fulltext.study @t Gmail

Influence of humic substances on the riboflavin photosensitized transformation of 2,4,6-trimethylphenol

Paper ID Volume ID Publish Year Pages File Format Full-Text
26530 43960 2012 6 PDF Available
Title
Influence of humic substances on the riboflavin photosensitized transformation of 2,4,6-trimethylphenol
Abstract

Humic substances are known to affect the fate of organic chemicals in the environment. While their capacity to produce reactive species upon irradiation has been intensively studied, their inhibiting properties have been much less investigated. In the present work, we studied the influence of various humic substances (humic acids, fulvic acids, natural organic matter) on the riboflavin photosensitized transformation of 2,4,6-trimethylphenol which takes place via oxidation of the phenol by the triplet excited state of riboflavin. Between 2 and 20 mg L−1 humic acids show an inhibiting effect on this reaction while below 2 mg L−1, a small accelerating effect is generally observed. At 25 μM 2,6-dimethyl-1,4-benzoquinone also inhibits the photoreaction significantly. It is proposed that the quinone traps the superoxide anion produced in the course of the reaction yielding semiquinone radicals. The reduction potential of the quinone is low enough for making possible a subsequent reduction of 2,4,6-trimethylphenoxyl radical by semiquinone and a regeneration of 2,4,6-trimethylphenol. In the case of humic substances, the trapping of superoxide anion might be achieved by humic quinone moieties. In accordance, soil fulvic acids and aquatic natural organic matter which show a much lower electron accepting capacity than soil extracted humic acids do not show any inhibiting effect.

► HAs are able to inhibit the photosensitized phototransformation of an electron rich phenol while not their FAs counterparts. ► Quinone DMBQ also inhibits the reaction. ► This effect might be due to the scavenging of superoxide anions. ► The inhibiting effect is linked to the electron accepting capacity measured by other authors.

Keywords
Humic acids; Fulvic acids; Inhibiting; Accelerating; Photochemistry
First Page Preview
Influence of humic substances on the riboflavin photosensitized transformation of 2,4,6-trimethylphenol
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 229, Issue 1, 1 February 2012, Pages 33–38
Authors
, , , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering