Intensification of degradation of Sunset Yellow using packed bed in a pulsed high-voltage hybrid gas-liquid discharge system: Optimization of operating parameters, degradation mechanism and pathways

Tris–Co(II)–H2O2 System-Mediated Durative Hydroxyl Radical Generation for Efficient Anionic Azo Dye Degradation by Integrating Electrostatic Attraction

“…First, the process is started by the cleavage of the NN bond of SY, which results in the generation of 4-aminobenzenesulfonate and 5-nitro-6-hydroxy-2-naphtalenesulfonate. Because of the high reactivity of these two intermediates, their mass signals were not observed, which is consistent with previously reported researches. , Second, the oxidation of 4-aminobenzenesulfonate occurs and produces compound 1 and compound 2 . Meanwhile, • OH attacks the substitution of nitroso groups on the naphthalene ring and produces compound 3 .…”

“…The possible structures of these components were identified from the MS data (Figure S11 and Table S1). , On the basis of MS results of previous reports, these five components were characterized as 4-hydroxybenzenesulfonate ion (1), hydroxylated derivative of 4- hydroxybenzenesulfonate ion (2), hydroxylated derivative of 1,4,6-trihydroxy-2-naphthalenesulfonate ion (3), 1,4-naphthoquinone (4), and cyclopentanecarboxylic acid (5), respectively. These compounds also appeared in SY degradation with the Co­(II)–H 2 O 2 Fenton-like system, indicating that the introduction of Tris did not change the degradation pathway.…”

“…In addition, the continuous changes of corresponding UV–vis absorption spectra of SY solution were recorded to further research the degradation pathway. SY has three characteristic absorption peaks around 482, 314, and 230 nm, respectively (Figure B) . The absorption peak in the visible light region (482 nm) is assigned to the n−π* transition of the azo group.…”

“…SY has three characteristic absorption peaks around 482, 314, and 230 nm, respectively (Figure 6B). 50 The absorption peak in the visible light region (482 nm) is assigned to the n−π* transition of the azo group. However, the absorption peaks in the ultraviolet region (314 and 230 nm) belong to the π−π* transition of the naphthalene ring and azo bond, respectively.…”

“…Because of the high reactivity of these two intermediates, their mass signals were not observed, which is consistent with previously reported researches. 50,51 Second, the oxidation of 4-aminobenzenesulfonate occurs and produces compound 1 and compound 2. Meanwhile, • OH attacks the substitution of nitroso groups on the naphthalene ring and suggested that the Tris−Co(II)−H 2 O 2 system is expandable for promoting the degradation of other anionic azo dyes.…”