Removal Of Elemental Mercury From The Metallurgy Flue Gas By H₂S-modified Transition Metal Supported Titanium Dioxide

Recently the situation of atmospheric mercury pollution in China has caused widespread concern.As Minamata Convention is implemented,the control of atmospheric mercury pollution affects China's compliance performance directly.Non-ferrous metal smelters are an important source of atmospheric mercury emissions in China.Usually mercury species in metallurgy plant contain elemental mercury?Hg⁰?,oxidized mercury(Hg²⁺)and particulate mercury?Hg^p?.Among the three types of mercury,elemental mercury?Hg⁰?is the most difficult to remove.It is Boliden-Norzink process developed by Sweden company that was widely used in the world.The supported catalyst widely used in the industry is an ideal Hg⁰ adsorbent of metallurgical flue gas,which has a simple preparation method and high yield.However,the activity of the oxide-supported adsorbent was very limited.It can meet requirements above by surface modification.Therefore,the research proposed to modify oxide-loaded adsorbents with H₂S to prepare metal sulfide-loaded adsorbents matching with metallurgical flue gas process innovatively,making a transition from metal oxide to metal sulfides.We also discuss the reaction mechanism of Hg⁰ on the surface of H₂S-modified transition metal oxides by several characterization.The main research results are as follows:?1?The article revealed the relationship and difference between the adsorption of Hg⁰ by P25 and ZnS/TiO₂ after vulcanization preliminary.H₂S pretreatment of P25 produced a small amount of active sulfur component on the surface,doping S element.Also TiO_1-xS_x formed on the surface.However,TiO_1-xS_x was unstable and easily oxidized in the air.Zn-loading could stabilize physicochemical properties of P25.On the other hand,the S^II-Zn-O^II-Ti-S structure led to an excellent mercury adsorption performance.The gaseous Hg⁰ was first adsorbed on the surface of ZnS/TiO₂,forming Hg⁰_?ad?.Then Hg⁰_?ad?reacted with S^II-Zn-O^II-Ti-S structure in the form of HgS after which the S^II-Zn bond was broken.?2?Cu/TiO₂ was also prepared.The adsorption capacity of modified Cu/TiO₂ at 100 ? was as high as 7.0 mg g^-1.Moreover,the adsorption amount of modified Cu/TiO₂ could still reach 6.8 mg g^-11 in the presence of SO₂ and H₂O.During the pretreatment of H₂S,a large amount of CuO on the surface of Cu/TiO₂ was converted into CuS.Under air conditions,both CuO and CuS could oxidize Hg⁰ to HgO and HgS,respectively.In the SO₂ and H₂O condition,CuO reacted with SO₂ and H₂O to form CuSO₄,while CuS was not interfered with.The mercury adsorbed on the surface of the adsorbent existed in the form of HgS,which could be rapidly desorb at a temperature to form high concentration Hg⁰.The desorption temperature was moderate.Thus it was easy to recycle.In conclusion,the adsorbent matched with the metallurgical flue gas was obtained by H₂S modification.Cu/TiO₂ showed an excellent performance to capture Hg⁰ and resistance to SO₂ and water vapor.It has wide practical application prospects.