Kinetics and mechanism of the uncatalyzed and Ag(I)-catalyzed oxidative decolorization of Sunset Yellow and Ponceau 4R with peroxydisulphate

摘要

The kinetics and mechanism of the oxidation of Sunset Yellow (E-110,C.I.15985),SY,and Ponceau 4R (E-124,C.I.16255),PR,monoazo dyes with peroxydisulphate have been investigated.The oxidation reaction of SY and PR was very slow and followed a zero-order kinetics for [dye] and a first-order kinetics for [S2O_8~(2-)].The reaction showed an activation energy of 102.3 kJ/mol and 96.2 kJ/mol for SY and PR,respectively.The rate of the Ag(I)-catalyzed oxidation reaction was higher with an activation energy of 46 kJ/mol and 45 kJ/mol for SY and PR,respectively.The activation parameters,DELTA H,DELTA G~(not=) and DELTA S~(not=) were also deduced.A reaction mechanism was proposed for the oxidation reaction of SY and PR in the absence and in the presence of Ag(I).