A. Stone
Oct 1, 1987
Citations
16
Influential Citations
433
Citations
Quality indicators
Journal
Environmental science & technology
Abstract
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.