Degradation Of Orange Ⅱ By Persulfate Catalyzed By Modified Bismuth Iodide

Dye wastewater is one of the common harmful industrial wastewater,which is characterized by high content of organic matter,high chroma,variable composition,serious threat to human body and ecological water bodies,and the traditional treatment technology has defects.Photocatalytic Persulfate（PS）technology not only improves the removal efficiency of organic pollutants,but also makes efficient use of persulfate（PMS）.It is of great significance to explore efficient photocatalytic materials as catalysts for PMS.In this paper,bismuth iodide oxide（Bi OI）and its modified photocatalyst were prepared,and orangeⅡ（AO7）was used as the degradation object to construct a photocatalytic persulfate coupling degradation system under visible light,and the degradation mechanism was explored.The specific research contents and conclusions are as follows:（1）The 3D spherical Bi OI photocatalyst was prepared at 120℃by solvothermal method with ethylene glycol as solvent,and the morphology of Bi OI was controlled by solvothermal temperature.The results show that the surface of 3D spherical Bi OI is composed of nanosheets,whose characteristic peaks coincide with Bi OI standard cards,showing tetragonal morphology.The Bi OI was prepared with a band gap of 1.80e V,showing a good visible light response.（2）The gradation of AO7 by bismuth iodide oxide/persulfate/visible light（Bi OI/PMS/light）system was established.The optimal parameters obtained by studying different influencing factors are as follows:when the preparation temperature is 120℃,the concentration of Bi OI photocatalyst is 0.2g/L,the concentration of PMS is 0.2mmol/L,and the concentration of AO7 is 100mg/L,the degradation efficiency of AO7 is as high as 97.0%,and the degradation process is in line with the pseudo-second-order kinetic model.At a wide p H（5-9）,the degradation effect was more than 95%.Superoxide radical（·O₂^-）and singlet oxygen（¹O₂）are the main active free radicals in the degradation process.（3）Bismuth iodide/metal-organic skeleton（Bi OI/HKUST-1,BH）heterojunction photocatalyst was prepared by solvothermal method.Bi OI/HKUST-1 presents a columnar structure with fracture at a molar ratio of 0.7 and a solvothermal temperature of 120℃（BH-0.7-120）.All the characteristic peaks in the composite belong to Bi OI and HKUST-1,with good crystallization and no other impurities.The band gap is 2.19e V,the specific surface area is120.74m²·g^-1,and the main valence states on the surface are Bi³⁺,I^-,Cu⁺,Cu²⁺.（4）The degradation of AO7 by BH-0.7-120/PMS/light system was investigated.The crystallinity and morphology of BH-0.7-120 were optimized by regulating the molar ratio of Bi OI/HKUST-1 to 0.7 and the solvothermal reaction temperature to 120℃.The optimal parameters were:When the concentration of BH-0.7-120 was 0.2g/L,the concentration of PMS was 0.5mmol/L,and the concentration of AO7 was 200mg/L,the degradation efficiency of AO7by BH-0.7-120/PMS/light system reached 94.9%.The degradation rate of AO7 reached more than80%in p H range of 3-11.Compared with pure Bi OI,the degradation efficiency was increased by1.81 times and the degradation rate was increased by about 18 times.Free radical quenching experiments and UV-vis spectra showed that the system contained·SO₄^-,·OH,·O₂^-,¹O₂ and h⁺acting on the chromaphore group and naphthalene ring structure of AO7 molecule,causing-N=N-to break,naphthalene ring structure to open,and AO7 molecule to be gradually decomposed.The high photocatalytic reactivity and low photogenerated carrier recombination were attributed to the construction of Bi OI/HKUST-1 typeⅠheterojunction structure.