Reductive dissolution of manganese(III/IV) oxides by substituted phenols
Kinetics of the reaction of manganese(III/IV) oxides with 11 substituted phenols were examined in order to assess the importance of manganese oxides in the abiotic degradation of phenolic pollutants. At pH 4.4, 10/sup -4/ M solutions of substituted phenols reduced and dissolved synthetic manganese oxide particles in the following order: p-methylphenol > p-ethylphenol > m-methylphenol > p-chlorophenol > phenol > m-chlorophenol > p-hydroxybenzoate > o-hydroxybenzoate > 4'-hydroxyacetophenone > p-nitrophenol. Rates of reductive dissolution generally decrease as the Hammett constants of ring substituents become more positive, reflecting trends in the basicity, nucleophilicity, and half-wave potential of substituted phenols. Evidence indicates that the fraction of oxide surface sites occupied by substituted phenols is quite low. The apparent reaction order with respect to (H/sup +/) is not a constant but varies between 0.45 and 1.30 as the pH range, phenol concentration, and phenol structure are varied. A mechanism for the surface chemical reaction has been postulated to account for these effects.
- Research Organization:
- Johns Hopkins Univ., Baltimore, MD (USA)
- OSTI ID:
- 5350671
- Journal Information:
- Environ. Sci. Technol.; (United States), Journal Name: Environ. Sci. Technol.; (United States) Vol. 21:10; ISSN ESTHA
- Country of Publication:
- United States
- Language:
- English
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54 ENVIRONMENTAL SCIENCES
AROMATICS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DECOMPOSITION
ENVIRONMENTAL EFFECTS
EXPERIMENTAL DATA
HYDROXY COMPOUNDS
INFORMATION
KINETICS
MANGANESE COMPOUNDS
MANGANESE OXIDES
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHENOLS
REACTION KINETICS
REDUCTION
SURFACE WATERS
TRANSITION ELEMENT COMPOUNDS
WATER CHEMISTRY