Iron (III) hydroxocomplex-methyl viologen dication system as a prospective tool for determination of hydroxyl radical reaction rate constants with environmental pollutants

Reactivity of oxidative species with target pollutants is one of the crucial parameters for application of any system based on advanced oxidation processes (AOPs). This work presents new useful approach how to determine the hydroxyl radical reaction rate constants (k(OH)) using UVA laser flash photolysis technique. Fe (III) hydroxocomplex at pH 3 was applied as a standard source of hydroxyl radicals and methyl viologen dication (MV2+) was used as selective probe for (OH)-O-center dot radical. Application of MV2+ allows to determine k(OH) values even for compounds which do not generate themselves optically detectable transient species in reaction with hydroxyl radicals. Validity of this approach was tested on a wide range of different persistent pesticides and its main advantages and drawbacks in comparison with existing steady-state and time-resolved techniques were discussed.