Kinetic of the degradation of CI Food Yellow 3 and CI Food Yellow 4 azo dyes by the oxidation with hydrogen peroxide

The kinetic of the degradation of Food Yellow 3 (FY3) and Food Yellow 4 (FY4) dyes by oxidation using hydrogen peroxide 30% in alkaline solution was studied. The kinetics were measured spectrophotometrically by UV-vis at 427 nm for FY4 and 485 run for FY3 and under a temperature range of 25-70 degrees C. The addition Of Sodium hydroxide was necessary for the beginning of the process, which resulted in an easier degradation for the FY3 dye. Kinetic studies showed that degradation and rate constants were favored by the temperature and pH increase. The kinetic activation parameters (E-a, Delta H-#, Delta G(#) and Delta S-#) were Calculated by the Arrhenius and Eyring equations. The following results were obtained for the FY4: E-a 101 kJ/mol, Delta H-# 103 kJ/mol, Delta G(#) 15.5 kJ/mol and Delta S-# 0.27 kJ/(K mol). For the FY3 dye the results were as follows: E-a 51 kJ/mol, Delta H-# 54 kJ/mol, Delta G(#) 10.3 kJ/mol and Delta S-# 0.14 kJ/(K mol). The degradation of the FY4 azo dye was processed using twice the energy required far the degradation of the FY3 azo dye. (C) 2008 Elsevier B.V. All rights reserved.