Study On Photocatalytic Oxidation Of Bismuth-based Modified Catalyst To Remove Hg~0 From Zinc Smelting Flue Gas

Mercury is a kind of heavy metal pollutant with strong biological toxicity.Due to its extreme toxicity and accumulation in the biological chain,it will harm human health through the food chain,so it has become a global circulating pollution element.Since the signing of the《Minamata mercury Convention》in 2013,china has faced the pressure between international environmental diplomacy and the balance of domestic economic development.Gaseous element mercury（Hg⁰）is difficult to remove due to its insoluble in water,stable chemical properties,high volatilization and diffusion capacity.Among the many anthropogenic gaseous mercury emission sources,mercury in the flue gas from zinc smelting has become one of the main sources of anthropogenic mercury emission.Therefore,the development and adoption of new mercury removal technology is one of the effective ways to solve this problem.In this study,zero valent mercury from zinc smelting flue gas was taken as the treatment object,and the photocatalytic oxidation of bismuth oxide semiconductor material with metal modification to remove gaseous elemental mercury（Hg⁰）was carried out,with a focus on the photocatalytic mercury removal of La₂O₃/Bi₂O₃composite material.The main research conclusions are as follows:A series of bismuth oxide composite nanomaterial catalysts doped with metal elements were prepared by impregnation method and their photocatalytic mercury removal performance was tested under ultraviolet light.Among them,La₂O₃/Bi₂O₃photocatalyst showed the best photocatalytic mercury removal efficiency.By changing the calcination temperature and the loading capacity of La₂O₃ and testing the activity of photocatalytic mercury removal,the results showed that the samples loaded with 6%La₂O₃ after calcination at 500℃showed relatively high efficiency of oxidative mercury removal.XRD,SEM,BET,Uv-vis DRS,PL,XPS and other characterization methods were used to characterize the crystal phase composition,morphology,specific surface area,surface element composition and optical properties of 6%La₂O₃/Bi₂O₃（500℃）.The results showed that 6%La₂O₃/Bi₂O₃ composite had the highest dispersion of active sites,which was promoted by the strong interaction between La₂O₃ and Bi₂O₃ under roasting conditions to generate Bi-O-La species.In addition,the material also exhibits excellent optical properties while the heterojunction formed in La₂O₃/Bi₂O₃ promotes the separation and migration of photoelectron-hole pairs and thus Hg⁰ oxidation efficiency is enhanced.The effects of various factors（e.g.,the reaction temperature and composition of the simulated flue gas（i.e.,O₂,NO,H₂O,and SO₂））on the photocatalytic oxidation efficiency of Hg⁰were also investigated and analyzed in detail.The results showed that O₂and SO₂ in simulated flue gas promoted the efficiency of photocatalytic mercury removal reaction,while the reaction temperature,NO and H₂O showed inhibition.