Inactivation Mechanism Of Fusarium Solani And Photocatalytic Fuel Cell Under Visible Light

The reuse of wastewater for agriculture irrigation has received much attention in recent years.However,wastewater contains various pathogens that must be removed before the irrigation.Among these pathogens are phytopathogenic fungi such as Fusarium,Pythium,Phytophthora and Olpidium species.The Fusarium genus,which is widely distributed in water and soil systems,causes decay of roots,stems and flowers.Fusarium spores,which develop into Fusarium fungal cells,are very difficult to inactivate owing to their thick cell walls and strong environmental resistance.The inactivation mechanism of photocatalytic disinfectants on bacteria is well known.In contrast,the potential inactivation of fungal spores by visible-light induced photocatalysis has been recognized,but the inactivation mechanism is poorly understood.We hypothesize that photocatalytically generated reactive oxygen species?ROSs?are directly involved in this mechanism.To test this hypothesis,we identified the roles of ROSs in the inactivation of Fusarium solani spores.As the photocatalysts,we doped TiO₂ with 3 typical dopants,forming Ag/TiO₂,N/TiO₂ and Er³⁺:YAlO₃/TiO₂.The Ag/TiO₂ photocatalysis was dominated by H2O₂,with the longest lifetime among the investigated ROSs.Ag/TiO₂ photocatalysis yielded almost 100% inactivation efficiency and preserved the cell-wall shape of the spores,thus minimizing the biomolecule leakage.Er³⁺:YAlO₃/TiO₂ was dominated by h+ ROSs,yielding an inactivation efficiency of 91%;however,the severe leakage released large numbers of molecular bio-products.Severe damage to the cell walls by the h+ species was confirmed in micrograph observations.Subsequent to cell wall breakage,the Er³⁺:YAlO₃/TiO₂ nanoparticles entered the spore cells and directly oxidized the intracellular material.The N/TiO₂ photocatalysis,with ·O₂-dominated ROSs,delivered intermediate performance.In conclusion,photocatalysts that generate H2O₂ dominated ROSs are most preferred for spore inactivation.In order to further realize the energy recovery and utilization,this paper studied the photocatalytic fuel cell?PFC?which can generate energy at the same time to kill the Fusarium solani spores.The Ag/TiO₂ catalyst with better performance was coated on the conductive glass by spin coating as the photoelectric anode of PFC.By examining the I-T curve,COD removal rate,Coulomb efficiency,lsv and eis of the electrodes with the load rates of 0.036,0.50,0.75 and 1.30wt% respectively,we found that the electrode with load rate of 0.75% showed higher electrochemical properties.Finally,the inactivation of Fusarium solani was detected by PFC system with a load rate of 0.75%.It was found that the bactericidal efficiency of PFC system was higher than that of pure photocatalytic sterilization.For the above analysis of the results can be concluded that in the destruction of fungi,the photocatalyst which can produce H2O₂-driven ROS had the best performance.The PFC system constructed using this optimal catalyst produces a stable current while killing the spores of Fusarium solani spores.This paper provides a reference for the application of photocatalytic fuel cell in wastewater treatment.