Modeling And Optimization Of Orange Ⅱ Degradation By Hydroxylamine Synergistic Fe²⁺ Activated Peroxymonosulfate

Orange II（AO7）is one of the most commonly applied azo dyes.When the wastewater of AO7 is discharged into the natural water,it will seriously threaten human health,causing ailments such as skin allergies,breathing difficulties and cancer.In recent years,scholars have developed a variety of advanced oxidation processes（AOPs）to degrade and mineralize AO7.Among them,persulfate with high solubility and stability has gained attention.Therefore,this paper studied the degradation efficiency and mechanism of AO7 by HA/Fe²⁺/PMS system and HA/Fe²⁺/Cu²⁺/PMS system,and constructed BP neural network model and response surface methodology model of HA/Fe²⁺/PMS system to enrich the research based on advanced oxidation processes of persulfate.It also provides an efficient method for degradation of azo dye AO7.In this paper,the main research contents and results are as follows:（1）To study the efficiency and mechanism of AO7 degradation by HA-enhanced Fe²⁺/PMS system.In a wide initial p H range（3-7）,HA enhanced the degradation of AO7 by Fe²⁺/PMS system by promoting Fe³⁺/Fe²⁺cycling,especially when the initial p H was in the range of 4-6,the degradation effect of AO7 by HA/Fe²⁺/PMS system was as high as96.0%.The identification of reactive oxygen species showed that the main reactive oxygen species was SO₄^·–.Cl^–and NO₃^–had no significant effect on the degradation of AO7 in the HA/Fe²⁺/PMS system,while CO₃^2–and humic acid inhibited the degradation of AO7 in the HA/Fe²⁺/PMS system.（2）Modeling and optimization of AO7 degradation in the HA/Fe²⁺/PMS system by BP neural network and response surface methodology were studied.The results show that both BP neural network and response surface methodology can be used to model and optimize the AO7 degradation in the HA/Fe²⁺/PMS system,and both models can accurately predict the experimental value.The individual and interactive effects of Fe²⁺concentration,HA concentration,and PMS concentration on the degradation effect of AO7 were as follows:HA concentration>Fe²⁺concentration>PMS concentration;Fe²⁺concentration/PMS concentration>HA/PMS concentration>Fe²⁺concentration/HA concentration.The maximum degradation effect of AO7 was 96.5%when Fe²⁺concentration was 34.00μmol.L^-1,HA concentration was 0.40mmol.L^-1and PMS concentration was 0.90 mmol.L^-1.（3）To study the efficiency and mechanism of HA synergistic Fe²⁺/Cu²⁺bimetallic activated PMS for AO7 degradation.The results show that the addition of Cu²⁺can significantly enhance the degradation of AO7 by HA/Fe²⁺/PMS system in the range of p H=7-10,which solves the problem that HA/Fe²⁺/PMS system can only efficiently degrade AO7under acidic conditions.When p H=5,the degradation effect of AO7 in the HA/Fe²⁺/Cu²⁺/PMS system did not change significantly when the concentration of Cu²⁺increased from 0μmol.L^-1to 15μmol.L^-1within 5min.The added Cu²⁺had no significant effect on the degradation of AO7in the HA/Fe²⁺/PMS system.When p H=9,the degradation effect of AO7in the HA/Fe²⁺/Cu²⁺/PMS system increased from 9.1%to 38.6%within 5min when Cu²⁺concentration increased from 0μmol.L^-1to 15μmol.l^-1.The added Cu²⁺can significantly enhance the degradation of AO7 in the HA/Fe²⁺/PMS system.On the one hand,hydroxylamine reduces Cu²⁺to Cu⁺and Cu⁺directly activates PMS to produce SO₄^·–degradation of AO7;On the other hand,Cu⁺and hydroxylamine jointly reduce Fe³⁺to Fe²⁺,and Fe²⁺activates PMS to produce SO₄^·–to degrade AO7.SO₄^·–is the main reactive oxygen species in the HA/Fe²⁺/Cu²⁺/PMS system.