Experimental Study On Synthesis And Catalytic Oxidation Of Sulfite By Quantum Dots And ZIF

SO₂ has become one of the important causes of acid rain and smog,and it can cause great harm to the human body.Wet desulfurization technology is the most mature and widely used flue gas desulfurization treatment process in the world,and the magnesium flue gas desulfurization process in wet desulfurization is characterized by simple system,low basic investment,low corrosivity and not easy to block.More and more people’s attention and attention.Sulfite catalytic oxidation is the core step of magnesium desulfurization.However,the catalysts currently used cannot be effectively recovered,which increases the operating cost,and the catalyst will remain in the by-products,causing the quality of by-products to drop and secondary pollution.Therefore,the development of high-efficiency,low-residue,long-life catalysts has practical application and promotion value.Co₃O₄QDs/g-C₃N₄ catalyst was prepared by impregnation method with g-C₃N₄as catalyst carrier and cobalt salt as active component.The effects of the size of the quantum dots,the calcination temperature and the loading of Co₃O₄ quantum dots on the catalytic properties of the catalyst on the surface morphology and morphology of the magnesium sulphate were investigated.The ICP results show that the actual loading of cobalt is 0.49%;the low temperature ESR results indicate that there are oxygen holes on the surface of the catalyst;and XPS results show that the content of surface adsorbed oxygen is increased due to the presence of oxygen holes,which promotes magnesium sulfite.Oxidation;by DFT calculation,after the oxygen vacancies are generated in Co₃O₄,the chemisorption of sulfite increases to-2.22 eV,while the adsorption capacity of sulfate decreases to-2.81 eV.Different sizes of ZIF-67 were prepared by hydrothermal synthesis using cetyltrimethylammonium bromide（CTAB）as a surfactant,cobalt as a central atom and dimethylimidazole as a ligand.Then further investigate the effect of calcination temperature on the morphology of ZIF-67,and obtain the best CTAB dosage and the best calcination temperature through experiments.According to the Kirkendall effect,the effects of factors such as the amount of cobalt nitrate added during reflow and the order of calcination and reflux were investigated to synthesize a catalyst having a hollow structure.The experimental results show that the catalytic efficiency of the catalyst is as high as 0.148 mmol·L^-1·s^-1,which is 13.8 times higher than that of non-catalytic.The SEM results show that the shape of the catalyst is polyhedron.The TEM results show that the catalyst with hollow structure is successfully synthesized and the active material distribution is uniform.The specific surface area of the catalyst is 605-1985m²/g by BET calculation.Both XRD and F-TIR results show that the low temperature calcination and etching did not change the bulk structure of the catalyst.Moreover,the calcination causes the hydroxyl group connected to the central atom in the catalyst to be broken,so that the active material is directly exposed,and the calcination also makes the surface of the catalyst relatively rough,which is more favorable for the reaction to occur.Repeated experiments were carried out on Co₃O₄ QDs/g-C₃N₄ and ZIF-67 series catalysts.ICP was used to determine the loss rate of active constituents before and after the two catalyst experiments and repeated experiments.The experiments showed that Co₃O₄ QDs/g-C₃N₄prepared by impregnation method has a high utilization rate of cobalt;the ZIF-67 series catalyst prepared by hydrothermal synthesis still has a high catalytic rate after repeated use,and has reached the expected target.