Kinetic Investigation of Oxidation of Aromatic Anils by Potassium Peroxymonosulfate in Aqueous Acidic Medium

Abstract

The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by potassium peroxymonosulfate has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that the variation in the ionic strength of the reaction has a negligible effect on the rate. Similarly, polymerization was not observed when acrylonitrile was added to the reaction mixture. This observation rules out the formation of any free radical in the reaction. The added Mn(II) increases the rate of the reaction, which indicates the involvement of two-electron transfer. Highly negative S # values indicate a structured transition state. The deviation of the Hammett plot was noted, and a concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log k obs versus σ is attributed to the transition state whereas the concave upward curve was observed for the substituents in the benzaldehyde moiety and in the combination of aniline and benzaldehyde moieties, and a suitable mechanism was proposed. C 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: [542][543][544][545][546][547][548][549][550] 2013

Impact of Peroxymonocarbonate on the Transformation of Organic Contaminants during Hydrogen Peroxide in Situ Chemical Oxidation

“…To assess the importance of HCO 4 – to the transformation of other compounds in the H 2 O 2 –ISCO process, we predicted the rate of transformation of the organic contaminants through the HCO 4 – -initiated transformation reaction. We fitted the data of phenol disappearance vs time as a pseudo first-order process to facilitate comparisons with reported values for other treatment processes. − The observed reaction rate constant in our system at 10 mM NaHCO 3 was (3.20 ± 0.23) × 10 –3 min –1 , which is over 4 times higher than rates of phenol loss observed when goethite was used to activate H 2 O 2 in borate buffer at the same pH (i.e., pH 8.4 ± 0.2) . The HCO 4 – reactions were also faster than those in other heterogeneous Fenton systems, ,, indicating that this process could be relevant for understanding the efficacy of H 2 O 2 -ISCO.…”

Disintegration of Waste Activated Sludge by Thermally-Activated Persulfates for Enhanced Dewaterability

“…The instantaneous decomposition of PMS in the initial stage of the reaction (both at RT and 80 °C) implies that specific substrates in WAS rapidly consume PMS via selective direct reactions. PMS has been reported to oxidize various organic compounds (e.g., indole, vanillin and aromatic anils) via nonradical mechanisms such as oxygen transfer and nucleophilic addition. − The decomposition of residual PMS in the second stage (i.e., the gradual pseudo-first-order decay) proceeded via the thermal decomposition of PMS itself which produces • OH and SO 4 •– (reaction ). The resultant radical species nonselectively oxidize substrates in WAS. In the second stage, the possibility for PMS to directly react with WAS substrates is excluded because the PMS decomposition rate in WAS is identical to that in deionized water (Figure S10a in the SI).…”

Persulfate-Based Advanced Oxidation: Critical Assessment of Opportunities and Roadblocks

“…Since the p K a values of many phenols are >7 (unlike aryl amines), significant decay of substituted phenol by the persulfate-AOP under acidic and neutral conditions cannot be attributed primarily to direct PDS oxidation. Nonactivated PMS also oxidizes select inorganic and organic substances, including As­(III), p- aminobenzoic acid, sulfonamides, β-lactam antibiotics, and FFA. ,− …”