A novel approach in revealing mechanisms and particular step predictors of pH dependent tartrazine catalytic degradation in presence of Oxone®

Photocatalytic Performance of Carbon-Containing CuMo-Based Catalysts under Sunlight Illumination

“…The second possibility is the cleavage of the N=N azo bond by the attack of •OH (Figure 12c) to form the structures ( 7) and ( 8) in agreement with Ali et al [63]. In addition, according to Popadić et al [62], the catalytic degradation of tartrazine follows different pathways as a function of the solution pH; at pH = 6, the dominant mechanism follows a pathway including the attack of •OH radical, suggesting that the existence of a hydrogen atom bound to a diazo group is an essential prerequisite for the radical cleavage of diazo compounds. In the present study, tartrazine is in equilibrium with the protonated form (solution pH ca.…”

“…This mechanism agrees with theoretical density functional theory studies reported by Mendoza-Huizar [64], who reported that if a nucleophilic attack is considered as initial attack, it is necessary a second attack by free S-based radicals or electrophiles such as superoxide radical (•O 2 -) to cleave the N=N bond. However, the formation of this S-based radical is only promoted at basic pH of solution [62], and the scavenger tests from Figure 11 show the formation of •O 2-is negligible in our case. All this confirms that the dominant mechanism for the degradation of tartrazine in Cu4-800-N2 catalyst involves successive attacks of •OH radical.…”

“…Accordingly, it can be proposed that in the present experimental conditions, the photodegradation of yellow 5 mainly occurred by the attack of •OH radicals as discussed as follows. Figure 12 shows two different proposed pathways for the degradation of yellow 5 on the basis of the scavenger tests, and compares to the results reported in the literature [62][63][64]. The first pathway proceeds through the cleavage of C-N bond (Figure 12b) due to the attack of both superoxide radical (•O2-) and hydroxyl radical (•OH) to form structures (3) and ( 4), which may suffer a successive attack of •OH to form the structures ( 5) and ( 6) and molecular N2.…”

Performance of a C-containing Cu-based photocatalyst for the degradation of tartrazine: Comparison of performance in a slurry and CPC photoreactor under artificial and natural solar light

“…This mechanism agrees with other studies reported in the literature based on experimental and computational methods [52], proposing the nucleophilic attack of the N=N bond as the initial step. Popadić et al [50] and Ali et al [51] also reported that the catalytic degradation of tartrazine follows different pathways as a function of the pH of solution, including the attack of •OH radicals at slight acidic pH. This is in agreement with our results, since the photocatalytic assays have been carried out at pH 5.…”

Spectroelectrochemistry of Electroactive Polymer Composite Materials

“…This is due to the existence of a wide range of electronic states, whose shares in the resulting spectrum are changing during redox transformations. There are several methods for deconvolution (peak fitting) of complex electronic absorption spectra, including use of Gaussian and/or Lorentzian approximations of the shapes of individual absorption bands [ 41 ] and Matrix Rank Analysis [ 42 ]. However, the number and shapes of the approximated individual absorption bands used for this deconvolution are usually chosen in a voluntary way.…”