Kinetic and spectroscopic study of heterogeneous oxidation of azo dyes using hypochlorite

Abstract

A combined kinetic and spectroscopic investigation is described of the heterogeneous oxidation (by hypochlorite) of an azo dye (Remazol Red RB) reactively bound to cotton. It is shown that the physical state of bound dye (e.g. its pKA and tautomeric form) and its oxidation profile with pH are similar to those of dye in homogeneous solution. Analyses are presented which suggest that the mechanism of oxidation in the two environments is similar. The oxidation of azo dyes of pyrazolone and pyridone types occurs at similar rates to arylazonaphthol dyes. This suggests that oxidation kinetics are independent of groups attached either side of the azo linkage, confirming that the site of attack is the more nucleophilic nitrogen atom of the azo group of the common anion.

Formulation of colour‐care and heavy‐duty detergents: a review

“…The azo tautomer is relatively unreactive to oxidation by peracids. Furthermore, the same mechanism of oxidation is operative whether dyes are in solution or bound to the textile [37]. These observations support the view that fading observed in controlled, low temperature detergent washes results from destruction of the chromophore by the peracid generated in situ.…”

“…On the other hand, peracids are known to oxidise many of the azo and sulphur dyes used in the dyeing of textiles [5][6][7][8][9]37]. The most susceptible azo dyes are those capable of azo-hydrazone tautomerism and which do not contain bulky (sulphonate) groups adjacent to the azo link (Scheme 3).…”

Azo dye location in textiles: a novel UV–vis approach

“…Methyl Orange has two properties in common with many other dyes that either exhibit positive solvatochromism or are solvent-insensitive: (a) only one species is detected; and (b) small red shifts are exhibited when absorbed to cellophane [29] and cotton [30][31][32].…”

Kinetics of the oxidative degradation of thionine dye by hydrogen peroxide catalyzed by supported transition metal ions complexes

“…As a consequence, the effective elimination of colored effluents originating from the textile and related industries has become an important problem due to their refractory nature 1–3. The most common methods employed to treat wastewater containing organic dyes and pigments are classified into three main categories: (i) physical (adsorption, filtration, and flotation),4–7 (ii) chemical (oxidation, reduction, and electrochemical),8–17 and (iii) biological (aerobic and anaerobic degradation) 18–20. Recently, experimental investigations related to textile effluent treatment have focused on alternative methods of treatment which are capable of removing compounds in an environmentally safer and economically more feasible way 21–23…”