Mechanism And Application Of Iron Copper Bimetal Aatalyst Activated PMS For Degradation Of Organic Pollution

Atrazine（ATZ）is a widely used triazine herbicide with endocrine disrupting effects and potential carcinogenicity.Due to its structural stability,it has a longer half-life in soil and water bodies and accumulates in farmland.Entering rivers and groundwater through irrigation,drainage,surface runoff,and infiltration can cause water pollution.The removal process based on oxidation reaction can degrade pesticides by destroying the molecular structure,avoiding their circulation in nature due to adsorption or enrichment of animals and plants.This requires the use of advanced oxidation technology with strong oxidation capacity to effectively remove ATZ.Therefore,this paper investigates the mechanism and application of zero-valent iron-copper bimetal activated peroxymonosulfate（nZVI-Cu⁰/PMS）to degrade ATZ in water.Firstly,nZVI-Cu⁰ was synthesized by co-precipitation method and its structure was characterized.Secondly,the effects of process parameters such as Cu⁰ loading in the catalyst,catalyst dosage,initial concentration of PMS,initial concentration of ATZ,initial pH of solution and reaction temperature on the degradation efficiency of ATZ in the nZVI-Cu⁰/PMS system were investigated.Furthermore,target competition experiments and EPR techniques,as well as pre and post catalyst characterization,were used to analyze the mechanism of nZVI-Cu0 activation of PMS.Finally,the performance of nZVI-Cu⁰/PMS for ATZ degradation under the background conditions of actual water was investigated based on the effects of common ions and organic matter in water on the degradation effect of ATZ.The main research results are as follows:（1）Characterized the changes in morphology,structure and other properties of nZVI-Cu⁰before and after the reaction with PMS.Characterization by field emission scanning electron microscopy（SEM）and transmission electron microscopy（TEM）indicates that nZVI-Cu⁰ is spherical in structure and the addition of Cu⁰ changed the surface structure of nZVI.nZVI-Cu⁰is cracked on the surface of the material after reaction with PMS,but the internal core spherical structure is not changed.The characterization results of X-ray diffraction（XRD）indicate that the surface of nZVI-Cu⁰ has already been partially oxidized before the reaction,and the degree of oxidation on the surface of nZVI-Cu⁰ after the reaction has intensified.The results of Raman spectroscopy show that the O-O bond of PMS has a significant vibration and the formation of Fe-O and Cu-O bonds in the reaction.nZVI-Cu⁰ has a decreased content of Fe⁰,Fe²⁺and Cu⁰and an increased content of Fe³⁺and Cu²⁺after the reaction with PMS as analyzed by X-ray photoelectron spectroscopy（XPS）.（2）The effects of operational parameters and water quality parameters on the degradation efficiency of ATZ in the nZVI-Cu⁰/PMS system were studied.The degradation efficiency of different oxidation systems for ATZ was compared.The effects of Cu⁰ loading of nZVI-Cu⁰,nZVI-Cu⁰ dosage,PMS dosage,initial ATZ concentration,solution pH,reaction temperature,common anions and natural organic matter（NOM）on the degradation efficiency of ATZ in the nZVI-Cu⁰/PMS system were analyzed.The experimental results showed that nZVI-Cu⁰ could effectively activate PMS to degrade ATZ in water.nZVI-Cu⁰/PMS system showed that the removal rate of ATZ increased and then decreased with the Cu⁰ loading（0.1-0.01 wt%）,and the maximum removal rate of ATZ was achieved at the Cu⁰ loading of 0.1 wt%.In the range of0.05-0.20 g·L^-1 of nZVI-Cu⁰ loading,the removal rate of ATZ increased with the increase of nZVI-Cu⁰ loading.In the range of 6-100μM,the increase of PMS dosage first promoted and then inhibited the degradation of ATZ,and the removal efficiency of ATZ was maximized at the PMS dosage of 25μM.The removal efficiency of ATZ gradually decreased with the increase of the initial concentration of ATZ.In the range of pH 3.0-9.0,the increase of pH showed an inhibitory effect on the degradation of ATZ.The addition of Cl^-,F^-,SO₄^2-,NO₃^-,NH₄⁺,NOM and HCO₃^-all inhibited the degradation of ATZ,and the inhibition of ATZ degradation was more obvious with the increase of each ion and NOM concentration.（3）The main active species for ATZ degradation by nZVI-Cu⁰/PMS were analyzed;the mechanism of PMS activation by nZVI-Cu⁰ was hypothesized based on the property changes before and after the reaction of nZVI-Cu⁰ and the electron transfer properties with nZVI-Cu⁰and PMS pairs.the results of EPR experiments and NB competition degradation experiments with ATZ confirmed that the main active species for ATZ degradation by nZVI-Cu⁰/PMS system,the main active species for degradation of ATZ were SO₄^·-and HO·.Furthermore,the kinetics of degradation between NB and ATZ led to a calculated SO₄^·-and HO·yield ratio of 8.70.The chronoamperometric method demonstrated that electron transfer occurred between nZVI-Cu⁰and PMS.The content of Fe²⁺in the nZVI-Cu⁰/PMS system is significantly higher than that in the nZVI/PMS system,indicating that the addition of Cu⁰ is more conducive to the release of Fe²⁺and the cycling between Fe²⁺and Fe³⁺,which can more effectively activate PMS to produce active species.（4）Explored the degradation efficiency of nZVI-Cu⁰/PMS on ATZ under different actual water conditions.We studied the effects of different water body backgrounds,nZVI-Cu⁰ laying methods,and coexisting pollutants on ATZ degradation efficiency or removal capacity.In groundwater,tap water,and surface water,nZVI-Cu⁰/PMS still has a significant degradation effect on ATZ,but the degradation effect is not the same.Among them,the degradation effect is fastest in natural water bodies and slowest in groundwater.In the simulated groundwater filter column experiment,it was found that the removal capacity of ATZ by the double layer nZVI-Cu⁰ filter column was greater than that by the single layer.Under the background of surface water,the presence of coexisting pollutants（Trimethoprim（TMP）,Enrofloxacin（EFX）,Nitrobenzene（NB）,and Benzoic acid（BA））inhibits the degradation of ATZ.In the context of tap water,the presence of coexisting pollutants has a weak promoting effect on the degradation of ATZ.