Preparation Of MO_x/TiO₂ Composites And Experimental Study On Photocatalytic Oxidation Of Mercury

Mercury,due to hypertoxicity and persistence,has gained considerable attention in recent years.In January 2013,Minamata Convention on Mercury,the first international legally binding treaty,was authorized by delegates from147 countries.It proposed a strict emission standard for coal-fired power plants.Therefore,it is imminent to explore efficient technologies to control mercury emissions from coal-fired power plants.Photocatalysis based on semiconductor nanoparticles is an advanced technology and utilization of photocatalytic technology to solve the environmental contaminations and energy crisis,which has been flourishing in recent years.Titanium dioxide?TiO₂?,one of the best-known semiconductor photocatalysts,the traditional TiO₂ nanoparticles are only active under UV light irradiation.Furthermore,the excited electron-hole pairs are easily recombined and difficultly transferred,which often leads to low quantum yield rate and a limited oxidation efficiency.This paper introduces the way to control the growth of TiO₂ crystal surface,the doping of non-metal and metal oxides to expand the absorbing boundary and enhance the separation efficiency of electrons and holes.First,the co-exposure?001?and?101?surface of anatase TiO₂ were prepared by hydrothermal method.Then,the V₂O₅/rutile-anatase photocatalyst system with homo-hetero junctions and the Carbon decorated In₂O₃/TiO₂ heterostructures were prepared by impregnation method.The samples were characterized by XRD,XPS,BET,UV-vis,PL and so on.At the same time,the photocatalytic experiments of the prepared samples under simulated flue gas were carried out,and the internal reaction mechanism was researched by analyzing the samples before and after the experiment.In addition,the cyclic stability of the sample is also studied.The as-prepared samples with different percentages of?001?facets display different photocatalytic performance,the optimal ratio of?001?and?101?facets can greatly suppress the recombination of photoexcited electrons and holes.The synergetic effects of both homo-hetero junctions have facilitated the charge separation and migration dramatically.Moreover,the redox couple(V⁵⁺/V⁴⁺)has an important role in promoting Hg⁰ oxidation.The as-prepared photocatalysts display highly cyclic stability also.Doping carbon can form additional carbon doping level,enabling TiO₂ can be stimulated under visible light.Synergistic effect of heterojunction and doping carbon facilitate the transfer of charge on the interface.In addition,the study found that the oxidation capacity of·O₂^-is less than that of·OH,the main active component in the reaction is·OH and the final product is HgO.