Determination of critical micelle concentration of several nonionic surfactants by azo-hydrazone tautomerism of anionic dye

Comparative studies of operational parameters of degradation of azo dyes in visible light by highly efficient WOx/TiO2 photocatalyst

“…Further lowering the solution pH (below 4.0) creates the agglomerates of particles which will reduce the surface area available for dye adsorption and photon absorption. Moreover, at low pH the concentration of H + is in excess and the H + ions interact with the azo linkage (-N N-) which is particularly susceptible to be electrophilic attacked by hydroxyl radical, decreasing the electron densities at azo group [37,38]. Conversely, acidic conditions would favor the reductive cleavage of AO7 and MO [7,39] as well as …”

Chromium and titanium/chromium-containing MCM-41 mesoporous silicates as promising catalysts for the photobleaching of azo dyes in aqueous suspensions. A multitechnique investigation

“…These forms originate from intermolecular hydrogen bonding tautomeric interactions between the oxygen of the naphthyl group and the b-hydrogen of the corresponding azo-linkage, respectively (inset Fig. 11A) [55,56] and, in aqueous solution, the two forms are in equilibrium. The other absorption peaks in the UV region, at 230 and 311 nm are ascribed to p-p ⁄ transitions in the benzene and naphthalene rings of AO7, respectively [57][58][59].…”

Evaluation of energy transfer and utilization efficiency of azo dye removal by different pulsed electrical discharge modes

“…The band at 485 nm corresponds to the hydrazone form, while the shoulder at 430 nm is linked to the azo form of the dye. The ratio of the azo form to the hydrazone form is much higher in organic solvents than in water, since the hydrazone form is favored by water while the azo form by polar organic solvents [37] . Therefore, this tautomerism of the aqueous solution of AO7 favors the hydrazone form and the main absorption band at 485 nm is linked to that form of AO7.…”