氯化铜改性石墨相氮化碳吸附剂的脱汞性能

针对燃煤电厂汞污染物排放控制的问题, 以尿素为前驱体, 通过直接热聚合法制得绒毛状石墨相氮化碳(g-C₃N₄), 并用于低温条件下吸附脱除单质汞(Hg⁰)。利用透射电子显微镜(TEM)、X射线衍射(XRD)、氮气吸附-脱附、X射线光电子能谱(XPS)等手段对吸附剂进行表征。结果表明:未改性g-C₃N₄具有良好的低温脱汞活性, 在120 ℃时其脱汞效率可达84.7%;CuCl₂改性可以有效提高g-C₃N₄的脱汞性能, 其脱汞效率在40~200 ℃范围内均可达到97%以上; 温度对吸附剂脱汞效率的影响较小。XPS表征测试结果表明, 铜离子和共价态氯原子均参与了单质汞的吸附脱除反应, Hg⁰被Cu²⁺离子和共价态Cl原子氧化成了Hg²⁺离子, 再吸附于g-C₃N₄表面而脱除。CO₂、SO₂和水蒸气对吸附剂脱汞效率影响较小, 但水蒸气可提高汞吸附量。

Removal of elemental mercury by cupric chloride-modified graphitic carbon nitride

To control the mercury emission from the coal-fired power plants, villous graphitic carbon nitride (g-C3N4) was synthesized via direct thermal polymerization of the precursor of urea, and it was used to adsorption removal of elemental mercury (Hg0) at low temperature. The sorbents were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm, and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that pristine g-C3N4 performs well toward Hg0 adsorption with Hg0 removal efficiency of up to 84.7% at 120 ℃. CuCl2 modification could effectively improve the Hg0 removal performance of g-C3N4, and its Hg0 removal efficiency could approach above 97% at 40~200 ℃. Temperature had a slight impact on Hg0 removal efficiency. XPS analysis indicated that both copper ions and covalent chlorine atoms participated in elemental mercury adsorption removal reaction, in which Hg0 was oxidized into Hg2+ by Cu2+ ions and covalent Cl atoms, and then Hg2+ was adsorbed on g-C3N4 surface for removal. CO2, SO2 and water vapor had slight effects on Hg0 removal efficiency, whereas water vapor could improve mercury adsorption capacity.