Oxidation and dechlorination of chlorophenols in dilute aqueous suspensions of manganese oxides: Reaction products

Abstract

Some monomeric and dimeric oxidation products of para‐ and/or ortho‐chlorinated phenols in dilute (1 mmol/L phenol), acidified, aqueous suspensions of manganese oxide (Na‐buserite) were identified by MS, Fourier‐transform IR spectroscopy and UV/visible spectroscopy. The para‐chlorinated phenols (4‐chlorophenol, 2,4‐dichlorophenol, 2,4,6‐trichlorophenol, 4‐chloro‐2‐methylphenol) gave corresponding p‐benzoquinones (benzoquinone, 2‐chlorobenzoquinone, 2,6‐dichlorobenzoquinone, 2‐methylbenzoquinone) as the detectable water‐soluble oxidation products. Dimeric products were present in the extracts obtained by washing the oxide with methylene chloride. Michael addition of phenolate to quinone seems to be the predominant mode of coupling. Chlorinated phenols without chlorine in the para‐position (2‐chlorophenol, 2,6‐dichlorophenol) were more difficult to oxidize and afforded diphenoquinones as the only detectable water‐soluble products. For all studied phenols, with the exception of 2,4,6‐trichlorophenol, the amount of water‐soluble products accounts only for a small fraction of oxidized phenol. The quinone and diphenoquinone products readily couple with phenols into humuslike materials.

A critical review of the reactivity of manganese oxides with organic contaminants

“…Although the degradation of organic compounds by manganese oxides has been widely studied, relatively few studies compare the degradation rates of a single organic compound in the presence of multiple, well-dened manganese oxide minerals. Organic compounds that have been studied include various model phenol compounds, 46,103,104,123 chloroanilines, 59 2-mercaptobenzothiazole, 98,99 sulfadiazine, 72 methylene blue, 91 and bisphenol A. 149 These studies provide insight into the role of manganese oxide physicochemical properties and mineralogy on organic contaminant oxidation rates.…”

The oxidative degradation of sulfadiazine at the interface of α‐MnO2 and water

“…15 Manganese dioxides, possibly the most important natural oxidants with redox potential of 1.23 V, 16 are reactive surfaces that play an important role in affecting the fate and degradation of organic pollutants in soil and aquatic environments. 16,17 In fact, manganese dioxides have been demonstrated to be powerful oxidizing agents in aqueous media to degrade a wide range of organic contaminants, such as phenol, 18 aniline, 19 aliphatic amine, 20 aromatic amine, 17 triazine, 21 benzothiazole, 22 and even antibiotics. This work has studied for the first time, the degradation of sulfonamides by manganese dioxides.…”

Soluble Colloidal Manganese Dioxide: Formation, Characterization and Application in Oxidative Kinetic Study of Ciprofloxacin

“…Soluble colloidal MnO2 is generally formed by the reduction of MnO4 -idizing a wide range of organic contaminants [18][19][20][21]. It has reactive surfaces that play important role in transformation of organic pollutants such as synthetic hormones, antiinflammatory drugs, antibacterial agents, bisphenol A, phenols, sulfides, 2-mercaptobenzothiazole (2MBT), and sulfadiazine in soil and aquatic environment [22,23]. The kinetics and mechanism of oxidation of simple organic reactants like lactic acid, aspartic acid, oxalic acid, mandelic acid, amino acid, D-fructose, D-glucose, Cysteine and glutathione [12,[24][25][26][27][28][29], etc.…”