Study On The Oxidation Of Trichloropropyl Phosphate (TCPP) By Hydroxyl Radicals And Sulfate Radicals Based On The Catalytic Action Of Nano-FeTiO₃

Organic phosphates?OPEs?,as the most important class of organic phosphorus flame retardants?OPFR?,are widely used in chemical,textile,electronics,building materials and other industries,and are put into the environment along with applications and treatments.Chlorinated alkyl organophosphates?Cl-OPEs?have potential carcinogenic effects and strong bioaccumulation capabilities.Chlorinated organophosphates in the environment can pose a threat to human health through the food chain enrichment.In addition,Cl-OPEs is a difficult-to-degrade organic pollutant,and it is difficult to effectively treat it with existing wastewater treatment processes.Fe Ti O₃ is an iron mineral present in red soil.Because it contains divalent iron,it has the potential to act as an excellent H₂O₂ and persulfate activator,and can be used to remove difficult-to-degrade organic matter.Therefore,in this paper,nano-Fe Ti O₃ was first prepared to characterize its surface morphology,junction structure and photochemical properties,and to study its activation performance for H₂O₂ and persulfate.Fe Ti O₃ was used to decompose trichloropropyl phosphate?TCPP?by Fenton-like method and ultraviolet persulfate oxidation method.The degradation efficiency of the two methods was discussed.The intermediate products and mechanism of TCPP degradation and the acute toxicity before and after degradation were analyzed.The main findings are as follows:?1?The effects of red soil,Fe₂O₃,and Fe Ti O₃ on the degradation of TCPP in Fenton and persulfate activation systems were compared,and the results showed that red soil did not promote the degradation of TCPP,while the degradation effects of Fe Ti O₃ in both systems were optimally,and it could effectively activate persulfate and promote the degradation of TCPP.Nano-scale Fe Ti O₃materials were prepared by sol-gel method and modified with CTAB as a surfactant.Qualitative analysis of the prepared Fe Ti O₃ nanomaterials by various characterization methods confirmed the feasibility of the preparation method,and the obtained Fe Ti O₃ had high crystallinity,uniform distribution,and regular shape,and could effectively absorb light in the range of 200?300 nm.?2?Fe Ti O₃ heterogeneous Fenton system can effectively degrade TCPP?TCEP and TDCP,and the degradation rate can reach 67.1%under the optimal conditions.By examining the effects of Fe Ti O₃ dosage,H₂O₂ concentration,and different p H on the degradation of TCPP by Fe Ti O₃ heterogeneous Fenton-like reaction system,the reaction kinetics of TCPP are calculated,and the active species of the reaction system are identified.Then the conclusions are:in the range of 0?2.0 g/L,the degradation efficiency of TCPP increases with the increase in the amount of Fe Ti O₃ added;in the range of 30%H₂O₂ in the range of 0?2.0 m L,the degradation efficiency of TCPP is proportional to the amount of H₂O₂ proportional;when the initial p H of the solution increases from 3.0 to 11.0,the degradation efficiency of TCPP decreases with increasing p H.The reaction conforms to the pseudo first-order reaction kinetic equation.Using tert-butanol?TBA?as a scavenger for hydroxyl radicals?·OH?,by studying the degradation of TCPP as a function of TBA concentration,it was concluded that the Fe Ti O₃ heterogeneous Fenton-like method degrades the oxidative effect of TCPP.The main active species is·OH.?3?In the combination system of Fe Ti O₃,UV and PS,the degradation rate of TCPP was only 10%?30%;while in the system in which Fe Ti O₃,UV and PS coexist,the degradation effect is significantly improved,and the degradation rate could reach about 80%in 240 minutes.And TCEP and TDCP can also be effectively degraded in Fe Ti O₃-UV/PS.By examining the influencing factors and kinetics of the degradation of TCPP by the Fe Ti O₃-UV/PS reaction system,identifying the active species of the reaction system,analyzing the degradation products and pathways,and the toxicity changes of the system before and after degradation,it is concluded that:It shows that the synergistic effect of Fe Ti O₃ and UV improves the oxidation ability of the system.Under other conditions,the greater the amount of Fe Ti O₃ added,the faster the degradation rate;the concentration of persulfate has a threshold during the degradation process.When the concentration of persulfate is too large,it will be consumed when the PS is excessive.Free radicals reduce the yield of free radicals and affect the degradation rate of TCPP;acidic environments are more favorable for TCPP degradation,and alkaline environments can inhibit them.In the free radical verification experiment,after adding Et OH and TBA to the Fe Ti O₃-UV/PS system,TCPP hardly degraded,and it is speculated that the free radicals generated in the system were captured and consumed by Et OH and TBA.EPR can directly detect the free radicals in the system,and found that·SO₄^-and·OH together play a decisive role in the system.The TCPP degradation products were detected by ion chromatography and GC-MS.The degradation reaction produced Cl^-,PO₄^3-and SO₄^2-ion products and C₆H₁₅O₃P and other small molecular organic compounds.The possible degradation pathways were deduced based on the calculation of front-line molecular orbital theory for dechlorination,dealkylation,and further oxidation of the alkyl group,carbon dioxide,water,chloride ions,and phosphate are eventually formed.Through the study of the change of the luminescence inhibition rate of the photobacterium by TCPP during degradation,it was found that the toxicity of the solution was increased due to the production of chlorine-containing organic compounds.