Study On The Performance Of Iron Oxide Composite Fiber Activated Persulfate To Degrade Organic Phosphorus And Remove Phosphate

Phosphorus（P）is a non-renewable resource that plays an important role in modern agriculture,animal husbandry,chemical industry and human life,and is an important part of life.With the rapid development of agriculture,industry and farming in China,the tailwater of farmland,livestock and poultry breeding wastewater and industrial effluent have led to excessive levels of total phosphorus in natural water bodies,which has become a limiting factor affecting the water quality of watersheds.In addition,organic phosphorus is an important component of total phosphorus,mostly with high toxicity and higher intensity of damage to the environment,therefore,the removal of organic phosphorus is of great significance,however,previous studies only focused on the removal of organic phosphorus and did not mention the recovery of phosphate after degradation,which could not effectively solve the problem of eutrophication in water bodies.The advanced oxidation process based on activated peroxynitrite has received wide attention as an emerging method for efficient removal of organic pollutants,and iron oxides have high catalytic performance for peroxynitrite,and iron oxides also have strong recognition ability for inorganic phosphorus,which can adsorb phosphate while degrading organic phosphorus,but iron oxides have the problem of difficult recovery in practical applications.Based on this,this thesis proposes to use the advantage of fiber carriers for easy recycling to construct iron oxide-loaded fibers to remove organic phosphorus from water bodies and simultaneously recover the generated phosphate,which is of great research significance to prevent and control phosphorus pollution in water bodies and alleviate the phosphorus resource crisis.Firstly,dopamine-functionalized polyacrylonitrile fibers（PDA/PANF-Fe₂O₃）with solid iron oxide loading were synthesized,optimized and characterized by hydrothermal-in-situ oxidation method.In this thesis,phenylphosphonic acid（PPOA）was chosen as the organophosphorus representative to carry out the performance study of iron oxide-fiber composites for degradation of PPOA and removal of phosphate.The degradation results showed that the functionalized fiber with optimized synthesis conditions could catalyze the complete removal of PPOA within 60 min with only 10 mg of peroxynitrite,while the removal effect without fiber addition was only 1/5 of it;in addition,the catalytic degradation had a wide p H adaptation range,with almost complete removal of PPOA at p H3-7 and 90%removal at p H 9-11;the coexisting ions The order of interference with PPOA degradation was HCO₃^->CO₃^2->Cl^->SO₄^2-,and the degradation rate of PPOA in the presence of SO₄^2-still reached 91.16%;the removal of PPOA in all four cycles exceeded90%,which proved the excellent cycle performance of functionalized fibers.The results of the adsorption study showed that the functionalized fiber exhibited better adsorption performance for phosphate at p H=4;the kinetic and isothermal model fitting results were more consistent with the secondary kinetic and Langmuir models,so the adsorption was more inclined to chemisorption,and the maximum adsorption amount estimated by the Langmuir model was 2.09 mg g^-1.Finally,the results of the adsorption of phosphate by free radical quenching,radical species analysis,the degradation mechanism of PPOA degradation to phenol and subsequently to CO₂ and water by Fe²⁺catalyzed PDS after the reduction of iron oxide by polydopamine was postulated,in which·OH radicals played a major role;the chemisorption mechanism of phosphate by iron oxide loaded on the fiber surface was determined by XPS.In summary,the PDA/PANF-Fe₂O₃ fiber is highly efficient in the removal of organic phosphorus and simultaneous recovery of phosphate by solid-loaded iron oxide,and the composite material,with its easy preparation,high removal efficiency,good recyclability,and high potential for practical applications,has potential practical value for the removal and recovery of organic phosphorus from water bodies and the prevention and control of phosphorus pollution in water bodies.