Study of degradation products and degradation pathways of sulfonated azo dyes under ultraviolet irradiation

Abstract

Monitoring the light-induced decomposition course of azo dyes is essential to understand their degradation pathways and mechanisms. In this study, two model dyes are synthesized and used for stimulating the photodegradation processes of azo and hydrazone dyes, respectively. Their intermediates formed during initial and final fading processes are characterized by high-performance liquid chromatography-electrospray ionization-mass spectrometry, gas chromatography-mass spectrometry and ion chromatography. Results reveal that no dramatic differences are observed between the two dyes, although hydrazone dye would undergo a more complicated degradation process. Hydroxyl radicals are the dominant reactive species involved in the photodegradation of both model dyes under ultraviolet irradiation. In the initial steps, the intermediates are almost hydroxylated derivatives, while low-molecular-weight dicarboxylic acids and their hydroxylated and esterified derivatives, as well as non-volatile inorganic ions, are detected and evidenced in the final steps. Furthermore, photodegradation pathways and mechanisms for the two model dyes are proposed accordingly.

Evaluation of the Dye Extraction Using Designed Hydrogels for Further Applications towards Water Treatment

“…This group of dyes is widely used in various industries (textile, leather, plastics, paper, pharmaceutical, food, and cosmetics industries) [ 38 , 39 , 40 ], implying a high probability of water pollution with the mentioned substances. Due to the complexity of the structural composition of sulfonated azo compounds (one or more azo groups having aromatic rings substituted by sulphonate groups), their degradation by chemical or biological decomposition is limited [ 40 , 41 , 42 ], which makes the method based on the adsorption phenomenon superior to others. Moreover, their high solubility in water and unique chemical structure are responsible for the intense color, decreasing light penetration within water bodies.…”

Peroxymonosulfate-based catalytic degradation of reactive dyes in real wastewater by Fe/N-codoped carbocatalysts loaded on carbon cloth

“…9 However, this technique cannot cover all dyes. 10 The past two decades have seen the development of a series of pollutant treatment methods, such as membrane separation, the Fenton method, and photo/electrocatalysis. [11][12][13][14] However, each of these methods has its limitations.…”