Oxidation of Chloroanilines at Metal Oxide Surfaces

Abstract

The oxidation reaction of chlorinated anilines by two manganese oxides, birnessite and pyrolusite, and by iron oxide has been investigated. The oxidation ability of the oxides was in the order birnessite . pyrolusite > iron oxide. Birnessite removed 100% of chloroanilines in 30 min, whereas pyrolusite and iron oxide removed from 5 to 96% of chloroanilines in 72 h. The differences in the reactivity of chloroanilines depended on the number and the position of chloro substituents on the aromatic ring. The activity of the oxides was maximal at pH 4.0 and decreased as the pH increased. The reaction kinetics in each of the systems investigated was adequately described by a secondorder rate expression. A free-radical mechanism for the oxidative coupling reaction of chlorinated anilines was suggested. Chloroazobenzene and chlorohydroxydiphenylamine dimers were detected among the oxidation products. The results obtained suggested that the oxidative mechanism occurred through a head-to-head and head-to-tail coupling of chloroanilino radicals.

Superparamagnetic Fe3O4 nanoparticles as catalysts for the catalytic oxidation of phenolic and aniline compounds

“…(1): Secondly, under acid or neutral condition protonated surface of iron oxide was beneficial to the formation of metal oxide-phenol/aniline inner-sphere complexes, which would promote reaction, while under basic condition the combination of OH − with Fe 3+ and Fe 2+ on the surface of the MNPs might separate the reactants from surface metal centers. So the decrease in activity of the oxide, as pH increases, could be caused by less favorable conditions for the formation of the protonated inner-sphere complex [32].…”

“…Heterogeneous Fenton-like systems, consisting of catalysts and hydrogen peroxide, are effective for the degradation of organic compounds [32,33]. Han et al have proved that Au/hydroxyapatite (Au/HAp) catalyst exhibits high activity and great potential for the complete oxidation of organic pollutants in aqueous media by peroxidation.…”

Structure of Synthetic K-rich Birnessite Obtained by High-Temperature Decomposition of KMnO4. I. Two-Layer Polytype from 800 °C Experiment

“…[32][33][34][35][36][37][38][39][40][41][42] In particular, because of its high affinity for pollutants, such as heavy metals and organic contaminants, this mineral plays a pivotal role in their fate in contaminated waters and soils. 16,[40][41][42][43][44][45][46][47][48][49][50][51][52][53] Even though in nature birnessite is typically disordered and occurs in finely dispersed state, monomineralic birnessites with an enhanced three dimensional (3D) ordering are easily synthesized under a variety of laboratory conditions. [1][2][3]15,[54][55][56][57][58][59][60][61][62] Because some synthetic varieties can be considered as analogs of the natural ones, they have been used to determine the structural mechanism of heavy metal sorption 31,40,51,63,64 and to investigate the structural modification of birnessite as a function of pH.…”

Structure of heavy-metal sorbed birnessite: Part 1. Results from X-ray diffraction

“…Partial dehydration of buserite leads to the formation of 7 Å birnessite with a single layer of H 2 O molecules and various interlayer cations Burns 1977, 1978;Chukhrov et al 1978Chukhrov et al , 1989Cornell and Giovanoli 1988). Buserite and birnessite have remarkable cation exchange (Healy et al 1966;Murray 1974;Balistrieri and Murray 1982;Stumm 1992;Le Goff et al 1996), sorption (Gray and Malati 1979;Catts and Langmuir 1986;Paterson et al 1994;Tu et al 1994;Appelo and Postma 1999), and redox properties (Oscarson et al 1983;Stone and Morgan 1984;Stone and Ulrich 1989;Manceau and Charlet 1992;Bidoglio et al 1993;Silvester et al 1995;Manceau et al 1997;Pizzigallo et al 1998;Daus et al 2000;Nico and Zasoski 2000;Chorover and Amistadi 2001).…”