A photophysical approach to investigate the photooxidation mechanism of pesticides: Hydroxyl radical versus electron transfer

Application of soluble bio-organic substances (SBO) as photocatalysts for wastewater treatment: Sensitizing effect and photo-Fenton-like process

“…Formation of similar CV-SBO complexes deserve to be investigated too. Mechanisms involving photosensitizer-pollutant complexes have already been proposed for organic photocatalysts, such as for the photochemical elimination of pesticides in the presence of triphenylpyrylim [26]. In order to gain further insight into this possible mechanistic route, the absorption spectra of CV were recorded in the range 400-800 nm with different amounts of SBO in aqueous solutions at pH = 7.…”

Fundamental Mechanistic Studies of the Photo-Fenton Reaction for the Degradation of Organic Pollutants

“…For this purpose, we (Machulek et al, 2006) used nanosecond laser flash photolysis to investigate the influence of added chloride ion on the photocatalytic step that converts Fe(III) back to Fe(II) (equation 5), deliberately omitting H 2 O 2 from the reaction mixture to prevent the thermal Fenton reaction. Although direct spectroscopic detection of the hydroxyl radical has proved elusive (Marin et al, 2011), the Cl 2…”

Kinetic studies of the reaction between pesticides and hydroxyl radical generated by laser flash photolysis

“…Competitive kinetic experiments between the pesticide of interest and TS, which cause a pesticide‐concentration‐dependent reduction in the signal at 390 nm due to the hydroxyl radical–TS adduct can then be used to determine the rate constant for reaction between the hydroxyl radical and the pesticide of interest …”

“…The rate constants for reaction of the pesticides (Table ) are slightly smaller than the diffusion controlled rate in CH 3 CN (1.9 × 10 10 M −1 s −1 ). The rate constants for reaction of the pesticides of this work are comparable to those of other pesticides under similar conditions: 2.6 × 10 9 M −1 s −1 for pyrimethanil; 3.6 × 10 9 M −1 s −1 for alachlor; 7.1 × 10 9 M −1 s −1 for methidathion; and 8.5 × 10 9 M −1 s −1 for dimethoate …”