The mechanism of aquatic photodegradation of organophosphorus sensitized by humic acid-Fe3+ complexes

Organic phosphorus is an important source of eutrophication. In this study, to understand the mechanism of organophosphorus photodegradation, humic acid-Fe3+ (HA-Fe3+) complexes were prepared as a sensitizer, and glyphosate (GP) was used as a substrate for photodegradation. The effects of the initial GP concentration, HA concentration, Fe3+ concentration and microbial factors on photodegradation were investigated. The initial concentrations of GP, HA and Fe3+ could significantly affect the degradation rate of GP. Phosphate is the main product of GP photodegradation. Based on the identification of the active species in the reaction process, t-butanol was found to have the most significant inhibitory effect on the degradation. The reaction rate after t-butanol treatment was reduced from 0.017 to 0.003. This confirmed that (OH)-O-center dot was the main oxidant in the system, which was also demonstrated by EPR spectroscopy. A possible mechanism of GP photodegradation sensitized by HA-Fe3+ complexes was revealed for the first time. The HA-Fe3+ complexes in the reaction system were photodegraded and oxidized to finally produce (OH)-O-center dot, which promotes GP photodegradation. This study facilitates understanding the phosphorus cycle in a water environment and provides a scientific basis for the restoration of eutrophic lakes.