Fe2+:H2O2 ratio, pH value, initial concentration of RB5, reaction time, and temperature were examined. Maximum decolorization (99%) and degradation (88% COD removal) efficiencies were achieved at the Fe2+:H2O2 ratio of 0.05 and pH 3 for 15-min reaction time. The decolorization kinetic of RB5 followed pseudo-second-order reaction kinetic. The increase of temperature caused decreasing of obtained rate constants and increasing of corresponding half-lives. The article also discussed thermodynamic parameters including changes in Gibbs free energy, enthalpy, and entropy for the decolorization of RB5 by Fenton and exposed that the oxidation process was spontaneous and exothermic under natural conditions. © 2010 American Institute of Chemical Engineers Environ Prog, 2010