Conversion of aniline contaminant to valuable polyaniline polymers from wastewater under alkaline conditions

Mediation of water-soluble oligoaniline by phenol in the aniline–persulfate system under alkaline conditions

“…The broad band around 3438 cm À1 in all samples represents the N-H stretching of the OANI backbone (Fig. 6), 55,57 indicating dehydrogenation of aniline during the oxidation processes. 58 The broad peak of the OANIs 2.0 at 3284 cm À1 represents the out-plane deformation (QN-H) of imines (Fig.…”

“…Likewise, our recent studies also supported that oxidation of phenolics, aniline and thiophene by metal oxide-activated persulfate under alkaline conditions was primarily via a non-radical pathway and the contributions of SO 4 À and OH were negligible. 35,55,56 In those processes, the O-O bond in persulfate was moderately elongated via the nonradical pathway after grabbing electrons from the surface of metal oxides, and the activated O-O bond was then cleavage after abstracting H from O-H in phenol with the formation of phenoxyl radicals. 32,35 , indicating that phenol apparently inhibits the polymerization degree of aniline.…”

“…80,82 In this regard, although PhNH + is a recognized intermediate in the aniline-SPS system under alkaline conditions, its formation pathway still needs to be further investigated. Three steps have been proposed in the formation of PANI and OANI in the reaction between aniline and persulfate: 55,83 (i) formation of PhNH after PhNH 2 loses 1e and 1 H + in the first step; 81,84,85 (ii) dimerization of PhNH with another PhNH , PhNH 2 , o-aminophenyl sulfate or its hydrolysis products with the formation of 4-aminodiphenylamine, benzidine, azobenzene and co-dimers containing aniline and ortho-aminophenyl sulfate units; 81,86 (iii) oligomerization/polymerization of the monomers with the produced dimers with the formation of OANI or PANI. 87,88 Actually, azobenzene is an inevitable by-product in the oxidation of aniline by persulfate under alkaline conditions via the one-electron pathway.…”

“…87,88 Actually, azobenzene is an inevitable by-product in the oxidation of aniline by persulfate under alkaline conditions via the one-electron pathway. 55,83,86 By means of DFT calculations, Marjanovic et al 86 suggested that recombination of PhNH always resulted in the formation of the by-product of azobenzene between persulfate and aniline under alkaline conditions. On the other hand, the absence of azobenzene in this study indicates that PhNH may not be the predominant intermediate in the aniline-phenol-SPS system under alkaline conditions (Fig.…”

Selective Oxidation of Cyclohexane to Cyclohexanol/Cyclohexanone by Surface Peroxo Species on Cu-Mesoporous TiO2

“…Apart from producing SO 4 •– , PS can also be moderately activated via the non-radical pathway. Our recent studies revealed the moderately activated O–O bond of PS on the surface of metal oxides, such as Co 3 O 4 , CuO, − and Bi 2.15 WO 6 in alkaline solutions, which then selectively abstracted H from various phenolics, thiophene, aniline, and bisphenol A (BPA), accompanied with the formation of the corresponding polyphenolics, polythiophene, polyaniline, and the BPA polymer. Till now, how to selectively mediate H-abstraction from the C–H bond of alkanes by PS via the non-radical pathway is still ambiguous and deserves to be investigated.…”