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Discoloration of waters containing azo dye Congo Red by Fenton oxidation process. Estimation of activation parameters

Domenii publicaţii > Chimie + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Madalina Dragoi, Adriana Samide, Anca Moanţã

Editorial: Revista de Chimie (Bucureşti), 62 (12), p.1195-1198, 2011.


The discoloration of waters containing Congo red using Fenton reagent was studied at different pH values
and different temperatures. The results reported a significant discoloration after 5 min, at pH = 3.50 and
temperature of 55 oC. In these conditions, it was obtained a color removal (CR) equal to 75.6 ± 5 and a
relative discoloration rate of 14.12 % / min. Apparent activation energy was determined using the Arrhenius
equation. The value of Ea was determined as being equal to 85.9 kJ/mol. The activation enthalpy (ΔH0) and
the activation entropy (ΔS0) were calculated from the diagram of the transition state. The value of the
enthalpy (83.44 kJ/mol) indicates an endothermic reaction. Positive values of entropy (30.78 J/mol) suggest
that entropy increases upon achieving the transition state, which often indicates a dissociating mechanism.

Cuvinte cheie: Congo red; Fenton reagent; discoloration process; UV-Vis spectra