Inhibition of Humic Substances Mediated Photooxygenation of Furfuryl Alcohol by 2,4,6-Trimethylphenol. Evidence for Reactivity of the Phenol with Humic Triplet Excited States

• DOI: 10.1021/es070656t
• Publication Date: 2007-08-02T13:00:21Z
• Authors: Sabrina Halladja; Alexandra ter Halle; Jean-Pierre Aguer; Abdelaziz Boulkamh; Claire Richard
• Keywords: Singlet Oxygen; Photochemistry; [SDE.ES]Environmental Sciences/Environmental and Society; 01 natural sciences; [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; Oxygen; [CHIM.THEO] Chemical Sciences/Theoretical and/or physical chemistry; Cresols; Kinetics; [SDE.ES] Environmental Sciences/Environment and Society; Soil Pollutants; [SDE.ES]Environmental Sciences/Environment and Society; Furans; Humic Substances; 0105 earth and related environmental sciences

To probe the reactivity of 2,4,6-trimethylphenol with humic triplet excited states, we investigated its influence on the humic substances-mediated photooxygenation offurfuryl alcohol. Elliott soil humic and fulvic acids were employed for these experiments. When added in the concentration range of 10(-4) - 10(-3) M, 2,4,6-trimethylphenol inhibited furfuryl alcohol photooxygenation to an extent depending on its concentration. The inhibiting effect decreased as the oxygen concentration was increased. By postulating that 2,4,6-trimethylphenol competes with oxygen for reaction with humic triplet excited states and with furfuryl alcohol for reaction with singlet oxygen, we obtained kinetic laws describing the consumption profiles of furfuryl alcohol and 2,4,6-trimethylphenol. Experimental rates of 2,4,6-trimethylphenol and furfuryl alcohol loss could be satisfactorily fitted with 1.09-1.16 for the ratio k2/k3, where k2 and k3 are the reaction rate constants of humic triplet excited states with oxygen and 2,4,6-trimethylphenol, respectively. These types of experiments could be extended to a variety of substrates to measure their reaction rate constants with humic triplet excited states.