Effect And Mechanism Of Diatomite Supported Copper Ferrite Activated Persulfate For Degradation Of Acid Orange 7

The low biodegradability and high concentration of organic matter of azo dye wastewater make it difficult to treat this kind of wastewater economically and effectively by conventional biological,chemical and physical methods.The transition metal activated persulfate advanced oxidation technology had the characteristics of strong oxidation and wide application range,and had a unique advantage in the treatment of dye wastewater.Therefore,this paper studied the preparation of diatomite supported Cu Fe₂O₄（CF/D）material by sol-gel method to activate persulfate（PMS）to degrade acid orange 7（AO7）.The research process and contents were as follows:（1）CF/D materials with load ratio of 0.5,1,3,5,7 and 9 were prepared,the material properties were tested and characterized.The results show that:The degradation processes of different materials were in line with the quasi-first-order kinetics（R²all greater than 0.95）,and the activation performance of 5CF/D was the best.The mass concentration of AO7 was50 mg/L,the initial p H of solution was 6.68,the mass concentration of 5CF/D was 0.50 g/L,and the mass concentration of PMS was 0.30 g/L.At the reaction temperature of 30℃,the degradation rate of AO7 in 5CF/D+PMS system was 96.88%and the quasi-first order kinetic rate constant（k₁）was 0.0581 min^-1,while the degradation rate of Cu Fe₂O₄+PMS system was84.10%and k₁was 0.0331 min^-1.The results show that CF/D has amorphous Si O₂（2θ=21.98°、28.44°）and Cu Fe₂O₄at the same time.Cu Fe₂O₄particles were dispersed on5CF/D surface,and O,Si,Fe and Cu elements were evenly distributed,the ratio of Fe and Cu elements was close to 2:1.Chemical bond and valence state:5CF/D mainly has Fe—O bond,Si—O—Si bond,adsorbed water and surface hydroxyl group;5CF/D underwent Fe³⁺/Fe²⁺and Cu²⁺/Cu⁺transformations before and after the reaction,and the surface hydroxyl content increased from 31.18%to 37.56%.（2）The effects of mass concentration,mass concentration of PMS,reaction temperature,mass concentration of AO7,initial p H of solution,common inorganic anions and different target dyes on 5CF/D+PMS were studied.The activation energy（E_a）of the reaction was35.76 k J/mol;when p H was 5～11,the degradation rate remained above 90%.Among the inorganic anions,HCO₃^-promoted the degradation(k₁=0.0908 min^-1),and H₂PO₄^-inhibited the degradation rate at 20%continuously.Response surface method was used to analyze and optimize the degradation process of AO7 in 5CF/D+PMS system.The results showed that the effects of different factors on the degradation rate of AO7 were as follows:Mass concentration of 5CF/D>AO7>reaction temperature>PMS mass concentration.According to the model calculation,under the optimal conditions of 35.96 mg/L AO7 mass concentration,0.72 g/L 5CF/D mass concentration,0.40 g/L PMS mass concentration and 28.58℃reaction temperature,The degradation rate of AO7 will be as high as 99%.（3）The degradation mechanism of the system was explored through quenching and free radical capture experiments:5CF/D+PMS system mainly plays an active role in ¹O₂and·O₂^-,followed by SO₄^-·,·OH.These active substances degrade AO7 by attacking benzene ring,naphthene ring,hydrazone structure and azo bond in AO7 molecules.The excellent activation properties made the degradation rate of AO7 of 5CF/D still 63.95%at the third recycling.The saturation magnetization of the material is 22.81 emu/g.