| The source of organic phosphorus in water is mainly divided into two parts:one is the discharge of industrial wastewater containing organic phosphorus in the production process;the other is that the residual part of the pesticide is directly discharged into the water environment.The eutrophication process of some water bodies could not be effectively alleviated by cutting off the input of phosphorus from the water source.The main reason may be that the release and conversion of phosphorus in the water did not significantly decrease the concentration.The organic phosphorus in the water can be converted into orthophosphate by biophotolysis and chemical oxidation,and is more easily absorbed and utilized by aquatic organisms.Studying the photolysis process of organic phosphorus in water is of great significance for understanding the role of organic phosphorus in water eutrophication.The complex formed by humic acid and Fe3+was used as the photosensitizer.The commonly used pesticide glyphosate was selected as the photolysis object.Through the indoor experimental study,the complex was analyzed to regulate the organic phosphorescence to explain the phosphate release process.Firstly,the complexes formed by humic acid and Fe3+were characterized.Then the effects of various factors on the photolysis process of glyphosate were studied.Finally,the kinetics and mechanism of photolysis of glyphosate driven by humic acid and Fe3+complex were discussed.The main conclusions are as follows:（1）Characterization analysis of humic acid-Fe3+complex.Characterization by scanning electron microscopy,infrared spectroscopy,and UV/Vis absorption spectroscopy shows that humic acid and Fe3+can form larger flocs;compared with pure humic acid,humic acid-Fe3+complexes There are many differences in the infrared spectrum;the ultraviolet absorption intensity of the humic acid-Fe3+complex is lower than the sum of the absorption strengths when the two are alone.It is proved that there is an interaction between humic acid and Fe3+,indicating the formation of humic acid-Fe3+complex.（2）Comparison of photolysis driving force.Compared with visible light and ultraviolet light,glyphosate is more sensitive to ultraviolet light.The photolysis effect of each photolysis driving force combination on glyphosate is glyphosate+humic acid-Fe3+>glyphosate+Fe3+>grass The photolysis effect of glyphosate was the best in phosphine>glyphosate+humic acid,glyphosate+humic acid-Fe3+reaction system.The photolysis degree of glyphosate reached 75.7%after 90min reaction.（3）Single factor influence experimental study.The results of single factor experiments showed that the higher the initial concentration of glyphosate,the more intense the competition for·OH,the lower the photolysis efficiency;the appropriate increase of humic acid concentration can increase the photolysis effect of glyphosate,After increasing to 20mg/L,the photolysis rate of glyphosate has no obvious change;increasing the concentration of Fe3+can improve the photolysis effect of glyphosate;temperature has little effect on the photolysis of glyphosate;photosensitive substance NO3-Photolysis of glyphosate can be promoted under ultraviolet light irradiation;in the reaction system where the actual lake water is the reaction environment,the microbial action can play a small role for the photolysis of glyphosate and release of phosphate due to the short reaction time.In this photolysis process,the photochemical action of humic acid and Fe3+complex dominates.（4）Reaction kinetics and mechanism analysis.By analyzing the reaction kinetics of photolysis reaction,UV absorption spectroscopy of glyphosate at different reaction times,qualitative analysis of phosphate,analysis of mineralization degree of humic acid and glyphosate,identification process The active species,the determination of the concentration of Fe2+and H2O2 during the reaction,and the mechanism of the reaction process were deduced.The results showed that the photodegradation process of glyphosate accorded with quasi-first-order kinetics;in the ultraviolet absorption spectrum analysis,the characteristic absorption peak of glyphosate The decrease further confirmed that glyphosate was degraded and transformed during the reaction;Humic acid and Fe3+complexes self-mineralize during the reaction and promote the mineralization of glyphosate;the main reactive oxygen species in the reaction process are·OH and O2.-,e-and h+also promote the reaction;the presence of humic acid and Fe3+complex enhances the solution Fe2+and H2O2 The concentration,and thus more·OH and O2.-generation,promotes photolysis of glyphosate. |
